Sustained control of viremia following therapeutic immunization in chronically HIV-1-infected individuals.

OBJECTIVE: Viral rebounds inevitably follow interruption of antiretroviral treatment in HIV-1-infected individuals. The randomized ANRS 093 aimed at investigating whether a therapeutic immunization was effective in containing the long-term viral replication following discontinuation of antiretroviral drugs in patients. METHODS: Seventy HIV-1-infected patients effectively treated with antiretroviral drugs were randomized to continue treatment alone or in combination with four boosts of ALVAC 1433 and HIV-LIPO-6T vaccines followed by three cycles of subcutaneous interleukin-2. The impact of vaccination on viral replication was assessed by interrupting antiretroviral drugs first at week 40 and thereafter during follow-up until week 100. Antiretroviral drugs were re-initiated according to predefined criteria. RESULTS: The median cumulative time (days) off treatment was greater in the vaccine group (177) than in the control group (89) (P = 0.01). The proportion of time (mean, SE) without antivirals per-patient was 42.8% (5.1) and 26.5% (4.2) in the vaccine and control groups, respectively (P = 0.005). Viremia (median log10 copies/ml), 4 weeks following the first, second and third treatment interruption was higher in control patients (4.81, 4.44, 4.53) in comparison with vaccinated patients (4.48, 4.00, 3.66) (P = 0.42, 0.015 and 0.024, respectively). HIV-specific CD4 and CD8 T-cell responses elicited by the therapeutic immunization strongly correlated with the reduction of the time of antiviral therapy (P = 0.0027 and 0.016, respectively). CONCLUSION: Our findings provide evidence that therapeutic immunization significantly impacts on HIV-1 replication. This translated into a decrease of up to 40% in the duration of exposure to antiretroviral drugs over 15 months of patients' follow-up.

Immunological and virological efficacy of a therapeutic immunization combined with interleukin-2 in chronically HIV-1 infected patients.

OBJECTIVE: Several lines of evidence suggest that the immune system may control HIV-1 replication, but that it could fail in the long term. Strategies aimed to elicit specific immune responses may enable patients to contain virus replication. METHODS: HIV-1-infected patients were randomized to continue either their antiviral therapy alone (controls; n = 37) or with four boosts of vaccination combining ALVAC-HIV (vCP1433) and Lipo-6T vaccines (weeks 0, 4, 8, 12) followed by three cycles of subcutaneous interleukin-2 (weeks 16, 24, 32) (Vac-IL-2 group; n = 34). RESULTS: Of the Vac-IL-2 group, 15/32 (47%) exhibited a stable HIV p24 antigen-proliferative response compared with 8/33 (24%) controls (P = 0.049). After vaccination, 19/33 (58%) of the Vac-IL-2 group exhibited a multiepitopic HIV-1-specific CD4 cell proliferative response compared with 9/36 (25%) of controls (P = 0.006). The breadth and the magnitude of HIV-specific interferon-gamma-producing CD8 T cells improved in the Vac-IL-2 group. After stopping antiviral drugs, 24% of the Vac-IL-2 group lowered their viral set point compared with 5% of controls (P = 0.027). Logistic-regression analysis demonstrated that vaccine-elicited immunological responses were predictive of virological control (P = 0.046 and 0.014 for stable and multiepitopic CD4 T cell responses, respectively). CONCLUSION: This study provides proof of the concept that therapeutic immunization before antiviral drug cessation may contribute to the containment of HIV replication.

Use of well-defined HIV-derived epitopes to evaluate CD4(+) and CD8(+) T cell responses in patients with chronic HIV-1 infection treated with HAART.

