WO2024184473A1

WO2024184473A1 - Immunogenic chikungunya compositions for administration to immunocompromised patients

Info

Publication number: WO2024184473A1
Application number: PCT/EP2024/056050
Authority: WO
Inventors: Katrin DUBISCHAR; Juan Carlos JARAMILLO; Susanne EDER-LINGELBACH; Martina Schneider; Robert Mader
Original assignee: Valneva Austria Gmbh
Priority date: 2023-03-08
Filing date: 2024-03-07
Publication date: 2024-09-12

Abstract

The present invention relates to a vaccine for the prevention or treatment of a Chikungunya virus infection in immunocompromised or immunosuppressed subjects.

Description

Immunogenic chikungunya compositions for administration to immunocompromised patients

FIELD OF THE INVENTION

The present invention is directed towards a Chikungunya composition for use in an immunocompromised subject for the prevention or treatment of disease caused by Chikungunya virus infection.

BACKGROUND OF THE INVENTION

CHIKV is a small spherical RNA virus and a member of the Alphavirus genus in the family Togaviridae. The arthropod-borne virus is closely related to other viruses in Africa, South America and Australia that cause similar symptoms, such as o’nyong-nyong -virus, Mayaro-virus, or Ross River Virus. The virus is vectored by the daytime-biting Aedes aegypti mosquito, which also transmits yellow fever, Zika and dengue viruses. CHIKV can also be transmitted by Aedes albopictus mosquitoes, a more cold-tolerant mosquito that could result in the spread of chikungunya to more temperate areas of the world, especially in view of climate change. CHIKV has been reported in over one hundred countries with more than three million suspected cases alone in the Americas reported to the Pan American Health Organization (PAHO) from affected areas. CHIKV epidemics are explosive and rapidly-moving and unpredictable.

An infection with CHIKV may result in chronic and incapacitating arthralgia in some participants affecting all gender and age groups which may be accompanied by an acute febrile disease with headache, muscle pain, and skin rashes. Individuals who are at higher risk of more serious complications include infants, elderly and individuals with underlying chronic medical conditions, many of which can result in compromised immunity. The consequences of Chikungunya fever and/or its sequelae in immunocompromised patients may be especially severe, potentially including life- threatening peritonitis, encephalitis and/or secondary infections (Kees et al., Atypical Chikungunya virus infections in immunocompromised patients (2010) Emerging Infectious Diseases 16(6): 1038- 1040). Furthermore, it was observed that more than 50% of the patients who died with a CHIKV infection during an outbreak in Brazil were patients with co-morbidities or who were immunocompromised (Fatal Outcome of Chikungunya Virus Infection in Brazil (2021) de Lima et al. Clinical Infectious Diseases 2021:73). However, there are also reports from patients who are immunocompromised as a consequence of solid organ transplants and consequent treatment, which show that in those patients chikungunya did not follow an aggravated course or was even described as milder compared to immunocompetent individuals (Darrigo, et al. Chikungunya, Dengue, and Zika in Immunocompromised Hosts (2018) Current Infectious Disease Reports 20:5; Mrzljak, et al. Emerging and neglected zoonoses in transplant population (2020) World J Transplant 10(3):47-63). These observations suggest the possibility that a live-attenuated chikungunya vaccine, in contrast to other live-atenuated vaccines which are typically contraindicated in immunocompromised individuals, might be safe for use in subjects with certain immunocompromised conditions.

The term immunocompromised as used herein can also mean immunosuppressed and includes any condition which results in a weakened immune system and therefore a reduced ability to fight infections and other diseases. An immunocompromised state may be caused by certain diseases or conditions, such as infection with Human Immunodeficiency Virus (HIV), Acquired Immunodeficiency Syndrome (AIDS), cancer, diabetes, malnutrition, and certain genetic disorders. Immunocompromise or immunosuppression may also be caused by certain medicines or treatments, such as anticancer drugs, radiation therapy, and stem cell or organ transplant. (See e.g., the definition of immunocompromised from the National Cancer Institute ;www. cancer.gov/ publications/dictionaries/cancer-terms/def/immunocompromised).

Prevention of infection with CHIKV is currently limited to non-treatment interventions, such as restricting exposure to vector mosquitoes, as neither specific antiviral treatments nor vaccines are yet available. The current disclosure provides a method for treating and/or preventing Chikungunya virus disease in immunocompromised subjects. The method encompasses the stimulation of a specific immune response to CHIKV such that CHIKV disease is prevented or less severe, wherein the subject is administered an immunogenic CHIKV composition. Further, the invention provides a CHIKV- A5nsP3 composition for administration to immunocompromised subjects. The CHIKV-A5nsP3 comprises a large deletion of 60 amino acids in the nsP3 (del5nsP3) non-structural replicase complex protein, which leads to atenuation of the virus in vivo. The candidate CHIKV-A5nsP3 vaccine is intended to prevent CHIKV infections in the general population living in CHIKV endemic regions, as well as to serve as a prophylactic measure for travelers to epidemic areas or areas at risk for an outbreak. As outlined in the current disclosure, this protection can be extended to especially vulnerable immunocompromised or immunosuppressed individuals living in or traveling to endemic areas. The method and compositions of the current invention are suitable for use in subjects suffering from any deficiency in immunity, whether moderate or severe, wherein CHIKV infection and/or its sequelae can be more extreme than in healthy subjects.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an atenuated CHIKV vaccine which is suitable for use in immunocompromised subjects. The vaccine represents the first prophylactic measure against Chikungunya infection and is suitable for use in endemic regions, to protect against outbreaks, or to vaccinate travelers to endemic areas. The vaccine is additionally suitable for use in subjects suffering from any deficiency in immunity, whether moderate or severe, wherein CHIKV infection and/or its sequelae can be more extreme than in healthy subjects. In particular, the present invention aims to provide a composition comprising an effective amount of a live attenuated Chikungunya virus which has an introduced deletion mutation in the 3 ’ coding region for non-structural protein 3 (nsP3). The live -attenuated virus, CHIKV-A5nsP3, is designed to be useful as a one-shot vaccine; i.e., to confer long-lived immunity after a single dose.

Each of the limitations of the invention can encompass various embodiments of the invention. It is therefore anticipated that each of the limitations of the invention involving any one element or combinations of elements can be included in each aspect of the invention. This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. The Figures are illustrative only and are not required for enablement of the disclosure. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

Figure 1. Currently characterized Inborn Errors of Immunity (lEIs) by type and sub-type/phenotype. A. Combined T- and B-cell immunodeficiencies; B. Congenital defects of phagocyte number, function, or both; C. Diseases of immune dysregulation; D. Other well defined immunodeficiency syndromes; E. Complement deficiencies; F. Phenocopies of primary immune deficiencies; G. Defects in innate immunity; H. Predominantly antibody deficiencies; I. Autoinflammatory disorders (adapted from: en.wikipedia.org/wiki/List_of_primary_immunodeficiencies, accessed 24-Feb-2023).

Figure 2. Study design for a phase 3 clinical study with the CHIKV-A5nsP3 vaccine in HIV -positive subjects as outlined in Example 1. Cohort I: CD4⁺ T cell counts >350 to >400/pL, ART for at least 6 months and HIV RNA <400 copies/mL; Cohort II: CD4⁺ T cell counts >200/pL (no upper limit), ART for at least 3 months and HIV RNA <50 copies/mL (see also Table 1).

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the current invention relates to a method of preventing and/or treating a Chikungunya virus (CHIKV) infection and/or Chikungunya virus-associated disease in an immunocompromised subject, comprising administering to said subject an immunoprotective dose of an immunogenic CHIKV composition, i.e., a composition directed to stimulating a protective and/or neutralizing immune response to Chikungunya virus in a subject. The immunogenic CHIKV composition may comprise any antigen or coding sequence for an antigen which effectively stimulates an immunoprotective response. For example, the composition may comprise a subunit antigen, such as a protein antigen or a nucleic acid encoding a protein antigen, a virus-like particle (VLP), an inactivated virus, a virus-vectored antigen or a live-attenuated CHIKV virus. In one aspect, the nucleic acid encoding a protein antigen may be a DNA or RNA molecule, preferably an RNA molecule, especially an mRNA molecule. As used herein, an immunoprotective dose is defined as a dose sufficient to elicit an immunoprotective response, i.e., a neutralizing immune response in a subject which reduces or prevents signs or symptoms of Chikungunya virus disease. In one embodiment, the immunogenic CHIKV composition is administered to the subject more than once, e.g., two or three times. In a preferred embodiment, the immunogenic CHIKV composition is administered to the subject only once.

In one embodiment, the immunogenic CHIKV composition of the current invention comprises a CHIKV -A5nsP3 particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1. The attenuated CHIKV- A5nsP3 virus, based on the La Reunion CHIKV strain LR2006-OPY1, was constructed by substituting amino acid residues 1656 to 1717 of the P1234 polyprotein with a small linker (7 amino acids) in the hypervariable region of the nsP3 protein (Novel Attenuated Chikungunya Vaccine Candidates Elicit Protective Immunity in C57BL/6 mice, Hallengard et al., 2014, Journal of Virology 88(5):2858-2866). In particular, the composition comprises CHIKV-A5nsP3 particles comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1, i.e., wherein the CHIKV-A5nsP3 particles comprise an E2 protein with the amino acid sequence according to SEQ ID NO: 2, and CHIKV-A5nsP3 particles comprise an E2 protein with at least one point mutation in the amino acid sequence of SEQ ID NO: 2, particularly at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2.

