Long-term specific immune responses induced in humans by a human immunodeficiency virus type 1 lipopeptide vaccine: characterization of CD8+-T-cell epitopes recognized

Conserved multiepitope vaccine constructs: A potent HIV-1 therapeutic vaccine in clinical trials

Despite the success of Antiretroviral Therapy (ART) in preventing HIV-1-associated clinical progression to AIDS, it is unable to eliminate the viral reservoirs and eradicate the HIV-1 infection. Therapeutic vaccination is an alternative approach to alter the HIV-1 infection course. It can induce effective HIV-1-specific immunity to control viremia and eliminate the need for lifelong ART. Immunological data from spontaneous HIV-1 controllers have shown that cross-reactive T-cell responses are the key immune mechanism in HIV-1 control. Directing these responses toward preferred HIV-1 epitopes is a promising strategy in therapeutic vaccine settings. Designing novel immunogens based on the HIV-1 conserved regions containing a wide range of critical T- and B-cell epitopes of the main viral antigens (conserved multiepitope approaches) supplies broad coverage of global diversity in HIV-1 strains and Human Leukocyte Antigen (HLA) alleles. It can also prevent immune induction to undesirable decoy epitopes theoretically. The efficacy of different novel HIV-1 immunogens based on the conserved and/or functional protective site of HIV-1 proteome has been evaluated in multiple clinical trials. Most of these immunogens were generally safe and able to induce potent HIV-1-specific immunity. However, despite these findings, several candidates have demonstrated limited efficacy in viral replication control. In this study, we used the PubMed and ClinicalTrial.gov databases to review the rationale of designing curative HIV-1 vaccine immunogens based on the conserved favorable site of the virus. Most of these studies evaluate the efficacy of vaccine candidates in combination with other therapeutics and/or with new formulations and immunization protocols. This review briefly describes the design of conserved multiepitope constructs and outlines the results of these vaccine candidates in the recent clinical pipeline.

Lipopeptides for Vaccine Development

The development of lipopeptides (lipidated peptides) for vaccines is discussed, including their role as antigens and/or adjuvants. Distinct classes of lipopeptide architectures are covered including simple linear and ligated constructs and lipid core peptides. The design, synthesis, and immunological responses of the important class of glycerol-based Toll-like receptor agonist lipopeptides such as Pam₃CSK₄, which contains three palmitoyl chains and a CSK₄ hexapeptide sequence, and many derivatives of this model immunogenic compound are also reviewed. Self-assembled lipopeptide structures including spherical and worm-like micelles that have been shown to act as vaccine agents are also described. The work discussed includes examples of lipopeptides developed with model antigens, as well as for immunotherapies to treat many infectious diseases including malaria, influenza, hepatitis, COVID-19, and many others, as well as cancer immunotherapies. Some of these have proceeded to clinical development. The research discussed highlights the huge potential of, and diversity of roles for, lipopeptides in contemporary and future vaccine development.

Palmitoylated antigens for the induction of anti-tumor CD8+ T cells and enhanced tumor recognition

Induction of tumor-specific cytotoxic CD8⁺ T cells (CTLs) via immunization relies on the presentation of tumor-associated peptides in major histocompatibility complex (MHC) class I molecules by dendritic cells (DCs). To achieve presentation of exogenous peptides into MHC class I, cytosolic processing and cross-presentation are required. Vaccination strategies aiming to induce tumor-specific CD8⁺ T cells via this exogenous route therefore pose a challenge. In this study, we describe improved CD8⁺ T cell induction and in vivo tumor suppression of mono-palmitic acid-modified (C16:0) antigenic peptides, which can be attributed to their unique processing route, efficient receptor-independent integration within lipid bilayers, and continuous intracellular accumulation and presentation through MHC class I. We propose that this membrane-integrating feature of palmitoylated peptides can be exploited as a tool for quick and efficient antigen enrichment and MHC class I loading. Importantly, both DCs and non-professional antigen-presenting cells (APCs), similar to tumor cells, facilitate anti-tumor immunity by efficient CTL priming via DCs and effective recognition of tumors through enhanced presentation of antigens.

A pilot clinical trial testing topical resiquimod and a xenopeptide as immune adjuvants for a melanoma vaccine targeting MART-1

A vaccine that could expand melanoma-specific T cells might reduce the risk of recurrence of resected melanoma and could provide an alternative or adjunct to standard immunotherapy options. We tested the safety and immunogenicity of a vaccine coupling a melanoma-associated peptide with a xenogenic peptide (to promote epitope spreading) and/or resiquimod (to activate antigen-presenting cells). HLA-A2-positive patients with resected stage II, III, and IV melanoma were assigned to treatment on one of three schedules. All patients received three subcutaneous doses of the peptide MART-1a mixed with Montanide. In addition, patients on schedule 1 received the xenoantigen peptide Gag267-274, patients on schedule 2 received topical resiquimod, and patients on schedule 3 received both Gag267-274 and resiquimod. Blood samples were tested for the frequency of antigen-specific T cells by tetramer assay, as well as immune cell subtypes and plasma cytokine levels. Patients enrolled from October 2012 to December 2014, with 10 patients enrolling to each schedule. The most common adverse events were injection site reaction (26 patients) and fatigue (15 patients). Tetramer analysis revealed antigen-specific responses (defined as doubling of MART-1a-specific T cells from pretreatment to post-treatment) in 20, 60, and 40% of patients treated on schedules 1, 2, and 3, respectively. Vaccine treatment consisting of MART-1a peptide, Gag267-274, Montanide, and topical resiquimod was well-tolerated. The addition of the Gag267-274 xenoantigen was not associated with an increase in the response to MART-1a, whereas use of topical resiquimod was associated with a higher frequency of MART-1a-specific T-cell responses that did not meet statistical significance.

Anti-HIV potency of T-cell responses elicited by dendritic cell therapeutic vaccination

Identification and characterization of CD8+ and CD4+ T-cell epitopes elicited by HIV therapeutic vaccination is key for elucidating the nature of protective cellular responses and mechanism of the immune evasion of HIV. Here, we report the characterization of HIV-specific T-cell responses in cART (combination antiretroviral therapy) treated HIV-1 infected patients after vaccination with ex vivo-generated IFNα Dendritic Cells (DCs) loaded with LIPO-5 (HIV-1 Nef 66-97, Nef 116-145, Gag 17-35, Gag 253-284 and Pol 325-355 lipopeptides). Vaccination induced and/or expanded HIV-specific CD8+ T cells producing IFNγ, perforin, granzyme A and granzyme B, and also CD4+ T cells secreting IFNγ, IL-2 and IL-13. These responses were directed against dominant and subdominant epitopes representing all vaccine regions; Gag, Pol and Nef. Interestingly, IL-2 and IL-13 produced by CD4+ T cells were negatively correlated with the peak of viral replication following analytic treatment interruption (ATI). Epitope mapping confirmed that vaccination elicited responses against predicted T-cell epitopes, but also allowed to identify a set of 8 new HIV-1 HLA-DR-restricted CD4+ T-cell epitopes. These results may help to better design future DC therapeutic vaccines and underscore the role of vaccine-elicited CD4+ T-cell responses to achieve control of HIV replication.

Identification of novel HIV-1-derived HLA-E-binding peptides

Non-classical class Ib MHC-E molecule is becoming an increasingly interesting component of the immune response. It is involved in both the adaptive and innate immune responses to several chronic infections including HIV-1 and, under very specific circumstances, likely mediated a unique vaccine protection of rhesus macaques against pathogenic SIV challenge. Despite being recently in the spotlight for HIV-1 vaccine development, to date there is only one reported human leukocyte antigen (HLA)-E-binding peptide derived from HIV-1. In an effort to help start understanding the possible functions of HLA-E in HIV-1 infection, we determined novel HLA-E binding peptides derived from HIV-1 Gag, Pol and Vif proteins. These peptides were identified in three independent assays, all quantifying cell-surface stabilization of HLA-E*01:01 or HLA-E*01:03 molecules upon peptide binding, which was detected by HLA-E-specific monoclonal antibody and flow cytometry. Thus, following initial screen of over 400 HIV-1-derived 15-mer peptides, 4 novel 9-mer peptides PM9, RL9, RV9 and TP9 derived from 15-mer binders specifically stabilized surface expression of HLA-E*01:03 on the cell surface in two separate assays and 5 other binding candidates EI9, MD9, NR9, QF9 and YG9 gave a binding signal in only one of the two assays, but not both. Overall, we have expanded the current knowledge of HIV-1-derived target peptides stabilizing HLA-E cell-surface expression from 1 to 5, thus broadening inroads for future studies. This is a small, but significant contribution towards studying the fine mechanisms behind HLA-E actions and their possible use in development of a new kind of vaccines.

