WO2016184973A1

WO2016184973A1 - Treatment of hiv-infected individuals

Info

Publication number: WO2016184973A1
Application number: PCT/EP2016/061304
Authority: WO
Inventors: Joël Crouzet; Raphaël Ho Tsong Fang
Original assignee: Innavirvax
Priority date: 2015-05-19
Filing date: 2016-05-19
Publication date: 2016-11-24

Abstract

The invention concerns an immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein, for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated ΗIV DNA level in an HIV-infected individual under anti-retroviral treatment.

Description

TREATMENT OF HIV-INFECTED INDIVIDUALS FIELD OF THE INVENTION

This invention relates to the treatment and prevention of HIV or HIV-related conditions in individuals.

BACKGROUND OF THE INVENTION

Among virus-related conditions, AIDS has developed into a worldwide pandemic. More than 30 million people are infected with Human Immunodeficiency Virus (HIV). Current therapies have succeeded in controlling the disease but long-term use of Anti-Retroviral Therapy (ART) is limited due to the nature of the viral replication cycle of those viruses, but also by issues of side effects.

Indeed, HIV-infected cells may persist in an individual even during antiretroviral therapy, due to the persistence of viral reservoirs.

One of the drawbacks of current HIV treatments is that HIV virions start multiplying again as soon as antiretroviral therapy (ART) is interrupted, which typically means daily, life-long treatment for patients.

There is currently evidence to support the existence of at least two distinct reservoirs during therapeutic suppression of HIV replication:

- the presence of latently-infected cells, in particular lymphocytes ; and

-a pool of cells where low-level of ongoing replication occur.

It is believed that the latently-infected cells are at some stage undergoing proliferation and production of the HIV virus leading to residual replication establishing the link between latently infected cells and residual replication (see Maldarelli F et al Science 345, 179 (2014) & Sahu GK, AIDS Res Hum Retroviruses, 31 (1) 25-35). Therefore decreasing the reservoir will lead to the decrease of the residual replication.

Thus, the reason which explains the residual replication in individuals under ART is that HIV is characterized by proviral latency, which is the ability of a virus to lie dormant within a cell. Latency is the phase of the viral replication cycle in which, after initial infection, proliferation of virus particles ceases without full eradication. The phenomenon of proviral latency is associated to the appearance of so-called "reservoirs" within the host, which are generally difficult to reach, and which are also one of the main reasons of the difficulty to provide with a sterilizing cure and / or a functional cure for HIV. It is thus possible to decrease residual replication by decreasing the reservoir.

The persistence of residual HIV replication is thus the reason why in individuals undergoing antiretroviral therapy, the decrease of the reservoir cells should lead to a decrease of residual replication.

Methods and uses for specifically targeting viral reservoirs, including "latent" reservoirs are thus actively pursued, in order to decrease residual replication in HIV- infected individuals.

Kay (Trends Biotechnol; (10):420-3; 2003) teaches that HIV treatment with

ART cannot eliminate latent reservoirs of HIV, and suggests that a compound comprising 5-helix (a gp41 -binding protein) may be useful for specifically killing HIV-infected cells from a broad range of HIV strains.

More recently, a so-called "shock and kill" strategy has been proposed. This strategy has been described by Katlama et al. (Lancet; vol. 381, no 9883; 2109-2117) and consists as a first step in administering compounds suitable for activating viral replication and reversing latency ("shock"). As a second step, this activation may lead to the killing of reactivated cells, either by the virus itself, by the patient's immune system, or by the mean of other antiviral strategy such as CTL therapeutic vaccines ("kill"). Advantageously, such compounds may be used in combination with antiretroviral therapy (ART) in order to avoid infection of previously uninfected cells.

Hill et al. (PNAS; vol. I l l; no.37; 13475-13480; 2014) teaches the use of latency-reversing agents (LRAs) as part of the shock strategy, among which histone deacetylase inhibitors (HDACI).

However there remains a continuing need for compounds acting through new and as yet unexplored mechanisms of action to achieve virological control in the absence of ART or functional cure.

There also remains a need for compounds for use for reducing residual HIV replication in an HIV-infected individual.

In particular there remains a need for compounds which are able to target HIV reservoirs, and/or which are able to prevent their appearance in an individual, even at early stages of the HIV infection. There also remains a need for compounds with no or limited side-effects.

SUMMARY OF THE INVENTION

The invention relates to an immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein, for use for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level in an HIV-infected individual.

In particular, the invention relates to an immunogenic compound as defined above, for reducing residual HIV replication in an HIV-infected individual.

The invention further relates to vaccine compositions comprising said immunogenic compound, for the uses described herein.

Accordingly, the invention relates to a vaccine composition comprising said immunogenic compound, for use for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated ΗΓν DNA level in an HIV-infected individual. BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Immunization Schedule. A. Schedule for three injections (DO, week 4 and week 8) at 0.1 μg and 20 μg of antigenic peptide equivalent. Follow-up visits are scheduled at week 24, week 36 and week 60. B. Schedule for three injections (DO, week 4 and week 8) at 1 μg and 10 μg of antigenic peptide equivalent, and an additional booster injection at week 24. Follow-up visits are scheduled at week 48, week 60, week 72 and week 84.

Figure 2: Dose-dependent Immunogenicity at week 12. The y-axis represents the percentage of each category of patient, depending on whether the anti-3S antibody titer is (light grey) above 31 arbitrary units (AU), or (dark grey) below 30 arbitrary units. From left to right: All doses (N=32); Placebo (N=8); 0.1 μg (N=6) of antigenic peptide equivalent; 1 μg (N=6) of antigenic peptide equivalent; 10 μg (N=6) of antigenic peptide equivalent; 20 μg (N=6) of antigenic peptide equivalent. Dose- dependent evolution over time P = 0.003.

Figure 3: Variation of the HIV DNA from baseline over time at week 60 and 84, in placebo vs non responder vs responder patients. The y-axis represents the HIV DNA change from baseline in log copies per 10⁶ Peripheral Blood Mononuclear Cells (PBMC). From left to right: placebo group, non-responder patients, responder patients. A. At week 60. B. At week 84. C. At week 84. p values of ANOVA test for differences between the groups are shown.

Figure 4: Evolution of HIV DNA per million of PBMCs over time, in Responders vs Non Responders + placebo. The y-axis represents the HIV DNA change from baseline in log copies per 10⁶ Peripheral Blood Mononuclear Cells (PBMC). The x- axis represents time, at 12, 36, 60 and 84 weeks after the first administration of the immunogenic compound. Non Responders + placebos are represented by "o". Responders are represented by "+".p values of ANOVA test for differences between the groups are shown, p corresponds to the significance of the changes from baseline

Figure 5: Anti-3S Dose-Dependent Change of Total HIV DNA over time at week 12, 36, 60 and 84. The y-axis represents the HIV DNA change from baseline in log copies per 10⁶ Peripheral Blood Mononuclear Cells (PBMC). The x-axis represents the anti-3S total antibodies at the corresponding time, expressed in log A.U. A. At week 12. B. At week 36. C. At week 60. D. At week 84. Figure 6: Variation of the CD4/CD8 ratio over time, in placebo vs non responder vs responder patients. The y-axis represents the CD4/CD8 ratio. The x-axis represents for each patient the measurements corresponding, from left to right, to the baseline (week 0) and at week 24. A. Placebo group (p=0,109). B. Non-responder patients (p=0,685). C. Responder patients (p=0,002).

Figure 7: Variation of the CD4 and CD8% at week 24 after injection of the immunogenic compound. A. Variation of the CD4 % in the 20 μg arm at week 24 after 3 administrations of the immunogenic compound at the dose of 20 μg (n=5). B. Variation of the CD 8 % in the 20 μg arm at week 24 after 20 μg injection of immunogenic compound (in of antigenic peptide equivalent) (n=5). C. Variation of the CD4/CD8 ratio in the 20 μg arm at week 24 after 20 μg injection of immunogenic compound (n=5) (in of antigenic peptide equivalent). The amount of immunogenic compounds is expressed in weight of 3S immunogenic peptide present in the vaccine candidate. P values for a one Tailed Wilcoxon Test are shown.

DETAILED DESCRIPTION OF THE INVENTION

The present invention has for purpose to meet the aforementioned needs.

The present invention provides anti-HIV immunogenic compounds, and compositions thereof, comprising antigenic peptides derived from the gp41 protein of HIV, for use for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level in an HIV-infected individual.

The invention relates to such immunogenic compounds, and/or compositions thereof, for use as a medicament; which includes compositions in the form of pharmaceutical compositions and/or vaccine compositions.

The invention also relates to such immunogenic compounds, and/or compositions thereof, for use as a medicament, or for the preparation of a medicament, for for for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated ΗΓ DNA level in an HIV-infected individual.

HIV-1 gp41 is composed of three domains, an extracellular domain (ectodomain), a transmembrane domain and an intracellular domain (endodomain). The gp41 ectodomain contains three major functional regions, i.e., the fusion peptide located at the N-terminus of gp41, followed by two 4-3 heptad repeats adjacent to the N- and C- terminal portions of the gp41 ectodomain, designated NHR (N-terminal heptad repeat) and CHR (C-terminal heptad repeat), respectively.

The N- and C-terminal repeats are also named as "HR1" and "HR2". Both NHR and CHR regions function as essential structures required for conformational changes during the process of membrane fusion between HIV-1 and CD4+ T cells.

WO2013/179262 teaches immunogenic compounds derived from a HIV gp41 peptide, for treating a condition caused by the infection of an individual with a HIV virus. This document showed that such immunogenic compounds were able to raise antibodies having the ability to reduce the NK-induced CD4 T cell lysis in individuals infected with an HIV virus. Vieillard et al. (JAIDS; 61(3):403-5; 2012) reports, in a SEROCO cohort, a correlation between the presence of naturally- occurring antibodies specific to gp41 in individuals and disease progression. It has now been unexpectedly found that immunogenic compounds comprising an antigenic peptide derived from the gp41 protein of a HIV virus can reduce Peripheral Blood Mononuclear Cells (PBMC)-associated ΗΓν DNA levels in HrV-infected individuals.

It has also been shown by the inventors that immunogenic compounds comprising an antigenic peptide derived from the gp41 protein of a HIV virus can maintain or restore T cell homeostasis and thus high level of CD4⁺ T cell count.