In a preferred embodiment, at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 structural protein with the amino acid sequence according to SEQ ID NO: 2, and 1-50% of the CHIKV -A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2. In one embodiment, the pharmaceutical composition comprises an effective amount of (i) CHIKV-A5nsP3 particles; and (ii) optionally a pharmaceutically acceptable excipient; wherein at least 30% of the CHIKV-A5nsP3 particles present in the composition express an E2 structural protein as defined by the amino acid sequence of SEQ ID NO: 2; and wherein 10-50% of the CHIKV- A5nsP3 particles present in the composition express an E2 structural protein having an E168K mutation in the amino acid sequence of SEQ ID NO: 2. In one embodiment, at least 50%, at least 75% or at least 90% of the CHIKV-A5nsP3 particles present in the composition express an E2 structural protein as defined by the amino acid sequence of SEQ ID NO: 2. In one embodiment, less than 50% or less than 25% of the CHIKV-A5nsP3 particles present in the composition express an E2 structural protein having one or more mutations with respect to the amino acid sequence of SEQ ID NO: 2. In one embodiment, less than 25% or less than 10% of the CHIKV-A5nsP3 particles present in the composition express an E2 structural protein having a G55R mutation in the amino acid sequence of SEQ ID NO: 2. In one embodiment, 10-30% or 10-20% of the CHIKV-A5nsP3 particles present in the composition express an E2 structural protein having the E168K mutation in the amino acid sequence of SEQ ID NO: 2. In one embodiment, the CHIKV-A5nsP3 in (i) above is defined by the polynucleotide sequence of SEQ ID NO: 1. The manufacture of the CHIKV-A5nsP3 composition includes the step of passaging the CHIKV-A5nsP3 particle comprising a genomic RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1 on Vero cells, during which it has been observed that mutations arise in the E2 protein sequence. Some of the mutations can result in loss of immunogenicity of the CHIKV-A5nsP3 particles; therefore, steps have been taken to minimize these mutations during manufacture, and for defining a threshold for their presence in an effective immunogenic composition. Further details regarding the CHIKV-A5nsP3 composition and methods for production can be found in WO2019/057793A1, which is incorporated herein by reference in its entirety.

In one aspect, an immunoprotective dose, i.e., an effective amount, of an immunogenic Chikungunya composition, especially an immunogenic CHIKV-A5nsP3 composition, is defined as an amount sufficient to elicit neutralizing antibodies to Chikungunya virus, particularly in an immunocompromised subject. In a further aspect, an effective amount of a Chikungunya virus vaccine, such as an immunogenic CHIKV-A5nsP3 composition, is defined as an amount to elicit an immune response in a vaccinated subject, such as a vaccinated immunocompromised subject, particularly a human subject, which confers protective immunity against Chikungunya virus infection. In one embodiment, an effective amount of the immunogenic Chikungunya composition is an amount which reduces or prevents signs or symptoms of Chikungunya virus disease in an immunized subject, e.g., an immunocompromised subject. In a preferred aspect, an effective amount of the CHIKV- A5nsP3 composition is defined as at least IO², at least IO³, at least I0⁴, at least IO⁵, at least IO⁶, preferably at least IO³ immunogenic CHIKV-A5nsP3 particles. In one aspect, immunogenic CHIKV- A5nsP3 particles are defined as CHIKV-A5nsP3 particles which express an E2 structural protein as defined by the polypeptide sequence of SEQ ID NO: 2. In a preferred aspect, the composition comprises between IxlO³ and 3xl0⁴ immunogenic CHIKV-A5nsP3 particles per dose, especially about IxlO³ immunogenic CHIKV-A5nsP3 particles per dose.

In one aspect, CHIKV-A5nsP3 virus titers, i.e., number of particles, are measured in “particle forming units” (pfu), which are determined on Vero cells using a Tissue Culture Infectious Dose (TCIDjso assay. As used herein, “particle” and “pfu” are used interchangeably. Briefly, as an example of a suitable TCID50 assay, Vero cells are seeded in microplates and infected with 10-fold serially diluted virus samples in Eagle’s Minimal Essential Medium (EMEM) supplemented with 0.5% Fetal bovine serum (FBS) and 2 mM glutamine. After a one week incubation at 35 °C / 5% CO2, virus-induced cytopathic effects are monitored and viral titers are calculated according to the Reed and Muench method (Reed, L.J.; Muench, H. A simple method of estimating fifty percent endpoints. (1938) The American Journal of Hygiene 27:493-497).

In one aspect, the E2 structural protein contains one or more point mutations that do not affect the immunogenicity of the virus, i.e., are not immunogenicity reducing. In one embodiment, the point mutations that do not affect the immunogenicity of the virus may be at amino acids 232 and/or 247 of the E2 protein, such as H232Y and/or E247K. In one embodiment, the E2 structural protein of the CHIKV-A5nsP3 contains no more than about ten point mutations. In one embodiment, the E2 structural protein of the CHIKV-A5nsP3 contains no more than 9, 8, 7, 6, 5 or 4 point mutations. In a preferred embodiment, the E2 structural protein of the CHIKV-A5nsP3 contains three or less point mutations, most preferably only one or two point mutations.

As defined herein, an immunogenic CHIKV-A5nsP3 is a CHIKV-A5nsP3 which is capable of stimulating an effective immune response in vivo when delivered e.g. at a dose of about 10³ to 3xl0⁴ TCID50, i.e., an immune response in which neutralizing antibodies are produced which are sufficient for reducing or preventing signs or symptoms of Chikungunya virus disease. In a preferred aspect, the immunogenic CHIKV-A5nsP3 as defined herein is a CHIKV-A5nsP3 which expresses an E2 structural protein according to the amino acid sequence provided by SEQ ID NO: 2. In a further preferred embodiment, the immunogenic CHIKV-A5nsP3 as defined herein is defined by the polynucleotide sequence according to SEQ ID NO: 1. As an alternative or additional definition, the immunogenic CHIKV composition, such as the immunogenic CHIKV-A5nsP3 composition, stimulates the production of antibodies with neutralizing capacity in an immunized subject, particularly in an immunocompromised subject, i.e., neutralization of Chikungunya virus in an in vitro assay of at least 50%, preferably at least 60%, preferably at least 70%, more preferably at least 80%, even more preferably at least 90%, most preferably at least 95% at a 1:80 or higher serum dilution.

As defined herein, a non-immunogenic CHIKV-A5nsP3 is a CHIKV-A5nsP3 which elicits levels of neutralizing antibodies in a vaccinated subject inadequate to prevent signs or symptoms of Chikungunya virus disease. In a preferred embodiment, a non-immunogenic CHIKV-A5nsP3 is a CHIKV -A5nsP3 which expresses an E2 structural protein with at least one amino acid substitution, especially amino acid substitutions in the E2 structural protein which reduce immunogenicity, especially E168K and/or G55R substitutions, particularly an E168K substitution. A non-immunogenic CHIKV-A5nsP3 is further defined as eliciting antibodies in an immunized subject which show poor capacity to neutralize infection of cells with Chikungunya virus (wild-type or attenuated) in an in vitro assay. In particular, a non-immunogenic CHIKV-A5nsP3 is defined as eliciting levels of neutralizing antibodies in an immunized subject which provide less than 60%, less than 50%, less than 40%, less than 30%, less than 20%, especially less than 10%, neutralization of Chikungunya virus in an in vitro neutralization assay at a 1:80 or higher serum dilution.

In one aspect, the said immunocompromised subject, i.e., the subject with altered immunocompetence, is a human. Any subject suffering from immunodeficiency, immunosuppression or immunocompromise can be said to have altered immunocompetence. An immunocompromised state is characterized by reduction or complete loss of the cellular and/or humoral immune response in a subject. The main functions of the immune system are a) to identify foreign tissue and b) to provide defense against infection. An immunocompromised person is more vulnerable to infection than a healthy individual because of issues with at least one of those two functions. As the immune system is complex and made up of many different types of immune cells that serve different functions, there is no one single ‘immunocompromised state’, but rather many occurring in a spectrum from moderate to severe (see “What Does It Mean To Be ‘Immunocompromised’?” Macmillan (2022) Yale Medicine News 29-Sep-2022). In one aspect, the immunocompromised subject may be moderately immunocompromised, i.e., having an intact, but weakened, immune response compared with a healthy subject. One example of a moderately immunocompromised subject is an HIV infected subject of Category Al, A2, Bl or B2 according to 1993 CDC classification (see Table A) or, alternatively, Stage 1 or 2 according to the 2014 CDC classification (Selik, et al., 2014, Revised Surveillance Case Definition for HIV Infection — United States. MMWR 63(3); see also Table B). In another aspect, the immunocompromised subject may be severely immunocompromised, i.e., having little to no detectable immune response compared with a healthy subject. One example of a severely immunocompromised subject is an HIV infected subject of Category Cl or C2 (see Table A) or, alternatively, Stage 3 (see Table B).

In one aspect of the invention, the immunocompromised subject suffers from a disease or condition that affects the immune system. In one aspect, said disease or condition is an acute or chronic disease or condition. In one aspect, said disease or condition is any primary immunodeficiency disorder, such as any heritable or congenital disorder or condition affecting immune function either directly or indirectly. In one aspect, said disease or condition is a secondary immunodeficiency disorder or condition, i.e. immunodeficiency due to an infection, e.g., an HIV infection, or due to autoimmunity or immunosuppression. As used herein, “secondary immunodeficiency” is interchangeable with “acquired immunodeficiency”. In one aspect, said acquired immunodeficiency or immunosuppression is due to drug therapy with immunosuppressive drugs such as, e.g., corticosteroids, or biologicals such as, e.g., cytokines or antibodies.

Primary immunodeficiencies, i.e., congenital or inherited immunodeficiencies, belong to a larger group referred to as “Inborn errors of immunity” or lEIs. More than 400 distinct defects were recognized in 2019, an increase of 200 disorders in only the previous 10 years. Intense study of these disorders has shifted the field from a focus on fundamental defects in the immune response toward a larger group of lEIs with different phenotypes including infection, autoinflammation, autoimmunity, allergy, and malignancy (Bucciol and Meyts; Recent advances in primary immunodeficiency: from molecular diagnosis to treatment. 2020. FlOOOResearch 9(F1000 Faculty Rev): 194 (https://doi.Org/10.12688/fl000research.21553.l)). The number of lEIs identified continues to increase; a recent review puts the number at 485 (Bousfiha et al , The 2022 Update of IUIS Phenotypical Classification for Human Inborn Errors of Immunity. 2022. J Clin Immunol 42: 1508- 1520.) See Figure 1 for a summary of identified lEIs. As used herein, “primary immunodeficiency” and “Inborn error of immunity” are used interchangeably.