Development of an epitope-based HIV-1 vaccine strategy from HIV-1 lipopeptide to dendritic-based vaccines

INTRODUCTION

Development of a safe, effective and globally affordable Human Immunodeficiency Virus strain 1 (HIV-1) vaccine offers the best hope for future control of the HIV-1 pandemic. However, with the exception of the recent RV144 trial, which elicited a modest level of protection against infection, no vaccine candidate has shown efficacy in preventing HIV-1 infection or in controlling virus replication in humans. There is also a great need for a successful immunotherapeutic vaccine since combination antiretroviral therapy (cART) does not eliminate the reservoir of HIV-infected cells. But to date, no vaccine candidate has proven to significantly alter the natural history of an individual with HIV-1 infection. Areas covered: For over 25 years, the ANRS (France Recherche Nord&Sud Sida-HIV hépatites) has been committed to an original program combining basic science and clinical research developing an epitope-based vaccine strategy to induce a multiepitopic cellular response against HIV-1. This review describes the evolution of concepts, based on strategies using HIV-1 lipopeptides towards the use of dendritic cell (DC) manipulation. Expert commentary: Understanding the crucial role of DCs in immune responses allowed moving from the non-specific administration of HIV-1 sequences with lipopeptides to DC-based vaccines. These DC-targeting strategies should improve HIV-1 vaccine efficacy.

HIV specific responses induced in nonhuman primates with ANRS HIV-Lipo-5 vaccine combined with rMVA-HIV prime or boost immunizations

We evaluated the immunogenicity of a prime/boost vaccine strategy combining 5 lipopeptides (HIV-Lipo-5) and a recombinant modified vaccinia virus Ankara (rMVA-HIV) in cynomolgus macaques. Both of these vaccine components deliver HIV LAI Gag, Pol, and Nef antigens. Systemic and local safety was excellent in all groups. Immunization with HIV-Lipo-5 alone induced significant serum anti-HIV antibody titers which were not modified by rMVA-HIV immunization. However, induction of T-cell responses, as measured by IFNγ and IL-2 producing cells upon short-term stimulation with HIV peptide pools, required combined immunization with rMVA-HIV. Responses were preferentially observed against Gag antigen. Interestingly, HIV-Lipo-5 efficiently primed HIV induced T-cell responses upon the injection of rMVA-HIV, which may help to reduce the required number of vector injections. Our results provide a rationale for the use of a strategy involving HIV-Lipo-5 priming followed by rMVA-HIV booster immunization as a prophylactic or therapeutic vaccine approach against HIV infection and AIDS.

Increasing cellular immunogenicity to peptide-based vaccine candidates using a fluorocarbon antigen delivery system

Traditionally, synthetic peptide vaccines for infectious diseases and cancer require adjuvants to achieve optimal immunogenicity. Here we describe a novel method of peptide modification using a fluorocarbon chain which can substantially increase peptide-specific cellular immune responses in the absence of adjuvant. We demonstrate that fluorocarbon-modified peptides (fluoropeptides) derived from HIV, influenza and hepatitis C virus can significantly increase interferon gamma ELISpot responses against cytotoxic and T-helper epitopes compared to unmodified peptides or lipopeptides in mice. Increases in both T-helper1 and T-helper2 cytokines are observed. Fluoropeptides show enhanced ability of the antigen to persist at the site of administration and persistence is associated with a prolonged and elevated immune response. Additionally we demonstrate that fluoropeptides have increased proteolytic resistance thereby potentially supporting their increased half-life in vivo. Fluorocarbon-modification of peptides provides a valuable tool for increasing cellular immunogenicity of vaccines for infectious diseases and cancer without requirement for traditional adjuvants.

Self-adjuvanting lipoimmunogens for therapeutic HPV vaccine development: potential clinical impact

The goal of therapeutic HPV vaccines is the induction of cytotoxic T lymphocyte immunity against HPV-associated cancers. Recombinant proteins and synthetic peptides have high safety profiles but low immunogenicity, which limits their efficacy when used in a vaccine. Self-adjuvanting lipid moieties have been conjugated to synthetic peptides or expressed as lipoproteins to enhance the immunogenicity of vaccine candidates. Mono-, di- and tri-palmitoylated peptides have been demonstrated to activate dendritic cells and induce robust cellular immunity against infectious diseases and cancer. Recently, a platform technology using the high-yield production of recombinant lipoproteins with Toll-like receptor 2 agonist activity was established for the development of novel subunit vaccines. This technology represents a novel strategy for the development of therapeutic HPV vaccines. In this review, we describe recent progress in the design of therapeutic HPV vaccines using lipoimmunogens.

Memory CD8(+) T cells elicited by HIV-1 lipopeptide vaccines display similar phenotypic profiles but differences in term of magnitude and multifunctionality compared with FLU- or EBV-specific memory T cells in humans

Differentiation marker, multifunctionality and magnitude analyses of specific-CD8(+) memory T cells are crucial to improve development of HIV vaccines designed to generate cell-mediated immunity. Therefore, we fully characterized the HIV-specific CD8(+) T cell responses induced in volunteers vaccinated with HIV lipopeptide vaccines for phenotypic markers, tetramer staining, cytokine secretion, and cytotoxic activities. The frequency of ex vivo CD8(+) T cells elicited by lipopeptide vaccines is very rare and central-memory phenotype and functions of these cells were been shown to be important in AIDS immunity. So, we expanded them using specific peptides to compare the memory T cell responses induced in volunteers by HIV vaccines with responses to influenza (FLU) or Epstein Barr virus (EBV). By analyzing the differentiation state of IFN-γ-secreting CD8(+) T cells, we found a CCR7(-)CD45RA(-)CD28(+int)/CD28(-) profile (>85%) belonging to a subset of intermediate-differentiated effector T cells for HIV, FLU, and EBV. We then assessed the quality of the response by measuring various T cell functions. The percentage of single IFN-γ T cell producers in response to HIV was 62% of the total of secreting T cells compared with 35% for FLU and EBV, dual and triple (IFN-γ/IL-2/CD107a) T cell producers could also be detected but at lower levels (8% compared with 37%). Finally, HIV-specific T cells secreted IFN-γ and TNF-α, but not the dual combination like FLU- and EBV-specific T cells. Thus, we found that the functional profile and magnitude of expanded HIV-specific CD8(+) T precursors were more limited than those of to FLU- and EBV-specific CD8(+) T cells. These data show that CD8(+) T cells induced by these HIV vaccines have a similar differentiation profile to FLU and EBV CD8(+) T cells, but that the vaccine potency to induce multifunctional T cells needs to be increased in order to improve vaccination strategies.

Trial Watch: Peptide vaccines in cancer therapy

Throughout the past 3 decades, along with the recognition that the immune system not only influences oncogenesis and tumor progression, but also determines how established neoplastic lesions respond therapy, renovated enthusiasm has gathered around the possibility of using vaccines as anticancer agents. Such an enthusiasm quickly tempered when it became clear that anticancer vaccines would have to be devised as therapeutic, rather than prophylactic, measures, and that malignant cells often fail to elicit (or actively suppress) innate and adaptive immune responses. Nonetheless, accumulating evidence indicates that a variety of anticancer vaccines, including cell-based, DNA-based, and purified component-based preparations, are capable of circumventing the poorly immunogenic and highly immunosuppressive nature of most tumors and elicit (at least under some circumstances) therapeutically relevant immune responses. Great efforts are currently being devoted to the identification of strategies that may provide anticancer vaccines with the capacity of breaking immunological tolerance and eliciting tumor-associated antigen-specific immunity in a majority of patients. In this sense, promising results have been obtained by combining anticancer vaccines with a relatively varied panels of adjuvants, including multiple immunostimulatory cytokines, Toll-like receptor agonists as well as inhibitors of immune checkpoints. One year ago, in the December issue of OncoImmunology, we discussed the biological mechanisms that underlie the antineoplastic effects of peptide-based vaccines and presented an abundant literature demonstrating the prominent clinical potential of such an approach. Here, we review the latest developments in this exciting area of research, focusing on high-profile studies that have been published during the last 13 mo and clinical trials launched in the same period to evaluate purified peptides or full-length proteins as therapeutic anticancer agents.