Surprisingly, the inventors were able to determine that the administration of those immunogenic compounds in HrV-infected individuals induces a reduction of the total HIV-1 DNA copies in Peripheral Blood Mononuclear Cells (PBMCs), of which the method used for the measurement has been disclosed in Rouzioux et al. ("Quantification of total HIV1-DNA in peripheral blood mononuclear cells"; Methods Mol. Biol; 1087:261-70; 2014).

The total cell- associated HIV DNA has been recently proposed as a standardized clinical marker for measuring HIV reservoirs in HIV-infected individuals. Most noticeably, it has been recently determined that this value represents the global capacity of the reservoirs to produce virus over time.

HIV DNA is a distinct marker from HIV RNA. HIV DNA is expressed as a number of copies per 10⁶ PBMCs, and is indicative of the integration of the HIV genome in cellular "reservoirs", which includes CD4⁺ T cells. HIV-DNA levels are positively correlated to HIV-RNA and negatively to CD4⁺ T cell count in individuals under anti- retroviral treatment. Thus, high HIV DNA is also indicative of the progression to AIDS, and ultimately to death. It is also predictive of progression to immunodeficiency when measured at the time of primary infection.

The inventors have further shown in the examples that the administration of an immunogenic compound comprising an antigenic peptide derived from gp41 in HIV- infected individuals, lead to an increase of the CD4/CD8 ratio in the responder group, 24 weeks after the first injection. The CD4/CD8 is established as an indicator of immune system health, and thus its restoration and/or increase is indicative of immune restoration (Serrano-Villar et al, PLOS Pathogens, vol. 10, 2014).

Indeed, long-term non-progressors and those who start antiretroviral treatment early on generally have a normal CD4/CD8 ratio.

The identification of a novel mechanism of action, in particular the identification of a dual effect on "latent" reservoirs in HrV-infected individuals coupled with immune restoration, allows for novel therapeutic strategies, as well as efficient treatment of novel groups of patients with an immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein that is described in the present specification.

The HIV-infected individuals which are specifically considered by the invention, at the time of the administration of said immunogenic compound are- individuals under anti-retroviral treatment.

According to a first embodiment, the invention relates to an immunogenic compound comprising an antigenic peptide derived from the gp41 protein of an HIV virus, for use for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level in an HIV-infected individual under anti-retroviral treatment.

The immunogenic compound can be administered to HIV-infected individuals in combination with, or in complement to the said anti-retroviral treatment.

The immunogenic compound is being administered to said HIV-infected individual for a time suitable for establishing an antibody response in said individual.

In general, the determination of an antibody response can be established by determining the presence in said individual of antibodies directed against the said antigenic peptide.

The detection of an antibody response directed against the said antigenic peptide derived from the HIV gp41 protein may be conventionally performed, for example by using an ELISA assay. Preferably, the results of the ELISA assay are analyzed against a control curve generated by using a serial of an ti- antigenic peptide antibodies at known dilutions or at known concentrations.

As used herein, the term "comprising" encompasses "consisting of. As used herein, the terms "patient" and "individual" encompass humans and non-human animals, which includes non-human mammals, and/or any organism that is prone to HIV infection.

As used herein, « preventing » also encompasses « reducing the likelihood of occurrence » or « reducing the likelihood of reoccurrence ».

As used herein the expressions "increased' and "decreased' are understood as relative values, determined based on a reference value established before in a same or similar individual, for instance at a previous stage of the disease. They may be determined over a variable length of time, as long as such length is clinically significant for assessing a variation in said individual.

As used herein the "HIV viral load" or "HIV viral titer" generally refers to:

- the number of copies of HIV RNA per mL of a plasma sample;

- the number of HIV particles per mL of a plasma sample; and/or

- the activity or concentration of a HIV-related protein in a plasma sample, which may for example include determining the reverse transcriptase (RT) activity in said plasma sample.

The HIV viral load test is used primarily to monitor HIV infection over time. It is generally a quantitative measurement of HIV nucleic acid (RNA) that reports how many copies of the virus are present in the blood.

As used herein, the term "residual HIV replication" relates to the replication of HIV in HIV-infected individuals under anti-retroviral treatment, said individuals being further characterized by a low or undetectable viral load, optionally below 40 copies of HIV RNA per mL of a plasma sample.

According to a particular embodiment, the invention relates to an immunogenic compound comprising an antigenic peptide derived from the gp41 protein of an HIV virus, for reducing residual HIV replication in said individual.

According to one particular embodiment, the invention relates to an immunogenic compound comprising an antigenic peptide derived from the gp41 protein of an HIV virus for its use as defined above, for reducing the number of latently-infected cells, in particular lymphocytes, including CD4+ cells in said individual. As used herein, an "anti-retroviral agent" or "anti-retroviral treatment", or more specifically an "anti-HIV agent" or "anti-HIV treatment" relates to the administration of a compound, or combination of compounds, for acting against an HIV infection.

Accordingly, an "individual under anti-retroviral treatment" relates to HIV- infected individuals who have been administered, or alternatively who are being administered at least one drug in the context of an anti-retroviral treatment for treating said HIV infection, thereby defining a reference anti-retroviral treatment.

An individual under anti-retroviral treatment further includes HIV-infected individuals for whom a reference anti-retroviral treatment is being modified, or reduced, (i.e. in the context of a structured or strategic treatment interruption).

An anti-retroviral treatment generally comprises the administration of at least one drug selected from: ART (Antiretroviral Therapy), and HAART (Highly Active Antiretroviral Therapy).

ART and HAART are known in the Art and generally relate to combinations of two, three or more antiretroviral medicines. Such antiretroviral medicines encompass:

(i) nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) also called nucleoside analogs, such as abacavir, emtricitabine, and tenofovir;

(ii) non-nucleoside reverse transcriptase inhibitors (NNRTIs), such as efavirenz, etravirine, and nevirapine;

(iii) protease inhibitors (Pis), such as atazanavir, darunavir, and ritonavir;

(iv) entry inhibitors, such as enfuvirtide and maraviroc;

(v) integrase inhibitors, such as dolutegravir and raltegravir.

Examples of anti-retroviral treatments include, in a non-limitative manner, the administration of at least one drug selected from: Zidovudine, Lamivudine, Emtricitabine, Didanosine, Stavudine, Abacavir, Zalcitabine, Tenofivir, Racivir, Amdoxovir, Apricitabine, Elvucitabine, Efavirenz, Nevirapine, Etravirine, Delavirdine, Rilpvirine, Tenofovir, Fosalvudine, Amprenavir, Tipranavir, Indinavir, Saquinavir, Fosamprenavir, Ritonavir, Darunavir, Atazanavir, Nelfinavir, Lopinavir, Raltegravir, Elvitegravir, Dolutegravir, Enfuvirtide, Maraviroc, Vicriviroc, and combinations thereof. In particular, it may be an HIV-infected individual under anti-retroviral treatment, wherein said anti-retrovival treatment comprises the administration of at least one drug selected from: ART (Antiretroviral Therapy) and HAART (Highly Active Antiretro viral Therapy).

Advantageously, the immunogenic compounds of the invention can be administered to an HIV-infected individual under anti-retroviral treatment characterised by:

- a low or decreased viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound; and/or

- a high or increased CD4+ cell count, optionally above 350 per mm³ of blood plasma at the time of the administration of said immunogenic compound; and/or

- a low or decreased Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level, optionally below 1000 copies per 10⁶ PBMCs, at the time of the administration of said immunogenic compound.

According to a second embodiment, the invention relates to a vaccine composition, comprising at least one immunogenic compound comprising an antigenic peptide derived from the gp41 protein of an HIV virus.

Accordingly, the invention relates to a vaccine composition comprising said immunogenic compound, for use for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated ΗΓν DNA level in an HIV-infected individual.

An immunogenic compound comprising an antigenic peptide derived from the gp41 protein of a HIV virus can also be used for the preparation of any composition, in particular any pharmaceutical composition and/or vaccine composition for a use as defined above.

Groups of HIV-infected individuals and immunogenic compounds which are more particularly considered will be described herebelow. HIV-infected individuals

As used herein, the term "HIV infection" encompasses the infection of a host animal, particularly a human host, by the HIV virus, including type 1 human immunodeficiency virus (HIV-1). "HIV" may include HIV-I, HIV-2 and all forms, subtypes, clades and variations thereof, which includes HIV-I strains belonging to the HIV-I B subtype, HIV-I C subtype, and HIV-I recombinants.

According to exemplary embodiments, the HIV virus is HIV-I.

"HIV-1 " can be used herein to refer to any strains, forms, subtypes, clades and variations in the HIV-1 family.

As used herein, the term « HIV-related condition » encompasses any symptom or set of symptoms commonly found in HIV-infected patients, including symptoms belonging to conditions associated with AIDS (Acquired Immune Deficiency Syndrome).

A carrier of HIV-1 may be identified by any methods known in the art. For example, a person can be identified as an HIV-1 carrier on the basis that the person is anti- HIV-1 antibody positive, or is HIV-1 -positive, or has symptoms of AIDS. That is, "treating HIV-1 infection" should be understood as treating a patient who is at any one of the several stages of HIV infection progression, in particular HIV-1, infection progression.

There are at least three main stages of HIV infection which define at least three sub-groups of HIV-infected individuals.

The first stage is referred herein as the "acute infection stage, or the "acute primary infection syndrome" (which can be asymptomatic or associated with an influenza- like illness with fevers, malaise, diarrhoea and neurologic symptoms such as headache). This stage generally corresponds to the period which extends from day 1 to about 1 to 3 months after HIV infection. During this early period, large amounts of virus are produced, thereby increasing the viral load (or HIV RNA level) in the HIV-infected individual. During this stage the CD4 cell count may also decrease rapidly to low levels. Then, by the end of the acute infection phase, the viral load (or HIV RNA) may decrease back to low levels. The median of HIV-DNA levels in individuals with a primary infection is generally higher than at a chronic state.

As used herein, a "primo-infected" individual refers in particular to an HIV- infected individual in the early stages of the infection, who has generally been contaminated within a period of less than one year, which includes less than 6 months or even less than 3 months. According to some embodiments, the HIV-infected individual is a primo- infected individual.

The second stage is referred herein as the "clinical latency stage" or "asymptomatic infection". This stage generally corresponds to the stage where the HIV- infected individual is asymptomatic, and where the disease enters into its chronic state. However, the HIV virus continues to reproduce at detectable levels. The viral load (or HIV RNA) generally remains stabilized and the CD4+ T cell count gradually declines. This stage is highly variable in length, and depends on multiple factors, such as the nature of the HIV strain, the efficacy of a treatment, host factors and so on. It may last for years, in particular if the individual is under antiretroviral treatment.