A typical sign of primary immunodeficiency is having more frequent, longer lasting or harder to treat infections than for someone with a healthy, optimally-functioning immune system. Further, opportunistic infections are more common. Signs and symptoms can vary depending on the individual, but generally include frequent and recurrent pneumonia, bronchitis, sinus infections, ear infections, meningitis or skin infections; inflammation and infection of internal organs; blood disorders, such as low platelet count or anemia; digestive problems, such as cramping, loss of appetite, nausea and diarrhea; delayed growth and development, and autoimmune disorders, such as lupus, rheumatoid arthritis or type 1 diabetes (www.mayoclinic.org/diseases-conditions/primary- immunodeficiency/symptoms-causes/syc-20376905, accessed 28-Feb-2023).

Secondary immunodeficiencies, in general, may be defined as an impairment of the immune response resulting from conditions or factors extrinsic to the immune system. They can occur as a consequence of malnutrition, metabolic disorders, use of immunosuppressive medications, chronic infections, malignancies, and severe trauma. Further, relative to healthy adults, individuals of either age extreme such as premature infants, neonates and the elderly may have decreased immune responses. Genetic defects that are not primary immunodeficiencies can also result in secondary immunodeficiency. A comprehensive review of secondary immunodeficiencies is provided in Tuano, et al. (Secondary immunodeficiencies: An overview. 2021. Ann Allergy Asthma Immunol 127:617-626).

In one aspect, the subject has at least one disease or condition selected from the group consisting of suffering from a hematologic malignancy, undergoing immunosuppressive therapy, receiving a hematopoietic stem cell transplant, receiving a solid organ transplant, infected with HIV, and suffering from an autoimmune disease. In one aspect, the immunocompromised subject suffers from a disease selected from the group consisting of bacterial or viral infections, cancer, and other chronic disorders or conditions, due to aging, malnutrition, or various drug treatments, such as immunosuppressant, antiretroviral or chemotherapy drug treatments. In one aspect, the immunocompromised subject has tuberculosis or a sexually transmitted disease, e.g., syphilis or hepatitis. In one aspect, the immunocompromised subject suffers from malnutrition. As used herein, a malnourished subject is one who weighs 70% or less than a healthy person of the same sex, age and height.

In one aspect, the immunocompromised subject has reduced immune function due to aging. In one aspect, the immunocompromised subject is a human adult 55 years of age or older, more preferably a human adult 65 years of age or older. In one aspect, the immunocompromised subject is a human adult 70 years of age or older, 75 years of age or older or 80 years of age or older. In one aspect, the immunocompromised subject has reduced immune function due to a developing immune system, i.e., due to a young age. In one aspect, the immunocompromised subject is a human aged less than 18 years, preferably less than 12 years, especially less than 5 years, less than 4 years, less than 3 years, less than 2 years, particularly less than 1 year or less than 6 months of age. In one aspect, the immunocompromised subject is immunocompromised due to two or more diseases, disorders or conditions affecting immune function.

In further aspects, the subject suffers from a disease or condition selected from the group consisting of HIV infection, acquired immunodeficiency syndrome (AIDS), chronic heart or lung disorders, congestive heart failure, diabetes mellitus, chronic liver disease, alcoholism, cirrhosis, fatty liver disease, spinal fluid leaks, cardiomyopathy, chronic bronchitis, emphysema, chronic obstructive pulmonary disease (COPD), spleen dysfunction (such as sickle cell disease), lack of spleen function (asplenia), blood malignancy, leukemia, multiple myeloma, Hodgkin's disease, lymphoma, kidney failure, nephrotic syndrome and asthma.

In one aspect, the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under therapy, said therapy consisting of taking at least one antiretroviral drug selected from the group consisting of a non-nucleoside reverse transcriptase inhibitor, a protease inhibitor and a nucleoside analog reverse transcriptase inhibitor (e.g. abacavir). In one aspect, the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under therapy, said therapy consisting of taking at least two nucleoside analogue reverse transcriptase inhibitors plus either a protease inhibitor or a non- nucleoside reverse transcriptase inhibitor. In one aspect, the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under highly active antiretroviral therapy (HAART), preferably consisting of a three drug regimen which includes a non-nucleoside reverse transcriptase inhibitor, a protease inhibitor and/or a nucleoside analog reverse transcriptase inhibitor (e.g. abacavir) or a two drug regimen which includes a combination of a non-nucleoside reverse transcriptase inhibitor and a protease inhibitor.

In one aspect, the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is not under highly active antiretroviral therapy (HAART), or is not under antiretroviral therapy, or said subject has never been exposed to antiretroviral drugs.

In one aspect, the immunocompromised subject suffering from HIV infection or AIDS is more moderately immunocompromised, such as in Stage Al, A2, Bl or B2 of disease according to the revised CDC classification system for HIV infection from 1993 (Castro, et al., 1993 revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. 1992-Dec-18. MMWR Recomm Rep. 41(RR-17): 1-19). This system categorizes persons on the basis of clinical conditions associated with HIV infection (categories A-C) and CD4⁺ T-lymphocyte counts (categories 1-3). See Table A for classification criteria for HIV infected adolescents and adults according to the 1993 CDC classification system. In an alternative or complementary aspect, the immunocompromised subject suffering from HIV infection or AIDS is more moderately immunocompromised, such as Stages 1 or 2 in the absence of AIDS defining conditions (see Table B; adapted from CDC www.cdc.gov/hiv/basics/syndication-test.html; 2021). Clinical categories 1-3 generally correspond to Categories A-C in the 1993 classification system and are used interchangeably herein. Furthermore, “clinical category” is used interchangeably with “stage” herein. In one aspect, the immunocompromised subject suffering from HIV infection or AIDS is more severely immunocompromised, such as in Stage Cl or C2 of disease as set forth in Table A (with “C” referring to clinical category and “1” or “2” referring to CD4⁺ T-lymphocyte category), or alternatively, Stage 3 of disease according to the classification set forth in Table B, i.e. AIDS.

Table A. Revised CDC classification system (1993) for HIV-infected adolescents and adults (>13 years).

Table B. CDC Stages of HIV (2014).

In one aspect, the immunocompromised subject is a non-viremic HIV infected patient. In one aspect, the immunocompromised subject is a viremic HIV infected patient. In one aspect, the HIV infected patient has an HIV plasma load of HIV RNA <100,000 copies/mL, preferably <50,000 copies/mL, more preferably <10,000 copies/mL, even more preferably <5,000 copies/mL, especially <1000 copies/mL. In a preferred aspect, the HIV infected patient has an HIV plasma load of HIV RNA <400 copies/mL or <200 copies/mL. In another preferred aspect, the HIV infected patient has an HIV plasma load of HIV RNA <50 copies/mL or <20 copies/mL. In one aspect, the HIV infected patient has a CD4⁺ T cell count of between 10 and 500 CD4⁺ T cells/pL. In one aspect, the HIV infected patient has a CD4⁺ T cell count in the range of >350 to >400/pL. In a preferred aspect, the HIV infected patient has a CD4⁺ T cell count >200/pL. In one aspect, the HIV infected patient is on longterm anti-retroviral therapy (ART); i.e., has been on ART for at least 3 months, for at least 6 months, or for at least one year. As used herein, “HIV infected patient” is used interchangeably with “HIV positive subject” or “HIV positive patient”.

In one aspect, the immunocompromised subject is taking a drug or treatment that lowers resistance to infection, in particular a drug selected from the group consisting of chemotherapy (e.g. cancer drugs), disease-modifying antirheumatic drugs, immunosuppressive drugs after organ transplantation, and glucocorticoids. In one aspect, the immunocompromised subject is taking an oral immunosuppressant drug selected from the group consisting of: tacrolimus (Prograf), mycophenolate mofetil (CellCept), sirolimus (Rapamune), prednisone, cyclosoporine (Neoral, Sandimmune, Gengraf) and azathioprine (Imuran).

In one aspect, the immunocompromised subject is taking an immunosuppressant drug selected from the group consisting of: Everolimus, Mycophenolic acid, Corticosteroids (such as Prednisolone or Hydrocortisone), Monoclonal anti-IL-2Ra receptor antibodies (such as Basiliximab or Daclizumab), Anti -thymocyte globulin (ATG) and Anti -lymphocyte globulin (ALG).

In one aspect, the immunocompromised subject has undergone organ transplantation, or bone marrow transplantation or cochlear implantation. In one aspect, the immunocompromised subject has undergone radiation therapy. In one aspect, the immunocompromised subject is a smoker. In one aspect, the immunocompromised subject suffers from asthma and is treated with oral corticosteroid therapy.

In one aspect, the immunocompromised subject has a white blood cell count (leukocyte count) below 5 x 10⁹ cells per liter, or below 4 x 10⁹ cells per liter, or below 3 x 10⁹ cells per liter, or below 2 x 10⁹ cells per liter, or below 1 x 10⁹ cells per liter, or below 0.5 x 10⁹ cells per liter, or below 0.3 x 10⁹ cells per liter, or below 0.1 x 10⁹ cells per liter.