Immunostimulation by synthetic lipopeptide-based vaccine candidates: structure-activity relationships

Peptide-based vaccines offer several advantages over conventional whole organism or protein approaches by offering improved purity and specificity in inducing immune response. However, peptides alone are generally non-immunogenic. Concerns remain about the toxicity of adjuvants which are critical for immunogenicity of synthetic peptides. The use of lipopeptides in peptide vaccines is currently under intensive investigation because potent immune responses can be generated without the use of adjuvant (thus are self-adjuvanting). Several lipopeptides derived from microbial origin, and their synthetic versions or simpler fatty acid moieties impart this self-adjuvanting activity by signaling via Toll-like receptor 2 (TLR2). Engagement of this innate immune receptor on antigen-presenting cell leads to the initiation and development of potent immune responses. Therefore optimization of lipopeptides to enhance TLR2-mediated activation is a promising strategy for vaccine development. Considerable structure-activity relationships that determine TLR2 binding and consequent stimulation of innate immune responses have been investigated for a range of lipopeptides. In this mini review we address the development of lipopeptide vaccines, mechanism of TLR2 recognition, and immune activation. An overview is provided of the best studied lipopeptide vaccine systems.

Safety, immunogenicity and efficacy assessment of HIV immunotherapy in a multi-centre, double-blind, randomised, Placebo-controlled Phase Ib human trial

BACKGROUND

Combination antiretroviral therapy (cART) is the main therapeutic management tool for HIV/AIDS. Despite its success in controlling viral load and disease progression, cART is expensive, associated with a range of significant side effects and depends for its efficacy on the patient's life-long commitment to high levels of treatment adherence. Immunotherapeutic agents can provide potential solutions to these shortcomings. Here we describe a Phase Ib trial of HIV-v, a synthetic immunotherapy that elicits T- and B-cell effector responses against HIV infected cells.

METHODS

Fifty-nine cART-naive HIV-infected males aged 18-50 years with viral load of 5000-500,000 copies/ml and CD4 counts >350/μl were recruited for this multi-centre, randomised, double blind study. Volunteers received one low (250 μg) or high (500 μg) dose of HIV-v, either alone or adjuvanted (ISA-51). Safety, immunogenicity, CD4 count and viral load were monitored over 168 Days.

RESULTS

HIV-v was well tolerated and the adjuvanted formulations elicited IgG responses in up to 75% of volunteers. The high adjuvanted dose also elicited cellular responses in 45% of tested volunteers. In these responding subjects viral loads were reduced by over 1 log (p=0.04) compared to Placebo and non-responders. No changes in CD4 count were observed.

CONCLUSIONS

HIV-v is safe and can elicit T- and B-cell responses in ART-naive HIV patients that significantly reduce viral load. Improved dosing regimens and further research on long term efficacy are required, but HIV-v appears to have potential as an immunotherapeutic anti-viral agent. Trial registered as EudraCT-2009-010593-37 (ClinicalTrials.gov Identifier: NCT01071031).

Targeting concatenated HIV antigens to human CD40 expands a broad repertoire of multifunctional CD4+ and CD8+ T cells

OBJECTIVE

Targeting HIV antigens directly to dendritic cells using monoclonal antibodies against cell-surface receptors has been shown to evoke potent cellular immunity in animal models. The objective of this study was to configure an anti-human CD40 antibody fused to a string of five highly conserved CD4 and CD8 T-cell epitope-rich regions of HIV-1 Gag, Nef and Pol (αCD40.HIV5pep), and then to demonstrate the capacity of this candidate therapeutic vaccine to target these HIV peptide antigens to human dendritic cells to expand functional HIV-specific T cells.

METHODS

Antigen-specific cytokine production using intracellular flow cytometry and multiplex bead-based assay, and suppression of viral inhibition, were used to characterize the T cells expanded by αCD40.HIV5pep from HIV-infected patient peripheral blood mononuclear cell (PBMC) and dendritic cell/T-cell co-cultures.

RESULTS

This candidate vaccine expands memory CD4 and CD8 T cells specific to multiple epitopes within all five peptide regions across a wide range of major histocompatibility complex (MHC) haplotypes from HIV-infected patient PBMC and dendritic cell/T-cell co-cultures. These in vitro expanded HIV antigen-specific CD4 and CD8 T cells produce multiple cytokines and chemokines. αCD40.HIV5pep-expanded CD8 T cells have characteristics of cytotoxic effector cells and are able to kill autologous target cells and suppress HIV-1 replication in vitro.

CONCLUSION

Our data demonstrate the therapeutic potential of this CD40-targeting HIV candidate vaccine in inducing a broad repertoire of multifunctional T cells in patients.

Long-term CD4(+) and CD8(+) T-cell responses induced in HIV-uninfected volunteers following intradermal or intramuscular administration of an HIV-lipopeptide vaccine (ANRS VAC16)

BACKGROUND

We have shown that the intradermal (ID) administration of an HIV-1 lipopeptide candidate vaccine (LIPO-4) is well tolerated in healthy volunteers, with one fifth the IM dose delivered by this route inducing HIV-1-specific CD8(+) T-cell responses of a magnitude and quality similar to those achieved by IM administration. In this long-term follow-up, we aimed to investigate the sustainability and epitopic breadth of the immune responses induced.

METHODS

In a prospective multicentre trial, 68 healthy volunteers were randomised to receive, at weeks 0, 4 and 12, either a 0.5 ml IM (500 μg of each lipopeptide; 35 volunteers) dose or a 0.1 ml ID (100 μg of each lipopeptide; 33 volunteers) dose of the LIPO-4 vaccine, in the deltoid region of the non-dominant arm. All 68 volunteers received the first two vaccinations, and 44 volunteers in the ID group and 22 in the IM group received the third. We describe here the long-term CD8(+) and CD4(+) T-cell immune responses, up to 48 weeks after the first immunisation.

RESULTS

Response frequency was highest at week 14 for CD4(+) T cells, at 85% (28/33) for the IM group and 61% (20/33) for the ID group (p=0.027), and at week 48 for CD8(+) T cells, at 36% (12/33) for the ID group and 31% (11/35) for the IM group (p=0.67). Response rates tended to be lower for volunteers receiving the third vaccination boost, whether IM or ID. Finally, we also observed a striking change in the specificity of the CD8(+) T-cell responses induced shortly (2 weeks) or several months (48 weeks) after LIPO-4 vaccination.

CONCLUSION

Lipopeptide vaccines elicited sustainable CD4(+) and CD8(+) T-cell responses, following IM or ID administration. CD8(+) T-cell responses had shifted and expanded to different epitopes after one year of follow-up. These results should facilitate the design of the next generation of prime-boost trials with repeated doses of lipopeptide vaccines.

Cytokine and gene transcription profiles of immune responses elicited by HIV lipopeptide vaccine in HIV-negative volunteers

OBJECTIVE

To dissect the biological mechanisms involved in the cellular responses to a candidate vaccine containing 5 HIV peptides coupled to a palmytoil tail (HIV-LIPO-5) in healthy volunteers, by using extensive immunogenicity assessments with different stimulation durations.

DESIGN

Immunogenicity substudy of a randomized phase II prophylactic HIV vaccine trial (ANRS VAC 18).

METHODS

HIV-LIPO-5 or placebo was administered at W0, W4, W12 and W24. Peripheral blood mononuclear cells from a subset of participants at W0 and W14 were stimulated with HIV-LIPO-5, Gag peptides contained in the vaccine and control peptides. ELISpot, lymphoproliferation, intracellular cytokine staining (ICS), cytokine multiplex and transcriptomic analyses were performed. Different time points and stimulation conditions were compared, controlling for test multiplicity.