The third stage is referred herein as the "AIDS phase". It corresponds to the symptomatic stage, wherein the HIV-infected individual exhibits an HIV -related condition, including symptoms belonging to the condition that is generally known as AIDS. It also corresponds to the stage, where the viral load increases up to high levels, while the CD4⁺ T cell count drops below the level of 200 cells/mm³. This stage also corresponds to a life-threatening stage, in the absence of treatment.

All the HIV-infected individuals belonging to the above-mentioned stages are considered by the invention. The HIV-infected individuals can be further characterized based on distinct biological markers at the time of the administration of said immunogenic compound.

The HIV-infected individuals who are particularly considered are individuals characterized by:

- a low or decreased Peripheral Blood Mononuclear Cells (PBMC)-associated

HIV DNA level, optionally below 1000 copies per 10⁶ PBMCs, at the time of the administration of said immunogenic compound. Preferably, the "HIV viral load" relates to the number of copies of HIV RNA per mL of blood plasma and is expressed in HIV RNA copies per mL of blood plasma, according to known methods, which includes nucleic acid-based tests such as reverse- transcriptase polymerase chain reaction (RT-PCR), branched DNA (bDNA), or nucleic acid sequence-based amplification (NASBA) analysis.

In general, a HIV viral load test is ordered when a person is first diagnosed. The test results function as a baseline measurement that shows how actively the virus is reproducing. The HIV viral load test is then performed over time and compared to said baseline measurement or to a reference value, in order to assess a relative variation of the HIV viral load.

Accordingly, conventional methods for determining HIV viral load include: (i) providing a whole blood sample obtained from a patient;

(ii) removing cells from the sample by centrifugation to provide plasma;

(iii) determining the number of copies of HIV RNA per milliliter of plasma, for example, by reverse-transcriptase polymerase chain reaction (RT-PCR), branched DNA (bDNA), or nucleic acid sequence-based amplification (NASBA) analysis.

(iv) optionally comparing the result obtained at step (iii) with a reference value and/or a baseline measurement.

If an individual has a high HIV viral load (for example, at least or above 1000 or even 10000 ΗΓ RNA copies/mL plasma), this may indicate treatment failure and/or viral rebound, i.e. that the virus is replicating and the disease may progress more quickly. If the HIV RNA level is low (for example, below 500 copies/mL of plasma), this indicates that the anti-retroviral treatment regimen is effective, i.e. that the virus may not be actively replicating and the disease may progress more slowly.

A low viral load is usually below 500 HIV RNA copies/mL of plasma; which includes below 350 HIV RNA copies /mL of plasma, depending on the type and sensitivity of the test that is used. This result indicates that HIV is not actively reproducing and that the risk of disease progression is low. A low viral load may consist of a viral load below 500 HIV RNA copies/mL of plasma; which includes below 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1 copies/mL.

A high viral load may consist of a viral load above 1000 HIV RNA copies/mL of plasma; which includes above 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 and 10000 copies/mL of plasma.

An undetectable viral load for routine methods is generally below 40 copies/mL of plasma, which includes below 20 copies/mL of plasma, in particular when measured with a method and/or kits selected from: COBAS® AmpliPrep/COBAS® TaqMan® HIV-1 Test and COBAS® AMPLICOR HPZ-l MONITOR Test sold by Roche Molecular Diagnostic or NucliSENS EasyQ®HIV-l sold by Biomerieux Diagnostics.

However, an undetectable viral load in a patient with diagnosed HIV infection does not mean that the patient is cured; it means only that the level of HIV RNA is currently below the limit of detection of the technique. What is more, an undetectable viral load does not necessarily rule out the presence of HIV in latent reservoirs.

Changes in viral load are generally more important during HIV monitoring than obtaining a single test result. An increasing viral load indicates either that the infection is getting worse or that the virus has developed resistance to the drugs that are being used for therapy and are no longer effective. A decreasing viral load indicates improvement, treatment effectiveness, and a decrease in HIV replication.

For reference, a restored CD4+ T cell count may correspond to a physiological (or "normal") CD4+ T cell count, which is generally equal or superior to 350 CD4+ cells/mm³ of plasma, which generally ranges from 350 to 1500 CD4+ T cells/mm³ of plasma, which generally ranges from 500 to 1500 CD4+ T cells/mm³ of plasma, though it may be lower for some individuals.

Alternatively a restored CD4+ T cell count may correspond to an increase in the CD4+ T cell count, compared to the CD4+ T cell count in said patient prior to said treatment. Accordingly, a low CD4+ T cell count includes a CD4+ T cell count inferior to 500 / mm³ in blood plasma, which includes inferior to 450; 350; 300; 250; 200; 150 and 100 / mm³ in blood plasma.

Accordingly, a high CD4+ T cell count includes a CD4+ T cell count superior to 500 / mm³ in blood plasma, which includes superior to 500; 600; 700; 800; 900; 1000; 1100; 1200; 1300; 1400 and 1500CD4+ T cells/mm³ of plasma.

A low PBMC-associated HIV DNA level may thus consist of an HIV DNA level below 1000 HIV DNA copies per million of PBMCs; which includes below 500 HIV DNA copies per million of PBMCs; which includes below, 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1 copie(s) per million of PBMCs.

PBMCs are known in the Art and refer to blood cells having a round nucleus, which includes lymphocytes (including T cells), monocytes and macrophages.

Protocols for isolating PBMCs are known in the Art.

According to exemplary embodiments, PBMCs are separated from whole blood on Ficoll-Hypaque so as to obtain a PBMC extract; the amount of total DNA is then quantified by real-time PCR from said PBMC extract.

For reference, the PBMC-associated ΗΓ DNA level is preferably determined according to the protocols disclosed in Rouzioux et al. ("Quantification of total ΗΓνΐ- DNA in peripheral blood mononuclear cells"; Methods Mol. Biol; 1087:261-70; 2014), and as further detailed in the Material & Methods section.

HIV-DNA levels are then reported in copies per million of PBMCs for total DNA extracted from PBMCs isolated by Ficoll-Hypaque.

According to some embodiments, the HIV-infected individual is characterized by a low or decreased viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound.

According to some embodiments, the HIV-infected individual is characterized by a low or decreased Peripheral Blood Mononuclear Cells (PBMC)-associated ΗΓ DNA level, optionally below 1000 copies per 10⁶ PBMCs, at the time of the administration of said immunogenic compound. According to some embodiments, the HIV-infected individual is characterized by a high CD4+ cell count, optionally above 350 per mm³ of blood plasma at the time of the administration of said immunogenic compound.

Each one of the above-mentioned parameters defines one sub-group of HIV- infected individual in the course of treatment interruption. However, those groups are not mutually exclusive, and can be further combined.

According to some embodiments, HIV-infected individual is characterized by: -a low or decreased viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound; and

- a high CD4+ cell count, optionally above 350 per mm³ of blood plasma at the time of the administration of said immunogenic compound.

According to some embodiments, HIV-infected individuals is characterized by:

-a low or decreased viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound; and

- a high CD4+ cell count, optionally above 350 per mm³ of blood plasma at the time of the administration of said immunogenic compound; and

- a low or decreased Peripheral Blood Mononuclear Cells (PBMC)-associated

HIV DNA level, optionally below 1000 copies per 10⁶ PBMCs, at the time of the administration of said immunogenic compound.

According to some embodiments, the invention relates to an immunogenic compound as defined above, for reducing residual HIV replication; wherein said individual is under anti-retroviral treatment and is further characterized by:

- a low or undetectable viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound; which includes below 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1 HIV RNA copies/mL of blood plasma. Immunogenic compounds and compositions thereof

Immunogenic compounds of the invention consist of compounds comprising an antigenic peptide derived from the gp41 protein of a HIV virus.

Advantageously, the antigenic peptide is a peptide derived from the gp41 protein and located between the N-terminal hep tad repeat 1 (HRl) and the HR2 regions.

For reference, the peptide sequence SEQ ID N°l is provided, which corresponds to an antigenic peptide fragment of gp41 located between the N-terminal heptad repeat 1 (HRl) and the HR2 regions.

Even more advantageously, the antigenic peptide is a peptide derived from the gp41 protein, and comprising at least one fragment of gp41 derived from the amino acid sequence SEQ ID N°l or 2; or of a functionally equivalent sequence thereof.

In particular, the immunogenic compound comprises an antigenic peptide derived from the gp41 protein of a HIV virus; said antigenic peptide comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 (preferably consecutive) amino acids from the amino acid sequence SEQ ID N°l, or of a functionally equivalent sequence thereof.

According to some more particular embodiments, the antigenic peptide is a peptide derived from the gp41 protein and located between the HRl and HR2 regions, and comprising at least 1, 2, 3, 4, 5 or 6 amino acids of the well-conserved 3S motif, also referred herein as the "SWSNKS" motif (SEQ ID N°2) when considering a reference gp41 protein isolated from HIV strains, including naturally- occurring and non-naturally occuring HIV strains, such as R5 and X4 HIV-1 strains.

Due to the variability of retroviruses such as HIV, antigenic peptides derived from the gp41 protein of strains obtained from HIV-infected patients are considered as functionally equivalent sequences in the sense of the invention, such as the ones disclosed in Curriu et al. (« Viremic HIV infected individuals with high CD4 T cells and functional envelope proteins show anti-gp41 antibodies with unique specificity and function; PLoS one ;7(2) ; 2012). According to some more particular embodiments, the antigenic peptide derived from the gp41 protein of a HIV virus, as defined above, comprises the amino acid sequence:

NH2-S-X2-S-N-X3 -X4-COOH,

wherein

- X₂ is selected from the group consisting of W (Tryptophane) and A (Alanine),

- X3 is selected from the group consisting of K (Lysine) and R (Arginine),

- X₄ is selected from the group consisting of S (Serine) and T (Threonine) According to some embodiments, the antigenic peptide derived from the gp41 protein of a HIV virus, as defined above, comprises at least 6 consecutive amino acids derived from the said gp41 protein, which includes at least 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 consecutive amino acids derived from the said gp41 protein, or of a functionally equivalent sequence thereof.

According to some particular embodiments, the antigenic peptide derived from the gp41 protein of a HIV virus, as defined above, comprises from 5 to 100 amino acids of the said gp41 protein; which includes 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67? 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 and 100 amino acids.

The antigenic peptide derived from the gp41 protein of a HIV virus as defined above, is preferably at least 6 amino acids long.

