EP0478689A1 - HUMAN MONOCLONAL ANTIBODIES TO HIV-1 MN? gp 120 - Google Patents

Abstract

In an antibody capable of neutralizing the MN prototype or a variant MN virus, an amino acid sequence contained in the main neutralization domain of the MN prototype comprises, at positions A1-A17 of the main neutralization domain, a subsequence formed of amino acid residues KRKRIHIGPGRAFYTTK. The corresponding amino acid subsequence of the variant MN virus comprises a sequence which is completely homologous between the residues I-G-P-G-R at positions A7-A11 and at least 36% of homologs in the remaining residues of the prototype prototype subsequence MN.

Description

HUMAN MONOCLONAL ANTIBODIES TO HIV-1 _MN qp 120

Background of the Invention

This application is a continuation-in-part of Scott et al., U.S.S.N. 431,281, filed November 3, 1989, which is a continuation-in-part of U.S.S.N. 361,541, filed June 5 , 19B9 .

This invention relates to antibodies specific for Human Immunodeficiency Virus (HIV).

HIV is the proposed causative agent of Acquired Immune Deficiency Syndrome (AIDS). (Popovic et al., 1984, Science 224:497). Different strains of HIV differ in the amino acid sequences of proteins encoded by the viral genome, particularly in the amino acid sequence of the external envelope glycoprotein gp120 (Starcich, 1986, Cell 45:637; Hahn et al., 1986, Science 232:1548). gp120 binds the cellular receptor of the virus, CD4. Cells expressing the envelope protein fuse with CD4-bearing cells in culture (Lipson et al. 1986, Nature 323:725; Sodroski et al., 1986, Nature 322:470), resulting in the formation of multinucleate syncytia. Both native gp120 and recombinant gp120 elicit antibodies that are capable of neutralizing HIV in cell culture (Robey et al., 1986, Proc. Nat. Aca. Sci. 83:7023; Mathews et al., 1986, Proc. Nat. Aca. Sci. 83:9709; Laskey et al., 1986, Science 233:209; and Putney et al., 1986, Science 234: 1392). These antibodies generally neutralize only the viral variant from which gp120 was derived.

Over 100 HIV variants have been identified; among them are RF (Popovic et al., supra), WMJ-1 (Hahn et al., supra), LAV (Wain-Hobson et al., 1985, Cell 40:9), ARV-2 (Sanchez-Pescador et al., 1985, Science 227:484), and III-B (Ratner et al., 1985, Nature 313:277). The majority of monoclonal antibodies that neutralize the HIV-III_B variant bind a specific region of the III_B gp120

molecule referred to as the principal neutralizing domain (PND), which has been mapped to a 24 amino acid highly variable region of gp120 (Matsushita et al., 1988, J.

Virol. 62:2107; and Skinner et al., 1988, AIDS Research and Human Retroviruses 4:187).

The principal neutralizing domain of the HIV gp120 molecule is a 36 amino acid region of the gp120 molecule between amino acids 303 and 338, inclusive, according to the gp120 numbering convention of Ratner et al., supra. Over its entire length, the gp120 polypeptide sequence varies from one HIV variant to the next by approximately 20-25%, whereas the amino acid sequence variation among principal neutralizing determinant regions is approximately 40-50%. This highly variable region is flanked by conserved cysteine residues which may form a disulfide bond and define a "loop" region containing the largely conserved sequence Gly-Pro-Gly in its center.

Synthetic loop region peptides, 8 amino acids or more in length, have been found to elicit the production of antibodies that neutralize virus only from the isolates or variants of it from which the amino acid sequence of the peptide was derived.

Human monoclonal antibodies directed against HIV-1 proteins have been produced by hybridoma formation or EBV transformation (Banapour et al., 1987, J. Immunol. 139:4027; Sugano et al., 1988, Biochem. and Biophys. Res. Comm. 155:1105; Morrow et al, 1988, J. Immunol. 140:941; Gorny et al., 1989, Proc. Nat. Aca. Sci. 86:1624; and Amadori et al., 1989, AIDS Res. and Human Retroviruses 5:73). Summary of the Invention

The invention is based in part on our discovery that the MN variant of HIV is very common among

HIV-infected patients; approximately 30% of humans

infected with HIV are, according to our estimates,

infected with an MN variant or a closely-related variant, essentially the equivalent of the MN variant.

Accordingly, the invention features an antibody capable of neutralizing the MN prototype of HIV, or a viral variant of the MN prototype. (As used herein,

'neutralization' refers to the ability of the antibody to inhibit HIV infection of cells by cell-free virions, or fusion of infected and uninfected cells, or both.) The MN prototype virus is defined by a particular amino acid sub-sequence within the principal neutralizing domain

(i.e., the loop region of the gp120 envelope protein) having positions A¹-A¹⁷:

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K. MN viral variants are herein defined as variants which exhibit complete amino acid sequence homology at residues I-G-P-G-R, i.e., at positions A⁷ through A¹¹, and at least 36% homology with the remaining 12 amino acids of the MN sequence given above.

In preferred embodiments, the antibody has a broad neutralizing capability. (As used herein, 'broad neutralization refers to the ability of the antibody to inhibit infection by MN prototype strains and/or MN viral variants and other HIV strains. Antibodies having broad neutralizing activity are identified upon demonstration of their ability to neutralize two or more HIV strains.) As used herein, a broadly neutralizing antibody is capable of neutralizing an HIV strain having an amino acid sequence within the center of the principal neutralizing domain that is present in at least 60% of HIV isolates found in Tables 1a-d; more preferably, the sequence is present in 70% of these HIV isolates. Preferably, the broadly neutralizing antibodies of the invention are capable of neutralizing at least two HIV strains which contain the amino acid sequence G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein

A comprises R or any conservative amino acid

substitution of R and A¹² comprises A or any

conservative amino acid substitution of A. As used herein a "conservative" amino acid substitution refers to a substitution in which the hydrophobic, hydrophilic, aromatic, or charge character of the amino acid is

maintained.

In other preferred embodiments, the PND amino acid sequence of HIV isolates broadly neutralized

according to the invention is 100% homologous at G-P-G-R-A of the MN consensus sequence; more preferably, it is 100% homologous with the sequence I-G-P-G-R-A or,

alternatively, with the sequence G-P-G-R-A-F. Preferably, one of the two strains broadly neutralized according to the invention may be the Ill_B prototype of HIV.

Alternatively, the PND epitope recognized by a broad neutralizing antibody according to the invention may be a noncontiguous epitope which contains the amino acid sequence I-A⁶-A⁷-G-P-G-R within the principal

neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ comprises, independently, any amino acid. (As used herein, "noncontiguous epitope" refers to a consensus PND sequence in which either or both of the two amino acid positions directly amino-terminal to G-P-G may include any amino acid substitution without disrupting antibody binding.) Preferably, a broadly neutralizing anitbody of the invention recognizes the epitope

I-A⁶-A⁷-G-P-G-R-A, or I-A⁶-I-G-P-G-R, or

I-A⁶-I-G-P-G-R-A. These epitopes are present in 69%, 68%, and 78%, respectively, of the HIV isolates in Table 1

The amino acids adjacent to the epitopes described above may also affect the binding affinity of a neutralizing antibody. The relative frequencies of HIV loop region sequences is shown in Table 2.

In preferred embodiments, an MN viral variant neutralized according to the invention has a sub-sequence of the gp120 loop region of the formula (1):

A¹-A²-A³-A⁴-A⁵-A⁶-I-G-P-G-R-A¹²-A¹³-A¹⁴-A¹⁵-A¹⁶-A¹⁷ wherein each A¹-A⁶ and A¹²-A¹⁷ can be,

independently, any amino acid; most preferably an MN viral variant of the invention has a gp120 loop region sub-sequence of the formula (1), wherein

A¹ = K, T, A, R, V, P, S, or I,

A² = R, T, I, M, or K,

A³ = K, R, T, N, or A,

A⁴ = R, S, G, or H,

A⁵ = I, M, or L,

A⁶ - H, P, S, Y, K, N, or R,

A¹² = A, P, T, S, or K,

A¹³ = F, V, I, W, or L,

A¹⁴ = Y, H, V, or F,

A¹⁵ = T, Y, or A

A¹⁶ = T, A, G, or R, and

A¹⁷ = K, G, E, S, Q, R, T, or A.

In other preferred embodiments, an HIV strain neutralized according to the invention has a

sub-sequence of the gp120 loop region of the formula (2):

A¹-A²-A³-A⁴-A⁵-A⁶-I-G-P-G-R-A¹²-A¹³-A¹⁴-A¹⁵-A¹⁶-A¹⁷ wherein any of A¹-A⁶ and ^A12-A¹⁷ can be, independently, any amino acid.

Preferably, an HIV strain neutralized according to the invention and having a sub-sequence of formula (2) above has the sub-sequence: wherein A⁷ is I,

A¹²=A, A¹³ is any ammo acid, and each of A¹

through A⁶ and each of A¹⁴ through A¹⁷ is,

independently, deleted, wherein the amino acid formula is I-G-P-G-R-A-A¹³; wherein A¹³ is F, each of A⁷

and A¹⁴ is, independently, any amino acid, and each of A through A⁶ and each of A¹⁵ through A¹⁷ is,

independently, deleted, wherein the amino acid formula comprises A⁷-G-P-G-R-A-F-A¹³; wherein A⁵ i.s I,

each of A⁶ and A⁷ is, independently, any amino acid, and A¹ through A⁴ and A¹³ through A¹⁷ is,

independently, deleted, wherein the amino acid sequence is I-A⁶-A⁷-G-P-G-R-A; or wherein A⁵ and A⁷ is,

independently, I, and A⁶ is any amino acid, wherein the amino acid sequence is I-A⁶-I-G-P-G-R-A.

The antibody of the invention may be monoclonal or polyclonal; it is preferably a human antibody. The antibody may also be a chimeric antibody having a variable region derived from a species other than human and a constant region derived from humans; it may also be conjugated to a carrier.

Where the antibody is monoclonal, it is made by (a) immunizing a mammal with a peptide or a polypeptide having either the MN prototype viral sequence of the PND region of gp120 or one of the amino acid sequences given above for MN variants, or where the antibody made is broadly neutralizing the immunogen has a prototype sequence containing either the G-P-G-R-A-F or

I-G-P-G-R-A or other consensus epitope sequences described above; (b) fusing the immunized spleen cells of the mammal with an immortal cell line to make

independent clones; and (c) selecting a clone that produces the monoclonal antibody. Preferably, the selection step may be by ELISA. The selection step may also include the capability of the antibody to

neutralize infection by the MN prototype or an MN variant virus or by a broad range of HIV strains

containing frequently occurring epitope sequences such as G-P-G-R-A-F and I-G-P-G-R-A, as defined above.