RESULTS

Cultured ELISpot and lymphoproliferation responses were detected at W14. Ex-vivo ICS showed mainly interleukin (IL)-2-producing cells. Secretion of interferon (IFN)-γ, tumour necrosis factor (TNF)-α, IL-5 and IL-13 increased significantly after culture and Gag stimulation at W14 compared to W0. Metallothionein genes were consistently overexpressed after HIV-LIPO-5 stimulation at W0 and W14. At W14, significant probes increased substantially, including IFN-γ, CXCL9, IL2RA, TNFAIP6, CCL3L1 and IL-6. Canonical pathway analyses indicated a role of interferon signalling genes in response to HIV-LIPO-5.

CONCLUSION

HIV-LIPO-5 vaccination elicited Th1 and Th2 memory precursor responses and a consistent modulation in gene expression. The response profile before vaccination suggests an adjuvant effect of the lipid tail of HIV-LIPO-5. Our combined immunogenicity analyses allowed to identify a specific signature profile of HIV-LIPO-5 and indicate that HIV-LIPO-5 could be further developed as a prime in heterologous prime-boost strategies.

Modern subunit vaccines: development, components, and research opportunities

Traditional vaccines, based on the administration of killed or attenuated microorganisms, have proven to be among the most effective methods for disease prevention. Safety issues related to administering these complex mixtures, however, prevent their universal application. Through identification of the microbial components responsible for protective immunity, vaccine formulations can be simplified, enabling molecular-level vaccine characterization, improved safety profiles, prospects to develop new high-priority vaccines (e.g. for HIV, tuberculosis, and malaria), and the opportunity for extensive vaccine component optimization. This subunit approach, however, comes at the expense of decreased immunity, requiring the addition of immunostimulatory agents (adjuvants). As few adjuvants are currently used in licensed vaccines, adjuvant development represents an exciting area for medicinal chemists to play a role in the future of vaccine development. In addition, immune responses can be further customized though optimization of delivery systems, tuning the size of particulate vaccines, targeting specific cells of the immune system (e.g. dendritic cells), and adding components to aid vaccine efficacy in whole immunized populations (e.g. promiscuous T-helper epitopes). Herein we review the current state of the art and future direction in subunit vaccine development, with a focus on the described components and their potential to steer the immune response toward a desired response.

Towards a rational design of an asymptomatic clinical herpes vaccine: the old, the new, and the unknown

The best hope of controlling the herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) pandemic is the development of an effective vaccine. However, in spite of several clinical trials, starting as early as 1920s, no vaccine has been proven sufficiently safe and efficient to warrant commercial development. In recent years, great strides in cellular and molecular immunology have stimulated creative efforts in controlling herpes infection and disease. However, before moving towards new vaccine strategy, it is necessary to answer two fundamental questions: (i) why past herpes vaccines have failed? (ii) Why the majority of HSV seropositive individuals (i.e., asymptomatic individuals) are naturally "protected" exhibiting few or no recurrent clinical disease, while other HSV seropositive individuals (i.e., symptomatic individuals) have frequent ocular, orofacial, and/or genital herpes clinical episodes? We recently discovered several discrete sets of HSV-1 symptomatic and asymptomatic epitopes recognized by CD4(+) and CD8(+) T cells from seropositive symptomatic versus asymptomatic individuals. These asymptomatic epitopes will provide a solid foundation for the development of novel herpes epitope-based vaccine strategy. Here we provide a brief overview of past clinical vaccine trials, outline current progress towards developing a new generation "asymptomatic" clinical herpes vaccines, and discuss future mucosal "asymptomatic" prime-boost vaccines that could optimize local protective immunity.

Mucosal Adjuvant Potential of Quillaja saponins and Cross-linked Dextran Microspheres, Co-administered with Liposomes Encapsulated with Tetanus Toxoid

Intranasal vaccination is particularly a striking route for mucosal immunization, due to the ease of administration and the induction of both mucosal and humoral immunity. However, soluble antigens (Ag) are not sufficiently taken up after the nasal administration and need to be co-administered with adjuvants, penetration enhancers or encapsulated in particles. So, in this study, tetanus toxoid (TT) as a model Ag was entrapped in nonionic liposomes. The effect of the co-administration of Quillaja saponin (QS) as an adjuvant and cross-linked dextran microspheres (CDM) as penetration enhancer on immune responses was also studied. TT or TT + QS loaded liposomes were prepared by dehydration-rehydration method (DRV), followed by the extrusion through 400 nm filters. Some formulations were mixed with CDM. Liposomes were first characterized for their size range, mean diameter and morphology using particle size analyzer, optical and transmission electron microscopes. The volume mean diameter of liposomes was determined as 3836 ± 179 and 624 ± 114 nm before and after the extrusion, respectively. Structural efficiency of TT extracted from liposomes was confirmed by SDS-PAGE method. Encapsulation efficiencies of TT and QS were 44 ± 8.50% and 60 ± 6.02%, respectively. Rabbits were nasally immunized with various formulations and serum IgG titers and nasal lavage sIgA titers were determined by an ELISA method. TT + QS liposomes induced higher sIgA levels in comparison with TT liposomes (p < 0.05), but the difference in serum IgG levels was not significant. Results indicated that neutral liposomes administered nasally, have a good potential for induction of mucosal immunity and co-encapsulation of QS and TT in liposomes improved the systemic and mucosal immune responses.

Experience with synthetic vaccines for cancer and persistent virus infections in nonhuman primates and patients

Synthetic vaccines, in particular long synthetic peptides of approximately 25-50 amino acids in length, are attractive for HIV vaccine development and for induction of therapeutic immune responses in patients with (pre-)malignant disorders. In the case of preventive vaccine development against HIV, no major success has been achieved, but the possibilities are by no means exhausted. A long peptide vaccine consisting of 13 overlapping peptides, which together cover the entire length of the two oncogenic proteins E6 and E7 of high-risk human papilloma virus type 16 (HPV16), caused complete regression of all lesions and eradication of virus in 9 out of 20 women with high-grade vulvar intraepithelial neoplasia, a therapy-resistant preneoplastic disorder. The nature and strength of the vaccine-prompted T cell responses were significantly correlated with the clinical response. Synthetic peptide vaccines are attractive, because they allow rational improvement of vaccine design and detailed pharmacokinetic and pharmacodynamic studies not possible with conventional vaccines. Improvements are possible by addition or conjugation of adjuvants, notably TLR ligands, to the synthetic peptides.

TLR-based immune adjuvants

This work describes the nature and strength of the immune response induced by various Toll-like receptor ligands and their ability to act as vaccine adjuvants. It reviews the various ligands capable of triggering individual TLRs, and then focuses on the efficacy and safety of those agents for which clinical results are available.

Immunogenicity and safety of an HIV-1 lipopeptide vaccine in healthy adults: a phase 2 placebo-controlled ANRS trial

BACKGROUND

French National Agency for Research on AIDS and Viral Hepatitis's HIV-LIPO-5 vaccine includes five HIV-1 peptides, containing multiple CD8 and CD4 T-cell epitopes and coupled to a palmitoyl tail. Whether HIV-LIPO-5 immunogenicity varies with the dose is unknown.

METHODS

HIV-negative volunteers were randomized to receive HIV-LIPO-5 vaccine at 50 microg/lipopeptide (N = 32), 150 microg/lipopeptide (N = 32), 500 microg/lipopeptide (N = 33) or placebo (N = 34) at weeks 0, 4, 12 and 24. HIV-1-specific CD8 (interferon-gamma ELISpot on peripheral blood mononuclear cells cultured for 12 days) and CD4 responses (peripheral blood mononuclear cell lymphoproliferation) were assessed at baseline, after each injection and at week 48.

RESULTS

Local reactions were dose-dependent but no differences in systemic reactions appeared between groups. Sustained (at least on two separate occasions) CD8 response rates to at least one given HIV-1 pool were obtained in 22 of 32 (69%), 21 of 33 (64%) and 21 of 34 (62%) individuals for LIPO-5 50, 150 and 500 groups, respectively (P < or = 0.0001 for all comparisons to the placebo). Cumulative CD4 response rates were obtained in 15 of 32 (47%), 18 of 33 (55%) and 15 of 34 (44%) individuals (P < 0.0001 for all comparisons to placebo). At week 48, CD8 responses persisted in 47 of 91 (52%) HIV-LIPO-5 recipients.