Immunogenic compounds suitable for the invention are notably disclosed in WO2004/070385, WO2005/076001, WO 2012140620 and WO2013/179262.

According to a preferred embodiment, the immunogenic compound is a compound as defined above, wherein the said antigenic peptide derived from gp41 is of the formula (I) :

PepNt- CORE-PepCt (I),

wherein: - "PepNt" consists of a polypeptide having an amino acid length varying from 0 to 20 amino acid residues and located at the N-terminal end of the polypeptide of formula (I);

- CORE consists of a polypeptide comprising the amino acid sequence:

NH2-S-X2-S-N-X3 -X4-COOH,

wherein

- X3 is selected from the group consisting of K (Lysine) and R (Arginine),

- X₄ is selected from the group consisting of S (Serine) and T (Threonine), and

- "PepCt" consists of a polypeptide having an amino acid length varying from 0 to 20 amino acid residues and located at the C-terminal end of the polypeptide of formula (I).

According to some embodiments, the antigenic peptide derived from the gp41 protein of a HIV virus, as defined above, or alternatively the CORE of said antigenic peptide of formula (I), comprises the amino acid sequence selected from:

NH2-SWSNKS-COOH (SEQ ID N° 2),

NH2-SASNKS-COOH (SEQ ID N° 3),

NH2-S WANKS- COOH (SEQ ID N° 4),

NH2-SWSAKS- COOH (SEQ ID N° 5),

NH2-SWSNKA- COOH (SEQ ID N° 6).

In certain embodiments of the antigenic peptide derived from gp41 of formula (I), « PepNt » consists of a peptide having from 1 to 10 amino acid residues in length, which includes from 1 to 5 amino acid residues in length. Thus, according to these embodiments, Nt is a peptide having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid residues in length.

In certain embodiments of the antigenic peptide derived from gp41 of formula (I), « PepNt » comprises or consists of the amino acid sequence NH2-PWNA-COOH (SEQ ID N°7).

In certain embodiments of the antigenic peptide derived from gp41 of formula (I), « PepCt » consists of a peptide having from 1 to 10 amino acid residues in length, which includes from 1 to 5 amino acid residues in length. Thus, according to these embodiments, Ct is a peptide having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid residues in length. In some embodiments, Ct has 5 or 6 amino acid residues in length. In certain embodiments of the antigenic peptide derived from gp41 of formula (I), « PepCt » comprises or consists of the amino acid sequence NH2-LDDIW-COOH (SEQ ID N° 8).

More preferably, the said antigenic peptide is of the following formula (II) : NH₂- [Nt]_y-P-W-N-Xi-S-X₂-S-N-X₃ -X4-X5-X6-X7-I-W-[Ct]_z-COOH (II), wherein:

- y is an integer meaning 0 or 1,

- z is an integer meaning 0 or 1,

- Nt consists of a peptide having from 1 to 16 amino acids in length,

- Ct consists of a peptide having from 1 to 15 amino acids in length,

- Xi is an amino acid selected from the group consisting of A (Alanine), T (threonine), S (Serine) and N (Asparagine),

- X₂ is an amino acid selected from the group consisting of W (Tryptophane) and A (Alanine),

- X₃ is selected from the group consisting of K (Lysine) and R (Arginine),

- X₄ is selected from the group consisting of S (Serine) and T (Threonine),

- X5 is selected from the group consisting of L (Leucine), Y (Tyrosine) and Q (Glutamine),

- X₆ is selected from the group consisting of D (Aspartic acid), N (Asparagine), E (Glutamic acid), S (Serine), G (Glycine) and K (Lysine),

- X7 is selected from the group consisting of D (Aspartic acid), Q (Glutamine), L (Leucine), A (Alanine), K (Lysine) and E (Glutamic acid).

For example, the antigenic peptide derived from gp41 may comprise at least one fragment of any one of any one of 3S regions of gp41 disclosed in Curriu et al. ("Viremic HIV infected individuals with high CD4 T cells and functional envelope proteins show anti-gp41 antibodies with unique specificity and function"; PLoS one ;7(2) ; 2012), especially in Table 1 and Figure 3A of Curriu. genie peptide may be selected from the group consisting of:

NH₂-(Al)_m- PWNASWSNKSLDDr -(A2)_n-COOH (Ilia), NH₂-(Al)_m- PWNASASNKSLDDr -(A2)_n-COOH (Illb), NH₂-(Al)_m- PWNSSWSNKSYEQIW -(A2)_n-COOH (IIIc),

NH₂-(Al)_m- PWNTSWSNKTLNDIW -(A2)_n-COOH (Hid), NH₂-(Al)_m- PWNASWSNKSLNDr -(A2)_n-COOH (Hie), NH₂-(Al)m- PWNTSWSNKSYHEr -(A2)_n-COOH (Illf), NH₂-(Al)m- PWNASWSNKSLDEr -(A2)_n-COOH (Illg),

NH₂-(Al)m- PWNSSWSNKSYEQRV -(A2)_n-COOH (Illh), NH₂-(Al)m- PWNSSWSNKSYKQIW -(A2)_n-COOH (Illi), NH₂-(Al)m- PWNSSWSNKSQKQIW -(A2)_n-COOH (Illj), NH₂-(Al)m- PWNSSWSNKTYNDIW -(A2)_n-COOH (Illk), NH₂-(Al)m- PWNASWSNKSLNDrW -(A2)_n-COOH (III1),

NH₂-(Al)m- PWNASWSNRSLNDIW -(A2)_n-COOH (Illm), NH₂-(Al)m- PWNASWSNKSLNAIW -(A2)_n-COOH (Illn), NH₂-(Al)m- PWNTSWSNKSYNKIW -(A2)_n-COOH (IIIo), NH₂-(Al)m- PWNTSWSNKSYNEIW -(A2)_n-COOH (IIIp), NH₂-(Al)m- PWNASWSNRTLGDrW -(A2)_n-COOH (Illq),

NH₂-(Al)m- PWNASWGNRTLGDIW -(A2)_n-COOH (Illr), NH₂-(Al)m- PWNTSWSNKSLSQrW -(A2)_n-COOH (Ills), NH₂-(Al)m- PWNTSWSNKSLNQTW -(A2)_n-COOH (lilt), NH₂-(Al)m- PWNTSWSNKSYNLIW -(A2)_n-COOH (IIIu), NH₂-(Al)m- PWNNSWSNKSYNLIW -(A2)_n-COOH (IIIv),

NH₂-(Al)m- PWNSSWSNKSIEARV -(A2)_n-COOH (IIIw), wherein :

- m is an integer meaning 0 or 1,

- n is an integer meaning 0 or 1,

- Al is an amino acid residue, and

- A2 is an amino acid residue.

Even more preferably, the antigenic peptide is selected from the group consisting of the following formulae (Ilia) and (Illb) :

NH₂-(Al)m- PWNASWSNKSLDDrW -(A2)_n-COOH (Ilia),

NH₂-(Al)m- PWNASASNKSLDDrW -(A2)_n-COOH (Illb), wherein : - m is an integer meaning 0 or 1,

- n is an integer meaning 0 or 1,

- Al is an amino acid residue, and

- A2 is an amino acid residue.

Advantageously, the immunogenic compound further includes amino acids which are not derived from gp41.

The C- and/or N-terminal ends of a peptide of formula (I) could deviate from the natural sequences expressly specified herein by modification of the terminal NH₂- group and/or COOH-group and/or by modification of a NH₂ group and/or a COOH group of a lateral chain of an amino acid residue contained therein. These groups may for instance be acylated, acetylated, amidated or modified to provide a binding site for a carrier molecule.

For example, amino acids may be added to the N-terminal end of the antigenic peptide such as cysteines.

Most preferably, the immunogenic compound comprises an antigenic peptide selected from the group consisting of

C-PWNASWSNKSLDDIW (SEQ ID NO 9), and

C-PWNASASNKSLDDIW (SEQ ID NO 10)

The 3S peptide of SEQ ID N°9 was previously identified as a candidate anti-

HIV antigen by Vieillard et al. (Vieillard et al., 2008, PNAS, Vol. 105 (6) : 2100-2104).

Advantageously, any one of the above-mentioned antigenic peptides is linked to a carrier molecule.

The types of carrier molecules used for generating an immunogenic product comprising a polypeptide of formula (I) linked to a carrier molecule are well in the general knowledge of the one skilled in the art. The function of the carrier molecule is to provide cytokine help (or T-cell help) in order to enhance the immune response against HIV- 1.

The carrier molecule to which the peptide is optionally bound can be selected from a wide variety of known carriers. Examples of carrier molecules for vaccine purposes encompass proteins such as human or bovine serum albumin and keyhole limpet haemocyanin (KLH) and fatty acids. Other embodiments of carrier molecules to which an antigenic peptide of formula (I) may be covalently linked include bacterial toxins or toxoids, such as diphtheria, cholera, E. coli heat labile or tetanus toxoids, the N. meningitidis outer membrane protein (European patent application n° EP0372501), synthetic peptides (European patent applications n° EP0378881 and n° EP0427347), heat shock proteins (PCT application n° W093/17712), Pertussis proteins (PCT application n° W098/58668), protein D from H. influenzae (PCT application n° WO00/56360.) and toxin A or B from C. difficile (International patent application WO00/61761).

According to a particular embodiment, the carrier molecule is an amine- containing carrier protein.

Any suitable conjugation reaction can be used, with any suitable linker where necessary.

Preferably, the antigenic peptide is covalently bound to the carrier molecule by its N-terminal end amino acid residue.

Most preferably, the carrier molecule is a CRM 197 protein, of sequence SEQ ID N°ll, as described for instance in WO2013/179262.

For reference, the CRM 197 protein consists of a non-toxic mutant of the well- known diphtheria toxin, which mutant was initially described by Uchida et al. (1973, J. Biol. Chem., Vol. 248 : 3838-3844). The CRM197 mutant protein was initially described as the translation product of the mutant tox97 gene where a G—A transition led to the substitution of the glycine (G) residue at position 52 of the wild-type diphtheria toxin with a glutamic acid residue (E).

According to the invention, the amount of antigenic peptide linked to one carrier molecule, such as CRM 197, is measured preferably by Amino Acid Analysis. This method is the methodology conventionally used to determine the amino acid composition of proteins. Proteins are macromolecules consisting of covalently bonded amino acid residues organized as a linear polymer. The peptide bonds are broken upon incubation under acid condition leading to the release of amino acids. An amino acid analysis is then performed on the product of the hydrolysis.