Where the antibody is polyclonal, it is made by screening human sera for the presence of antibodies that react with a peptide or a polypeptide having either the MN prototype viral sequence within the PND region of gp120 or one of the sequences of an MN variant, or a commonly occurring (i.e., G-P-G-R-A-F-containing) HIV sequence within the PND, as defined above for monoclonal antibodies. Plasma is then removed by plasmapheresis from a human who has high titers of antibodies that react with these peptides. The IgG fraction of the serum is used as the source of polyclonal antibody. The polyclonal antibody may be further purified using conventional methods, e.g., by protein A affinity chromatography.

In another aspect, the invention features a method of identifying a broadly neutralizing antibody, as defined above, which includes testing the antibody for one or both of (a) its ability to bind to a peptide or protein including (l) the amino acid sequence

G-P-G-A¹¹-A¹² within the principal neutralizing

domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and

A¹² is A or any conservative ammo acid substitution of A or (2) the amino acid sequence I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is,

independently, any amino acid, and (b) its biological activity in HIV neutralization.

Preferably, the method includes testing the antibody in one or more of the following assays

(a) an ELISA assay in which the antibody is tested for binding to a peptide or protein including (1) the amino acid sequence G-P-G-A¹¹-A¹² within the

principal neutralizing domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any

conservative amino acid substitution of A or (2) the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is,

independently, any amino acid;

(b) a competition ELISA assay in which the antibody is tested for lack of binding to a peptide or protein due to competition by a second peptide or protein including the amino acid sequence (1) or (2) above;

(c) a syncytium inhibition assay in which the antibody, when added to HIV infected cells, inhibits the formation of syncytia by at least 80%, more preferably, by at least 90%, wherein the HIV includes the amino acid sequence (1) G-P-G-A¹¹-A¹² within the principal

neutralizing domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any conservative ammo acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is,

independently, any amino acid;

(d) a competition syncytium inhibition assay in which the antibody is tested for lack of syncytium inhibition by incubating the antibody with a peptide having the amino acid sequence defined in (1) or (2) above, and added to HIV infected cells;

(e) an HIV-infection neutralization assay in which the antibody, when incubated with HIV and added to HIV susceptible cells, neutralizes HIV infection; and

(f) an HIV infectivity reduction assay in which the antibody, when incubated with HIV and added to HIV susceptible cells, reduces the titer of HIV.

The invention also features a method of treating or inhibiting HIV infection in a patient which includes administering to the patient an antibody that is capable of neutralizing

(a) an MN prototype virus or an MN variant virus thereof, wherein an amino acid sequence within the principal neutralizing domain of the MN prototype includes the sub-sequence, at positions A¹-A¹⁷ of the principal neutralizing domain, of amino acid residues

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K,

and the corresponding amino acid sub-sequence of the MN variant comprises a completely homologous sequence at the I-G-P-G-R residues at positions A⁷-A¹¹ and at least 36% homology over the remaining residues of the MN prototype sub-sequence, and

(b) at least two HIV strains which contain the amino acid sequence G-P-G-A¹¹-A¹² within the

principal neutralizing domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any conservative amino acid substitution of A, or

(c) at least two HIV strains which contain the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is,

independently, any amino acid.

Preferably, the antibody is monoclonal, or is polyclonal.

in another aspect, the invention features a recombinant vaccinia virus capable of expressing, upon infection of a eukaryotic cell, HIV envelope protein of a first strain containing the principal neutralizing domain of a second HIV strain. The virus includes DNA encoding the envelope protein, the DNA includes a DNA sequence encoding the principal neutralizing domain of the second HIV strain, the envelope protein-encoding DNA being under the transcriptional control of a vaccinia virus promoter.

Preferably, the HIV envelope protein encoding

DNA of the recombinant virus is derived from a

recombinant vector. The vector includes a DNA sequence encoding the envelope protein, and the DNA includes a DNA sequence encoding the principal neutralizing domain of the second HIV strain, and DNA capable of causing integration of the envelope protein-encoding DNA into the vaccinia virus genome.

The HIV envelope protein-encoding DNA is a hybrid sequence, i.e., the principal neutralizing domain-encoding sequence and the remainder of the sequence are derived from different HIV strains. Thus, for example, the virus or the vector from which it is derived can function as a cassette in which the principal neutralizing domain-encoding region from any desired strain can be inserted, without changing any other portion of the virus or vector, including the remainder of the envelope-encoding region. The encoded envelope protein, despite its hybrid nature, will exhibit the immunological properties with regard to HIV neutralization of the strain from which the principal neutralizing domain-encoding sequence was derived. In other words, where, for example, the principal

neutralizing domain is MN or an MN variant, the encoded envelope protein is neutralized specifically by MN variant-specific antibodies; or, for example, where the principal neutralizing domain is derived from the right side of the tip of the gp120 loop, i.e., contains

G-P-G-R-A-F, the encoded envelope protein is neutralized by broadly neutralizing antibodies that are capable of neutralizing both MN strains or MN variants and other HIV strains containing the G-P-G-R-A-F sequence. A hybrid envelope-encoding virus, therefore, can be used as an infectious agent capable of conferring upon a eukaryotic cell the ability to express the hybrid envelope protein on its surface. A hybrid

envelope-encoding vector can be used to screen

antibodies for the ability to neutralize any strain of HIV and to identify antibodies which might usefully neutralize more than one strain, e.g., RF, WMJ-1, LAV, or ARV-2.

In another aspect, the invention features a human monoclonal antibody which specifically neutralizes the MN variant of Human Immunodeficiency Virus Type I and may also be capable of neutralizing a broad range of HIV strains, for example, those containing the sequences described above, and a method of treating a human patient infected with HIV by administering to the patient a virus-neutralizing amount of the antibody.

In preferred embodiments, the antibody may be produced by an immortalized B cell derived from a human patient infected with HIV; the B cell may be

immortalized by infection with Epstein Barr Virus. In other preferred embodiments, the patient may be treated by administration of a composition containing the human monoclonal antibody in combination with a

pharmaceutically acceptable carrier substance.

Preferably, the composition may include an antibody which is capable of neutralizing at least two

HIV strains including the amino acid sequence (1)

G-P-G-A¹¹-A¹² within the principal neutralizing

domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any conservative ammo acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is, independently, any amino acid.

The invention also features methods of obtaining a human monoclonal antibody capable of neutralizing HIV_MN which may also be a broadly

neutralizing antibody that is capable of neutralizing HIV strains containing commonly occurring epitopes such as G-P-G-R-A-F or I-G-P-G-R-A, as described above, the method including the steps of providing an anti-HIV monoclonal antibody, and first testing the monoclonal antibody for the ability to bind to a fragment of the gp120 envelope protein of HIV_MN, the fragment

comprising the principal neutralizing domain, binding being an indication of the ability of the antibody to neutralize HIV_MN. In preferred embodiments, the antibody is capable of neutralizing at least two HIV strains

comprising the ammo acid sequence (1) G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any

conservative amino acid substitution of A, or (2)

I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is, independently, any amino acid. Preferably, the fragment used for testing MN variant binding ability is a fragment comprising one of the commonly occurring PND epitope sequences described above, or may include all, a fragment, or an analog of the archetypal MN gp120 PND region with the amino acid sequences I-G-P-G-R, I-G-P-G-R-A, G-P-G-R-A-F, I-A⁶-A⁷-G-P-G-R-A,

I-A⁶-I-G-P-G-R, I-A⁶-I-G-P-G-R-A, or

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K, which sequences are contained within the principal neutralizing domain of the MN gp120 protein; the method may further include the step before or following the first testing step, of secondly testing the monoclonal antibody for the ability to neutralize HIV_MN by, for example, determination of inhibition of syncytium formation; and may further include the step before or following the first and second steps, of, thirdly, testing the antibody for the ability to neutralize a broad range of HIV strains.

Preferably, the fragment is a peptide derived from the PND of gp120; more preferably, it is a closed loop peptide.

Preferably, the method may further include the step before or following the first or second steps, of thirdly testing the antibody for the abiliyty to neutralize at least one HIV strain other than HIV_MN, wherein said strain includes the amino acid sequence (1)

G-P-G-A¹¹-A¹² within the principal neutralizing

domain of the HIV envelope protein, wherein A¹¹ is R or any conservative amino acid substitution of R and A¹² is A or any conservative amino acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ is, independently, any amino acid.

More preferably, the sequence includes R-I-H-I-G-P-G-R-A-F and has less than 36% homology over the remaining residues of the MN prototype sub-sequence, wherein the prototype sub-sequence includes

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K.

Antibodies of the invention can be used to inhibit HIV infection in a human patient infected with or suspected of having been infected with HIV.

Administration of the human antibody to a patient shortly after exposure or suspected exposure to the infectious agent may prevent the establishment of infection by the virus. For example, a patient may have accidently come into contact with HIV-contaminated blood, blood products, or bodily secretions. The antibodies may also prevent the transfer of HIV from a seropositive gravid female to her offspring by

administering the antibody prior to or during pregnancy, and/or by administration to the offspring at birth and thereafter. The antibodies may also be used for passive immunization therapy; e.g., members of high risk groups who are still HIV-seronegative can be treated at regular intervals with an antibody preparation in order to prevent the establishment of a chronic HIV infection. The antibodies of the invention are, because of the widespread distribution of MN variants in infected persons, useful for detecting HIV in biological samples, for screening blood supplies, and, potentially, for treating a large percentage of HIV-infected patients.

Broadly neutralizing antibodies of the invention, because they recognize both MN or MN variants and HIV strains containing common epitope sequences, are especially useful for applications described above.

Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.

Description of Preferred Embodiments

The drawings will be described briefly. Fig. 1 is a Western blot analysis of human monoclonal antibody (HMab) reactivity with two strains of HIV-1.

Fig. 2 is a dot blot showing reactivity of four HMabs with gp120 from different HIV strains.

Fig. 3 is a graph showing ELISA reactivity of

K24-3b and N70-23.a, two of the antibodies of Fig. 2, with Con-A immobilized gp120 from nine strains of HIV-1.

Fig. 4 is a graph showing ELISA reactivity of N70-23.a, N70-15.e, N70-19.b HMabs with Con-A

immobilized gp120 from eight strains of HIV-1.

Fig. 5 is a Western blot showing reactivity of K24-3b and N70-23.a HMabs with eight independent HIV-1 strains.

We now describe the preparation and use of antibodies of the invention.

Preparation of the Immunogen

The immunogen used to generate antibodies of the invention can be a synthetic peptide, a protein fragment, a gp160 polypeptide of the MN prototype or an MN variant, or may contain a sub-sequence of the MN prototype sequence which is common to a large number of HIV strains. The immunizing peptide, polypeptide, or protein should be at least 8, and more preferably at least 17, amino acids in length, and may contain a 5 amino acid or greater sequence that is 100% homologous with the MN prototype neutralizing domain sub-sequence within gp120 identified above, or more preferably an amino acid sequence in which 5 of the central amino acids are 100% homologous and, in addition, the

surrounding amino acids are at least 36% homologous. An immunogen used to generate broadly neutralizing

antibodies of the invention is also an amino acid sequence in which 6 of the central amino acids are G-P-G-R-A-F or I-G-P-G-R-A.