CONCLUSION

Doses of 50, 150 and 500 microg of French National Agency for Research on AIDS and Viral Hepatitis's HIV-LIPO-5 vaccine were able to elicit HIV-specific sustained CD8 and CD4 T-cell responses in healthy adults. Safety is good and all doses appear appropriate in further 'prime-boost' trials.

Phase III HIV vaccine trial in Thailand: a step toward a protective vaccine for HIV

The large human efficacy trail in Thailand, RV144, was concluded in the summer of 2009. This is the first Phase III trial to show limited, but significant, efficacy in preventing HIV acquisition. This trial represents the first sign that a preventive vaccine for HIV may be feasible. The vaccine regimen tested in Thailand consisted of priming with a Canarypox vector carrying three synthetic HIV genes. The priming was followed by booster inoculations with two recombinant envelope proteins from HIV, clade B and E. The need to understand the role in protection from HIV acquisition of the new responses, induced by this vaccine combination, has brought together many researchers with the common goal of improving the development of a safe and effective vaccine for HIV.

Human papillomavirus 16-specific T cell responses in classic HPV-related vulvar intra-epithelial neoplasia. Determination of strongly immunogenic regions from E6 and E7 proteins

Cell-mediated immunity directed against human papillomavirus 16 (HPV-16) antigens was studied in 16 patients affected with classic vulvar intra-epithelial neoplasia (VIN), also known as bowenoid papulosis (BP). Ten patients had blood lymphocyte proliferative T cell responses directed against E6/2 (14-34) and/or E6/4 (45-68) peptides, which were identified in the present study as immunodominant among HPV-16 E6 and E7 large peptides. Ex vivo enzyme-linked immunospot-interferon (IFN)-gamma assay was positive in three patients who had proliferative responses. Twelve months later, proliferative T cell responses remained detectable in only six women and the immunodominant antigens remained the E6/2 (14-34) and E6/4 (45-68) peptides. The latter large fragments of peptides contained many epitopes able to bind to at least seven human leucocyte antigen (HLA) class I molecules and were strong binders to seven HLA-DR class II molecules. In order to build a therapeutic anti-HPV-16 vaccine, E6/2 (14-34) and E6/4 (45-68) fragments thus appear to be good candidates to increase HPV-specific effector T lymphocyte responses and clear classic VIN (BP) disease lesions.

Obstacles to the successful development of an efficacious T cell-inducing HIV-1 vaccine

An efficacious vaccine to HIV-1 is direly needed to stem the global pandemic. Immunogens that elicit broadly cross-neutralizing antibodies to HIV-1 remain elusive, and thus, most HIV-1 vaccine efforts are focusing on induction of T cells. The notion that T cells can mediate protection against HIV-1 has been called into question by the failure of the STEP trial, which was designed to test this concept by the use of an E1-deleted Ad vaccine carrier. Lack of efficacy of the STEP trial vaccine underscores our limited knowledge about correlates of immune protection against HIV-1 and stresses the need for an enhanced commitment to basic research, including preclinical and clinical vaccine studies. In this review, we discuss known correlates of protection against HIV-1 and different vaccine strategies that have been or are being explored to induce such correlates, focusing on T cell-inducing vaccines and particularly on Ad vectors.

A genital tract peptide epitope vaccine targeting TLR-2 efficiently induces local and systemic CD8+ T cells and protects against herpes simplex virus type 2 challenge

The next generation of needle-free mucosal vaccines is being rationally designed according to rules that govern the way in which the epitopes are recognized by and stimulate the genital mucosal immune system. We hypothesized that synthetic peptide epitopes extended with an agonist of Toll-like receptor 2 (TLR-2), that are abundantly expressed by dendritic and epithelial cells of the vaginal mucosa, would lead to induction of protective immunity against genital herpes. To test this hypothesis, we intravaginally (IVAG) immunized wild-type B6, TLR-2 (TLR2(-/-)) or myeloid differentiation factor 88 deficient (MyD88(-/-)) mice with a herpes simplex virus type 2 (HSV-2) CD8+ T-cell peptide epitope extended by a palmitic acid moiety (a TLR-2 agonist). IVAG delivery of the lipopeptide generated HSV-2-specific memory CD8+ cytotoxic T cells both locally in the genital tract draining lymph nodes and systemically in the spleen. Moreover, lipopeptide-immunized TLR2(-/-) and MyD88(-/-) mice developed significantly less HSV-specific CD8+ T-cell response, earlier death, faster disease progression, and higher vaginal HSV-2 titers compared to lipopeptide-immunized wild-type B6 mice. IVAG immunization with self-adjuvanting lipid-tailed peptides appears to be a novel mucosal vaccine approach, which has attractive practical and immunological features.

Human dendritic cells pulsed with specific lipopeptides stimulate autologous antigen-specific T cells without the addition of exogenous maturation factors

Serum-free culture conditions to generate immature human monocyte-derived DC (Mo-DC) were optimized, and the parameters that influence their maturation after exposure to lipopeptides containing CD4(+) and CD8(+) T-cell epitopes were examined. The lipopeptides contained a single CD4(+) helper T-cell epitopes, one of a number of human leucocyte antigen (HLA)-A2-restricted cytotoxic T-cell epitope and the lipid Pam2Cys. To ensure complete maturation of the Mo-DC, we examined (i) the optimal lipopeptide concentration, (ii) the optimal Mo-DC density and (iii) the appropriate period of exposure of the Mo-DC to the lipopeptides. The results showed that a high dose of lipopeptide (30 microm) was no more efficient at upregulating maturation markers on Mo-DC than a low dose (6 microm). There was an inverse relationship between Mo-DC concentration and the mean fluorescence intensity of maturation markers. In addition, at the higher cell concentrations, the chemotactic capacity of the Mo-DC towards a cognate ligand, CCL21, was reduced. Thus, high cell concentrations during lipopeptide exposure were detrimental to Mo-DC maturation and function. The duration of exposure of Mo-DC to the lipopeptides had little effect on phenotype, although Mo-DC exposed to lipopeptides for 48 rather than 4 h showed an increased ability to stimulate autologous peripheral blood mononuclear cells to release interferon-gamma in the absence of exogenous maturation factors. These findings reveal conditions for generating mature antigen-loaded DC suitable for targeted immunotherapy.

Peptide inhibition of HIV-1: current status and future potential

More than 2 decades of intensive research has focused on defining replication mechanisms of HIV type 1 (HIV-1), the etiologic agent of AIDS. The delineation of strategies for combating this viral infection has yielded many innovative approaches toward this end. HIV-1 is a lentivirus in the family retroviridae that is relatively small with regard to both structure and genome size, having a diploid RNA genome of approximately 9 kb, with only three major genes and several gene products resulting from alternate splicing and translational frameshifting. Most marketed drugs for treating AIDS are inhibitors of HIV-1 reverse transcriptase or protease enzymes, but new targets include the integrase enzyme, cell surface interactions that facilitate viral entry, and also virus particle maturation and assembly. The emergence of drug-resistant variants of HIV-1 has been the main impediment to successful treatment of AIDS. Thus, there is a pressing need to develop novel treatment strategies targeting multiple stages of the virus life-cycle. Research efforts aimed at developing successful means for combating HIV-1 infection have included development of peptide inhibitors of HIV-1. This article summarizes past and current endeavors in the development of peptides that inhibit replication of HIV-1 and the role of peptide inhibitors in the search for new anti-HIV drugs.

The safety and tolerability of an HIV-1 DNA prime-protein boost vaccine (DP6-001) in healthy adult volunteers

This report describes the safety observations following administration of a polyvalent DNA prime-protein boost HIV-1 vaccine formulated with adjuvant QS21. Local injection site reactions were the most common (65% of subjects), and included type IV delayed-type hypersensitivity (DTH) reactions at prior DNA inoculation sites in 12 of 28 (43%) subjects following protein vaccination. Systemic reactions revealed two cases of vasculitis temporally related to inoculation with recombinant Env protein+QS21 adjuvant. Questions remain regarding the cause of the vasculitis, but the unique DTH observation may have contributed to the high level of immune responses previously reported for this vaccine.