According to the present invention, Amino Acid Analysis is preferably used to determine the rate of coupling of the antigenic peptide on a carrier molecule such as CRM 197. This was possible since some amino acids may be both present on the carrier molecule and the grafted peptides and others may be only present on the carrier molecule. Based on the results of the amino acids present, a calculation allowed to determine the coupling ratio of the peptide of formula (I) onto CRM 197.

Typically, after hydrolysis of the conjugate between a carrier molecule such as CRM 197 and antigenic peptides, the amino acids present in the test samples are separated by reverse phase high pressure liquid chromatography (RP-HPLC). Usually, this instrument has a pre- or post-column derivatization capability and the detector is an ultraviolet-visible or fluorescence detector depending on the derivatization method used. An integrator is used for the transforming the analog signal from the detector and for quantitation of each amino acid. (Amino acid analysis of peptide loading ratios in conjugate vaccines: a comparison of electrochemical detection and 6-aminoquinolyl-N- hydroxysuccinimidyl carbamate pre-column derivatization methods Nahas DD et al Bioconj Chem 2008 Jan 19(1) 322-6 Epub 2007 dec 12). The amount of peptides of formula (I) which are linked to one molecule of CRM 197 can also be measured by mass spectrometry analysis.

According to a reference method, the quantification of the peptide -protein conjugates is performed by integration of the monomer peak at 215 nm obtained by isocratic SE-HPLC in 50 mM phosphate buffer pH6.8 using a Phenomenex column (BioSep SEC S2000) at a defined flow.

Optionally, the determination of the protein content can also be made by BCA assay using the BCA Protein Assay Kit (Thermo Scientific). This kit is a detergent- compatible bicinchoninic acid formulation for the colorimetric detection and quantification of total protein. BSA is used as the reference material in the protein determination. Absorbance at 562nm is linear with increasing protein concentrations. Also preferably, the said antigenic peptide is covalently bound to the carrier molecule through a linker moiety.

The said restricted family of linker agents encompasses, or even consists of, the linker agents named GMBS, sulfo-GMBS, SMPB and sulfo-SMPB.

Thus, in some preferred embodiments of an immunogenic compound as defined above, the said linker agent is selected form the group consisting of GMBS (Ν-[γ- maleimidobutyryl-oxy]succinimide ester), Sulfo-GMBS (N-[y-maleimidobutyryl- oxy]sulfosuccinimide ester), SMPB (succinimidyl 4-[/?-maleimidophenyl]butyrate) and Sulfo-SMPB (sulfosuccinimidyl 4-[/?-maleimidophenyl]butyrate).

Methods for conjugating two proteins with a linker agent in general, and more particularly with a linker agent selected from the group consisting of GMBS, Sulfo- GMBS, SMPB and Sulfo-SMPB, are well known by the one skilled in the art. Illustratively, such protocols are disclosed in the leaflets that are made publicly available by the Pierce Company (Illinois, Etats-Unis). GMBS, Sulfo-GMBS, SMPB and Sulfo-SMPB consist of heterobifunctional linker agents that contain both a N- hydroxysuccinimide (NHS) ester group and a maleimide group. Conjugation using GMBS, Sulfo-GMBS, SMPB or Sulfo-SMPB is usually performed by a two-step procedure. In a first step, the amine-containing protein (e.g. CRM197) is reacted with a several-fold molar excess of the linker agent at pH 7-9 to form amide bonds, followed by removal of excess non-reacted linker agent, usually by desalting or dialysis. In a second step, the sulfhydryl-containing molecule (e.g. peptide of formula (I)) is added to react with the maleimide groups already attached to the first protein (e.g. free maleimide groups of the linker chain that is already covalently linked to CRM197) at pH 6.5-7.5 to form stable thioether bonds.

Using SMPB or Sulfo-SMPB as linker agents for covalently linking peptides of formula (I) to the amine-containing carrier protein, in particular the CRM 197 carrier protein, leads to a conjugate of formula (VII) below:

(VII),

wherein :

- Rl consists of one reactive group of the amine-containing carrier protein, and wherein the NH group attached thereto derives from (i) the alpha amino group located at the N-terminal end of the amine-containing carrier protein or (ii) a lateral chain amino group from a Lysine (K) amino acid residue of the amine-containing carrier protein. - R2 consists of a peptide of formula (I), and wherein the sulphur (S) atom attached thereto derives from a sulfhydryl (SH) group of a cysteine residue located at the N-terminal end or at the C-terminal end of a peptide of formula (I). In some embodiments, the sulfhydryl moiety could be part of an unnatural amino acid, or any other molecule present at the end of the peptide of formula (I).

Using GMBS or Sulfo-GMBS as linker agents for covalently linking peptides of formula (I) to the amine-containing carrier protein, in particular the CRM 197 carrier, protein leads to a conjugate of formula (VIII) below:

wherein :

- Rl consists of one reactive group of the amine-containing carrier protein, and wherein the NH group attached thereto derives from (i) the alpha amino group located at the N-terminal end of the amine-containing carrier proteinor (ii) a lateral chain amino group from a Lysine (K) amino acid residue of the amine-containing carrier protein.

- R2 consists of a peptide of formula (I), and wherein the sulphur (S) atom attached thereto derives from a sulfhydryl (SH) group of a cysteine residue located at the N-terminal end or at the C-terminal end of a peptide of formula (I). In some embodiments, the sulfhydryl moiety could be part of an unnatural amino acid, or any other molecule present at the end of the peptide of formula (I).

As it is known in the art, an amine-containing carrier protein such as the CRM197 protein, comprises a plurality of reactive groups Rl, so that a plurality of peptides of formula (I) may be linked to CRM 197 in a conjugate of formula (VII) or (VIII).

Thus, most preferred embodiments of an immunogenic compound as defined above are those wherein a plurality of reactive groups of the amine-containing carrier protein, in particular CRM 197, are covalently linked to an antigenic peptide, which peptide generally possesses a cysteine residue at its N-terminal end, according to the covalent linkage represented by formula (VII) or (VIII) above.

In some embodiments of an immunogenic compound as defined above, a mean number of antigenic peptides ranging from 2 to 20 are covalently linked to one molecule of CRM 197. In preferred embodiments, a mean number of from 5 to 10 antigenic peptides, which includes a mean number of from 7-8 peptides of formula (I), are covalently linked to one molecule of CRM 197.

This invention also relates to compositions comprising an immunogenic compound as defined above, in combination with one or more immunoadjuvant substances.

A composition as defined herein which comprises an immunogenic compound as defined above, and which further comprises one or more immuno-adjuvant substances, may also be termed an "immunogenic composition" or alternatively a "vaccine composition" in the present specification.

In some embodiments, there is no substantial distinction to be made between an immunogenic composition according to the invention and a vaccine composition according to the invention, beyond the terms employed to designate such compositions, excepted that the features of the vaccine composition shall comply with the technical requirements of the various drug agencies for the grant of marketing authorizations for human or veterinary use.

Instead, an immunogenic composition according to the invention may not comply to the requirements of drug agencies while being usable for administration to animals, e.g. for producing antibodies in a given individual, wherein the generated antibodies are expected to exert a preventive or a therapeutic effect in the HIV-infected individual.

Thus, compositions according to the invention encompass both (i) immunogenic compositions and (ii) vaccine compositions.

Compositions according to the invention are disclosed as such, but also for uses as defined above.

In some embodiments of an immunogenic composition or of a vaccine composition as defined herein, an immunoadjuvant may be selected form the group consisting of (i) mineral salts, (ii) emulsions, (iii) microbial natural or synthetic derivatives, (iv) combination adjuvants, (v) cytokine-derived or accessory molecules- derived adjuvants, and (vi) particulate formulations.

Accordingly, lists of suitable immunoadjuvants have been described in the Art, and especially in WO2013/179262 which provides a complete list of immunoadjuvants suitable for preparing compositions of the invention.

In a non-limitative manner, emulsion-based immunoadjuvants are also selected from the group consisting of Montanide™ (SEPPIC) adjuvants, including Montanide ISA 51 which is a water- in-oil stabilized emulsion, and (4) ISA-720 which is a stabilized composition comprising water and squalene.

The formulation of such immunogenic compositions is well known to persons skilled in the art. Immunogenic compositions of the invention preferably include a pharmaceutically acceptable carrier. Suitable pharmaceutically acceptable carriers and/or diluents include any and all conventional solvents, dispersion media, fillers, solid carriers, aqueous solutions, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like. Suitable pharmaceutically acceptable carriers include, for example, one or more of water, saline, phosphate buffered saline, dextrose, glycerol, ethanol and the like, as well as combinations thereof. Pharmaceutically acceptable carriers may further comprise minor amounts of auxiliary substances such as wetting or emulsifying agents, preservatives or buffers, which enhance the shelf life or effectiveness of the antibody. The preparation and use of pharmaceutically acceptable carriers is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, use thereof in the immunogenic compositions of the present invention is contemplated. Such immunogenic compounds, and compositions thereof, can be administered parenterally, e.g., by injection, either by subcutaneous, intradermal or intramuscular route, as well as orally or intranasally. Other modes of administration employ oral formulations, pulmonary formulations, suppositories, and transdermal applications, for example, without limitation. Oral formulations, for example, include such normally employed excipients as, for example, pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate, and the like, without limitation.

According to exemplary embodiments, the immunogenic compounds, and compositions thereof, are administered parenterally, and most preferably intramuscularly.

As used herein, an amount of antigenic peptide is expressed as "antigenic peptide equivalent" , which consists of the amount of antigenic peptide that is contained in the considered immunogenic compound material.

In view of the above, when the antigenic peptide is coupled to a carrier molecule, the antigenic peptide equivalent only corresponds to the amount of antigenic peptide present and does not include the amount of other ingredients that are effectively administered.

In certain embodiments, an immunogenic compound, or composition thereof, used according to the invention comprises an antigenic peptide of the invention in an amount which is adapted to the administration of from 10 ng to 10 mg of the said antigenic peptide to an individual in need thereof, when expressed as an antigenic peptide equivalent.