In one aspect, the immunocompromised subject suffers from neutropenia. In one aspect, the immunocompromised subject has a neutrophil count below 2 x 10⁹ cells per liter, or below 1 x 10⁹ cells per liter, or below 0.5 x 10⁹ cells per liter, or below 0.1 x 10⁹ cells per liter, or below 0.05 x 10⁹ cells per liter. In one aspect, the immunocompromised subject has a CD4⁺ cell count below 500/pL, or CD4⁺ cell count below 300/pL, or CD4⁺ cell count below 200/pL, CD4⁺ cell count below 100/pL, CD4⁺ cell count below 75/pL, or CD4⁺ cell count below 50/pL.

In one aspect, the immunocompromised subject is overweight, obese and/or diabetic. In one aspect, the immunocompromised subject disclosed herein is a human male or a human female.

In one aspect of the current disclosure, a composition for use in a method of immunizing an immunocompromised subject is provided, wherein said composition comprises a A5nsP3-CHIKV particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1; particularly wherein at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with the amino acid sequence according to SEQ ID NO: 2, and wherein 1-50% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2.

In one aspect, the current invention provides a composition for use in the manufacture of a medicament for the prevention or treatment of diseases caused by Chikungunya virus in an immunocompromised subject, wherein said composition comprises a A5nsP3-CHIKV particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1; particularly wherein at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with the amino acid sequence according to SEQ ID NO: 2, and wherein 1-50% of the CHIKV- A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicityreducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2. In a preferred embodiment, in the method or composition for use provided by the current invention, the composition is a vaccine. In a further preferred embodiment, the vaccine is a one-shot vaccine; i.e., the administration of a single dose of the vaccine confers long-lived protection, especially lifelong protection against CHIKV infection and/or disease. In one embodiment, the vaccine of the disclosure is provided in a lyophilized format; i.e. freeze-dried to allow stable long-term storage under refrigeration (e.g. 2-6°C) or at room temperature (i.e. 18-25°C).

EXAMPLES

Example 1: A Clinical Phase 3 Study of a Single-dose CHIKV-A5nsP3 Vaccine in Adult Participants with Human Immunodeficiency Virus (HIV)

Study Description

This is a multicenter, prospective, open-label, uncontrolled, single arm, phase 3 clinical study evaluating the final dose of the single-dose (a.k.a. “single-shot”) CHIKV-A5nsP3 vaccine (IxlOE⁴ TCID50 per 0.5 mb). The safety, tolerability, and immunogenicity of CHIKV-A5nsP3 will be assessed in moderately immunocompromised adult participants infected with HIV living in CHIKV endemic areas. Approximately 75 male and female adults (aged 18 years or above) infected with HIV will be enrolled. Participants will be screened by ELISA for evidence of previous CHIKV exposure excluding CHIKV seropositive participants (defined as IgM⁺ and IgG⁺ or IgM and IgG⁺) from study participation.

As a precautionary safety measure, the study will be initiated with cohorts and sentinels. All Sentinel participants (from Cohort I and Cohort II) and the full Cohort I will be recruited at a single site. See Table 1 for a summary of arms, interventions and cohorts.

The first three Sentinel participants of Cohort I (CD4⁺ T cell count >350 to <400 cells/pL, ART for at least 6 months and HIV RNA <400 copies/ mb) will be enrolled into the study starting with three participants monitored for safety signals over a period of 14 days post vaccination (Visit 4, Day 15). If no safety concerns arise as determined by the Principal Investigator (PI) of the study site vaccinating the sentinel participants, by the Sponsor and by an independent Data and Safety Monitoring Board (DSMB), Cohort I will continue without limitations. After all Cohort I participants have completed Day 29 (Visit 5), a Cohort I Part A analysis of initial immunogenicity and safety will be done. If the safety and immunogenicity profile are considered favorable by the DSMB and sponsor the three sentinel participants of Cohort II (CD4⁺ T cell counts >200/pL, ART for at least 3 months and HIV RNA < 50 copies/ mb) will be vaccinated and monitored over a period of 14 days post vaccination (Visit 4, Day 15). If no safety concerns arise as determined by the Principal Investigator of the study site vaccinating the sentinel participants, by the Sponsor, and by the DSMB, Cohort II will continue without limitations.

Table 1. Arms, Interventions and Cohorts

Before enrollment and any study-related procedures are performed, written informed consent of the participant(s) will be obtained.

At Day 1 (Visit 1) CHIKV-A5nsP3 will be administered intramuscularly as a single-dose immunization. Participants will return to study site at Day 4 (i.e. Visit 2, three days after vaccination) and Day 8 (i.e. Visit 3, seven days after vaccination) for physical examination, safety evaluation and viremia assessments. Furthermore, participants will visit the study site at Day 15 (Visit 4), Day 29 (Visit 5), Day 57 (Visit 6), Month 3 (Day 85, Visit 7), and Month 6 (Day 180, Visit 8) for safety evaluations and collection of samples for immunogenicity assessments. Viremia samples will be collected at Visits 1 through 8, and, if applicable, at an unscheduled Visit, acute Visit, convalescent Visit and/or Early Termination Visit. Samples from Visit 1, 2, 3 and 4 will be analyzed. The collected viremia sample of Visit 5 and Visit 6 will only be analyzed if the preceding sample of Visit 4 or Visit 5 is positive. In addition, for clinically indicated retrospective analysis viremia samples will be collected throughout the study from all participants. The study design is outlined in Figure 2.

Safety laboratory parameters will be evaluated starting at baseline (screening and Visit 1) and at every visit at study site after vaccination (Visit 2 to Visit 8).

Outcome Measures

Primary:

1. To assess solicited adverse events captured for 14 days following vaccination [Time Frame: until Day 15]

Secondary: . Immune response as measured by CHIKV-specific neutralizing antibody titers post-vaccination as determined by pPRNT assay [Time Frame: Day 15, Day 29, Day 57, Day 85 and Day 180]

3. Proportion of participants with seroresponse levels post-vaccination as determined by pPRNT assay [Time Frame: Day 15, Day 29, Day 57, Day 85 and Day 180]

4. Proportion of participants with seroconversion as compared to baseline as determined by pPRNT assay [Time Frame: Day 29 and Day 180]

5. Fold increase of CHIKV-specific neutralizing antibody titers determined by pPRNT assay postvaccination as compared to baseline [Time Frame: Day 15, Day 29, Day 57, Day 85 and Day 180]

6. Proportion of participants reaching an at least 4-fold, 8-fold, 16-fold or 64-fold increase in CHIKV-specific neutralizing antibody titer compared to baseline as measured by pPRNT assay

7. Frequency and severity of unsolicited Adverse Events (AEs) [Time Frame: until Day 29 and Day 180]

8. Frequency and relatedness of any serious adverse event (SAE) [Time Frame: until Day 180]

9. Frequency and severity of any early onset adverse event of special interest (AESI) [Time Frame: between Day 3 and Day 22]

10. Frequency and severity of any late onset adverse event of special interest (AESI) [Time Frame: between Day 23 and Day 180]

11. Assessment of CHIKV viremia after vaccination [Time Frame: Day 1, Day 4, Day 8, and Day 15 (also Day 29 and Day 57, if applicable)]

12. Assessment of HIV viral load [Time Frame: Day 1, Day 15, Day 29, Day 57, Day 85 and Day 180]

Inclusion Criteria

Participants who meet ALL of the following criteria are eligible for this study:

1. Adult participant aged 18 years or above infected with HIV of either gender

2. Participant has an understanding of the study and its procedures, agrees to its provisions, and voluntarily gives written informed consent prior to any study-related procedures

3. Stage of disease Al, A2, Bl or B2 according to the revised CDC classification system for HIV infection from 1993 (see Table A) or Stages 1 or 2 in the absence of AIDS defining conditions (CDC update from 2014)

4. Participants are recruited in Cohorts: a. For Cohort I:

Participant has CD4⁺ T cell counts >350-<400 cells/pL, is receiving antiretroviral therapy (ART) for at least 6 months and plasma HIV RNA < 400 copies/ mb prior enrollment b. For Cohort II: Participant has CD4⁺ T cell counts >200 cells/pL (no upper limit), is receiving ART for at least 3 months and plasma HIV RNA < 50 copies/ mL prior enrollment

5. Participant is seronegative for previous CHIKV exposure (i.e. IgM- and IgG-) as screened by CHIKV-specific ELISA

6. If participant is of childbearing potential: a. Participant has a negative urine pregnancy test at screening (Visit 0) or Day 1 (Visit 1), respectively b. Participant has practiced an adequate method of contraception during the 30 days before screening (Visit 0) c. Participant agrees to employ adequate birth control measures for the first three months postvaccination (i.e. until Day 85, Visit 6).