The immunizing peptide, polypeptide or protein may be in linear form or alternatively may contain the prinicipal neutralizing domain portion formed into a closed loop by creation of a disulfide bond between cysteine residues at the termini of the PND sequence. If the immunizing peptide contains more than one PND, each may be separately formed into a loop through disulfide bonding.

Synthetic peptides containing the complete amino acid sequence of thegp160 principal neutralizing domain of the HIV-MN viral prototype or an MN viral variant, or containing the sequence G-P-G-R-A-F or I-G-P-G-R-A were synthesized by automated peptide synthesis using an automated peptide synthesizer. In addition, intact envelope polypeptide was produced in insect cells using a baculovirus expression system and purified as described in Rusche et al., U.S.S.N. 091,481, filed August 31, 1987, assigned to the same assignee as the present invention, hereby incorporated by reference. A 180 amino acid protein fragment with an amino acid sequence spanning the principal neutralizing domain, denoted PB1 (Putney et al., 1986, Science

234:1392), was expressed from an approximately 540bp DNA fragment generated by PvuII + Bglll cleavage of the full-length env gene, as described in U.S.S.N. 107,703, filed October 9, 1987, assigned to the same assignee as the present application, hereby incorporated by

reference. Synthetic peptides or protein fragments to be used as immunogens were either unconjugated or were conjugated to an immunogenic carrier, e.g., keyhole limpet haemocyanin (KLH) or ovalbumin, using succinyl maleimidomethyl cyclohexanylcarboxylate (SMCC) as a conjugation agent (Yoshitake et al., 1982, J. Biochem., 92:1413-1424), as follows.

Briefly, 1 mg of SMCC dissolved in 50ul of dimethylformamide was added to 6 mg of carrier (at a concentration of 10-20 mg/ml in 0.1M NaPO₄, pH 6.5) and incubated at room temperature for 0.5 h. The solution was passed through a Sephadex G-25 column to remove excess unreacted SMCC and 2 mg of peptide was added (suspended in a degassed solution of 0.1M NaPO₄, pH 8, ImM EDTA at a concentration of 10 mg/ml). The solution was mixed by N₂ gas and incubated at 4°C overnight. The sample was dialyzed in 6M urea, 0.1M NaPO₄, pH 7 until the precipitate dissolved and was then eluted through a BioGel P-10 column equilibrated in 6M urea, 0.1M NaPO₄. The voided protein was collected and dialyzed in distilled H₂O.

A number of these immunogens, designated RP142, RP70, RP342, RP100, RP102, RP108, RP123C, and RP174C have the amino acid sequences in the neutralizing domain sub-sequence of the gp120 loop region shown in Table 3.

Peptides RP70, RP123c, and RP174c were formed into closed loops by creation of a disulfide bond between the two cysteine residues near the ends of the amino acid sequence. A method for creating such a bond is described in Zhang et al., (1988, Biochemistry

27:3785-3794).

The peptides were prepared for immunization by emulsification in complete Freund's adjuvant according to standard techniques. (CFA, Difco Labs, Grand Island,

NY).

Production of Non-Human MN-Specific

Monoclonal Antibodies

Mouse strains (Balb/c, C57BL/6, A.SW, B10.BR, or B10.A, Jackson Labs., Bar Harbor, ME) were immunized intraperitoneally with 10-50ug per mouse of one of the peptides described above. The mice were given booster immunizations of the immunogen, either in an

emulsification of incomplete Freund's adjuvant or in soluble form, two to three times at two to four week intervals following the initial immunization. Mice were bled and the sera assayed for the presence of antibodies reactive with the immunogen. Mice showing a strong serological response were boosted and, 3-5 days later, spleen cells from these mice were fused with NS-1

(A.T.C.C. No. TIB18), SP2-0 (A.T.C.C. No. CRL8287, CRL8006), or P3.X63.AG8.653 myeloma cells incapable of secreting both heavy and light immunoglobulin chains (Kearney et al., J. Immunol., 1979, 123:1548), by standard procedures based on the method of Kohler and Milstein, Nature (1975) 256:495. Supernatants from hybridomas which appeared 6-21 days after fusion were screened for production of antibodies reactive with one or more of the peptides shown in Table 3 by an ELISA screening assay, as follows.

Each well of a 96-well Costar flat-bottom microtiter plate was coated with the peptide by placing a fifty microliter aliquot of a PBS solution containing the peptide at a final concentration of 0.1-10 μg/ml in each well. The peptide solution was aspirated and replaced with PBS + 0.5% BSA. Following incubation, the wells were then aspirated, washed, and 50 ul of the hybridoma supernatant was added. Following incubation, the wells were washed 3 times with PBS, and then

incubated with 50 ul of an appropriate dilution of goat anti-mouse immunoglobulin conjugated with horseradish peroxidase (HRP, Zymed Laboratories, San Francisco, CA). The wells were washed again 3 times with PBS and 50 ul of 1 mM ABTS (2,2 azino-bis

(3-ethylbenzthiazoline-6-sulfonic acid) in 0.1M

Na-Citrate, pH 4.2, to which a 1:1000 dilution of 30% H₂O₂ had been added), the substrate for HRP, was added to detect bound antibody. The ABTS samples were then read at OD₄₁₀ on a Dynatech spectrophotometric autoreader (Virginia).

Hybridomas that tested positive by the ELISA method were assayed for inhibition of syncytium

formation as follows. In general, recombinant vaccinia virus expressing the envelope gene of the HIV strain of interest (e.g., vac-env_MN) was used to infect cells of CD4+ human T-lymphoma line CEM (A.T.C.C. Accession No. CCL119), and hybridoma supernatants were then added to the cells to screen for blockage of HIV envelope mediated cell fusion by the monoclonal antibodies. Construction of a Recombinant Vaccinia

Virus/HIV Envelope-Encoding Vector

Construction of a recombinant vaccinia virus capable of expressing the full-length HIV envelope gene from a vaccinia virus promoter is described in EP

Publication No. 0 243 029, hereby incorporated by reference. The recombinant vector pSC25, containing the HIV env gene and the lacZ gene of E. coli expressed from a second vaccinia virus promoter, and flanked by

vaccinia viral sequences which together encode thymidine kinase (TK), was used to produce the recombinant virus.

For purposes of the present invention, it was necessary to construct a recombinant vector that

contained DNA encoding an envelope gene having the specificity of the HIV-MN variant. This was done by removing a 570 bp Bqlll fragment (encoding 180 amino acids) from the HIV-III_B env gene which spans the region of the principal neutralizing domain in pSC25, and replacing it with the analogous Bglll fragment from the HIV-MN env gene. The resulting plasmid, pSCR2502, contained a hybrid envelope gene which encoded an envelope protein having the principal neutralizing domain of the MN virus and the remainder of the env gene sequence from the HIV-III_B envelope.

A smaller region of the HIV-MN gp160 protein can be used in place of the 180 amino acid replacement just described; e.g., DNA encoding the 36 amino acid principal neutralizing domain can be inserted into the envelope-encoding DNA in place of the corresponding III DNA sequence., or a PND from any HIV env gene can be replaced with the PND from any other variant.

Alternatively, a recombinant could be used which contains the complete HIV-MN env gene. Multiple HIV envelope expressing strains are useful for determining if an antibody has broad neutralizing activity.

The recombinant vector pSCR2502 was transfected into CV-1 host cells that had been pre-infected with vaccinia virus containing an intact TK gene. The HIV envelope gene was integrated into the viral DNA by homologous recombination between the TK sequences on the vector and the TK sequences within the viral genome.

Recombinants containing the HIV envelope gene were selected by infection of TK~cells and plating on media containing bromodeoxyuridine (BUdR) and X-gal. BUdR is toxic to TK⁺ cells and thus selects for

TK-recombinants; X-gal is a chromogenic substrate cleaved by the product of the lacZ gene which results in the production of blue plaques where the lacZ gene is expressed and further identifies the recombinant virus which also contains the HIV-env gene.

The recombinant virus expressing the env gene was used to infect CD4+ cells. The HIV envelope protein presented on the surface of these cells will bind to the cell surface receptor, CD4, resulting in the fusion of the cells and the formation of giant multinucleated cells called syncytia.

Syncytium formation was assayed in the presence or absence of a hybridoma supernatant or purified monoclonal antibodies at a series of dilutions. The number of syncytia that formed were quantified at 24 hr post-infection. A positive hybridoma supernatant, i.e., having neutralizing activity, is defined as one that inhibits syncytium formation by at least 90%.

Hybridomas that tested positive for both peptide binding (ELISA assay) and neutralizing activity (inhibition of syncytium formation) were subcloned by the limiting dilution method. Hybridoma cells and irradiated splenocytes from nonimmunized syngeneic mice (final concentration 5 cells and 2.5 x 10⁶ cells per cc, respectively) were mixed and 200 ul of the mixed suspension were plated in microtiter wells to give 1 hybridoma cell per well. Subclones which appeared 7-14 days later were assayed again by the ELISA procedure described above. Representative positive subclones were subcloned a second time.

Many positive monoclonal antibody secreting hybridomas have been obtained. The isotypes of the antibodies were determined by the ELISA method using goat anti-mouse-HRP preparations which corresponded to each of the five major mouse immunoglobulin isotypes (IgM, IgG1, IgG2A, IgG2B and IgG3).

Amplification and Purification

of Monoclonal Antibodies

Purified antibodies were prepared by injecting hybridoma subclones that repeatedly tested positive by ELISA and syncytium inhibition intraperitoneally into pristane-primed syngeneic mice. The ascites which developed were recovered two to three weeks after injection and the monoclonal antibodies were purified as follows, using procedures which were dependent on the isotype of the antibody. Following elution, all IgG antibodies were dialyzed against PBS.

IgM antibodies were purified by 50% NH₂SO₄ precipitation of ascites fluid from mice injected with the corresponding hybridoma cells, and then dialysis of the precipitate against 4X PBS. The dialyzed antibody was then passed over an Ultrogel A-6 column (Biotechnics, Villeneuve-La-Garenne, France)

pre-equilibrated with 4X PBS. The antibody-containing fraction was identified using ELISA.

Ascites fluid containing IgG1 antibodies was diluted 4-fold in 0.1M Tris-HCl, 3M NaCl, pH 8.9, and isolated by passage through a Protein A-Sepharose affinity column equilibrated with the same Tris-NaCl buffer. The antibody was eluted using 0.1M Na-Citrate, pH 6.0.

Ascites fluid containing IgG2 antibodies was diluted two-fold in PBS, and then bound to a

Protein-A-Sepharose affinity column equilibrated with PBS. It was then eluted from the column with 0.15 M NaCl, 0.1 M acetic acid, pH 3.0. Following elution, the antibody was immediately neutralized by the addition of 1 M Na₂HCO₃.