An equivalent amount of an antigenic peptide of from 10 ng to 10 mg encompasses an amount of peptide of about 20 ng, 30 ng, 40 ng, 50 ng, 60 ng, 70 ng, 80 ng, 90 ng, 100 ng, 150 ng, 200 ng, 250 ng, 300 ng, 350 ng, 400 ng, 450 ng, 500 ng, 550 ng, 600 ng, 700 ng, 800 ng, 900 ng, 1 μg, 2 μg, 3 μg, 4 μg, 5 μg, 6 μg, 7 μg, 8 μg, 9 μg, 10 μg, 20 μg, 30 μg, 40 μg, 50 μg, 60 μg, 70 μg, 80 μg, 90 μg, 100 μg, 110 μg, 120 μg, 130 μg, 140 μg, 150 μg, 160 μg, 170 μg, 180 μg, 190 μg, 200 μg, 250 μg, 300 μg, 350 μg, 400 μg, 450 μg, 500 μg, 550 μg, 600 μg, 650 μg, 700 μg, 750 μg, 800 μg, 850 μg, 900 μg, 950 μg and 1 mg.

Said amounts may also be referred herein as a « dose ».

Preferably, the antigenic peptide is administered in an equivalent amount ranging from l μg to 80 μg.

In some embodiments, the equivalent amount of antigenic peptide may be of about 1 μg, 5 μg, 10 μg, 20 μg, 30 μg, 40 μg, 50 μg, 60 μg, 70 μg, or 80 μg. In certain embodiments, an immunogenic compound, or composition thereof, used according to the invention comprises an antigenic peptide of the invention in an equivalent amount which is adapted to multiple parenteral administrations, which includes 1, 2, 3, 4, 5 and 6 administrations, and preferably 6 doses per year. The first cycle is composed of three administrations every 4 weeks.

Advantageously, the immunogenic compound, or composition thereof, is administered, as a booster injection, about every 12 weeks after the first cycle, which includes being administered, as a booster injection, in a period ranging from 8 to 48 weeks after the latest administration, which includes 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 and 48 weeks after.

According to some embodiments, the immunogenic compound is administered parenterally, for example intramuscularly, in 3 to 6 administrations, and preferably 6 doses within a year, wherein the fourth, fifth and sixth administration is administered, as a booster injection, in a period ranging from 8 to 48 weeks after the latest administration.

The immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein is administered to the HIV-infected individuals at a time period when the anti-retroviral treatment is also administered. As described elsewhere herein, the administration of the said immunogenic compound raises, in said HIV-infected individuals, an antibody response directed against the antigenic peptide derived from the gp41 protein, which antibody response has been shown by the inventors to cause a reduction in the PBMC-associated DNA, and thus a reduction of the HIV reservoir in the said HIV-infected individuals.

In some embodiments, the said immunogenic compound is administered only once.

However, as it is known in the art, the raising of a relevant antibody response often requires at least two administration of the immunogenic compound of interest. In some other embodiments, the said immunogenic compound is administered a plurality of times.

According to some of these other embodiments, the said immunogenic compound is administered a number of times ranging from 2 to 6.

Illustratively, according to these other embodiments, the said immunogenic compound may be administered twice, with the second administration being performed about four weeks subsequent to the first administration.

Illustratively, according to these other embodiments, the said immunogenic compound may be administered three times, with the second administration being performed about four weeks subsequent to the first administration and the third administration being performed about four weeks subsequent to the second administration

Illustratively, according to these other embodiments, the said immunogenic compound may be administered according to the following treatment schedule :

- TO : lrst administration of the immunogenic compound,

- T1 = T0 + about four weeks : 2^nd administration of the immunogenic compound,

- T2 = Tl + about four weeks :3^rd administration of the immunogenic compound,

- T3 = T2 + about twelve weeks : 4^th administration of the immunogenic compound,

- T4 = T3 + about twelve weeks :5^th administration of the immunogenic compound, and

- T5 = T4 + about twelve weeks: 6^th administration of the immunogenic compound.

As it is well known in the art, maintaining an immune response against an antigen, and herein against an antigenic peptide derived from the HIV gp41 protein, may require timely booster administration of an immunogenic compound comprising the said antigen.

Thus, in some embodiments, the immunogenic compound comprising the antigenic peptide derived from the gp41 protein may be administered at appropriate time intervals.

According to these embodiments, one or more subsequent administrations of the immunogenic compound comprising the antigenic peptide derived from the gp41 protein may be performed at time intervals ranging from 3 months to 24 months, which includes at time intervals ranging from 6 months to 12 months.

In some embodiments, the HIV-infected individual is subject to a regular monitoring of one or more of the following physiological parameters including (i) the level of PBMC-associated HIV DNA, (ii) the level of the HIV RNA and (iii) the level of CD4+ T cells.

In some embodiments, a further administration of an immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein may be decided in the HIV-infected individuals when one or more of the following physiological changes is detected or determined:

- an increase of the level of PBMC-associated HIV DNA as compared to a previous measurement of this parameter in the said HIV-infected individual,

- an increase in the HIV RNA level as compared to a previous measurement of this parameter in the said HIV-infected individual, and

- a decrease in the level of CD4+ T cells as compared to a previous measurement of this parameter in the said HIV-infected individual,

The said further administration of the immunogenic compound that is decided is aimed at maintaining or increasing the immune response against the antigenic peptide derived from the HIV gp41 protein and thus maintaining or increasing the viral control by the HIV-infected individual.

Because, as it is shown in the examples herein, the administration of an immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein drastically reduce the PBMC-associated ΗΓ DNA level, the inventors believe that the administration of the said compound may lead, at least for some of the HIV-infected individuals treated therewith, to a total eradication of the HIV virus and thus to a complete cure to the said individuals.

The immunogenic compound may be administered alone or in combination with other compounds, including Latency Reversing Agents (LRA) or compounds that have either a shock, or a kill effect, and compounds behaving as immune boost.

The immunogenic compound may also be administered in combination with Latency Reversing Agents (LRA), such as agents can be selected in a group consisting of histone deacetylase inhibitors (HDACi), including romidepsin, panobinostat, vorinostat, givnostat, belinostat, sirtuin inhibitors, NF-KB-inducing agents, protein kinase C agonists, T cell activators and TLR agonists, immune checkpoint inhibitors selected in a group comprising PD-1 inhibitors and PDL-1 inhibitors (including Pembrolizumab, Nivolumab, Pidilizumab, BMS 936559, MPDL3280A), LAG-3 inhibitors, TIGIT inhibitors, and CTLA-4 inhibitors, pro-apoptotic and cell differentiating molecules including JQ1, Nutlin3, Disulfiram, aphidicolin, Wnt small molecules inhibitors and Notch inhibitors.

The immunogenic compound may also be administered in combination with at least one drug selected from one or more immunotherapy inducing an HIV-antigen specific immune response with either a Thl and or a Th2 type immune response, and other immunotherapies acting more as immune boost and including IL-15, IL-7 or revlimid could be also used in synergy. The present invention is illustrated by, without being limited to, the examples hereafter.

EXAMPLES

Methods for preparing immunogenic compounds derived from the gp41 protein, and compositions thereof, have been disclosed in WO2012140620 and WO2013/179262. Relevant parts of the Material & Method sections are further reported herein for reference.

Example 1. Preparation of an immunogenic compound derived from gp41, and compositions thereof.

A. Preparation of immunogenic compounds

The following immunogenic compounds or conjugates were synthesized. There were derived from KLH and CRM 197 using either MBS or SMPB as crosslinker molecules. The used peptide was the 3S peptide consisting of SEQ ID N°2 with either an additional cysteine residue at its amino-terminus end or at its carboxy-terminus end.

- CRM197-MBS-Nter(Cys)- 3S

- CRM197-SMPB-Nter(Cys)- 3S

- CRM197-SMPB-Cter(Cys)- 3S

- KLH-MBS-Nter(Cys)- 3S

For the sake of clarity, the peptide which is termed "Nter(Cys)-3S" above comprises the 3S reference peptide of SEQ ID N°2 herein. Two heterobifunctional cross-linkers were tested: sulfo-SMPB (Sulfo- (Succinimidyl-4-(p-maleimidophenyl) Butyrate) and sulfo-MBS (Sulfo-(m- Maleimidobenzoyl-N-hydroxysuccinimide) ester). These molecules consist of a maleimide moiety linked by a polyethylene chain to an ester of N-hydroxysuccinimide (Cross-linking of protein by w-maleimido alkanoyl N-hydroxysuccinimido esters. Partis M.D and al. Journal of Protein Chemistry, vol.2, No 3, 1983). The succinimide moiety can react with amino groups of the protein. Once this reaction has occurred, the maleimide moiety reacts with sulfhydryl groups of the 3S peptides. They are different in length, 7,3 A for sulfo-

MBS and 11.6 A for sulfo-SMPB. The linker elimination and buffer exchange were made by size exclusion chromatography (SEC).

The coupling reaction was a two-step reaction. The first step was the activation of the CRM 197 with the cross-linker. 15 milligrams of linker, diluted in dimethyl sulfoxide were added to 20 milligrams of CRM 197 in a volume of 5-20 mL of conjugation buffer (PBS 10 mM pH 7-pH 7.4) and mixed gently for 30-90 min at room temperature (Protective immunogenicity of two synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit SI. Askelof P. and al. PNAS, vol.87, pp 1347-1351, February 1990). This reaction was followed by a purification of the activated CRM 197 by SEC (PD10 column (GE Healthcare, Chalfont St. Giles United Kingdom) or Bio-Gel P2 column (Biorad Marnes-la-Coquette, France)). Secondly, the activated CRM 197 and the 3S-derived peptide were mixed for 30 min - 2 hours at room temperature allowing the covalent coupling of the peptide onto the activated CRM 197. To block unreacted maleimide groups of activated CRM197, cystein-HCl (SIGMA, Missouri, USA) is added in excess to the solution after the conjugation reaction (A practical approach to crosslinking. Mattson G. and al. Molecular Biology Reports 17: 167-183, 1993). This step limited the creation of multimers. The immuno-conjugates were then purified by size exclusion chromatography. The immuno-conjugates were analyzed using an amino acid analysis (AAA) to determine the peptide/CRM197 ratio. The CRM197-3S peptide was lyophilized with a lyoprotector (Lyophilisation and development of solid protein pharmaceuticals. Wang W. International Journal of Pharmaceutics 203 (2000) 1- 60; Fundamentals of freeze-drying. Nail S.L and al. Pharm Biotechnol. 2002; 14:281-360). B. Preparation of injectable compositions/vaccine

VAC-3S is a sterile suspension for intramuscular injection containing the 3S drug substance adsorbed on aluminium hydroxide in buffered isotonic saline. The manufacturing of VAC-3S was performed in compliance with the GMP.