Exclusion Criteria

Participants who meet ANY of the following criteria are NOT eligible for this study:

1. Participant is taking medication or other treatment for unresolved symptoms attributed to a previous CHIKV infection; or has participated in a clinical study involving an investigational CHIKV vaccine

2. Participant has an acute or recent infection (and who is not symptom free in the week prior to the Screening Visit (Visit 0) and Visit 1)

3. Participant tests positive for human immunodeficiency virus (HIV) and fulfills AIDS indicator T cell counts or AIDS indicator conditions (disease stages Cl, C2 or C3 or stage 3. Participant tests positive for HIV with the actual target disease stages Al, A2, Bl or B2 (or stage 1 or 2), but was classified in the past at least once as fulfilling AIDS indicator conditions (disease stage Cl, C2 or C3) or AIDS indicator T cell counts (CD4⁺ lymphocyte count <200/pL or CD4⁺ percentage <14%)

5. Participant tests PCR positive for active hepatitis B or hepatitis C virus (HCV)

6. Participant has received any vaccine within 28 days prior to vaccination in this study or plans to receive any vaccine within 28 days after vaccination

7. Participant has abnormal findings in any required study investigations (e.g. medical history, physical examination, and laboratory findings) considered clinically relevant by the Investigator and which pose a risk for participation in the study based on his/her judgement

8. Participant currently has or has a history of significant cardiovascular, respiratory, metabolic, neurological, hepatic, rheumatic, autoimmune, hematological, gastrointestinal or renal disorder. (Mild asthma that requires low dose corticosteroid inhalation only, during limited time periods of the year is not an exclusion criterion)

9. Participant has an abnormal, clinically significant 12-lead electrocardiogram (ECG) at screening.

10. Participant has a history of immune-mediated or clinically relevant arthritis/arthralgia 11. Participant has a history of malignancy

12. Participant has a known or suspected defect of the immune system that can be expected to influence the immune response to the vaccine other than asymptomatic or moderately symptomatic HIV infection, such as participants with congenital immunodeficiency, status post organ transplantation or immuno-suppressive therapy within four weeks prior to Visit 1. Immuno-suppressive therapy is defined as administration of chronic (longer than 14 days) prednisone or equivalent >0.05 mg/kg/day within 4 weeks prior to study entry, radiation therapy or immunosuppressive cytotoxic drugs/ monoclonal antibodies in the previous three years; topical and inhaled steroids are allowed

13. Participant has a history of any vaccine related contraindicating event (e.g., anaphylaxis, allergy to components of the candidate vaccine, other known contraindications including febrile convulsions)

14. Participant presents with clinical conditions representing a contraindication to intramuscular vaccination and blood draws

15. Participant is pregnant (positive urine pregnancy test at screening or Visit 1), is lactating at the time of enrollment, has plans to become pregnant or subject’s female partner plans to become pregnant during the first three months postvaccination or practices unreliable contraception

16. Participant received blood-derived products (e.g. plasma) within 90 days prior to vaccination in this study

17. Participant has a rash, dermatological condition or tattoos that would, in the opinion of the Investigator, interfere with injection site reaction rating

18. Participant has participated in another clinical study involving an investigational medicinal product (IMP) or device within 30 days prior to vaccination or is scheduled to participate in another clinical study involving an IMP, or device during the course of this study

19. Participant is a member of the team conducting the study or in a dependent relationship with one of the study team members. Dependent relationships include close relatives (i.e., children, partner/spouse, siblings, parents) as well as employees of the Investigator or site personnel conducting the study.

SEQUENCES

SEQ ID NO: 1

Nucleotide sequence of the CHIKV-A5nsP3 GATGGCTGCGTGAGACACACGTAGCCTACCAGTTTCTTACTGCTCTACTCTGCAAAGCAAGAGATTAATAACCCATCATGGATCCTGTGT ACGTGGACATAGACGCTGACAGCGCCTTTTTGAAGGCCCTGCAACGTGCGTACCCCATGTTTGAGGTGGAACCAAGGCAGGTCACACC GAATGACCATGCTAATGCTAGAGCGTTCTCGCATCTAGCTATAAAACTAATAGAGCAGGAAATTGACCCCGACTCAACCATCCTGGATAT CGGCAGTGCGCCAGCAAGGAGGATGATGTCGGACAGGAAGTACCACTGCGTCTGCCCGATGCGCAGTGCGGAAGATCCCGAGAGACT CGCCAATTATGCGAGAAAGCTAGCATCTGCCGCAGGAAAAGTCCTGGACAGAAACATCTCTGGAAAGATCGGGGACTTACAAGCAGTA ATGGCCGTGCCAGACACGGAGACGCCAACATTCTGCTTACACACAGACGTCTCATGTAGACAGAGAGCAGACGTCGCTATATACCAAGA CGTCTATGCTGTACACGCACCCACGTCGCTATACCACCAGGCGATTAAAGGGGTCCGAGTGGCGTACTGGGTTGGGTTCGACACAACCC CGTTCATGTACAATGCCATGGCGGGTGCCTACCCCTCATACTCGACAAACTGGGCAGATGAGCAGGTACTGAAGGCTAAGAACATAGG ATTATGTTCAACAGACCTGACGGAAGGTAGACGAGGCAAGTTGTCTATTATGAGAGGGAAAAAGCTAAAACCGTGCGACCGTGTGCTG TTCTCAGTAGGGTCAACGCTCTACCCGGAAAGCCGCAAGCTACTTAAGAGCTGGCACCTGCCATCGGTGTTCCATTTAAAGGGCAAACT CAGCTTCACATGCCGCTGTGATACAGTGGTTTCGTGTGAGGGCTACGTCGTTAAGAGAATAACGATGAGCCCAGGCCTTTATGGAAAAA CCACAGGGTATGCGGTAACCCACCACGCAGACGGATTCCTGATGTGCAAGACTACCGACACGGTTGACGGCGAAAGAATGTCATTCTC GGTGTGCACATACGTGCCGGCGACCATTTGTGATCAAATGACCGGCATCCTTGCTACAGAAGTCACGCCGGAGGATGCACAGAAGCTG TTGGTGGGGCTGAACCAGAGAATAGTGGTTAACGGCAGAACGCAACGGAATACGAACACCATGAAAAATTATCTGCTTCCCGTGGTCG CCCAAGCCTTCAGTAAGTGGGCAAAGGAGTGCCGGAAAGACATGGAAGATGAAAAACTCCTGGGGGTCAGAGAAAGAACACTGACCT GCTGCTGTCTATGGGCATTCAAGAAGCAGAAAACACACACGGTCTACAAGAGGCCTGATACCCAGTCAATTCAGAAGGTTCAGGCCGA GTTTG ACAGCTTTGTG GTACCG AGTCTGTG GTCGTCCG GGTTGTCAATCCCTTTG AG G ACTAG AATCAAATG GTTGTTAAG CAAG GTG C CAAAAACCGACCTGATCCCATACAGCGGAGACGCCCGAGAAGCCCGGGACGCAGAAAAAGAAGCAGAGGAAGAACGAGAAGCAGAA CTGACTCGCGAAGCCCTACCACCTCTACAGGCAGCACAGGAAGATGTTCAGGTCGAAATCGACGTGGAACAGCTTGAGGACAGAGCGG GCGCAGGAATAATAGAGACTCCGAGAGGAGCTATCAAAGTTACTGCCCAACCAACAGACCACGTCGTGGGAGAGTACCTGGTACTCTC CCCGCAGACCGTACTACGTAGCCAGAAGCTCAGTCTGATTCACGCTTTGGCGGAGCAAGTGAAGACGTGCACGCACAACGGACGAGCA GGGAGGTATGCGGTCGAAGCGTACGACGGCCGAGTCCTAGTGCCCTCAGGCTATGCAATCTCGCCTGAAGACTTCCAGAGTCTAAGCG AAAGCGCAACGATGGTGTATAACGAAAGAGAGTTCGTAAACAGAAAGCTACACCATATTGCGATGCACGGACCAGCCCTGAACACCGA CGAAGAGTCGTATGAGCTGGTGAGGGCAGAGAGGACAGAACACGAGTACGTCTACGACGTGGATCAGAGAAGATGCTGTAAGAAGG AAGAAGCCGCAGGACTGGTACTGGTGGGCGACTTGACTAATCCGCCCTACCACGAATTCGCATATGAAGGGCTAAAAATCCGCCCTGCC TGCCCATACAAAATTGCAGTCATAGGAGTCTTCGGAGTACCGGGATCTGGCAAGTCAGCTATTATCAAGAACCTAGTTACCAGGCAGGA CCTGGTGACTAGCGGAAAGAAAGAAAACTGCCAAGAAATCACCACCGACGTGATGAGACAGAGAGGTCTAGAGATATCTGCACGTACG GTTGACTCGCTGCTCTTGAATGGATGCAACAGACCAGTCGACGTGTTGTACGTAGACGAGGCGTTTGCGTGCCACTCTGGAACGCTACT TGCTTTGATCGCCTTGGTGAGACCAAGGCAGAAAGTTGTACTTTGTGGTGACCCGAAGCAGTGCGGCTTCTTCAATATGATGCAGATGA AAGTCAACTATAATCACAACATCTG CACCCAAGTGTACCACAAAAGTATCTCCAGG CG GTGTACACTG CCTGTG ACCG CCATTGTGTCAT CGTTGCATTACGAAGGCAAAATGCGCACTACGAATGAGTACAACAAGCCGATTGTAGTGGACACTACAGGCTCAACAAAACCTGACCCT GGAGACCTCGTGTTAACGTGCTTCAGAGGGTGGGTTAAACAACTGCAAATTGACTATCGTGGATACGAGGTCATGACAGCAGCCGCAT CCCAAGGGTTAACCAGAAAAGGAGTTTACGCAGTTAGACAAAAAGTTAATGAAAACCCGCTCTATGCATCAACGTCAGAGCACGTCAAC GTACTCCTAACGCGTACGGAAGGTAAACTGGTATGGAAGACACTTTCCGGCGACCCGTGGATAAAGACGCTGCAGAACCCACCGAAAG GAAACTTCAAAGCAACTATTAAGGAGTGGGAGGTGGAGCATGCATCAATAATGGCGGGCATCTGCAGTCACCAAATGACCTTCGATAC ATTCCAAAATAAAG CCAACGTTTGTTG GG CTAAG AGCTTG GTCCCTATCCTCG AAACAG CGG G G ATAAAACTAAATG ATAG GCAGTG GT CTCAGATAATTCAAGCCTTCAAAGAAGACAAAGCATACTCACCTGAAGTAGCCCTGAATGAAATATGTACGCGCATGTATGGGGTGGAT CTAGACAGCGGGCTATTTTCTAAACCGTTGGTGTCTGTGTATTACGCGGATAACCACTGGGATAATAGGCCTGGAGGGAAAATGTTCGG ATTTAACCCCGAGGCAGCATCCATTCTAGAAAGAAAGTATCCATTCACAAAAGGGAAGTGGAACATCAACAAGCAGATCTGCGTGACTA CCAGGAGGATAGAAGACTTTAACCCTACCACCAACATCATACCGGCCAACAGGAGACTACCACACTCATTAGTGGCCGAACACCGCCCA GTAAAAGGGGAAAGAATGGAATGGCTGGTTAACAAGATAAACGGCCACCACGTGCTCCTGGTCAGTGGCTATAACCTTGCACTGCCTA CTAAGAGAGTCACTTGGGTAGCGCCGTTAGGTGTCCGCGGAGCGGACTACACATACAACCTAGAGTTGGGTCTGCCAGCAACGCTTGG TAGGTATGACCTAGTGGTCATAAACATCCACACACCTTTTCGCATACACCATTACCAACAGTGCGTCGACCACGCAATGAAACTGCAAAT GCTCGGGGGTGACTCATTGAGACTGCTCAAACCGGGCGGCTCTCTATTGATCAGAGCATATGGTTACGCAGATAGAACCAGTGAACGA GTCATCTGCGTATTGGGACGCAAGTTTAGATCGTCTAGAGCGTTGAAACCACCATGTGTCACCAGCAACACTGAGATGTTTTTCCTATTC AGCAACTTTGACAATGGCAGAAGGAATTTCACAACTCATGTCATGAACAATCAACTGAATGCAGCCTTCGTAGGACAGGTCACCCGAGC AGGATGTGCACCGTCGTACCGGGTAAAACGCATGGACATCGCGAAGAACGATGAAGAGTGCGTAGTCAACGCCGCTAACCCTCGCGG GTTACCGGGTGGCGGTGTTTGCAAGGCAGTATACAAAAAATGGCCGGAGTCCTTTAAGAACAGTGCAACACCAGTGGGAACCGCAAAA ACAGTTATGTGCGGTACGTATCCAGTAATCCACGCTGTTGGACCAAACTTCTCTAATTATTCGGAGTCTGAAGGGGACCGGGAATTGGC AGCTGCCTATCGAGAAGTCGCAAAGGAAGTAACTAGGCTGGGAGTAAATAGTGTAGCTATACCTCTCCTCTCCACAGGTGTATACTCAG GAGGGAAAGACAGGCTGACCCAGTCACTGAACCACCTCTTTACAGCCATGGACTCGACGGATGCAGACGTGGTCATCTACTGCCGCGA CAAAGAATGGGAGAAGAAAATATCTGAGGCCATACAGATGCGGACCCAAGTAGAGCTGCTGGATGAGCACATCTCCATAGACTGCGAT ATTGTTCGCGTGCACCCTGACAGCAGCTTGGCAGGCAGAAAAGGATACAGCACCACGGAAGGCGCACTGTACTCATATCTAGAAGGGA CCCGTTTTCATCAGACGGCTGTGGATATGGCGGAGATACATACTATGTGGCCAAAGCAAACAGAGGCCAATGAGCAAGTCTGCCTATAT GCCCTGGGGGAAAGTATTGAATCGATCAGGCAGAAATGCCCGGTGGATGATGCAGACGCATCATCTCCCCCCAAAACTGTCCCGTGCCT TTGCCGTTACGCTATGACTCCAGAACGCGTCACCCGGCTTCGCATGAACCACGTCACAAGCATAATTGTGTGTTCTTCGTTTCCCCTCCCA AAGTACAAAATAG AAG G AGTG CAAAAAGTCAAATGCT CTAAG GTAATG CTATTTG ACCACAACGTG CCATCGCG CGTAAGTCCAAGG G CTTATAGAGGTGCCGCTGCCGGTAACCTTGCGGCCGTGTCTGATTGGGTAATGAGCACCGTACCTGTCGCGCCGCCCAGAAGAAGGCG AGGGAGAAACCTGACTGTGACATGTGACGAGAGAGAAGGGAATATAACACCCATGGCTAGCGTCCGATTCTTTAGGGCAGAGCTGTGT CCGGTCGTACAAGAAACAGCGGAGACGCGTGACACAGCAATGTCTCTTCAGGCACCACCGAGTACCGCCACGGAACCGAATCATCCGC CGATCTCCTTCGGAGCATCAAGCGAGACGTTCCCCATTACATTTGGGGACTTCAACGAAGGAGAAATCGAAAGCTTGTCTTCTGAGCTAC TAACTTTCGGAGACTTCTTACCAGGAGAAGTGGATGACTTGACAGACAGCGACTGGTCCACGTGCTCAGACACGGACGACGAGTTAAG ACTAGACAGGGCAGGTGGGTATATATTCTCGTCGGACACCGGTCCAGGTCATTTACAACAGAAGTCAGTACGCCAGTCAGTGCTGCCGG TGAACACCCTGGAGGAAGTCCACGAGGAGAAGTGTTACCCACCTAAGCTGGATGAAGCAAAGGAGCAACTATTACTTAAGAAACTCCA GGAGAGTGCATCCATGGCCAACAGAAGCAGGTATCAGTCGCGCAAAGTAGAAAACATGAAAGCAGCAATCATCCAGAGACTAAAGAG AGGCTGTAGACTATACTTAATGTCAGAGACCCCAAAAGTCCCTACTTACCGGACTACATATCCGGCGCCTGTGTACTCGCCTCCGATCAA