Ascites fluid containing IgG3 antibodies was diluted 4-fold in 0.1 M Tris-HCl, 3 M NaCl, pH 8.9, passed over a Protein-A-Sepharose affinity column, and antibody was eluted from the Protein A column with 0.15 M NaCl, 0.1 M acetic acid.

Alternatively, all IgG subclasses can be purified by the following procedure. Ascites fluid is diluted 2-fold in 0.1M Tris-HCl, 3M NaCl pH 8.9, passed over Protein A Sepharose affinity column, and eluted with 0.15 M NaCl, 0.1M acetic acid, pH 3.0.

Characterization of Purified Antibodies

Monoclonal or polyclonal antibodies were characterized with respect to binding specificity and potency in blocking HIV envelope-induced syncytia and HIV infection. The potential therapeutic value of an antibody is initially determined using a combination of biochemical (i.e., binding) and biological (i.e., virus neutralization) assays, the results of which indicate the potency and specificity of an antibody preparation.

Mapping of Binding Site

The binding sites of antibodies of the invention were measured in standard ELISA assays

(described above), competition ELISA assays, and

competition syncytium inhibition assays using the peptides described below. Three groups of peptides were used: (1) a series of 24 or 25-mers representing the PND sequences from a variety of HIV variants (Table 5); (2) the MN substitution series, which includes a series of 12-mers corresponding to the MN PND tip sequence (C)-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-(C), each having an alanine residue substituted for one of the amino acids starting at the first arginine (R) residue and

proceeding to the tyrosine (Y) residue (Table 6). (A glycine was substituted for the naturally occurring alanine.) Antibody recognition of an epitope contained within the MN sequence is revealed by loss of binding of the antibody to an alanine-substituted peptide, the alanine substitution having disrupted the binding interaction; and (3) a series of peptides corresponding to frequently occurring sequences at the tip-of-the-PND loop (Table 7).

Competition ELISA assays were performed as for standard ELISAs with the following modifications. Prior to applying the antibody to the plate, the antibody preparation is incubated with a test peptide from the groups listed above at concentrations ranging from 10μM to 0.0045 μM. If the test peptide competes with the immobilized immunogen for binding to the antibody, the ELISA will reveal little or no binding of the antibody to the plate. Determination of Antibody Potency and

Specificity

The potency or relative neutralizing activity of the antibodies of the invention was determined using three biological measurements. First, a recombinant vaccinia virus syncytium assay measures the endpoint concentration at which the antibody will inhibit 90% of giant cell formation. The antibody containing sample is serially diluted and each dilution is tested for fusion inhibition activity. The potency of the sample is expressed as the concentration at which syncytium formation is inhibited by at least 90%.

In addition, competition syncytium inhibition assays were performed according to standard syncytium inhibition assays described above with the following modifications. Prior to adding the antibody to the culture of gp160 expressing CD4⁺ cells, the antibody is mixed with a test peptide at concentrations ranging from 100 to 0.1 μg/ml. If the test peptide competes with the cell surface gp160 epitope for binding with the

neutralizing antibody, syncytia will form. Conversely, if the test peptide does not compete with the cell surface epitope for binding with the neutralizing antibody, syncytia formation will be inhibited. This assay allows one to survey viral polypeptide sequences for blocking biological activity without actually using the viral isolate.

The second biological measurement is an HIV neutralization assay. Dilutions of antibody are incubated with HIV and then added to HIV susceptible CD4⁺ cells.

An antibody dilution that reduces viral protein production by 90% is defined as the endpoint dilution. This assay is described generally in Robey et al, 1986, Proc. Nat. Aca. Sic. 83:7023, and Robert-Guroff, 1985, Nature 316:72.

The third biological measurement is the Infectivity Reduction Assay (IRA), which measures the difference between the infectious dose of a virus in tissue culture in the presence and absence of a standard dilution of antibody. Antibody potency is measured by the amount of reduction in total virus titer. A 100% block of 10 infectious units is highly significant in this assay, in contrast with the standard serum

neutralization assay described above, due to IRA assay conditions, which promote cell division and virus replication. Characterization of Murine Monoclonal Antibodies

The steps taken to characterize an antibody preparation are shown in Table 8. Table 8 also

summarizes the assays described above. Table 3 shows examples of peptides used as immunogens or screening reagents. The following examples describe the

characteristics of murine and human HIV neutralizing antibodies, as well as specific antibodies demonstrating broad neutralization. Purification and Binding

Specificity of P7E4

The RP142 peptide immunization of mice yielded a hybridoma clone designated P7E4 (or F4/P7E4).

The P7E4 clone, which produced anti-RP142 IgM antibody, was expanded by intraperitoneal injection into Balb/c mice. Ascites fluid was recovered from the mice and P7E4 antibody was purified by gel filtration

chromatography, as described above. The P7E4 purified antibody was tested in the ELISA for binding with the loop containing peptide sequences from MN (RP142, RP70, RP342), III_B (RP135) and RF (RP339) variants (Table 9). P7E4 was capable of binding with all peptides tested.

In a syncytium inhibition assay, based on recombinant vaccinia virus expressing the envelope of the MN variant, the neutralizing activity observed was type specific (Table 10). CEM cells were infected with recombinant vaccinia virus expressing the envelope having the principal neutralizing domain of either the III_B, RF or MN variants. Monoclonal antibodies P7E4 or FE1/5C5 (a murine IgG2a which binds RP135 and neutralizes the III_B variant of HIV) were added at the initiation of culturing. The number of syncytia in each well were counted after 24 hours. Results are expressed as number of syncytia formed in the presence of

antibody/number of syncytia formed in the absence of antibody.

Purification and Binding Specificity

of Neutralizing Monoclonal Antibodies

MN Neutralizing Monoclonal Antibodies In subsequent fusions (F31, F50, F52, F58), the RP70 peptide immunization of mice yielded hybridoma clones designated F31/P2B10 , F50/P8D10 , F52/P7F12 , F52/P8C9, F52/P7B9, F52/P5E9, F52/P6E9, F52/P8G10, and F52/P8F11 which were MN specific.

The clones, which produced anti-RP70 IgG2a antibodies, were expanded by intraperitoneal injection into nude mice. Ascites fluid was recovered from the mice and antibodies were purified by gel filtration chromatography, as described above. The MN neutralizing antibodies isolated from the F31, F50, and F52 fusions were assayed for binding specificity. The results, shown in Table 11, show that the MN antibodies show specificity towards the left side of the MN loop, i.e., to the R-I-H-I-G sequence.

In a syncytium inhibition assay, based on recombinant vaccinia virus expressing the envelope of the MN variant (vac-env _MN), all antibodies were

capable of inhibiting syncytia formation at

concentrations less than or equal to 0.5 μg/ml.

Additional fusions were carried out following immunization of C57/BL6 mice with linear peptides

conjugated to KLH. Hybridoma clones designated F54/P5F4 and F56/P6G4 arose from immunization with RP108-KLH and RP100-KLH, respectively. In addition, a hybridoma clone designated F60/P5C2 arose from immunization of a BALB/C mouse with RP100-KLH. Antibodies produced by these clones were tested for MN specificity by ELISA and

syncytia inhibition in the vac-env assay. The PND

epitopes recognized by each of these antibodies were mapped as described. Antibody F54/P5F4 recognizes

H-I-G-P-G-R-A-F-Y; F56/P6G4 recognizes H-I-G-P-G-R-A;

and F60/P5C2 recognizes I-H-I-G-P-G-R.

Broadly Neutralizing Antibodies

Fusions F58, F59 and F64 were generated from immunization of BALB/C mice with the closed loop immunogen RP70, and F53 was generated by immunization of C57B1/6 mice with RP102-KLH. Antibodies, designated F59/P7E3, F59/P5B3, F64/P6G5 (64.10) and F53/P7C4 (53.4), were identified that are potentially broadly neutralizing antibodies. Two of these antibodies, F59/P7E3 and

F59/P5B3 demonstrated significant ELISA titers to RP108, a peptide having an amino acid sequence which corresponds to the sequence of the right side of the tip-of-the PND loop. Alanine-subsituted peptides that were capable of competing with RP70 for binding to the F59/P7E3 and

F59/P5B3 antibodies did not contain alanine substitutions within the G-P-G-R-A-F sequence. Similarly, peptides that contained the G-P-G-R-A-F sequence were able to compete with RP70 for binding to the F59/P7E3 or F59/P5B3

antibodies, while those that did not contain this sequence (i.e., RP129 and RP175) were not able to compete. These results indicate that the F59/P7E3 and F59/P5B3 antibodies recognize the G-P-G-R-A-F epitope. This sequence is present in a wide range of HIV variants. The F64 antibody recognizes the non-contiguous I-A⁶-A⁷-G-P-G-R epitope and neutralizes the IIIB and MN strains. The F53.4 antibody recognizes the I-G-P-G-R-A-F epitope and

neutralizes the MN and WMJ2 strains. An anti-HIV antibody which recognizes a common sequence is more likely to possess broad neutralizing capabilities. The breadth of neutralization of an antibody of the invention may be tested using syncytium inhibition assays in which both MN and other HIV strains are used.

The F59/P7E3 and F59/P5B3 antibodies were tested for broad neutralizing capability in the recombinant vaccinia virus syncytium inhibition assay described above and were shown to be capable of neutralizing the

recombinant vaccinia viruses expressing IIl_B, MN or WMJ2 envelopes (Table 12). In addition, these monoclonal antibodies were tested in HIV infectivity reduction assays and reduce titers of HIV variants IIl_B, MN, SF2, and

WMJ2. The ability of an antibody of the invention to neutralize viruses with both the MN prototype sequence (or an MN variant sequence) and a G-P-G-R-A-F-containing HIV strain reveals broad neutralizing activity. Additional monoclonals having this pattern of binding and

neutralization are F64.8, F64.9, and F64.10. (Table 13(a and b) is a key for the current and former names for the cell lines which produce these monoclonal antibodies.)

Another antibody specificity of the invention is directed to the epitope I-G-P-G-R-A. These antibodies would be expected to bind to and neutralize a slightly higher percentage of HIV isolates than G-P-G-R-A-F- directed antibodies (see Table 2). We have isolated and characterized an antibody, F53.4, which demonstrates the binding and neutralization properties expected of an antibody binding the sequence I-G-P-G-R-A (Table 12). One distinguishing feature of this antibody type is the inability to neutralize the HIV-III_B isolate, which contains the sequence R-G-P-G-R-A.

Thus, we have identified and characterized antibodies to the two most frequently occurring hexameric epitopes of the principal neutralizing domain of HIV:

I-G-P-G-R-A, which occurs with a frequency of 64% among the isolates tested, and G-P-G-R-A-F, which occurs with a frequency of 60%. These properties distinguish these antibodies as having therapeutic value in preventing and/or treating HIV infection.