To obtain VAC-3S, the 3S drug substance is formulated at concentrations ranging from 1 to 40 μg/mL of 3S16Nter peptide equivalent with aluminium hydroxide (1 mg/mL of Al³⁺ ions) provided by Brenntag (Alhydrogel 85 2%-Ph Eur), 150 mM sodium chloride (European pharmacopoeia) and 1 mM sodium phosphate (European pharmacopoeia). Products for injection are used for the formulation of the vaccine. The final pH is at 6.8. VAC-3S contains no preservative.

C. Injection

After shaking, the vaccine is a homogeneous white suspension ready to use. If needed to achieve the needed concentration of 3S16Nter the vaccine is diluted in aluminium hydroxide (1 mg/mL of Al³⁺ ions) provided by Brenntag (Alhydrogel 85 2%- Ph Eur), 150 mM sodium chloride (European pharmacopoeia) and 1 mM sodium phosphate (European pharmacopoeia), equilibrated at pH 6.8. The vaccine could be injected intramuscularly in the deltoid. A sterile syringe with sterile needle is used for injection. Patients should receive at least 6 doses of 0.5 mL each, with a minimum interval of 2 to 4 weeks between vaccinations.

Example 2. Preparation of an immunogenic compound derived from gp41, and compositions thereof, for clinical use.

A. Preparation of immunogenic compounds

The following immunogenic compound or conjugate was synthesized. It was derived from CRM 197 using SMPB as crosslinker molecule (as shown in example 1). The used peptide was a mutated 3S (m3S) peptide consisting of SEQ ID N°13 (NH₂- PWNASASNKSLDDrW-COOH) with an additional cysteine residue at its amino- terminus end to allow the chemical coupling the cross linker leading to CRM197-SMPB- Nter(Cys)-m3S

For the sake of clarity, the peptide which is termed "Nter(Cys)-m3S" above consists of the 3S peptide of SEQ ID N°14 herein. The heterobifunctional cross-linker sulfo-SMPB (Sulfo-(Succinimidyl-4-(p- maleimidophenyl) Butyrate) was used. These molecules consist of a maleimide moiety linked by a polyethylene chain to an ester of N-hydroxysuccinimide (Cross-linking of protein by w-maleimido alkanoyl N-hydroxysuccinimido esters. Partis M.D and al. Journal of Protein Chemistry, vol.2, No 3, 1983). The succinimide moiety can react with amino groups of the protein. Once this reaction has occurred, the maleimide moiety reacts with sulfhydryl groups of the 3S peptides. They are different in length, 7,3 A for sulfo-

The coupling reaction was a two-step reaction. The first step was the activation of the CRM 197 with the cross-linker. 15 milligrams of linker, diluted in dimethyl sulfoxide were added to 20 milligrams of CRM 197 in a volume of 5-20 ml of conjugation buffer (PBS 10 mM pH7-pH7.4) and mixed gently for 30-90 min at room temperature (Protective immunogenicity of two synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit SI. Askelof P. and al. PNAS, vol.87, pp 1347-1351, February 1990). This reaction was followed by a purification of the activated CRM 197 by SEC (PD10 column (GE Healthcare, Chalfont St. Giles United Kingdom) or Bio-Gel P2 column (Biorad Marnes-la-Coquette, France)). Secondly, the activated CRM 197 and the 3S-derived peptide were mixed for 30 min - 2 hours at room temperature allowing the covalent coupling of the peptide onto the activated CRM 197. To block unreacted maleimido groups of activated CRM197, cystein-HCl (SIGMA, Missouri, USA) is added in excess to the solution after the conjugation reaction (A practical approach to crosslinking. Mattson G. and al. Molecular Biology Reports 17: 167-183, 1993). This step limited the creation of multimers. The immuno-conjugates were then purified by size exclusion chromatography. The immuno-conjugates were analyzed using an amino acid analysis (AAA) to determine the peptide/CRM197 ratio.

B. Properties of these immunogenic compounds

The immuno-conjugate obtained and corresponding to the m3S peptide of SEQ ID N° 9 which comprises a Cys residue at the N-terminal end, the CRM 197 carrier and SMPB as a linker was found spontaneously soluble in water or in 0.9% NaCl solution. C. Preparation of vaccine

The immuno-conjugate compounds tested have been prepared as disclosed in Example 1. VAC-3S is a sterile suspension for intramuscular injection containing the 3S drug substance adsorbed on aluminium hydroxide in buffered isotonic saline. The manufacturing of VAC-3S was performed in compliance with the GMP.

To obtain VAC-3S, the 3S drug substance is formulated at the concentration of 0.02 mg/mL of 3S16Nter peptide, comprising the antigenic peptide of sequence SEQ ID N°9, equivalent in 0.5 mL with aluminium hydroxide (1 mg/mL of Al³⁺ ions) provided by Brenntag (Alhydrogel 85 2 -Ph Eur), 150 mM sodium chloride (European pharmacopoeia) and 1 mM sodium phosphate (European pharmacopoeia). Products for injection are used for the formulation of the vaccine. The final pH is at 6.8. VAC-3S contains no preservative.

D. Immunisation Schedule and Injection

After shaking, the vaccine is a homogeneous white suspension ready to use.

The vaccine could be injected intramuscularly in the deltoid. A sterile syringe with sterile needle is used for injection. Patients should receive at least 6 doses of 0.5 mL each, with a minimum interval of 2 to 4 weeks between vaccinations.

The immunogenicity of such immuno-conjugates was further studied, and their effect on HIV latent "reservoirs" assessed. Doses of 0.1 μg; 1 μg; 10 μg; and 20 μg have been considered for each tested group, along with the placebo group.

The four patient populations are further detailed in Table 1 here below.

The administration protocol is also detailed in figures 1A and IB. Table 1. Demographic characteristics in study groups

Patient

Dose 1^§ Dose 2^§ Dose 3^§ Dose 4^§ Placebo Disposition

0.1 1 10 μ_§ 20 μ_§ Adj.

Mean +/- SD

(N=6) (N=6) (N=6) (N=6) (N=9*)

Gender M/F 6/0 5/1 6/0 5/1 7/2*

Age (years) 41 +/- 8 48 +/- 6 44 +/- 5 41 +/- 8 49 +/- 6

Weight (kg) 74 +/- 12 75 +/- 12 71 +1- 1 70 +/- 14 75 +/- 10 Body Mass

25 +/- 5 24 +/- 4 24 +/- 1 23 +/- 2 25 +/- 5 Index

Patients who

received 3 6 6 6 6 8 administrations

Nadir CD4 335 +/- 60 330 +/- 145 459 +/- 229 318 +/- 101 298 +/- 97

CD4 at day 0

759 +/- 194 640 +/ 193 734 +/- 145 592 +/- 169 655 +/- 141 (cells/mm³)

* N=8; 7 M / 1 F for modified As Treated (mAI population ( patient replaced after 1^st vaccination).

^§ antigenic peptide equivalent Example 3. Assessment of the dose-dependent immunogenicity at week 12 based on the amount of immunogenic compound that is administered.

A. Material & Methods.

1. ELISA assay for determiner antibody titers.

The ELISA assay was designed to perform the measurement of total Ig antibodies that would recognize the peptides of SEQ ID N°9, also called anti-3S peptide antibodies.

The anti-3S IgG antibody titers were determined by an Enzyme-Linked Immunosorbent Assay (ELISA).

Eight dilutions were tested (1/3000, 1/6000, 1/12000, 1/24000, 1/48000, 1/96000, 1/192000, and 1/384000). The antigen coated to the Nunc Maxisorp micro plates is a 3S peptide conjugated to bovine serum albumin (BSA) with a different linker than the one used for the synthesis of the immuno-conjugates: SMCC (succinimidyl-4-(N- maleimidomethyl)cyclohexane-l-carboxylate) (produced from Imject® Maleimide Activated BSA Protein Kits purchased from Thermo Fisher Scientific, Waltham, USA) . The anti-m3S IgG antibodies are revealed by a colorimetric reaction using a goat anti- mouse IgG (Fc), conjugated to the HorseRadish Peroxydase (HRP) (Jackson Immunoresearch, West Grove, USA), and the HRP substrate: the tetramethylbenzidine (TMB) (Sigma, Missouri, USA). 2. Determination of CD4+/CD8+ T cell counts from whole blood samples. B. Results

Results are provided in figure 2, which show that the percentage of responsive patients increases with a higher amounts of immunogenic compounds, at week 12.

Results further show in figure 6 that, at week 24, the CD4+/CD8+ ratio significantly increases in responders (N=l l) when compared to non-responders + placebo (N=21). The increase is due both to a statistically (P<0.05) significant increase in CD4⁺ T cell count and to a statistically significant decrease in CD8⁺ T cell count.

This result provides evidence towards immune restoration in the responder group, when compared to the non-responder group.

Indeed, studies have shown that, in HIV-infected individuals, a low CD4/CD8 ratio during otherwise effective ART (after CD4 count recovery above 500 cells/mm³) is associated with a number of immunological abnormalities (see for reference Serrano- Villar et al. \ PLoS Pathogens; 10(5); 2014).

Example 4. Assessment of HIV DNA Baseline and variation over time in responsive and non-responsive groups.

A. Material & Methods.

1. Assessment of the HIV DNA level from PBMCs.

The HIV DNA level is measured using the protocols described in Rouzioux et al. ("Quantification of total HIV1-DNA in peripheral blood mononuclear cells"; Methods Mol. Biol; 1087:261-70; 2014). The HIV DNA level can be expressed either in log copies per 10⁶ PBMC cells or in log copies per mL of whole blood. 1.1 Isolation of total DNA from patient EDTA blood samples.

Aliquots of PBMC pellets are stored at -80°C until use. The total DNA is isolated from PBMC (Peripheral Blood Mononuclear Cells). PBMC pellets are prepared by Ficoll-Hypaque gradient, while cell pellets are obtained from whole blood after centrifugation (2,500 rpm, 10 min) and plasma decantation. Purified CD4+ T cells, cell pellet, or even whole blood can be used.

Total DNA is extracted from PBMCs using a QIAamp DNA mini kit (QIAGEN, Courtaboeuf, France) according to the manufacturer's instructions, to obtain 100 μΐ_^ of eluate. The kit NucleoSpin® Blood (Macherey-Nagel) is preferred for DNA extraction from cell pellets and whole blood samples.

The procedure is standardized in order to obtain an absolute quantification of HIV-DNA as described in Rouzioux et al. ("Quantification of total HIV 1 -DNA in peripheral blood mononuclear cells"; Methods Mol. Biol; 1087:261-70; 2014).