CGTCCGATTGTCCAATCCCGAGTCCGCAGTGGCAGCATGCAATGAGTTCTTAGCTAGAAACTATCCAACTGTCTCATCATACCAAATTAC CGACGAGTATGATGCATATCTAGACATGGTGGACGGGTCGGAGAGTTGCCTGGACCGAGCGACATTCAATCCGTCAAAACTCAGGAGC TACCCGAAACAGCACGCTTACCACGCGCCCTCCATCAGAAGCGCTGTACCGTCCCCATTCCAGAACACACTACAGAATGTACTGGCAGCA GCCACGAAAAGAAACTGCAACGTCACACAGATGAGGGAATTACCCACTTTGGACTCAGCAGTATTCAACGTGGAGTGTTTCAAAAAATT CGCATGCAACCAAGAATACTGGGAAGAATTTGCTGCCAGCCCTATTAGGATAACAACTGAGAATTTAGCAACCTATGTTACTAAACTAAA AGGGCCAAAAGCAGCAGCGCTATTCGCAAAAACCCATAATCTACTGCCACTACAGGAAGTACCAATGGATAGGTTCACAGTAGATATGA AAAGGGACGTAAAGGTGACTCCTGGTACAAAGCATACAGAGGAAAGACCTAAGGTGCAGGTTATACAGGCGGCTGAACCCTTGGCGA CAGCATACCTATGTGGGATTCACAGAGAGCTGGTTAGGAGGCTGAACGCCGTCCTCCTACCCAATGTACATACACTATTTGACATGTCTG CCGAGGATTTCGATGCCATCATAGCCGCACACTTTAAGCCAGGAGACACTGTTTTGGAAACGGACATAGCCTCCTTTGATAAGAGCCAA GATGATTCACTTGCGCTTACTGCTTTGATGCTGTTAGAGGATTTAGGGGTGGATCACTCCCTGCTGGACTTGATAGAGGCTGCTTTCGGA GAGATTTCCAGCTGTCACCTACCGACAGGTACGCGCTTCAAGTTCGGCGCCATGATGAAATCAGGTATGTTCCTAACTCTGTTCGTCAAC ACATTGTTAAACATCACCATCGCCAGCCGAGTGCTGGAAGATCGTCTGACAAAATCCGCGTGCGCGGCCTTCATCGGCGACGACAACAT AATACATGGAGTCGTCTCCGATGAATTGATGGCAGCCAGATGTGCCACTTGGATGAACATGGAAGTGAAGATCATAGATGCAGTTGTAT CCTTGAAAGCCCCTTACTTTTGTGGAGGGTTTATACTGCACGATACTGTGACAGGAACAGCTTGCAGAGTGGCAGACCCGCTAAAAAGG CTTTTTAAACTGGGCAAACCGCTAGCGGCAGGTGACGAACAAGATGAAGATAGAAGACGAGCGCTGGCTGACGAAGTGATCAGATGG CAACGAACAGGGCTAATTGATGAGCTGGAGAAAGCGGTATACTCTAGGTACGAAGTGCAGGGTATATCAGTTGTGGTAATGTCCATGG CCACCTTTG CAAGCTCCAG ATCCAACTTCG AG AAG CTCAG AG G ACCCGTCATAACTTTGTACGG CG GTCCTAAATAG GTACG CACTACAG CTACCTATTTTG CAG AAG CCG ACAG CAAGTATCTAAACACTAATCAG CTACAATG G AGTTCATCCCAACCCAAACTTTTTACAATAG GAG GTACCAGCCTCGACCCTGGACTCCGCGCCCTACTATCCAAGTCATCAGGCCCAGACCGCGCCCTCAGAGGCAAGCTGGGCAACTTGCCC AGCTGATCTCAGCAGTTAATAAACTGACAATGCGCGCGGTACCACAACAGAAGCCACGCAGGAATCGGAAGAATAAGAAGCAAAAGCA AAAACAACAGGCGCCACAAAACAACACAAATCAAAAGAAGCAGCCACCTAAAAAGAAACCGGCTCAAAAGAAAAAGAAGCCGGGCCG CAGAGAGAGGATGTGCATGAAAATCGAAAATGATTGTATTTTCGAAGTCAAGCACGAAGGTAAGGTAACAGGTTACGCGTGCCTGGTG GGGGACAAAGTAATGAAACCAGCACACGTAAAGGGGACCATCGATAACGCGGACCTGGCCAAACTGGCCTTTAAGCGGTCATCTAAGT ATGACCTTGAATGCGCGCAGATACCCGTGCACATGAAGTCCGACGCTTCGAAGTTCACCCATGAGAAACCGGAGGGGTACTACAACTG GCACCACGGAGCAGTACAGTACTCAGGAGGCCGGTTCACCATCCCTACAGGTGCTGGCAAACCAGGGGACAGCGGCAGACCGATCTTC GACAACAAGGGACGCGTGGTGGCCATAGTCTTAGGAGGAGCTAATGAAGGAGCCCGTACAGCCCTCTCGGTGGTGACCTGGAATAAA GACATTGTCACTAAAATCACCCCCGAGGGGGCCGAAGAGTGGAGTCTTGCCATCCCAGTTATGTGCCTGTTGGCAAACACCACGTTCCC CTG CTCCCAGCCCCCTTG CACG CCCTG CTG CTACG AAAAG GAACCGGAG G AAACCCTACG CATG CTTG AG G ACAACGTCATG AG ACCTG G GTACTATCAG CTG CTACAAG CATCCTTAACATGTTCTCCCCACCGCCAG CGACG CAG CACCAAG G ACAACTTCAATGTCTATAAAG CCA CAAGACCATACTTAGCTCACTGTCCCGACTGTGGAGAAGGGCACTCGTGCCATAGTCCCGTAGCACTAGAACGCATCAGAAATGAAGCG ACAGACGGGACGCTGAAAATCCAGGTCTCCTTGCAAATCGGAATAAAGACGGATGACAGCCACGATTGGACCAAGCTGCGTTATATGG ACAACCACATGCCAGCAGACGCAGAGAGGGCGGGGCTATTTGTAAGAACATCAGCACCGTGTACGATTACTGGAACAATGGGACACTT CATCCTGGCCCGATGTCCAAAAGGGGAAACTCTGACGGTGGGATTCACTGACAGTAGGAAGATTAGTCACTCATGTACGCACCCATTTC ACCACGACCCTCCTGTGATAGGTCGGGAAAAATTCCATTCCCGACCGCAGCACGGTAAAGAGCTACCTTGCAGCACGTACGTGCAGAGC ACCGCCGCAACTACCGAGGAGATAGAGGTACACATGCCCCCAGACACCCCTGATCGCACATTAATGTCACAACAGTCCGGCAACGTAAA GATCACAGTCAATGGCCAGACGGTGCGGTACAAGTGTAATTGCGGTGGCTCAAATGAAGGACTAACAACTACAGACAAAGTGATTAAT AACTGCAAGGTTGATCAATGTCATGCCGCGGTCACCAATCACAAAAAGTGGCAGTATAACTCCCCTCTGGTCCCGCGTAATGCTGAACTT GGGGACCGAAAAGGAAAAATTCACATCCCGTTTCCGCTGGCAAATGTAACATGCAGGGTGCCTAAAGCAAGGAACCCCACCGTGACGT ACGGGAAAAACCAAGTCATCATGCTACTGTATCCTGACCACCCAACACTCCTGTCCTACCGGAATATGGGAGAAGAACCAAACTATCAA GAAGAGTGGGTGATGCATAAGAAGGAAGTCGTGCTAACCGTGCCGACTGAAGGGCTCGAGGTCACGTGGGGCAACAACGAGCCGTAT AAGTATTGGCCGCAGTTATCTACAAACGGTACAGCCCATGGCCACCCGCATGAGATAATTCTGTATTATTATGAGCTGTACCCCACTATG ACTGTAGTAGTTGTGTCAGTGGCCACGTTCATACTCCTGTCGATGGTGGGTATGGCAGCGGGGATGTGCATGTGTGCACGACGCAGAT GCATCACACCGTATGAACTGACACCAGGAGCTACCGTCCCTTTCCTGCTTAGCCTAATATGCTGCATCAGAACAGCTAAAGCGGCCACAT ACCAAGAGGCTGCGATATACCTGTGGAACGAGCAGCAACCTTTGTTTTGGCTACAAGCCCTTATTCCGCTGGCAGCCCTGATTGTTCTAT GCAACTGTCTGAGACTCTTACCATGCTGCTGTAAAACGTTGGCTTTTTTAGCCGTAATGAGCGTCGGTGCCCACACTGTGAGCGCGTACG AACACGTAACAGTGATCCCGAACACGGTGGGAGTACCGTATAAGACTCTAGTCAATAGACCTGGCTACAGCCCCATGGTATTGGAGATG GAACTACTGTCAGTCACTTTGGAGCCAACACTATCGCTTGATTACATCACGTGCGAGTACAAAACCGTCATCCCGTCTCCGTACGTGAAG TGCTGCGGTACAGCAGAGTGCAAGGACAAAAACCTACCTGACTACAGCTGTAAGGTCTTCACCGGCGTCTACCCATTTATGTGGGGCGG CGCCTACTGCTTCTGCGACGCTGAAAACACGCAGTTGAGCGAAGCACACGTGGAGAAGTCCGAATCATGCAAAACAGAATTTGCATCAG CATACAGGGCTCATACCGCATCTGCATCAGCTAAGCTCCGCGTCCTTTACCAAGGAAATAACATCACTGTAACTGCCTATGCAAACGGCG ACCATGCCGTCACAGTTAAGGACGCCAAATTCATTGTGGGGCCAATGTCTTCAGCCTGGACACCTTTCGACAACAAAATTGTGGTGTACA AAGGTGACGTCTATAACATGGACTACCCGCCCTTTGGCGCAGGAAGACCAGGACAATTTGGCGATATCCAAAGTCGCACACCTGAGAGT AAAGACGTCTATGCTAATACACAACTGGTACTGCAGAGACCGGCTGTGGGTACGGTACACGTGCCATACTCTCAGGCACCATCTGGCTT TAAGTATTGGCTAAAAGAACGCGGGGCGTCGCTGCAGCACACAGCACCATTTGGCTGCCAAATAGCAACAAACCCGGTAAGAGCGGTG AACTGCGCCGTAGGGAACATGCCCATCTCCATCGACATACCGGAAGCGGCCTTCACTAGGGTCGTCGACGCGCCCTCTTTAACGGACAT GTCGTGCGAGGTACCAGCCTGCACCCATTCCTCAGACTTTGGGGGCGTCGCCATTATTAAATATGCAGCCAGCAAGAAAGGCAAGTGTG CGGTGCATTCGATGACTAACGCCGTCACTATTCGGGAAGCTGAGATAGAAGTTGAAGGGAATTCTCAGCTGCAAATCTCTTTCTCGACG G CCTTAG CCAG CG CCG AATTCCG CGTACAAGTCTGTTCTACACAAGTACACTGTGCAG CCG AGTG CCACCCCCCG AAG G ACCACATAGT CAACTACCCGGCGTCACATACCACCCTCGGGGTCCAGGACATCTCCGCTACGGCGATGTCATGGGTGCAGAAGATCACGGGAGGTGTG G G ACTG GTTGTTG CTGTTG CCG CACTG ATTCTAATCGTG GTG CTATGCGTGTCGTTCAG CAGG CACTAACTTG ACAATTAAGTATG AAG G TATATGTGTCCCCTAAGAGACACACTGTACATAGCAAATAATCTATAGATCAAAGGGCTACGCAACCCCTGAATAGTAACAAAATACAAA ATCACTAAAAATTATAAAAACAGAAAAATACATAAATAGGTATACGTGTCCCCTAAGAGACACATTGTATGTAGGTGATAAGTATAGAT CAAAGGGCCGAATAACCCCTGAATAGTAACAAAATATGAAAATCAATAAAAATCATAAAATAGAAAAACCATAAACAGAAGTAGTTCAA AGGGCTATAAAACCCCTGAATAGTAACAAAACATAAAATTAATAAAAATCAAATGAATACCATAATTGGCAAACGGAAGAGATGTAGGT ACTTAAGCTTCCTAAAAGCAGCCGAACTCACTTTGAGAAGTAGGCATAGCATACCGAACTCTTCCACGATTCTCCGAACCCACAGGGACG TAGGAGATGTTATTTTGTTTTTAATATTTCAAAAAAAAAAAAAAAAAAAAAAAA