Characterization of Human Monoclonal Antibodies

Isolation of MN Neutralizing Antibody

Producing Cell Line N70-19.b

Cell line N70-19.b (ATCC Accession No. HB10290) which produces a human monoclonal antibody which

neutralizes HIV_MN, was obtained from Dr. James E.

Robinson of Louisiana State University Medical School. Dr. Robinson's procedure involved isolation of lymphoid cells from a human patient asymptomatic for HIV

infection but HIV-1-seropositive, followed by

transformation of the cells with Epstein Barr Virus (EBV) to immortalize them, and an initial screening step for gp120 specificity. We then rescreened the resultant lymphoblastoid cell lines for anti-HIV_MN antibody production.

Transformation of Human Lymphoid Cells

It has been observed (Gorny et al., 1989, supra; Yarchoan et al., J. Clin. Invest., 1986;

78:439-447) that peripheral blood B cells from HIV-1 infected subjects vary greatly in their susceptibility to EBV transformation. In general, B cells from

patients with severely impaired immune function and relatively low CD4 cell counts are the most resistant to transformation, whereas B cells from asymptomatic patients with relatively high CD4 cell counts tend to transform more readily. However, transformation rates even within the population of apparently healthy

asymptomatic patients are variable, and not all attempts to produce human monoclonal antibodies (HMabs) from this group have been successful.

We determined the antigenic specificity of the N70-19.b antibody producing clone by ELISA using the gp120 envelope protein containing the principal

neutralizing domain from HIV_MN, and the antibody was investigated for HIV neutralization activity by

inhibition of syncytium formation. The epitope

recognized by N70-19.b would also be expected to be expressed in the virus strain infecting the N70 donor. Other HMabs that recognize the PND of HIV-MN and that are capable of neutralizing the MN variant of HIV may be found by transforming human B cells from field isolates of HIV-1-seropositive patients and screening the antibody producing cells for binding to HIV_MN gp160 or a fragment thereof containing the PND, or neutralization of HIV_MN infection, as described below.

Epstein Barr Virus transformation of peripheral blood mononuclear cells (PBMC) from two adult HIV-1 seropositive male subjects was carried out by

Dr. J. Robinson as follows. PBMC were isolated on

Ficoll-Hypaque gradients and were depleted of CD3 positive T cells using an indirect panning technique (Wysocki et al., Proc. Natl. Acad. Sci. USA, 1980, 75:2844-2848) in which cells reacting with the OKT3 monoclonal antibody were absorbed to petri dishes coated with F(ab)₂ antibodies to mouse IgG. Non-adherent cells, enriched in B cells, were inoculated with the B95-8 strain of EBV (Miller et al., Proc. Natl. Acad. Sci. USA, 1973, 70:190-194) and plated at 10³ or 10⁴ cells per well in 96 well tissue culture plates with irradiated human umbilical cord blood lymphocytes (HUCL) (10⁵ cells per well) as feeder cells. Cultures were maintained in RPMI 1640 containing 5% fetal calf serum

(FCS) and 1% Nutridoma-Hu (Boehringer-Mannheim), a serum substitute of low protein content.

Isolation of Antibody Producing B cell Lines

A critical factor in HMab production is the availability of an efficient and sensitive immunoassay for screening hundreds of microwell cultures for

antibody production. In the conventional ELISA, which is the basis of most commercial ELISA kits for serologic testing, purified viral antigens are passively coated in wells of ELISA plates. The preparation of antigens for this assay requires the production of very large amounts of virus, which then must be purified and inactivated.

The process of virus purification may result in

significant losses of gp120. Hence, this assay may be inefficient in detecting antibodies to gp120 and favor detection of antibodies to other HIV antigens. This may explain in part the predominance of HMabs reacting with gag proteins or gp41 (Banapour et al., 1987, supra;

Sugano et al., 1988, supra; Morrow et al., 1988, supra;

Gorny et al., 1989, supra; Amadori et al., 1989 supra).

Using the conventional antibody screening assay, 1 HMab was isolated, as follows.

In Dr. Robinson's first transformation experiment, EBV exposed, T cell-depleted PBMC from an HIV-1 infected donor were plated at 10³ cells per well in 96 well culture plates with irradiated HUCL feeder cells. Approximately 50% of the cultures were

transformed after 4-5 weeks of culture. Culture fluids were then screened by ELISA for IgG antibodies reacting with fixed, immobilized HIV-infected H9 cells, as follows.

HIV-1 infected H9 cells were immobilized in

Concanavalin-A (Con-A) coated assay wells and then fixed with 1:1 acetone-methanol. The wells were blocked with

RPMI-10% FCS for 1 hour. Fluids from 96 well cultures were transferred to wells in the assay plates. After 1 hour, wells were washed with phosphate buffered saline

(PBS) containing 0.1% Triton-X 100 (PBS-TX) and then reacted with peroxidase-conjugated antibody to human IgG

(Protos Labs, San Francisco, CA). Color was developed with 100 ul tetramethylbenzidine (TMB)-H₂O₂ as

substrate. The reaction was stopped by the addition of H₂SO₄ and color was read as Optical Density at 450 nm in a Titertek Multiskan ELISA reader.

One transformed culture, designated K24-3b, was a stable producer of an antibody, which on further testing reacted by indirect immunofluorescence with both fixed and unfixed HIV-1 infected cells but not with uninfected cells. Multiple subcultures of K24-3b cells were established at low cell density and all continued to produce antibody, although they ceased to grow after about 8 months. Because the original cells were plated at a relatively low cell density and the incidence of transformation was less than 50%, it is likely that the K24-3b cell line was established as a clone.

Because the initial conventional ELISA screening gave only one HIV specific HMab, a novel immunoassay was used to screen EBV transformed B cells from another HIV-1-seropositive patient. This

immunoassay is based on the observation that HIV

envelope glycoproteins bind via their carbohydrate moieties to Con-A (Montagnier et al., 1985, Virology 144:283). In this immunoassay, HIV-1 glycoproteins released by infected cells grown in serum free medium are affinity-immobilized in Con-A coated assay wells. This procedure greatly simplifies the preparation of solid-phase glycoprotein antigens for large scale antibody screening. The assay is highly sensitive and selective in detecting antibodies to gp120. Virus need not be purified; only small volumes of cells grown in serum free medium are needed to yield ample quantities of antigen for Con-A immobilization. Indeed, many serum free virus stocks can be diluted 1:2 or 1:4 without diminished antigen activity and thus, as little as 100 ul of supernatant fluid can be used to prepare 20-40 96-well ELISA plates.

In the second experiment, EBV exposed T cell-depleted PBMC from another HIV positive patient were seeded at 10⁴ cells/well with irradiated HUCL in two 96 well plates. Transformation occurred in 100% of the wells. Culture fluids were screened by the novel ELISA for IgG antibodies reacting with Con-A immobilized viral glycoproteins derived from the J62 strain of HIV-1 grown in MT4 cells in serum free medium, as follows.

Wells of Immulon-2 assay plates (Dynatech) were coated with 200 ug/ml Con-A in PBS and then incubated with 100 ul of detergent disrupted supernatant fluids from HIV-1 producer cell lines grown for 2-3 days in serum free RPMI supplemented with 1% Nutridoma-Hu. In absence of serum components, disrupted viral

glycoproteins present in such culture fluids bind to Con-A in amounts sufficient to function as solid phase antigens in a highly sensitive ELISA. Unreacted Con-A binding sites were blocked with RPMI-10% FCS for 1 hour. Control antigens were similarly prepared from culture fluids of uninfected MT4 cells. Transformed B cell culture fluid were transferred to both antigen coated and control wells of assay plates which were incubated at room temperature for 1 hour. Binding of antibodies was measured as described above. This ELISA was also used in later experiments to test the

reactivity of HMabs with glycoproteins from different virus strains.

Ten transformed cultures produced IgG antibodies reacting with J62 glycoproteins but not with control antigen. Seven cultures produced antibodies for less than two months. Three cell lines, designated N70-23.a, N70-15.e, andN70-19.b, respectively, were stable antibody producers and were cloned at 10 cells per well. Clones of each line were stable with respect to growth and antibody production for over 10 months.

IgG subclass and light chain type of each antibody was determined by reactivity with murine monoclonal antibodies to the four heavy chain subclasses (Behring Diagnostics) or polyclonal goat antibodies to lambda and kappa light chains in a sandwich ELISA, according to conventional isotyping techniques. All four HMabs are of the IgG1 subclass; K24-3b, N70-15.e, and N70-19.b contain kappa light chains and N70-23.a contains lambda light chains.

Characterization of HMab Specificity

by Western Blot and Dot Blot Assays

The antigenic specificity of each HMab was determined using dot blot and Western blot assays. In the initial screening of the antibodies. Dr. Robinson used twelve HIV-1 strains as target antigens: strains

C39, J62, SA90, SA96, and L86 were isolated from mitogen activated T cells of five asymptomatic HIV-1 infected subjects by co-cultivation with activated normal T cells in medium supplemented with interleukin-2; strain SA3 was similarly isolated from a patient with AIDS; strain

HiTi is described in Rasheed et al., Virology, 1986,

154:395-400; strain K3 was obtained from the Tulane

Delta Primate Center, New Orleans, LA; HTLV-IIIB

(Popovic et al . , Science , 1984 , 224 : 497-500 ) , the prototype HIV-1 strain, was obtained from American Type

Culture Collection, ATCC No. CRL 8543;

HTLV-III_MN (Gallo et al., Science, 1984, 224:500-502; Shaw et al., Science, 1984, 226:1165-1170); baculovirus- produced recombinant LAV gp120 (American

Biotechnologies, Inc., Cambridge, MA); as well as glycosylated recombinant gp120 from HIV-l_SF2 (Levy et al., Science, 1984, 225:840-842), were obtained from the AIDS Research and Reference Reagent Program. Strains C39, J62, SA96, and SA90 were grown in MT4 cells (Harada et al., Science, 1985, 229:563-566); HTLV-IIIB,

HTLV-III_MN, SA3, HiTi, and K3 were grown in H9 cells.

Strain L86, isolated from the B cell donor of one monoclonal antibody (K24-3b), did not replicate in continuous T cell lines and was propagated in mitogen activated cord blood T cells in medium containing 100 units per ml recombinant IL-2. To prepare antigens for Con-A immobilization, cells infected with each virus strain were grown for 2-3 days in serum free medium RPMI supplemented with 1% Nutridoma-Hu. Clarified fluids were treated with 1% Triton-X and stored in aliquots at

-20°C until use.

Western blots were performed as follows.

