A pharmaceutical preparation and a conjugate of a bactericide and an antibody directed against plaque forming or caries-inducing bacteria.
The invention relates to a conjugate of a bactericide and an antibody directed against at least a certain type of dental plaque-forming and/or caries-forming bacteria, and to a pharmaceutical preparation for the treatment of dental plaque and/or caries. Furthermore, it relates to a method of treating dental plaque and/or caries. Background
It is generally accepted that dental caries and plaque result from the action of certain bacteria in the saliva. Some of these species produce adhesive substances that enable the bacteria to adhere to the tooth surfaces. Bacteria in plaque convert sugars in the diet into acids that dissolve mineral components of the teeth and produce cavities. The plaque-forming bacteria can also colonize crevices between the teeth and gums, moving down along the roots of the teeth, enlarging the crevices and destroying gums, ligaments and bone holding the teeth in the jaw. The disease is a major cause of tooth loss, and the treatment can be both painful and costly. The most important bacterium causative of human dental caries and plaque is Streptococcus mutans, but there are several other bacteria which may participate in the formation of dental plaque and caries and in causing tooth-loosening.
The common way of preventing the formation of plaque and caries is tooth-brushing and mechanical cleaning of the teeth by a dentist. Also various agents incorporated into tooth-pastes and mouth-washes help, but they are far from being completely effective.
Antibiotics have previously been used for the treatment of caries, but the treatment has required long treatment periods (hours) during which the antibiotic has to be in contact with the infected areas to be effective.
The present invention provides a new method of treating dental plaque and caries, in which use is made of a conjugate of a bactericide and an antibody directed against at least a certain type of dental plaqueforming and/or caries-forming bacteria. It has previously been shown that if an antibody is binding to an antigen this will take place in but a few seconds. The conjugate of the invention will attach rapidly to the bacteria against which the antibody of the conjugate is directed, thus keeping the conjugate in place while the bactericide of the conjugate rapidly acts on the target bacteria. Description of the invention
The present invention provides a new conjugate of a bactericide and an antibody directed against at least a certain type of dental plaque-forming and/or caries-forming bacteria. The conjugate, preferably comprised in a pharmaceutical preparation, is useful in the local treatment of an infection caused by said certain type of dental plaque-forming and/or caries forming bacteria.
Thus, the invention also provides a method of treating dental plaque and/or caries comprising local application of a bactericidal amount of a conjugate of the invention or a pharmaceutical preparation of the invention, to a surface infected by dental plaque-forming and/or caries-forming bacteria.
The bactericide of the conjugate is preferably an antibiotic selected with regard to effectiveness against a certain target bacterium. In a preferred embodiment of the invention, the antibiotic is Netilmicin (O-3-deoxy-4-C-methyl-3(methyl-amino)-β-L-arabinopyranosyl-(1→4)-O-[2,6-diamino-2,3,4,6-tetradeoxy-α-D-gly
cero-hex-4-enopyranosyl-(1→6)-2-deoxy-N -ethyl-L-streptamine sulfate (2:5) salt). The antibody of the conjugate is either polyclonal or monoclonal and is directed against at least a certain type of dental plaque-forming and/or caries-forming bacteria.
In said preferred embodiment of the invention, the antibody of the conjugate is preferably directed against at least a certain type of bacteria selected from the group consisting of Streptococcus mutans, Streptococcus sanguis, Bacteroides gingivalis, Actinobacillus actinomycetemcomitans, Eikenella corrodens, Veronella alcalescens and Actinomyces viscosus. In a particularly preferred embodiment of the invention, the antibody is directed against Streptococcus mutans.
The invention further provides a pharmaceutical preparation comprising a conjugate of a bactericide and an antibody directed against at least a certain type of dental plaque-forming and/or caries-forming bacteria, together with a pharmaceutically acceptable carrier and/or diluent and, optionally, other pharmaceutically acceptable additives. The concentration of the conjugate in the pharmaceutical preparation is preferably such that a single local treatment of an infection caused by a certain type of dental plaque-forming and/or caries-forming bacteria against which the antibody of the conjugate is directed, will provide a bactericidal effect. The pharmaceutically acceptable carrier and diluent which can be used in the pharmaceutical preparation of the invention are not critical, and examples of useful carriers and diluents can be found in the U.S. Pharmacopoeia.
The pharmaceutical preparation according to the invention is preferably in the form of a paste, a toothpaste, a suspension, a solution or a mouth-wash. The optional pharmaceutically acceptable additives are such as are needed for the above listed forms of the pharmaceutical preparation.