Figures 3 to 5 report HIV-DNA levels corresponding to HIV-DNA in copies per million of PBMCs for total DNA extracted from PBMCs isolated by Ficoll-Hypaque. Figure 6 reports the corresponding value but expressed in copies per mL of whole blood.

2. Assessment of the Anti-3S antibody titer

The protocol is set up as described previously.

B. Results.

Figure 3 provides evidence of a decrease in the HIV-DNA levels in the responder group at weeks 60 and 84, which thus provides evidence of a decrease in the HIV latent reservoirs.

The results correlate inversely with the anti-3S antibody titers (see figures 5 to 7), which thus suggests that the decrease in HIV viral "reservoir" is associated with the immunogenic response after administration of the immunogenic compound.

In particular, Figure 4 reports that the HIV-DNA level is decreased in the

Responders group at week 60 (p=0.06) and week 84 (p=0.001), which thus establishes a link between the antigenic response provoked by the administration of the immunogenic compound and the decrease in HIV reservoirs. This link is confirmed by Figures 5 A, 5B, and 5C showing at the 60 and 84 weeks an inverse correlation between the level of anti-3S antibodies in patients participating to the trial and level of HIV DNA change from baseline (in Log of copies per million of PBMC). There is clearly a correlation between the achieved levels of anti-3S Ab at week 12 in patients, and the decrease of the total HIV DNA, a recognized marker of the reservoir. These data make a direct link between the anti-3S Ab induced by VAC-3S and the decrease of the reservoir.

Figures 6 and 7 also report a significant increase of the CD4/CD8 ratio in

Responders (P=0,002) and not the non-Responders (P=0,94) and Placebo (P=0,29) groups, at week 24 and thus immune restoration since an increase of the CD4/CD8 ratio corresponds to improved immune functions (Serrano- Villar et aL , PLOS Pathogens, vol. 10, 2014).

These results in HIV-infected patients vaccinated with VAC-3Sclearly show the dual capacity of VAC-3S to improve immune functions of patients, but also and unexpectedly to decrease the HIV reservoir through the decrease of the HIV DNA.

SEQUENCE LISTING

SEQ ID Type Description

1 Peptide gp41 or 3S reference sequence

NH2-CLLGFWGCSGKLICTTTVPWNASWSNK

SLDDr NNMTWMQWEREIDNYTS-COOH

2 Peptide NH2-SWSNKS-COOH

3 Peptide NH2-SASNKS-COOH

4 Peptide NH2-SWANKS-COOH

5 Peptide NH2-SWSAKS-COOH

6 Peptide NH2-SWSNKA-COOH

7 Peptide NH2-PWNA-COOH

8 Peptide NH2-LDDIW-COOH

9 Peptide NH2 -CPWNAS WSNKSLDDIW-COOH

10 Peptide NH₂-CPWNASASNKSLDDrW-COOH

11 Peptide CRM 197

12 Peptide Reference antigenic peptide 3S

NH₂-PWNASWSNKSLDDrW-COOH

13 Peptide Mutated 3S-peptide

NH₂-PWNASASNKSLDDrW-COOH

14 Peptide Nter(Cys)-m3S peptide

NH₂-CPWNASASNKSLDDrW-COOH

15 Peptide NH2-S-X2-S-N-X3-X4-COOH

16 Peptide NH2-P-W-N-X1-S-X2-S-N-X3-X4-X5-X6-X7-I-W-COOH (II)

17 Peptide NH₂-(Al)_m- PWNASWSNKSLDDr -(A2)_n-COOH (Ilia) SEQ ID Type Description

18 Peptide NH₂-(Al)_m- PWNASASNKSLDDr -(A2)_n-COOH (Illb)

19 Peptide NH₂-(Al)m- PWNSSWSNKSYECtfW -(A2)_n-COOH (IIIc)

20 Peptide NH₂-(Al)_m- PWNTSWSNKTLNDr -(A2)_n-COOH (Hid)

21 Peptide NH₂-(Al)_m- PWNASWSNKSLNDr -(A2)_n-COOH (Hie)

22 Peptide NH₂-(Al)m- PWNTSWSNKSYHEr -(A2)_n-COOH (Illf)

23 Peptide NH₂-(Al)m- PWNASWSNKSLDEr -(A2)_n-COOH (Illg)

24 Peptide NH₂-(Al)m- PWNSSWSNKSYEQIW -(A2)_n-COOH (IID )

25 Peptide NH₂-(Al)m- PWNSSWSNKSYKQIW -(A2)_n-COOH (Illi)

26 Peptide NH₂-(Al)m- PWNSSWSNKSQKQIW -(A2)_n-COOH (Illj)

27 Peptide NH₂-(Al)m- PWNSSWSNKTYNDIW -(A2)_n-COOH (Illk)

28 Peptide NH₂-(Al)m- PWNASWSNKSLNDIW -(A2)_n-COOH (III1)

29 Peptide NH₂-(Al)m- PWNASWSNRSLNDIW -(A2)_n-COOH (Illm)

30 Peptide NH₂-(Al)m- PWNASWSNKSLNAr -(A2)_n-COOH (Illn)

31 Peptide NH₂-(Al)m- PWNTSWSNKSYNKIW -(A2)_n-COOH (IIIo)

32 Peptide NH₂-(Al)m- PWNTSWSNKSYNEr -(A2)_n-COOH (IIIp)

33 Peptide NH₂-(Al)m- PWNASWSNRTLGDr -(A2)_n-COOH (Illq)

34 Peptide NH₂-(Al)m- PWNASWGNRTLGDr -(A2)_n-COOH (Illr)

35 Peptide NH₂-(Al)m- PWNTSWSNKSLSQIW -(A2)_n-COOH (Ills)

36 Peptide NH₂-(Al)m- PWNTSWSNKSLNQTW -(A2)_n-COOH (lilt)

37 Peptide NH₂-(Al)m- PWNTSWSNKSYNLr -(A2)_n-COOH (IIIu)

38 Peptide NH₂-(Al)m- PWNNSWSNKSYNLr -(A2)_n-COOH (IIIv)

39 Peptide NH₂-(Al)m- PWNSSWSNKSIEARV -(A2)_n-COOH (IIIw)

Claims

1. An immunogenic compound comprising an antigenic peptide derived from the HIV gp41 protein, for reducing a Peripheral Blood Mononuclear Cells (PBMC)- associated ΗΓ DNA level in an HIV-infected individual under anti-retroviral treatment.

2. The immunogenic compound for its use according to claim 1, for reducing residual HIV replication in said individual.

3. The immunogenic compound for its use according to any one of the preceding claims, wherein said individual is under an anti-retroviral treatment comprising the administration of at least one drug selected from: ART (Antiretro viral Therapy), HAART (Highly Active Antiretro viral Therapy).

4. The immunogenic compound for its use according to anyone of the preceding claims, wherein said individual has a low or decreased viral load, optionally below 40 HIV RNA copies / mL of blood plasma, at the time of the administration of said immunogenic compound.

5. The immunogenic compound for its use according to anyone of the preceding claims, wherein the individual has a low or decreased Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level, optionally below 1000 copies per 10⁶ PBMCs, at the time of the administration of said immunogenic compound.

6. The immunogenic compound for its use according to anyone of the preceding claims, wherein the individual has a high or increased CD4+ cell count, optionally above 350 per mm³ of blood plasma at the time of the administration of said immunogenic compound.

7. The immunogenic compound for its use according to any one of the preceding claims, wherein the said antigenic peptide is of the formula (I) :

PepNt- CORE-PepCt (I), wherein:

- "PepNt" consists of a polypeptide having an amino acid length varying from 0 to 20 amino acid residues and located at the N-terminal end of the polypeptide of formula (I);

- CORE consists of a polypeptide comprising the amino acid sequence :

NH2-S-X2-S-N-X3 -X4-COOH,

wherein

- X₂ is selected from the group consisting of W (Tryptophane) and A (Alanine), - X₃ is selected from the group consisting of K (Lysine) and R (Arginine),

- "PepCt" consists of a polypeptide having an amino acid length varying from 0 to 20 amino acid residues and located at the C-terminal end of the polypeptide of formula (I),

8. The immunogenic compound for its use according to any one of the preceding claims, wherein the said antigenic peptide is of the following formula (II) :

NH₂- [Nt]_y-P-W-N-Xi-S-X₂-S-N-X₃ -X4-X5-X6-X7-I-W-[Ct] z-COOH (II), wherein :

- y is an integer meaning 0 or 1,

- z is an integer meaning 0 or 1,

- Nt consists of a peptide having from 1 to 16 amino acids in length,

- Ct consists of a peptide having from 1 to 15 amino acids in length,

- Xi is selected from the group consisting of A (Alanine), T (threonine), S (Serine) and N (Asparagine),

- X₃ is selected from the group consisting of K (Lysine) and R (Arginine),

- X₄ is selected from the group consisting of S (Serine) and T (Threonine),

- Χό is selected from the group consisting of D (Aspartic acid), N (Asparagine), E

(Glutamic acid), S (Serine), G (Glycine) and K (Lysine),

9. The immunogenic compound for its use according to any one of the preceding claims, wherein the said antigenic peptide is selected from the group consisting of the following formulae (Ilia) and (Illb) :

NH₂-(Al)_m- PWNASWSNKSLDDIW -(A2)_n-COOH (Ilia), NH₂-(Al)_m- PWNASASNKSLDDIW -(A2)_n-COOH (Illb), wherein :

- m is an integer meaning 0 or 1,

- n is an integer meaning 0 or 1,

- Al is an amino acid residue, and - A2 is an amino acid residue,

10. The immunogenic compound for its use according to any one of the preceding claims, wherein the said antigenic peptide is selected from the group consisting of

C-PWNASWSNKSLDDIW (SEQID NO 8), and

C-PWNASASNKSLDDIW (SEQID NO 9)

11. The immunogenic compound for its use according to any one of the preceding claims, wherein the said antigenic peptide is linked to a carrier molecule.

12. The immunogenic compound for its use according to the preceding claim, wherein the carrier molecule is a CRM 197 protein.

13. The immunogenic compound for its use according to any one of the preceding claims, wherein the HIV virus is HIV- 1.

14. A vaccine composition comprising at least one immunogenic compound according to any one of claims 1 to 13, for reducing a Peripheral Blood Mononuclear Cells (PBMC)-associated HIV DNA level in an HIV-infected individual under anti-retroviral treatment.