Extracts of 1-2 x 10⁷ HIV-1 infected cells prepared by solubilizing cells for 30 min in 1% Triton-X followed by removal of insoluble material by centrifugation in a microcentrifuge. Samples were mixed 1:1 with SDS sample buffer without reducing agents and heated for 5 min at 95°C. Cell lysates of uninfected H9 and MT4 cells were similarly prepared. Samples were fractionated by electrophoresis in 7.5.% sodium dodecyl

sulfate-polyacrylamide gels in a BioRad mini-gel

apparatus. Proteins were then electrophoretically transferred to nitrocellulose membranes. Western blot strips were incubated with blocking buffer (1% bovine serum albumin, 0.5% Tween 20, in 0.5 M NaCl, 10 mM Tris, pH 8), reacted first with each antibody preparation and then with alkaline phosphatase-conjugated antibodies to human or sheep IgG, as appropriate. Colored bands were developed using nitroblue tetrazolium and

5-bromo-4-chloro-3-indolyl-phosphate (NBT-BCIP, Sigma, St. Louis, MO) as substrate. A sheep antiserum to gp120 of HTLV-IIIB, obtained from the AIDS Research and

Reference Reagent Program, was used as positive control in detecting gp120/160.

Figure 1 shows the reactivity of four HMabs on Western blots of antigens of two HIV-1 strains,

HTLV-IIIB and J62. Lanes 1-5 of each of panels A and B are as follows: Lane 1, K24-3b; Lane 2, N70-23.a; Lane 3, N70-15.e; Lane 4, N70-19.b; Lane 5, sheep

anti-HTLV-IIIB gp120. On blots of HTLV-IIIB as the target antigen (Panel A), three HMabs (K24-3B, N70-2.3a, and N70-1.5e) reacted strongly with a prominent band of approximately 120 Kd and with a less intense band of 160 kd. Although N70-19.b appeared to react weakly with gp120 on this blot (Panel A, lane 4), in other assays it did not react with HTLV-IIIB at all. On blots prepared from strain J62 as the target antigen (Panel B), all four HMabs showed identical binding to a prominent band at 160 Kd below which was a diffuse band extending to approximately 120 Kd; this pattern is characteristic for this strain. The staining patterns obtained with a polyclonal sheep antibody to gp120 on blots of both strains were identical to that observed with the

monoclonals (lane 5 in panels A and B). The HMabs did not react with blots of uninfected MT4 or H9 cells (not shown).

These results indicated that these four HMabs react with gp120 and its uncleaved cellular precursor, gp160. However, in view of the possibility that bands identified as gp160/120 in some commercially available HIV-1 Western blot strips are actually multimers of gp41 (Zolla-Pazner et al., New Engl. J. Med., 1989,

320:1280), the specificity of the four Hmabs for gp120 was tested using dot blots of recombinant LAV gp120 and lentil lectin purified J62 glycoproteins.

For dot blot assays, strips of nitrocellulose were dotted with 1 ul of baculovirus-produced

recombinant LAV gp120 at 100 ug/ml and J62 envelope glycoproteins, which were partially purified from detergent treated serum-free culture medium by lentil lectin affinity chromatography (Montagnier et al., Virology, 1985, 144:283-289) and concentrated to 10 ug/ml. Recombinant gp120 was also dotted after being heated for 5 min at 95°C in the presence or absence 2-mercaptoethanol. Antibody assays on dot blot strips were performed as for Western blots, except a goat antiserum to gp160 of HTLV-IIIB (Rusche et al., Proc. Natl. Acad. Sci. (USA), 1987, 84:6924-6928) was used as a positive control.

As shown in Figure 2, three of the four HMabs (K24-3b, N70-23.a and N70-15.e) reacted strongly with recombinant gp120. N70-19.b did not bind to LAV gp120 but did bind to J62 antigen. Fig. 2 is keyed as follows: "gp120 J62" is purified gp120 of strain J62, "rgp120 LAV is non-reduced recombinant LAV gp120,

"rgp120 reduced" is reduced recombinant LAV gp120, and "rgp120 heated" is nonreduced, heated LAV gp120. The amount of J62 antigen dotted was about 10 fold less than the recombinant antigen, explaining the weaker staining observed with this antigen. These results, therefore, indicate that the bands of 120 and 160 Kd observed on our Western blots indeed represent gp120/160. In preliminary Western blot studies, neither K24-3b nor N70-23.a reacted with blots prepared from cell lysates heated in sample buffer containing

2-mercaptoethanol (not shown), suggesting that the epitopes identified were sensitive to reduction. To further test the effect of reduction on these epitopes, the antibodies were tested on dot blots of recombinant gp120 LAV that was heated at 95ºC in the presence or absence of 2-mercaptoethanol. The results shown in Figure 2 demonstrate that K24-3b and N70-15.e did not bind to reduce antigen and binding of N70-23.a to reduced antigen was significantly diminished, while heating alone only slightly diminished antigenic

activity. As N70-19.b did not bind to LAV gp120, the effect of reduction on its epitope was not determined in this experiment. N70-19.b was subsequently tested on dot blots of reduced and non-reduced J62 glycoproteins and no reactivity was observed with reduced antigen. Thus, all four HMabs identified reduction sensitive epitopes.

Analysis of Strain Specificity of HMabs by ELISA

Because multiple virus strains isolated from each asymptomatic B cell donor generally do not

replicate in continuous cell lines (Cheng-Mayer et al., Science, 1988, 240:80-82) and usually can be propagated only in IL-2 dependent activated primary T cells or in monocytes, the preparation of solid phase antigens in sufficient amounts to develop screening immunoassays based on the passive coating method presented a

problem. The Con-A immobilization technique offered a potential solution to this problem, because only small volumes of virus are needed rather than large quantities of purified viral antigen. Dr. Robinson tested the four HMabs by ELISA for reactivity with Con-A immobilized viral glycoproteins from different HIV-1 strains. Theoretically, the binding of gp120 to Con-A could block access of

antibodies to some epitopes. However, Dr. Robinson found that murine monoclonals known to react either with the CD4 binding region or the V3 hypervariable domain react strongly with Con-A immobilized gp120

(unpublished), indicating that epitopes within these two regions are represented in the assay.

As illustrated in Figure 3, one strain (L86) was grown in a serum free culture of IL-2 dependent, activated primary T cells and gp120 released into the medium functioned well in the Con-A immobilization assay. Similar results may be achieved with other strains isolated from asymptomatic B cell donors; thus, it may become feasible to screen for antibodies reacting with antigens of homologous isolates.

In one experiment (Figure 3), culture fluids of K24-3b and N70-23.a, and a HIV-1 positive control serum (H72) were tested by Dr. Robinson on a panel of nine different strains, which included L86, the strain isolated from the B cell donor of K24-3b. N70-23.a reacted with all nine strains. Results shown as mean O.D. of triplicate determinations; standard deviation bars are shown. Although some differences in binding of this antibody on the panel were observed, generally parallel differences were observed with the positive control serum. Thus it is likely that the binding levels of both N70-23.a and the H72 serum provide a relative measure of the amounts of gp120 immobilized from each strain. The explanation for the much weaker reactivity of N70-23.a with the L86 strain compared to the positive serum was uncertain, but may be that L86 was the only strain grown in IL-2 dependent primary T cells which release less virus than continuous cell lines. It is possible that more gp41 than gp120 was immobilized in the L86 virus preparation and antibodies to gp41 account for the greater serum reactivity.

By comparison to N70-23a, the K24-3b monoclonal showed remarkable variability in reactivity with these viruses. This antibody reacted with six of the nine strains but did not bind to strains SA3 or K3, and showed minimal binding to strain SA96. Whereas the reactivity of both N70-23.a and K24-3b with strains L86 and J62 were very nearly the same, the binding of K24-3b to strains SA90 and C39 was much less than N70-23.a, the difference being greatest with SA90. These observations have been reproducible in assays performed with

different batches of antigens. Smaller differences in binding of these two antibodies were also apparent with strains HiTi and HTLV-III. These differences were not related to antibody concentrations, since preparations of both antibodies used in these assays appeared to saturate available antigenic sites on immobilized antigens; optical densities obtained with serial dilutions of both antibodies up to 1:32 were very nearly the same (data not shown) when tested against the J62 isolate. These data indicate that N70-23.a identifies a conserved epitope, while K24-3b identifies a variant epitope which is heterogeneously expressed in this panel of virus strains.

Figure 4 illustrates the results of a similar experiment in which Dr. Robinson compared the

reactivities of N70-15.e and N70-19.b with Con-A

immobilized glycoproteins derived from eight strains. (Results are a single determination.) In this

experiment, N70-23.a served as a positive control. Both N70-15.e and N70-23.a reacted strongly with all eight strains, whereas N70-19.b reacted only with J62, the strain that was used in the screening of the original B cell cultures for antibody production. The results indicate that N70-15.e, like N70-23.a, reacts with an epitope shared by all strains tested thus far, while N70-19.b reacts with a strain-restricted epitope. The reactivity of the four HMabs was investigated further by us using two additional target gp160 antigens,

HIV-III_MN,and recombinant HIV-1_SF2. The results, presented in Table 14, show that N70-19.b, as well as the other three HMabs, reacted strongly by ELISA with Con-A immobilized glycoproteins from HIV-1_MN and

HIV-1_SF2. It is not clear from this experiment to what portion of the MN or SF2 gp160 molecules the human monoclonal antibodies bind.

Strain Specificity of HMabs

by Western Blot Analysis

The strain specificity of two of the four

HMabs, K24-3b and N70-23.a, was also tested by Dr.

Robinson on Western blots prepared from the above panel of HIV-l strains. The results, shown in Figure 5, are in agreement with results obtained by ELISA. Fig. 5, panel A, shows reactivity of K24-3b; panel B, reactivity of N70-23.a. The different strains are indicated at the top of each blot lane; "IIIB" refers to HTLV-IIIB.

N70-23.a reacted with gp120/160 of all eight strains. K24-3b reacted with gp120/160 of the same strains it identified by ELISA. Similarly, K24-3b failed to react with SA3 and K3; its minimal reactivity with strain SA969 was below the sensitivity of photography. Although N70-15.e and N70-19.b have not been similarly tested by Western blots on all of viruses, the strain restricted reactivity of N70-19.b observed by ELISA is corroborated by its failure to react with recombinant LAV gp120 in dot blot assays.

Two additional transformation experiments, one involving B cells from the N70 donor, yielded over 60 transformed B cell cultures, including the

anti-HIV-antibody producing clone N70-II.3a discussed below, that produce IgG antibodies reacting specifically with Con-A immobilized HIV glycoproteins. Approximately 30% of these cultures may yield stable antibody

producing clones, thus indicating the feasibility of generating sizeable numbers of HMabs which together represent a broad representation of human antibody responses to variant and conserved epitopes of gp120 during asymptomatic infection.