Highly active antiretroviral therapy (HAART) is associated with a dramatic clinical benefit to HIV-infected patients through significant plasma viremia reduction and CD4(+) T cells increase. In previous reports, HIV-specific CD4(+) and/or CD8(+) T cell responses have been studied separately during HAART; therefore the relationship between these two virus-specific populations is currently not well understood. In this study, both HIV-specific CD4(+) and CD8(+) T cell responses were investigated using a large panel of well-defined T cell epitope peptides in 24 HIV-1-infected patients undergoing HAART, with undetectable viral load and CD4(+) T cell count >/= 350/mm(3). One-third of the patients had CD4(+) T cells able to proliferate when exposed to HIV-1 protein fragments but only two patients displayed polyclonal responses. In addition the majority (78%) of HAART-treated patients displayed no or monospecific CD8(+) T cell responses and the phenotypic analysis of these HIV-specific CD8(+) T cells demonstrated the absence of terminally differentiated effectors. In conclusion, the experimental approach used in this study shows that CD4(+) T cell responses may persist during HAART but are not associated with strong CD8(+) T cell responses

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

We studied the effect of booster injections and the long-term immune response after injections of an anti-human immunodeficiency virus type 1 (HIV-1) lipopeptide vaccine. This vaccine was injected alone or with QS21 adjuvant to 28 HIV-uninfected volunteers. One month later, after a fourth injection of the vaccine, B- and T-cell anti-HIV responses were detected in >85% of the vaccinated volunteers. One year after this injection, a long-term immune response was observed in >50% of the volunteers. At this point, a positive QS21 effect was observed only in the sustained B-cell and CD4(+)-T-cell responses. To better characterize the CD8(+)-T-cell response, we used a gamma interferon enzyme-linked immunospot method and a bank of 59 HIV-1 epitopes. For the six most common HLA molecules (HLA-A2, -A3, -A11, -A24, -B7 superfamily, and -B8), an average of 10 (range, 3 to 15) HIV-1 epitopes were tested. CD8(+)-T-cell responses were evaluated according to the HLA class I molecules of the volunteers. Each assessment was based on 18 HIV-1 epitopes in average. We showed that 31 HIV-1 epitopes elicited specific CD8(+)-T-cell responses after vaccination. The most frequently recognized peptides were Nef 68-76 (-B7), Nef 71-79 (-B7), Nef 84-92 (-A11), Nef 135-143 (-B7), Nef 136-145 (-A2), Nef 137-145 (-A2), Gag 259-267 (-B8), Gag 260-268 (-A2), Gag 267-274 (-A2), Gag 267-277 (-B7), and Gag 276-283 (A24). We found that CD8(+)-T-cell epitopes were induced at a higher number after a fourth injection (P < 0.05 compared to three injections), which indicates an increase in the breadth of HIV CD8(+)-T-cell epitope recognition after the boost.

HLA-DP4, the most frequent HLA II molecule, defines a new supertype of peptide-binding specificity.

Among HLA-DP specificities, HLA-DP4 specificity involves at least two molecules, HLA-DPA1*0103/DPB1*0401 (DP401) and HLA-DPA1*0103/DPB1*0402 (DP402), which differ from each other by only three residues. Together, they are present worldwide at an allelic frequency of 20-60% and are the most abundant human HLA II alleles. Strikingly, the peptide-binding specificities of these molecules have never been investigated. Hence, in this study, we report the peptide-binding motifs of both molecules. We first set up a binding assay specific for the immunopurified HLA-DP4 molecules. Using multiple sets of synthetic peptides, we successfully defined the amino acid preferences of the anchor residues. With these assays, we were also able to identify new peptide ligands from allergens and viral and tumor Ags. DP401 and DP402 exhibit very similar patterns of recognition in agreement with molecular modeling of the complexes. Pockets P1 and P6 accommodate the main anchor residues and interestingly contain only two polymorphic residues, beta86 and beta11, respectively. Both positions are almost dimorphic and thus produce a limited number of pocket combinations. Taken together, our results support the existence of three main binding supertypes among HLA-DP molecules and should significantly contribute to the identification of universal epitopes to be used in peptide-based vaccines for cancer, as well as for allergic or infectious diseases.

Lipopeptide-based melanoma cancer vaccine induced a strong MART-27-35-cytotoxic T lymphocyte response in a preclinal study.