SEQ I D NO: 2 Amino acid sequence of E2 protein from LR2006_OPY1 Chikungunya virus strain— amino acids 339-742 from structural polyprotein GenBank Accession: ABD95938.1 (1-1248 aa)

STKDNFNVYKATRPYLAHCPDCGEGHSCHSPVALERIRNEATDGTLKIQVSLQIGIKTDDSHDWTKLRYMDNHMPADAERAGLFVRTSAPCTI

TGTMGHFILARCPKGETLTVGFTDSRKISHSCTHPFHHDPPVIGREKFHSRPQHGKELPCSTYVQSTAATTEEIEVHMPPDTPDHTLIVISQQSG NVKITVNGQTVRYKCNCGGSNEGLTTTDKVINNCKVDQCHAAVTNHKKWQYNSPLVPRNAELGDRKGKIHIPFPLANVTCRVPKARNPTVTY

GKNQVIMLLYPDHPTLLSYRNMGEEPNYQEEWVMHKKEVVLTVPTEGLEVTWGNNEPYKYWPQLSTNGTAHGHPHEIILYYYELYPTIVITVV VVSVATFILLSMVGMAAGIVICIVICARRRCITPYELTPGATVPFLLSLICCIRTAKA

Claims

1. A method of preventing or treating a Chikungunya virus (CHIKV) infection and/or Chikungunya virus-associated disease in an immunocompromised subject, comprising administering to said subject an immunoprotective dose of an immunogenic CHIKV composition, wherein an immunoprotective dose is defined as a dose sufficient to elicit a neutralizing immune response in the subject which reduces or prevents signs or symptoms of Chikungunya virus disease.

2. The method according to claim 1 wherein said immunogenic CHIKV composition comprises a subunit antigen, such as a protein antigen or nucleic acid encoding a protein antigen, a viruslike particle (VLP), an inactivated virus, a virus-vectored antigen or a live -attenuated CHIKV virus.

3. The method according to claim 2, wherein said nucleic acid encoding a protein antigen is a DNA or RNA molecule, preferably an RNA molecule, especially an mRNA molecule.

4. The method according to claim 1 wherein said immunogenic CHIKV composition comprises a CHIKV -A5nsP3 particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1, wherein at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with the amino acid sequence according to SEQ ID NO: 2, and wherein 1-50% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2.