Screening for HIV_MN Specificity

we rescreened some of the gp160-binding human monoclonal antibodies identified by Dr. Robinson using ELISA and Western Blot (WB) assays, N70-19.b, N70-15.e, K24-3b, and N70-II.3a, to determine if any were specific for the MN prototype of the gp160 molecule. In the ELISA, we used five different recombinant proteins or protein fragments as test antigens: gp160-IIIB,

gp160-RF, PB-1-IIIB, PB-1-RF, and PB-1-MN. In the Western Blot, we used three different test antigens: gp160-IIIB, PB-1-IIIB, and PB-1-MN. Intact gp160 polypeptide was produced in insect cells using a baculovirus expression system and purified as described in Rusche et al., U.S.S.N. 091,481, filed August 31, 1987, assigned to the same assignee as the presenn invention, hereby incorporated by reference. A 180 amino acid protein fragment with an amino acid sequence spanning the principal neutralizing domain, denoted PB1 (Putney et al., 1986, Science 234:1392), was expressed from an approximately 540bp DNA fragment generated by PvuII + Bglll cleavage of the full-length env gene, as described in U. S . S .N . 107 , 703 , f iled October 9 , 1987 , assigned to the same assignee as the present

application, hereby incorporated by reference.

ELISA was performed as follows. Each well of a

96-well Costar flat-bottom microtiter plate was coated with the antigen by placing a fifty microliter aliquot of a PBS solution containing the antigen at a final concentration of 2-10 ug/ml in each well. The Con-A method described above was not used here because the antigens (proteins or peptides) are purified and, therefore, immobilized in sufficient amounts for

antibody binding. The antigen solution was aspirated and replaced with PBS + 0.5% BSA and incubated for 1 hour. Following incubation, the wells were then

aspirated, washed, and 50 ul of the antibody was added. Following incubation, the wells were washed 3 times with PBS, and then incubated for 30 min. with 50 ul of an appropriate dilution of goat anti-human immunoglobulin conjugated with horseradish peroxidase (HRP, Boehringer Mannheim, West Germany). The wells were washed again 3 times with PBS and 50 ul of 1 mM ABTS (2,2 azino-bis (3-ethyl benzth, azoline 6-sulfonic acid) in 0.1M

Na-Citrate, pH 4.2, to which a 1:1000 dilution of 30% H₂O₂ had Deen added), the substrate for HRP, was added to detect bound antibody. The ABTS samples were then read at OD₄₁₀ on a Dynatech spectrophotometric autoreader (Virginia). Tables 15-18 give ELISA results. Table 15 also gives results of a Western blot. Numbers in Table 15 indicate the number of times positive/number of times tested. Positive and negative controls for the ELISA were HIV + serum and HIV - serum, respectively; the positive control in the Western Blot was goat anti-gp160 IIIB antisera.

In the ELISAs, one of the five antibodies, N70-19.b was positive for the recombinant protein PB-1 MN. This result was clearly confirmed in the Western Blot (Table 15) and Tables 16 and 17 show results of ELISAs in which the PB-1 fragments from the envelope protein from different HIV variant strains (IIIB, RF, and MN) were test antigens for binding. In the

experiments presented in Tables 15-17, the reagents were in reducing buffer. This may explain the apparently contradictory results of antibody binding in Table 6 versus Tables 15-17; i.e., the ELISA of Table 14 did not contain reducing buffer and consequently, all of the antibodies bound gp120/160. We conclude that the presence of reducing buffer results in more selective antibody binding.

The results in Tables 15-17 demonstrate that N70-19.b binds specifically to the MN prototype but not to the IIIB or RF prototypes of the gp160 molecule.

Table 10 shows results of another ELISA in which

N70-19.b, N70-15.e, and N70-II.3a were tested for their ability to bind a fragment of the envelope protein from either the HIV-MN or the HIV-IIIB strain. "RP70" is the "full-loop closed" and "RP142" is the open 24mer from the principal neutralizing domain (PND) of the MN envelope protein; and "RP135" is a 24mer from the PND of the IIIB strain. These fragments contain amino acid sequences in the neutralizing domain sub-sequence of the gp120 loop region as defined in Table 3. The results presented in Table 18 demonstrate that the N70-19.b monoclonal binds the principal neutralizing domain, or loop region, of the HIV_MN gp160 molecule (RP70, RP142) but not to the PND of the IIIB variant (RP135).

Neutralization of HIV_MN

We then assayed two of the antibodies, one of which was N70-19.b, for their neutralizing ability for HIV infection. The assay we used was inhibition of syncytium formation by HIV_MN infected cells. In this assay, as described above, recombinant Vaccinia Virus expressing the envelope gene of the HIV_MN strain of interest was used to infect cells of CD4+ human

T-lymphoma line CEM (A.T.C.C. Accession No. CCL119), and the antibody was then added to the cells to screen for blockage of HIV envelope mediated cell fusion. A positive result, indicating the ability of the antibody to neutralize the virus, was defined to be at least a 90% inhibition of syncytia formation.

CEM cells were infected with recombinant

Vaccinia Virus expressing HIV_MN gp160 derived from plasmid pSCR2502, which contains the PB-1 fragment of MN; the remainder ofgp160 was of IIIB origin. In this assay, syncytia are induced which are inhibitable by antisera or monoclonal antibodies directed against the PND. The results, shown in Table 19, show that N70-19.b completely inhibits syncytia induced by vaccinia

gp160-MN over a range of concentrations of the antibody, whereas N70-15.e does not inhibit the formation of syncytia. Use

The human monoclonal antibody of the present invention can be incorporated into conventional

pharmaceutical formulations for use in treating

individuals that are afflicted with HIV or for

prophylaxis in individuals at risk for such infections. In addition, such formulations may comprise

pharmaceutically-acceptable carriers, diluents, salts and other materials well-known in the art. Isotonic saline, sterile water, 10% maltose, human serum albumin, glycine or other pharmaceutically-acceptable material may be used as diluents, carriers or solvents in

preparing the pharmaceutical formulations comprising the antibody of the invention.

When employed to treat individuals infected by HIV or suffering from AIDS, the human monoclonal

antibody of the present invention may be administered as a passive immunization agent in effective amounts broadly ranging between about 200 mg and about 15 grams and preferably between 50 mg and 1 gram.

Polyvalent immune globulin for use in passive immunization can be prepared by immunization of horses or by pooling immune human sera and fractionation of the IgG component from plasma or sera. Human or mouse monoclonal antibody producing cell lines may be prepared by standard transformation and hybridoma technology (Methods in Enzymology, Vol 121, Sections I and II, 1986, eds, Langone and Vunakis, Academic Press). HIV monoclonal antibody can be prepared in accord with the procedures disclosed by Matsushita et al., 1988, J.

Virol. 62:2107, or EPO 295,803, published Dec. 21,

1988. Since, for the most part, monoclonal antibodies are produced in species other than humans, they are often immunogenic to humans. In order to successfully use these monoclonal antibodies in the treatment of humans, it may be necessary to create a chimeric

antibody molecule wherein the portion of the polypeptide involved with ligand binding (the variable region) is derived from one species, and the portion involved with providing structural stability and other biological functions (the constant region) is derived from a human antibody. Methods for producing chimeric antibodies in which the variable domain is derived from one host and the constant domain is derived from a second host are well known to those skilled in the art. See, for example, Neuberger et al., WO Publication No. 86/01533, priority Sept. 3, 1984; Morrison et al, EP Publication No. 0,173,494, priority Aug. 27, 1984. An alternative method, in which an antibody is produced by replacing only the complementarity determining regions (CDRs) of the variable region with the CDRs from an immunoglobulin of the desired antigenic specificity, is described by Winter (GB Publication No. 2,188,638, priority March 27, 1986). Murine monoclonals can be made compatible with human therapeutic use by producing an antibody

containing a human Fc portion (Morrison, 1985, Science 229:1202). Established procedures would allow

construction, expression, and purification of such a hybrid monoclonal antibody. Regimens for administering immune globulin therapuetically have previously been used for a number of infectious diseases.

The antibody of the invention is administered parenterally, either via the intravenous or

intramuscular route. A typical treatment regimen would comprise administration of an effective amount of antibody administered over between about one week and about 6 months. The number of treatments required to control a patient's disease may vary from individual to individual, depending upon the severity and stage of the illness and the individual characteristics of each patient being treated. The total dose required for each treatment may be administered by multiple doses or in a single dose. The human monoclonal antibody may be administered alone or in conjunction with other HIV treatments, such as AZT, in order to control a patient's disease. The anti-HIV treatment may be administered one or two times a week or more as determined by the

patient's condition and the stage of the patient's disease.

An antibody of the invention may also be used to prevent vertical transmission of HIV from a mother to a neonate by administering the antibody to the mother or the neonate, or to both.

Other Embodiments

Other embodiments are within the following claims. The antibodies may be conjugated to a carrier, e.g., a molecule, a liposome, or another antibody (i.e., to form a heteroconjugate), to improve its activity. For example, the antibodies may be conjugated to

cytotoxic agents and used as immunotoxins (as described in Vitetta et al., 1987, Science 238: 1098), or

incorporated onto the surface of liposomes containing anti-HIV drugs or toxins to specifically target such drugs or toxins to infected cells. As employed herein, the term immunotoxin refers to a conjugate of an

antibody with one or more toxins, drugs, radionuclides or cytotoxic agents. Among the cytotoxic agents that may be conjugated to antibodies of the invention are ricin, diphtheria toxin and radionuclides. Ricin is an extremely potent toxin produced by the bean of the plant Ricinus communis. In a typical treatment employing antibodies of the invention as immunotoxins, the antibody (which binds to a protein that is expressed in HIV-infected cells) is conjugated to a toxin (e.g, ricin) that is toxic to the HIV-infected cells (and to non-infected cells as well). By coupling the cytotxic agent to the antibody, a high level of toxic efficacy can be achieved against the target cell with a markedly lower level of non-specific toxicity. The use of the toxic agent is possible because the antibody to which the agent is coupled will carry the agent directly to the target (in this case, HIV-infected cells), thereby sparing non-infected cells from the toxin. Techniques that may be employed to conjugate antibodies to

cytotoxic agents are described in detail in Vitetta et al, supra, and in European Patent Application No.

279,668, published August 24, 1988.

3

* Background reactivity of HMabs with blocked Con-A coated wells without antigen was < 0.100

**

HTLV-III_MN and J62 viruses grown in serum free medium as in Figs. 4 and 5

*** Recombinant glycosylated gp120 from HIV-1 _SF produced in Chinese hamster ovary cells; gp120 incubated at 1 ug/ml in Con-A coated wells

Claims

Claims 1. An antibody capable of neutralizing the MN prototype of HIV or an MN variant virus thereof, wherein an amino acid sequence within the principal neutralizing domain of said MN prototype comprises the sub-sequence, at positions A¹-A¹⁷ of said principle neutral izing domain, of amino acid residues

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K, and the corresponding amino acid sub-sequence of said MN variant comprises a completely homologous sequence at said I-G-P-G-R residues at positions A⁷-A¹¹ and at least 36% homology over the remaining residues of said MN prototype sub-sequence.