Preferred embodiments of the pharmaceutical preparations of the invention comprise at least one of the preferred conjugates of the invention. In practical use it is possible that a pharmaceutical preparation according to the invention will comprise several conjugates of perhaps different bactericides and different antibodies each directed against at least a certain type of dental plaque-forming and/or caries-forming bacteria. Furthermore, it may be necessary to mechanically, e.g. by tooth-brushing, break the polysaccaride capsule of the target bacteria in order to lay bare the immunologically active parts of said bacteria so that the conjugate can attach to and act on the bacteria. As stated above, the most important bacterium causative of dental plaque and caries is Streptococcus mutans, and the invention will therefore be illustrated by a conjugate of an antibiotic and antibodies directed against Streptococcus mutans. Description of the preparation and testing of a preferred conjugate of the invention. Bacterial strain
A large number of bacteria were cultivated in conventional LB-medium (the medium was autoclaved before use, and one litre of medium contained 10 g tryptone soya broth (Oxoid code CM 129), 5 g yeast extract (Oxoid code L 21), 10 g NaCl, pH adjusted to 7.5 with 1 M NaOH, and the balance water). The cultivation was performed in an incubator at 37°C and constant agitation overnight. The bacteria for the immunization and affinity purification were washed repeatedly with phosphate buffered saline solution (PBS). The bacteria for testing were stored in a refrigerator until use (bacterial medium).
Antibodies were produced by repeated immunization of hens (White Leghorn line) with formaline-killed Streptococcus mutans (strain AHT) bacteria. The bacterial
strain was received from the Department of Oral Microbiology, Huddinge Hospital, Sweden. The IgG fraction of hyperimmune serum from these animals was received from Immun System AB, Uppsala, Sweden. Purification of antibodues by affinity chromatography Ultrasonicated Streptococcus mutans bacteria of the same strain where coupled to BrCN-activated Sepharose 4B (Pharmacia, Uppsala, Sweden) in a column in conventional manner, and the antibodies were applied onto the column, and then the column was washed with PBS. Bound antibodies were eluted with 0.1 M glycine pH 2.25. The bound specific antibodies were concentrated by precipitation with 50% ammonium sulphate and dialysed against PBS (without azide) for three days. Preparation of conjugate
The conjugation of an antibody to a bactericide can be performed in any conventional manner. The method selected was a one-step method using glutaraldehyde. 200 μl Netilmicin (ESSEX Läkemedel, Box 27190, Stockholm, Sweden) in PBS (5 mg/ml ) was mixed with 50 μl of 0.2% glutaraldehyde. The mixture was incubated for 1 hour at room temperature. To the mixture was added 100 μl of antibodies in water (0.4 mg antibodies in 0.6 ml H2O). The mixture was further incubated for two hours at room temperature, whereupon 100 μl 1 M lysine, pH 7.0, was added. As a control, a non-specific conjugate of bovine serum albumin (BSA), and Netilmicin was produced. Excess Netilmicin was removed by dialysis against
PBS in four stages in two days. The success of the conjugation was verified by using isotope labelled (125I)
Netilmicin. For comparison, also a solution in which
Netilmicin was conjugated to itself, was prepared. The anti-bacterial effect of the conjugates I. The anti-bacterial effect of the conjugates was tested using a conventional technique where the conjugate is placed in wells punched in agar and the size of the inhibition zones is measured.
5 ml of LB agar (LB medium to which 0.7% agar-agar has been added) was poured into a petri dish and allowed to solidify. An additional 5 ml LB agar were heated to
45°C. The stored bacterial medium in a final dilution of 10-3-10-6 was added to the warm LB agar and rapidly mixed therewith, whereupon the mixture was immediately poured onto the LB agar in the petri dish. Wells were punched in the agar layer, and 20 μl each of the different samples of conjugate were added to separate wells. The plate was incubated overnight at 37°C, and the next day the diameter of the inhibition zones was measured.
Results:
Conjugate of Inhibition zone (mm) Antibody-Netilmicin 8
Netilmicin-Netilmicin 7
BSA-Netilmicin 4
II. In order to make conditions as realistic as possible, a system was used where the bacteria grew on a solid surface (simulated tooth), and this surface was subjected to test solutions for a short period of time (simulated mouth-wash) . Nitrocellulose paper strips were incubated for
3-4 hours at room temperature in LB medium containing the bacterial medium diluted 10,000-1,000,000. The paper strips were washed four times with PBS to remove bacteria which had not adhered to the paper. The strips were incubated in A: a specific conjugate (Netilmicin-antibody), B: a non-specific conjugate (Netilmicin-bovine serum albumin), C: Netilmicin conjugated to itself, and D: buffer, for the shortest possible reproducible time, one minute, whereupon they were washed four times with PBS. The incubation solutions A, B and C contained approximately equimolar amounts of Netilmicin. The paper strips were placed on LB agar plates prepared in the same way as above, with the exception that no bacterial
agar layer was added. The plates were incubated overnight at 37°C and read the next day. The strips were evaluated as growth or no growth.
Results:
Conjugate of Growth (+) No growth (-)
A. Antibody-Netilmicin - - -
B. BSA-Netilmicin +++
C. Netilmicin-Netilmicin +++ D. Buffer (blank) +++
From the above results, it can be established that the conjugate of antibody-antibiotic has a clearly better anti-bacterial effect on Streptococcus mutans than the same antibiotic conjugated to a non-specific protein. The major advantage of using a conjugate according to the invention for the treatment of dental caries and plaque is the short period of exposure needed for sufficient anti-bacterial effect.