5. The method according to claim 1 wherein said neutralizing immune response which reduces or prevents signs or symptoms of Chikungunya virus disease is defined by the production of serum neutralizing antibodies, wherein said antibodies are capable of neutralization of Chikungunya virus in an in vitro assay of at least 50%, preferably at least 60%, preferably at least 70%, more preferably at least 80%, even more preferably at least 90%, most preferably at least 95% at a 1:80 or higher serum dilution.

6. The method according to the preceding claims wherein said signs and symptoms of Chikungunya virus-associated disease includes one or more of fever, headache, joint pain, skin rashes, peritonitis, encephalitis and secondary infections.

7. The method according to any one of the preceding claims, wherein said immunoprotective dose is defined as at least 10², at least 10³, at least 10⁴, at least 10⁵, at least 10⁶, preferably at least 10³ CHIKV-A5nsP3 particles which express an E2 structural protein as defined by the amino acid sequence of SEQ ID NO: 2.

8. The method according to claim 7, wherein the CHIKV-A5nsP3 particle number is measured in plaque -forming units (pfii) determined using a TCID50 assay in Vero cells.

9. The method according to any one of the preceding claims, wherein said immunocompromised subject is a human.

10. The method according to any one of the preceding claims, wherein said immunocompromised subject suffers from a disease or condition that affects the immune system, such as an acute or chronic disease or condition.

11. The method according to claim 10, wherein said disease or condition is any of the primary immunodeficiency disorders or inborn errors of immunity as disclosed herein, e.g., as listed in Figure 1.

12. The method according to claim 10, wherein said disease or condition is an acquired immunodeficiency disorder, preferably any of the acquired immunodeficiency disorders disclosed herein.

13. The method according to any one of the preceding claims, wherein said immunocompromised subject is moderately immunocompromised, i.e., having an intact, but weakened, immune response compared with a healthy subject.

14. The method according to any one of the preceding claims, wherein the subject has at least one condition selected from the group consisting of: suffering from a hematologic malignancy, undergoing immunosuppressive therapy, receiving a hematopoietic stem cell transplant, receiving a solid organ transplant, infected with HIV, and suffering from an autoimmune disease.

15. The method according to any one of the preceding claims, wherein the subject has at least one disease or condition selected from the group consisting of bacterial or viral infections; cancers, and other chronic disorders or conditions due to aging, malnutrition, or various drug treatments, such as immunosuppressant, antiretroviral or chemotherapy drug treatments.

16. The method according to any one of the preceding claims, wherein the subject has at least one disease selected from the group consisting of HIV infection, acquired immunodeficiency syndrome (AIDS), chronic heart or lung disorders, congestive heart failure, diabetes mellitus, chronic liver disease, alcoholism, cirrhosis, fatty liver disease, spinal fluid leaks, cardiomyopathy, chronic bronchitis, emphysema, Chronic obstructive pulmonary disease (COPD), blood malignancy, kidney failure, nephrotic syndrome and asthma.

17. The method according to any one of the preceding claims, wherein the subject has at least one disease selected from the group consisting of spleen dysfunction (such as sickle cell disease), lack of spleen function (asplenia), leukemia, multiple myeloma, Hodgkin's disease and lymphoma.

18. The method according to any one of the preceding claims, wherein the subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS).

19. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under therapy, said therapy consisting of taking at least one antiretroviral drug selected from the group consisting of a non-nucleoside reverse transcriptase inhibitor, a protease inhibitor and a nucleoside analog reverse transcriptase inhibitor (e.g. abacavir).

20. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under therapy, said therapy consisting of taking at least three drugs belonging to at least two classes of antiretroviral drugs selected from the group consisting of non-nucleoside reverse transcriptase inhibitor, protease inhibitor and nucleoside analog reverse transcriptase inhibitor (e.g. abacavir).

21. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under therapy, said therapy consisting of taking at least two nucleoside analogue reverse transcriptase inhibitors plus either a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor.

22. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is under highly active antiretroviral therapy (HAART), preferably consisting of a three drug regimen which includes a non-nucleoside reverse transcriptase inhibitor, a protease inhibitor and/or a nucleoside analog reverse transcriptase inhibitor (e.g. abacavir) or a two drug regimen which includes a combination of a non-nucleoside reverse transcriptase inhibitor and a protease inhibitor.

23. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from HIV infection or acquired immunodeficiency syndrome (AIDS) and is not under highly active antiretroviral therapy (HAART), or is not under antiretroviral therapy, or said subject has never been exposed to antiretroviral drugs.

24. The method according to any one of the preceding claims, wherein the immunocompromised subject is a non-viremic HIV infected patient.

25. The method according to any one of the preceding claims, wherein the immunocompromised subject is a viremic HIV infected patient.

26. The method according to any one of the preceding claims, wherein the immunocompromised subject has a CD4⁺ cell count in the range of 350 to 400 cells/pL.

27. The method according to any one of the preceding claims, wherein the immunocompromised subject has a CD4⁺ cell count of >200 cells/pL.

28. The method according to any one of claims 18 to 27, wherein the immunocompromised subject is receiving long-term anti-retroviral therapy (ART); i.e., has been receiving ART for at least 3 months, preferably for at least 6 months, preferably for at least one year.

29. The method according to any one of claims 18 to 28, wherein the immunocompromised subject has an HIV plasma load of HIV RNA <400 copies/mL.

30. The method according to any one of claims 18 to 29, wherein the immunocompromised subject has an HIV plasma load of HIV RNA <50 copies/mL.

31. The method according to any one of claims 18 to 30, wherein the immunocompromised subject is moderately immunocompromised, e.g., such as in Stage Al, A2, Bl or B2 of HIV disease according to the revised CDC classification system for HIV infection from 1993 (outlined in Table A).

32. The method according to any one of the preceding claims, wherein the immunocompromised subject has tuberculosis or a sexually transmitted disease, e. g., syphilis or hepatitis.

33. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from malnutrition.

34. The method according to any one of the preceding claims, wherein the immunocompromised subject is a human adult 55 years of age or older, more preferably a human adult 65 years of age or older.

35. The method according to any one of the preceding claims, wherein the immunocompromised subject is a human adult 70 years of age or older, 75 years of age or older or 80 years of age or older.

36. The method according to any one of the preceding claims, wherein the immunocompromised subject is taking a drug or treatment that lowers resistance to infection, in particular a drug selected from the group consisting of chemotherapy (e.g. cancer drugs), disease-modifying antirheumatic drugs, immunosuppressive drugs after organ transplantation and glucocorticoids.

37. The method according to any one of the preceding claims, wherein the immunocompromised subject is taking an oral immunosuppressant drug selected from the group consisting of: tacrolimus (Prograf), mycophenolate mofetil (CellCept), sirolimus (Rapamune), prednisone, cyclosoporine (Neoral, Sandimmune, Gengraf) and azathioprine (Imuran).

38. The method according to any one of the preceding claims, wherein the immunocompromised subject is taking an immunosuppressant drug selected from the group consisting of: Everolimus, Mycophenolic acid, Corticosteroids (such as Prednisolone or Hydrocortisone), Monoclonal anti-IL-2Ra receptor antibodies (such as Basiliximab or Daclizumab), Antithymocyte globulin (ATG) and Anti -lymphocyte globulin (ALG).

39. The method according to any one of the preceding claims, wherein the immunocompromised subject has undergone organ transplantation, or bone marrow transplantation or cochlear implantation.

40. The method according to any one of the preceding claims, wherein the immunocompromised subject has undergone radiation therapy.

41. The method according to any one of the preceding claims, wherein the immunocompromised subject is a smoker.

42. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from asthma and is treated with oral corticosteroid therapy.

43. The method according to any one of the preceding claims, wherein the immunocompromised subject has a white blood cell count (leukocyte count) below 5 x 10⁹ cells per liter, or below 4 x 10⁹ cells per liter, or below 3 x 10⁹ cells per liter, or below 2 x 10⁹ cells per liter, or below 1 x 10⁹ cells per liter, or below 0.5 x 10⁹ cells per liter, or below 0.3 x 10⁹ cells per liter, or below 0.1 x 10⁹ cells per liter.

44. The method according to any one of the preceding claims, wherein the immunocompromised subject suffers from neutropenia.

45. The method according to any one of the preceding claims, wherein the immunocompromised subject has a neutrophil count below 2 x 10⁹ cells per liter, or below 1 x 10⁹ cells per liter, or below 0.5 x 10⁹ cells per liter, or below 0.1 x 10⁹ cells per liter, or below 0.05 x 10⁹ cells per liter.

46. The method according to any one of the preceding claims, wherein the immunocompromised subject is overweight, obese and/or diabetic.

47. The method according to any one of the preceding claims, wherein the immunocompromised subject is a human male or a human female.

48. A composition for use in a method of immunizing an immunocompromised subject, wherein said composition comprises a A5nsP3-CHIKV particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1, wherein at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with the amino acid sequence according to SEQ ID NO: 2, and wherein 1-50% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2.

49. A composition for use in the manufacture of a medicament for the prevention or treatment of diseases caused by Chikungunya virus in an immunocompromised subject, wherein said composition comprises a CHIKV-A5nsP3 particle comprising an RNA sequence corresponding to the DNA sequence according to SEQ ID NO: 1, wherein at least 30% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with the amino acid sequence according to

SEQ ID NO: 2, and wherein 1-50% of the CHIKV-A5nsP3 particles in the composition comprise an E2 protein with at least one immunogenicity-reducing mutation selected from G55R and E168K in the amino acid sequence of SEQ ID NO: 2.

50. The method or composition for use according to any one of the previous claims, wherein said composition is a vaccine.

51. The method or composition for use according to claim 50, wherein said vaccine is a one-shot vaccine.

52. The method or composition for use according to claim 50 or 51, wherein said vaccine is provided in a lyophilized format.