2. The antibody of claim 1 wherein said antibody is broadly neutralizing, said broad

neutralization comprising the ability of said antibody to neutralize at least two HIV strains which contain the amino acid sequence G-P-G-A¹¹-A¹² within the

principal neutralizing domain of the HIV envelope protein, wherein A¹¹ comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A.

3. The antibody of claim 2 wherein said amino acid sequence comprises G-P-G-R-A.

4. The antibody of claim 3 wherein said amino acid sequence comprises G-P-G-R-A-F.

5. The antibody of claim 3 wherein said amino acid sequence comprises I-G-P-G-R-A.

6. The antibody of claim 1 wherein said antibody is broadly neutralizing, said broad

neutralization comprising the ability of said antibody to neutralize at least two HIV strains which contain the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A ⁶ and A⁷ comprises,

independently, any amino acid.

7. The antibody of claim 2 or 6 wherein said amino acid sequence comprises I-A⁶-A⁷-G-P-G-R-A.

8. The antibody of claim 6 wherein said amino acid sequence comprises I-A⁶-I-G-P-G-R.

9. The antibody of claim 7 wherein said amino acid sequence comprises I-A⁶-I-G-P-G-R-A.

10. The antibody of claim 2, one of said strains being the III. prototype of HIV.

11. The antibody of claim 1 wherein said MN variant sub-sequence is of the amino acid formula: A¹-A²-A³-A⁴-A⁵-A⁶-l-G-P-G-R-A¹²-A¹³-A¹⁴-A¹⁵-A¹⁶-A¹⁷ wherein each A¹-A⁶ and A¹²-A¹⁷, independently,

is any amino acid residue.

12. The antibody of claim 11 wherein

A¹ = K, T, A, R, V, P, S, or I,

A² = R, T, I, M, or K,

A³ = K, R, T, N, or A,

A⁴ = R, S, G, or H,

A⁵ = I, M, or L,

A⁶ = H, P, S, Y, K, N, or R,

A¹² = A, P, T, S, or K,

A¹³ = F, V, I, W, or L,

A¹⁴ = Y, H, V, or F,

A¹⁵ = T, Y, or A

A¹⁶ = T, A, G, or R, and

A¹⁷ = K, G, E, S, Q, R, T, or A.

13. The antibody of claim 3 wherein said HIV strain sequence comprises the amino acid formula:

A¹-A²-A³-A⁴-A⁵-A⁶-A⁷-G-P-G-R -A¹³-A¹⁴-A¹⁵-A¹⁶-A¹⁷ wherein each A¹-A⁷ and A¹³ - A¹⁷, independently, is any amino acid residue or is deleted.

14. The antibody of claim 13 wherein A⁷ is I, A¹³ is any ammo acid, and each of A¹ through

A⁶ and each of A¹⁴ through A¹⁷ is, independently, deleted, wherein said amino acid formula comprises I-G-P-G-R-A-A¹³.

15. The antibody of claim 13 wherein A¹³ is F, each of A⁷ and A¹⁴ is, independently, any ammo acid, and each of A¹ through A⁶ and each of A¹⁵ through A¹⁷ is, independently, deleted, wherein said amino acid formula comprises A⁷-G-P-G-R-A-F-A⁴.

16. The antibody of claim 13 wherein A⁵ is I, each of A⁶ and A⁷ is, independently, any amino acid, and A¹ through A⁴ and A¹³ through A¹⁷ is,

independently, deleted, wherein said amino acid sequence comprises I-A⁶-A⁷-G-P-G-R-A.

17. The antibody of claim 13 wherein A⁵ and A⁷ is, independently, I, and A⁶ is any amino acid, wherein said amino acid sequence comprises

I-A⁶-I-G-P-G-R-A.

18. The antibody of any of claims 1-17, said antibody being monoclonal.

19. The antibody of claim 18, said antibody being a human monoclonal.

20. The antibody of any of claims 1-17, said antibody being a chimeric antibody having a variable region derived from a species other than human and a constant region derived from humans.

21. The antibody of any of claims 1-17, said antibody being a human polyclonal antibody.

22. The antibody of any of claims 1-17, said antibody being conjugated to a carrier.

23. A method of identifying the broadly neutralizing antibody of claims 2-17, said method comprising testing said antibody for one or both of (a) its ability to bind to a peptide or protein comprising (1) the amino acid sequence G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein A¹¹ comprises R or any conservative ammo acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A or (2) the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ comprises,

independently, any amino acid, and (b) its biological activity in HIV neutralization.

24. The method of claim 23 wherein said method comprises testing said antibody in one or more of the following assays

(a) an ELISA assay in which said antibody is tested for binding to a peptide or protein comprising (1) the amino acid sequence G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein A¹¹ comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A or (2) the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ comprises,

independently, any amino acid;

(b) a competition ELISA assay in which said antibody is tested for lack of binding to a peptide or proteindue to competition by a second peptide or protein comprising said amino acid sequence (1) or (2) in which any amino acid residue of said sequence is substituted with Alanine;

(c) a syncytium inhibition assay in which said antibody, when added to HIV infected cells, inhibits the formation of syncytia by at least 90%, wherein said HIV comprises the amino acid sequence (1) G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein A¹¹ comprises R or anyy conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷ comprises, independently, any

amino acid; (d) a competition syncytium inhibition assay in which said antibody is tested for lack of syncytium inhibition by incubating said antibody with a peptide having said amino acid sequence (1) or (2) and added to HIV infected cells;

(e) an HIV-infection neutralization assay in which said antibody, when incubated with said HIV and added to HIV susceptible cells, neutralizes said HIV infection; and

(f) an HIV infectivity reduction assay in which said antibody, when incubated with said HIV and added to HIV susceptible cells, reduces the titer of said HIV.

25. A method of treating or inhibiting HIV infection in a patient, said method comprising

administering to said patient an antibody that is capable of neutralizing

(a) an MN prototype virus or an MN variant virus thereof, wherein an amino acid sequence within the principal neutralizing domain of said MN prototype comprises the sub-sequence, at positions A¹-A¹⁷ of said principle neutralizing domain, of amino acid residues

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K,

and the corresponding amino acid sub-sequence of said MN variant comprises a completely homologous sequence at said I-G-P-G-R residues at positions A⁷-A¹¹ and at least 36% homology over the remaining residues of said MN prototype sub-sequence, and (b) at least two HIV strains which contain the amino acid sequence G-P-G-A¹¹-A¹² withm the

principal neutralizing domain of the HIV envelope protein, wherein A¹¹ comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A, or

(c) at least two HIV strains which contain the amino acid sequence I-A⁶-A⁷-G-P-G-R within the

principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ amd A⁷ comprises,

independently, any amino acid.

26. The method of claim 25, said antibody being monoclonal.

27. The method of claim 25, said antibody being polyclonal.

28. A recombinant vaccinia virus capable of expressing, upon infection of a eukaryotic cell, HIV envelope protein of a first HIV strain containing the principal neutralizing domain of a second HIV strain, said virus comprising DNA encoding said envelope

protein, said DNA including a DNA sequence encoding said principal neutralizing domain of said second HIV strain, said envelope protein-encoding DNA being under the transcriptional control of a vaccinia virus promoter.

29. The recombinant virus of claim 28, said HIV envelope protein encoding DNA of said virus being derived from a recombinant vector, said vector

comprising a DNA sequence encoding said envelope protein, said DNA including a DNA sequence encoding said neutralizing domain of said second HIV strain, and DNA capable of causing integration of said envelope

protein-encoding DNA into said vaccinia virus.

30. The recombinant virus of claim 28 wherein said principal neutralizing domain further comprises at least 5 amino acids from a third HIV strain.

31. A pharmaceutical formulation for treating a patient infected with HIV, comprising an effective amount of the antibody of claim 1.

32. The formulation of claim 31, further comprising a pharmaceutically acceptable carrier.

33. A composition for treating a human patient infected with Human Immunodeficiency Virus comprising a virus-neutralizing amount of a human monoclonal antibody which neutralizes the MN variant of Human

Immunodeficiency Virus Type I, admixed with a

pharmaceutically acceptable carrier substance.

34. The composition of claim 33 wherein said antibody is also capable of neutralizing at least two HIV strains comprising the amino acid sequence (1)

G-P-G-A¹¹-A¹² within the principal neutralizi .nngg domain of the HIV envelope protein, wherein A¹¹ comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R

within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷

comprises, independently, any amino acid.

35. The composition of claim 33 or 34, said antibody being produced by an immortalized B cell derived from a human patient infected with HIV.

36. The composition of claim 33 or 34 wherein said B cell is immortalized by infection with Epstein Barr Virus.

37. A method of treating a human patient infected with Human Immunodeficiency Virus comprising administering to said patient a virus-neutralizing amount of the human monoclonal antibody of claim 33.

38. A method of obtaining a human monoclonal antibody capable of neutralizing HIV_MN, said method comprising the steps of

providing an anti-HIV monoclonal antibody; and first testing said monoclonal antibody for the ability to bind to a fragment of the gp120 envelope protein of said HIV_MN, said fragment comprising the principal neutralizing domain, said binding being an indication of the ability of said antibody to neutralize ^HIVMN^. 39. The method of claim 38, said antibody further being capable of neutralizing at least two HIV strains comprising the amino acid sequence (1)

G-P-G-A¹¹-A¹² within the principal neutralizing

domain of the HIV envelope protein, wherein A¹¹

comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R

within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷

comprises, independently, any amino acid.

40. The method of claim 39, said fragment comprising one of G-P-G-R-A, G-P-G-R-A-F, I-G-P-G-R-A, I-A⁶-A⁷-G-P-G-R-A, I-A⁶-I-G-P-G-R,

I-A⁶-I-G-P-G-R-A, and

K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K.

41. The method of claim 38 or 39, said method further comprising the step before or following said first testing step, of secondly testing said monoclonal antibody for the ability to neutralize HIV_MN.

42. The method of claim 41, said second testing step comprising determination of inhibition of syncytium formation.

43. The method of claim 38 or 39 wherein said fragment is a peptide derived from the PND of gp120.

44. The method of claim 43 wherein said fragment comprises a closed loop.

45. The method of claim 41, further comprising the step before or following said first or second steps, of thirdly testing the antibody for the ability to neutralize at least one HIV strain other than HIV_MN, wherein said strain comprises the amino acid sequence (l) G-P-G-A¹¹-A¹² within the principal neutralizing domain of the HIV envelope protein, wherein A¹¹

comprises R or any conservative amino acid substitution of R and A¹² comprises A or any conservative amino acid substitution of A, or (2) I-A⁶-A⁷-G-P-G-R

within the principal neutralizing domain of the HIV envelope protein, wherein each of A⁶ and A⁷

comprises, independently, any amino acid.

46. The method of claim 45 said sequence comprising R-I-H-I-G-P-G-R-A-F and having less than 36% homology over the remaining residues of said MN

prototype sub-sequence, wherein said sub-sequence comprises K-R-K-R-I-H-I-G-P-G-R-A-F-Y-T-T-K.