Identification of tumor antigens and their optimal antigenic peptides raised hopes for the development of peptide-based immunotherapeutic vaccine strategies for human melanoma, however. Synthetic peptides alone are not immunogenic enough, and adequate formulation is critical for elaboration of peptide vaccines. To improve formulation, we evaluated 2 lipopeptide constructs, both including HLA-A2-restricted MART 27-35-CD8+ T lymphocyte (CTL) epitope covalently linked to universal tetanus toxoid (TT) 830-843 helper T lymphocyte (HTL) epitope, in HLA-A2 transgenic mouse models that mimic human CTL responses in vivo. These 2 constructs only differed in the formulation of their lipid tail. We showed that lipopeptide constructs were strongly recognized, in vitro, by human MART 27-35 cytotoxic T cells derived from tumor-infiltrating lymphocytes. The transgenic Mice immunized with these 2 MART lipopeptide formulations containing covalently linked HTL-CTL epitopes induced strong MART 27-35 cytotoxic T cells. This CTL induction was critically dependent on the presence of the helper T lymphocyte epitope. These results also showed that a single palmitoyl-lysine chain is enough to assure immunogenicity of a given peptide and that the presence of a lipid tail bypass the need for adjuvant. These results support the selection of MART-lipopeptide melanoma vaccine for evaluation in a clinical trial.

Distinct roles of adenovirus vector-transduced dendritic cells, myoblasts, and endothelial cells in mediating an immune response against a transgene product.

Adenovirus-mediated gene delivery via the intramuscular route efficiently promotes an immune response against the transgene product. In this study, a recombinant adenovirus vector encoding beta-galactosidase (Ad beta Gal) was used to transduce dendritic cells (DC), which are antigen-presenting cells, as well as myoblasts and endothelial cells (EC), neither of which present antigens. C57BL/6 mice received a single intramuscular injection of Ad beta Gal-transduced DC, EC, or myoblasts and were then monitored for anti-beta-galactosidase (anti-beta-Gal) antibody production, induction of gamma interferon-secreting CD8(+) T cells, and protection against melanoma tumor cells expressing beta-Gal. While all transduced cell types were able to elicit an antibody response against the transgene product, the specific isotypes were distinct, with exclusive production of immunoglobulin G2a (IgG2a) antibodies following injection of transduced DC and EC versus equivalent IgG1 and IgG2a responses in mice inoculated with transduced myoblasts. Transduced DC induced a strong ex vivo CD8(+) T-cell response at a level of 50% of the specific response obtained with the Ad beta Gal control. In contrast, this response was 6- to 10-fold-lower in animals injected with transduced myoblasts and EC. Accordingly, only animals injected with transduced DC were protected against a beta-Gal tumor challenge. Thus, in order to induce a strong and protective immune response to an adenovirus-encoded transgene product, it is necessary to transduce cells of dendritic lineage. Importantly, it will be advantageous to block the transduction of DC for adenovirus-based gene therapy strategies.

Adenovirus hexon protein is a potent adjuvant for activation of a cellular immune response.

The capacity of recombinant adenoviruses (rAd) to induce immunization against their transgene products has been well documented. In the present study, we evaluated the vaccinal adjuvant role of rAd independently of its vector function. BALB/c mice received one subcutaneous injection of a mixture of six lipopeptides (LP6) used as a model immunogen, along with AdE1 degrees (10(9) particles), a first-generation rAd empty vector. Although coinjected with a suboptimal dose of lipopeptides, AdE1 degrees significantly improved the effectiveness of the vaccination, even in the absence of booster immunization. In contrast to mice that received LP6 alone or LP6 plus a mock adjuvant, mice injected with AdE1 degrees plus LP6 developed both a polyspecific T-helper type 1 response and an effector CD8 T-cell response specific to at least two class I-restricted epitopes. The helper response was still observed when immunization was performed using LP6 plus a mixture of soluble capsid components released from detergent-disrupted virions. When mice were immunized with LP6 and each individual capsid component, i.e., hexon, penton base, or fiber, the results obtained suggested that hexon protein was responsible for the adjuvant effect exerted by disrupted Ad particles on the helper response to the immunogen. Our results thus have some important implications not only in vaccinology but also for gene therapy using rAd vectors.