Immunological responses and long-term treatment interruption after human immunodeficiency virus type 1 (HIV-1) lipopeptide immunization of HIV-1-infected patients: the LIPTHERA study

We studied the time course of immunological and virological markers after highly active antiretroviral therapy (HAART) interruption in chronically human immunodeficiency virus type 1 (HIV-1)-infected patients immunized with an HIV lipopeptide preparation. In a prospective open pilot study, 24 HIV-1-infected HAART-treated patients with undetectable plasma viral loads (pVLs) and CD4(+) T-cell counts above 350/mm(3) were immunized at weeks 0, 3, and 6 with a candidate vaccine consisting of six HIV lipopeptides. At week 24, patients with pVLs of <1.7 log(10) copies/ml were invited to stop taking HAART. Antiretroviral therapy was resumed if the pVL rose above 4.47 log(10) copies/ml and/or if the CD4(+) cell count fell below 250/mm(3). Immunological and virologic parameters were studied before and after HAART interruption. The median baseline and nadir CD4(+) cell counts were 482 (interquartile range [IQR], 195 to 826) and 313 (IQR, 1 to 481)/mm(3), respectively. New specific CD8(+) cell responses to HIV-1 epitopes were detected after immunization in 13 (57%) of 23 assessable patients. Twenty-one patients were evaluated 96 weeks after HAART interruption. The median time to pVL rebound was 4 weeks (IQR, 2 to 6), and the median peak pVL was 4.26 (IQR, 3 to 5) log(10) copies/ml. Thirteen of these 21 patients resumed HAART a median of 60 weeks after immunization (IQR, 9.2 to 68.4 weeks), when the median pVL was 4.8 (IQR, 2.9 to 5.7) log(10) copies/ml and the median CD4(+) cell count was 551 (IQR, 156 to 778)/mm(3). Eight patients were still off therapy at 96 weeks, with a median pVL of 4 (IQR, 1.7 to 4.6) log(10) copies/ml and a median CD4(+) cell count of 412 (IQR, 299 to 832)/mm(3). No clinical disease progression had occurred. Despite the lack of a control arm, these findings warrant a randomized study of therapeutic vaccination with HIV lipopeptides followed by long-term HAART interruption in AIDS-free chronically infected patients.

[Designing an effective AIDS vaccine: strategies and current status]

PURPOSE

The human immunodeficiency virus (HIV) and the acquired immunodeficiency syndrome induce account for over 40 million deaths in the past 20 years. Given that the currently available treatments to prevent HIV transmission and disease are not effective in eradicating the virus, vaccination likely represents the only efficacious adapted response to the global impact of this infection. This paper reviews the challenges encountered in the development of an HIV vaccine as well as the different vaccine approaches and main HIV vaccine candidates evaluated in clinical trials.

CURRENT KNOWLEDGE AND KEY POINTS

In spite the tremendous progress in HIV research, the major challenges that are encountered in the development of an HIV vaccine remain of scientific order and include viral specificities, absence of correlates of immune protection and limitations of existing animal models. Over 30 vaccine candidates have been evaluated in clinical trials. These vaccine approaches include the use of recombinant envelope proteins, DNA vaccines, live-vectored recombinant vaccines, subunit vaccines and prime-boost regimens combining various vaccine candidates. Although the protective efficacy of these candidate vaccines has yet to be demonstrated, some vaccination regiments appear to dampen initial viremia and prolong disease-free survival.

FUTURE PROSPECTS AND PROJECTS

Faced with the challenges in developing an HIV vaccine, international consortia and new methodologies have been proposed in order to accelerate the development and screening process of new candidate HIV vaccines. Moreover, in the absence of a protective vaccine, the impact of a vaccine that confers partial protection needs to be seriously considered.

[From fundamental immunology to development of vaccinology]

In the last ten years research in vaccinology has been developed in the world to conceive new vaccine approaches against infections like HIV/AIDS. Jean-Gérard Guillet is a pioneer in the development of new vaccine strategies. From the first results he obtained in the late 80's on the presentation of antigenic peptides to T cells, he axed his work on the study of induction mechanisms of T cell mediated immune responses. The selection of antigenic peptides and the search to enhance antigen immunogenicity led him to elaborate lipopeptides as new vaccine formulae. The efficacy of these preparations was tested in animal models (mouse, macaque) and, thereafter, in humans with clinical trials promoted by the French National Agency for AIDS and viral hepatitis (ANRS). The study of T-cell induced responses in vaccinated volunteers was implemented following the creation of two facilities, an immuno-monitoring platform and the Clinical Investigation Centre Cochin-Pasteur, a structure specialized in vaccinology.

Vaccine adjuvant systems containing monophosphoryl lipid A and QS21 induce strong and persistent humoral and T cell responses against hepatitis B surface antigen in healthy adult volunteers

A randomised, double-blind study assessing the potential of four adjuvants in combination with recombinant hepatitis B surface antigen has been conducted to evaluate humoral and cell-mediated immune responses in healthy adults after three vaccine doses at months 0, 1 and 10. Three Adjuvant Systems (AS) contained 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and QS21, formulated either with an oil-in-water emulsion (AS02B and AS02V) or with liposomes (AS01B). The fourth adjuvant was CpG oligonucleotide. High levels of antibodies were induced by all adjuvants, whereas cell-mediated immune responses, including cytolytic T cells and strong and persistent CD4(+) T cell response were mainly observed with the three MPL/QS21-containing Adjuvant Systems. The CD4(+) T cell response was characterised in vitro by vigorous lymphoproliferation, high IFN-gamma and moderate IL-5 production. Antigen-specific T cell immune response was further confirmed ex vivo by detection of IL-2- and IFN-gamma-producing CD4(+) T cells, and in vivo by measuring increased levels of IFN-gamma in the serum and delayed-type hypersensitivity (DTH) responses. The CpG adjuvanted vaccine induced consistently lower immune responses for all parameters. All vaccine adjuvants were shown to be safe with acceptable reactogenicity profiles. The majority of subjects reported local reactions at the injection site after vaccination while general reactions were recorded less frequently. No vaccine-related serious adverse event was reported. Importantly, no increase in markers of auto-immunity and allergy was detected over the whole study course. In conclusion, the Adjuvant Systems containing MPL/QS21, in combination with hepatitis B surface antigen, induced very strong humoral and cellular immune responses in healthy adults. The AS01B-adjuvanted vaccine induced the strongest and most durable specific cellular immune responses after two doses. These Adjuvant Systems, when added to recombinant protein antigens, can be fundamental to develop effective prophylactic vaccines against complex pathogens, e.g. malaria, HIV infection and tuberculosis, and for special target populations such as subjects with an impaired immune response, due to age or medical conditions.

Cellular immune responses induced with dose-sparing intradermal administration of HIV vaccine to HIV-uninfected volunteers in the ANRS VAC16 trial

OBJECTIVE

The objective was to compare the safety and cellular immunogenicity of intradermal versus intramuscular immunization with an HIV-lipopeptide candidate vaccine (LIPO-4) in healthy volunteers.

METHODOLOGY

A randomized, open-label trial with 24 weeks of follow-up was conducted in France at six HIV-vaccine trial sites. Sixty-eight healthy 21- to 55-year-old HIV-uninfected subjects were randomized to receive the LIPO-4 vaccine (four HIV lipopeptides linked to a T-helper-stimulating epitope of tetanus-toxin protein) at weeks 0, 4 and 12, either intradermally (0.1 ml, 100 microg of each peptide) or intramuscularly (0.5 ml, 500 microg of each peptide). Comparative safety of both routes was evaluated. CD8+ T-cell immune responses to HIV epitopes (ELISpot interferon-gamma assay) and tetanus toxin-specific CD4+ T-cell responses (lymphoproliferation) were assessed at baseline, two weeks after each injection, and at week 24.

RESULTS AND CONCLUSION

No severe, serious or life-threatening adverse events were observed. Local pain was significantly more frequent after intramuscular injection, but local inflammatory reactions were more frequent after intradermal immunization. At weeks 2, 6, 14 and 24, the respective cumulative percentages of induced CD8+ T-cell responses to at least one HIV peptide were 9, 33, 39 and 52 (intradermal group) or 14, 20, 26 and 37 (intramuscular group), and induced tetanus toxin-specific CD4+ T-cell responses were 6, 27, 33 and 39 (intradermal), or 9, 46, 54 and 63 (intramuscular). In conclusion, intradermal LIPO-4 immunization was well tolerated, required one-fifth of the intramuscular dose, and induced similar HIV-specific CD8+ T-cell responses. Moreover, the immunization route influenced which antigen-specific T-cells (CD4+ or CD8+) were induced.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00121121.

HLA-DR-restricted peptides identified in the Nef protein can induce HIV type 1-specific IL-2/IFN-gamma-secreting CD4+ and CD4+ /CD8+ T cells in humans after lipopeptide vaccination

We screened the Neflaiprotein to identify new HLA-DR-restricted epitopes, because this small protein is expressed early during infection, and specific CD4(+) T cells are critical for effective immunity in HIV-1 infection. We synthesized a set of peptides that covers the sequence of the Nef protein, and performed binding assays using 10 common HLA-DR molecules. We defined four large regions in this protein able to bind very efficiently to eight HLADR molecules. We took advantage of healthy volunteers immunized with an HIV-1 lipopeptide vaccine that contains three of the four HLA DR-restricted regions to investigate their capacities to stimulate T cells. In 11 vaccinated volunteers, typed for their class II molecules, we were able to correlate sequences of the vaccine displaying binding activities to specific HLA-DR molecules and the induction of CD4(+) T cell proliferation. To identify potential HLA-DR epitopes, we synthesized 31 15-mer peptides and showed that 26 bound to one or more HLA-DR molecules. Interestingly, 12 of the 26 15-mer peptides identified are included in the sequence of lipopeptides. We used IFN-gamma ELISPOT and flow cytometer assays to investigate the capacity of these potential CD4(+) T cell epitopes to induce specific T cell responses. We showed that seven of these peptides were able to stimulate HIV-specific T cell responses in five of six tested volunteers. These cells are Nef-specific CD4(+) and CD4(+) CD8(+) T cells secreting IL-2/INF-gamma or IL-2 alone. To conclude, these 26 Nef HLA-DR-restricted peptides could be helpful to better evaluate CD4(+) deficiencies in HIV infection and, for new vaccine designs.

Protective immunity to genital herpes simplex virus type 1 and type 2 provided by self-adjuvanting lipopeptides that drive dendritic cell maturation and elicit a polarized Th1 immune response

Genital herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) infections are a significant health problem worldwide. While it is believed that CD4+ Th1 cells are among the effectors to herpes immunity, developing an epitope-based clinical vaccine capable of inducing an effective anti-herpes CD4+ Th1-mediated protection is still under investigation. Few molecules achieve this target without the aid of external immuno-adjuvant. The present study was undertaken to examine the immunogenicity in mice of five CD4+ T cell epitope peptides (gD1-29, gD49-82, gD146-179, gD228-257, and gD332-358), recently identified from the HSV-1 glycoprotein D (gD), covalently linked to a palmitic acid moiety (lipopeptides) using the high-yielding chemoselective ligation method and delivered subcutaneously in free-adjuvant saline. Their protective efficacy was evaluated in a progestin-induced susceptibility mouse model of genital herpes following intravaginal challenge with either HSV-1 or HSV-2. Four out of five gD lipopeptides effectively induced virus-specific CD4+ Th1 responses associated with a reduction of virus replication in the genital tract and protection from overt signs of genital disease. A cocktail of three highly immunogenic lipopeptides provoked maturation of dendritic cells, induced interferon gamma (IFN-gamma)-producing CD4+ T cells, and protected against both HSV- 1 and HSV-2 infections. Depletion of specific T cell subsets from lipopeptideimmunized mice before intravaginal HSV challenges demonstrated that CD4+ T cells were primarily responsible for this protection. The strength of induced T cell immunity, together with the ease of construction and safety of these totally synthetic self-adjuvanting lipopeptides, provide a molecularly defined formulation that could combat genital herpes and other human viral infections for which induction of Th1 immunity is crucial.

New CD4+ and CD8+ T cell responses induced in chronically HIV type-1-infected patients after immunizations with an HIV type 1 lipopeptide vaccine

We showed that an anti-HIV lipopeptide vaccine injected to HIV-uninfected volunteers was well tolerated and able to induce a specific CD4(+) and CD8(+) T cell responses. The same vaccine was injected in HIV-1 chronically infected patients controlled by HAART to evaluate its immunogenicity. In this trial, 24 patients were immunized three times with a mixture of six lipopeptides (Nef 66-97, Nef 117-147, Nef 182-205, Gag 183-214, Gag 253-284, and Env 303-335) at 0, 3, and 6 weeks. We studied the HIV-1-specific CD4(+) T cell proliferative responses. The IFN-gamma secretion by activated CD8(+) T cells was evaluated, using an ex vivo ELISpot assay and 60 CD8(+) T cell epitopes derived from the vaccine. Before immunization (W0), anti-HIV CD4(+) T cell responses to Gag, Nef, and Env large peptides were detected in 7/23 (30%) analyzable patients. After three injections, 17/23 (74%) patients had a proliferative response and 16 of them induced new specific CD4(+) T cell responses. At W0, CD8(+) T cell responses to HIV-1 epitopes were detected in 6/23 (26%) patients. After vaccination, 16/23 (70%) patients showed CD8(+) T cell responses and 13 of these patients induced new T cell responses to 25 different HIV-1 epitopes. These HIV-1 epitopes were detected in patients with various HLA class I molecules (HLA-A2, -A3/A11, -A24, -B7 superfamily, -B8), as found in the majority of the white population. Lipopeptides induce new anti-HIV T cell responses in vaccinated infected patients and could be used as a new immunotherapy strategy. The majority of these responders induced specific new CD4(+) and CD8(+) T cell responses.

Induction of multifunctional human immunodeficiency virus type 1 (HIV-1)-specific T cells capable of proliferation in healthy subjects by using a prime-boost regimen of DNA- and modified vaccinia virus Ankara-vectored vaccines expressing HIV-1 Gag coupled to CD8+ T-cell epitopes

A double-blind randomized phase I trial was conducted in human immunodeficiency virus type 1 (HIV-1)-negative subjects receiving vaccines vectored by plasmid DNA and modified vaccinia virus Ankara (MVA) expressing HIV-1 p24/p17 gag linked to a string of CD8(+) T-cell epitopes. The trial had two groups. One group received either two doses of MVA.HIVA (2x MVA.HIVA) (n=8) or two doses of placebo (2x placebo) (n=4). The second group received 2x pTHr.HIVA followed by one dose of MVA.HIVA (n=8) or 3x placebo (n=4). In the pTHr.HIVA-MVA.HIVA group, HIV-1-specific T-cell responses peaked 1 week after MVA.HIVA vaccination in both ex vivo gamma interferon (IFN-gamma) ELISPOT (group mean, 210 spot-forming cells/10(6) cells) and proliferation (group mean stimulation index, 37), with assays detecting positive responses in four out of eight and five out of eight subjects, respectively. No HIV-1-specific T-cell responses were detected in either assay in the 2x MVA.HIVA group or subjects receiving placebo. Using a highly sensitive and reproducible cultured IFN-gamma ELISPOT assay, positive responses mainly mediated by CD4(+) T cells were detected in eight out of eight vaccinees in the pTHr.HIVA-MVA.HIVA group and four out of eight vaccinees in the 2x MVA.HIVA group. Importantly, no false-positive responses were detected in the eight subjects receiving placebo. Of the 12 responders, 11 developed responses to previously identified immunodominant CD4(+) T-cell epitopes, with 6 volunteers having responses to more than one epitope. Five out of 12 responders also developed CD8(+) T-cell responses to the epitope string. Induced T cells produced a variety of anti-viral cytokines, including tumor necrosis factor alpha and macrophage inflammatory protein 1 beta. These data demonstrate that prime-boost vaccination with recombinant DNA and MVA vectors can induce multifunctional HIV-1-specific T cells in the majority of vaccinees.

Clinical safety of HIV lipopeptides used as vaccines in healthy volunteers and HIV-infected adults

BACKGROUND

HIV-1 lipopeptides have been developed by the French National Agency for AIDS Research (ANRS) for use as candidate vaccine against HIV since 1994. Between 1996 and 2005, four different lipopeptide constructs were tested alone or in combination with recombinant canarypox HIV vaccines in 10 trials conducted in France. The aim of this study was to review clinical safety of HIV lipopeptides.

METHODS

A meta-analysis based on individual subject data examined clinical safety data collected in eight preventive trials and two therapeutic trials enrolling 200 HIV-1-uninfected healthy volunteers and 48 HIV-1-infected patients.

RESULTS

Of 248 trial participants, eight (3.2%) did not complete follow-up: seven among the 200 healthy volunteers, and one among the 48 HIV-1 infected patients. During the 354 person-years of follow-up, 860 lipopeptides injections were administered. Local reactions were common. However, in trials where lipopeptides were tested without adjuvant and appropriate diluents, none of the vaccinees experienced severe local response. Systemic reactions were generally mild and transient. No grade 4 reaction was reported; 18 subjects experienced grade 3 systemic events related to the vaccination, mainly asthenia, fever, headache and arthralgia. Multivariate analysis showed that female sex, number of injections and diluent (more reactions in 5% glucose alone than in combination with Tris-HCl buffer) significantly increased systemic reactions related to the vaccination.

CONCLUSION

These data demonstrate that reactogenicity and systemic safety of HIV lipopeptides vaccine are acceptable both in healthy volunteers and HIV-infected adults.

Th-cytotoxic T-lymphocyte chimeric epitopes extended by Nepsilon-palmitoyl lysines induce herpes simplex virus type 1-specific effector CD8+ Tc1 responses and protect against ocular infection

Molecularly defined vaccine formulations capable of inducing antiviral CD8+ T-cell-specific immunity in a manner compatible with human delivery are limited. Few molecules achieve this target without the support of an appropriate immunological adjuvant. In this study, we investigate the potential of totally synthetic palmitoyl-tailed helper-cytotoxic-T-lymphocyte chimeric epitopes (Th-CTL chimeric lipopeptides) to induce herpes simplex virus type 1 (HSV-1)-specific CD8+ T-cell responses. As a model antigen, the HSV-1 glycoprotein B498-505 (gB498-505) CD8+ CTL epitope was synthesized in line with the Pan DR peptide (PADRE), a universal CD4+ Th epitope. The peptide backbone, composed solely of both epitopes, was extended by N-terminal attachment of one (PAM-Th-CTL), two [(PAM)2-Th-CTL], or three [(PAM)3-Th-CTL] palmitoyl lysines and delivered to H2b mice in adjuvant-free saline. Potent HSV-1 gB498-505-specific antiviral CD8+ T-cell effector type 1 responses were induced by each of the palmitoyl-tailed Th-CTL chimeric epitopes, irrespective of the number of lipid moieties. The palmitoyl-tailed Th-CTL chimeric epitopes provoked cell surface expression of major histocompatibility complex and costimulatory molecules and production of interleukin-12 and tumor necrosis factor alpha proinflammatory cytokines by immature dendritic cells. Following ocular HSV-1 challenge, palmitoyl-tailed Th-CTL-immunized mice exhibited a decrease of virus replication in the eye and in the local trigeminal ganglion and reduced herpetic blepharitis and corneal scarring. The rational of the molecularly defined vaccine approach presented in this study may be applied to ocular herpes and other viral infections in humans, providing steps are taken to include appropriate Th and CTL epitopes and lipid groups.

Cross-clade conservation of HIV type 1 Nef immunodominant regions recognized by CD8+ T cells of HIV type 1 CRF02_AG-infected Ivorian (West Africa)

Most HIV vaccine trials in the world are conducted with clade B while most circulating viral strains in Africa are non-B subtypes. We determined whether CD8+ T cells from HIV-1 intersubtype CRF02_AG-infected Ivorian individuals were able to recognize clade B epitopes. CD8+ T cell responses of nine HIV-1 intersubtype CRF02_AG-infected Ivorian patients and nine HIV-1 subtype B-infected French patients were studied using pools of HIV-1 clade B peptides (110 well-defined HIV CD8+ T cell epitopes) in an ELISPOT IFN-gamma assay. There was no difference in the number of recognized peptide pools between Ivorian and French cohorts (mean of four pools in both cases). Ivorian individuals had generated CD8+ T cell responses cross-reactive against HIV-1 subtype B and some individual peptides had been identified. Furthermore, sequence analysis of nef HIV genes of the Ivorian patients and nef cloning in two patients revealed very few variations between HIV- 1 intersubtype CRF02_AG and subtype B in nef immunodominant regions included in HIV clade B lipopeptide vaccines, currently tested in France.

Sequences of clustered epitopes in Gag and Nef potentially presented by predominant class I human leukocyte antigen (HLA) alleles A and B expressed by human immunodeficiency virus type 1 (HIV-1)-infected patients in Vietnam

The aim of this study was to define pluriepitopic regions in Gag and Nef possibly relevant in the perspective of a vaccine design in a vietnamese population. The protein sequences derived from gag and nef genes and phenotyping of the class I human leukocyte antigens (HLA) A and B alleles were established for 28 human immunodeficiency virus type 1 (HIV-1)-infected patients from Ho Chi Minh City, Vietnam. The protein sequences display polymorphism mutations as compared with a B reference strain (HXB2). The most frequently represented HLA-A and -B alleles were HLA-A11, A02, and A33 expressed by 35.7, 23.2, and 21.4% of the patients, respectively, and HLA-B75, B46, and B62 expressed by 35.7, 25, and 17.9% of the patients, respectively. This study allows us to determine four pluriepitopic regions in Gag and Nef that should be chosen for a vaccine design in a Vietnamese population.

Novel peptide-based HIV-1 immunotherapy

Therapeutic immunisation of human immunodeficiency virus type 1-infected individuals should be actively pursued in the first instance to augment highly active antiretroviral therapy regimens. Peptide-based immunotherapeutic strategies offer considerable advantages over conventional approaches, particularly regarding safety. Peptide design itself is becoming increasingly sophisticated, with the rapid evolution of bioinformatics tools that can analyse not only T cell epitopes, but also their potential for successful presentation on diverse human leukocyte antigen (HLA) class I or II following intracellular processing by antigen-presenting cells (APCs). By targeting conserved viral domains, peptides acquire improved reactivity to diverse viral strains. Dendritic cells represent a powerful route of administration, as they are the most potent APCs and can present exogenous peptides on both HLA class I and II through the process of cross-presentation. In this way, soluble peptides can thereby stimulate both CD4+ and CD8+ T cells.

Spontaneous regression of grade 3 vulvar intraepithelial neoplasia associated with human papillomavirus-16-specific CD4(+) and CD8(+) T-cell responses

Cell-mediated immunity directed against human papillomavirus 16 (HPV-16) antigens was studied in six patients affected with grade 3 vulvar intraepithelial neoplasia (VIN3, also known as bowenoid papulosis). Five of the patients presented with a chronic and persistent disease that relapsed after destructive treatments. They showed no detectable anti-HPV blood T-cell responses and no T-cell intraepidermal vulvar infiltrate containing both CD4+ and CD8+ lymphocytes. The last patient had a complete clearance of viral lesions, 8 months after disease onset and 2 months after electrocoagulation of <50% of the VIN3 lesions. She showed high frequency anti-E6 and anti-E7 effector blood T cells by ex vivo ELISpot-IFNgamma assay before clinical regression. Immunohistochemical study of her vulvar biopsy revealed a marked dermal infiltrate containing a majority of CD4+ T lymphocytes and an epidermal infiltrate made up of both CD4(+) and CD8(+) T cells. This seems to be the first evidence of an association between spontaneous regression of VIN3 lesions and HPV-specific T-cell responses detectable in the blood. Hence, an increase of HPV-specific effector T lymphocyte responses by vaccine-based therapeutic strategies might be useful to clear the lesions in bowenoid papulosis disease.