Cytokine responses to human immunodeficiency virus type 1 (HIV-1) induced by immunization with live recombinant canarypox virus vaccine expressing HIV-1 genes boosted by HIV-1(SF-2) recombinant GP120

Phase I/II randomized trial of safety and immunogenicity of LIPO-5 alone, ALVAC-HIV (vCP1452) alone, and ALVAC-HIV (vCP1452) prime/LIPO-5 boost in healthy, HIV-1-uninfected adult participants

Finding an effective human immunodeficiency virus type 1 (HIV-1) vaccine remains a major global health priority. In a phase I/II, placebo-controlled trial, healthy, HIV-1-negative adults were randomized to receive one of 5 vaccine regimens: LIPO-5 (combination of 5 lipopeptides) alone (250 μg), ALVAC-HIV (vCP1452) alone, or 3 groups of ALVAC-HIV (vCP1452) followed by ALVAC-HIV (vCP1452) plus LIPO-5 (250, 750, and 2,500 μg). Only 73/174 participants (42%) received all four vaccinations due to a study halt related to myelitis. There were no significant differences in systemic reactions between groups or in local reactogenicity between groups receiving ALVAC-HIV (vCP1452). Significant differences in local reactogenicity occurred between groups receiving LIPO-5 (P ≤ 0.05). Gag and Env antibodies were undetectable by ELISA 2 weeks after the fourth vaccination for all but one recipient. Antibodies to Gag and Env were present in 32% and 24% of recipients of ALVAC-HIV (vCP1452) alone and in 47% and 35% of ALVAC-HIV (vCP1452)+LIPO recipients, respectively. Coadministration of LIPO-5 did not significantly increase the response rate compared to ALVAC-HIV (vCP1452) alone, nor was there a significant relationship between dose and antibody responses among ALVAC-HIV (vCP1452)+LIPO groups. Over 90% of study participants had no positive gamma interferon (IFN-γ) enzyme-linked immunosorbent spot assay (ELISpot) responses to any peptide pool at any time point. The study was halted due to a case of myelitis possibly related to the LIPO-5 vaccine; this case of myelitis remains an isolated event. In general, there was no appreciable cell-mediated immunity detected in response to the vaccines used in this study, and antibody responses were limited. The clinical trial is registered on ClinicalTrials.gov with registry number NCT00076063.

Humoral response and antiviral cytokine expression following vaccination of thoroughbred weanlings--a blinded comparison of commercially available vaccines

Previous studies in experimental ponies using interferon gamma (IFN-γ) as a marker for cell mediated immune (CMI) response demonstrated an increase in IFN-γ gene expression following vaccination with an ISCOM subunit, a canarypox recombinant and more recently, an inactivated whole virus vaccine. The objective of this study was to carry out an independent comparison of both humoral antibody and CMI responses elicited following vaccination with all these vaccine presentation systems. Antibody response of 44 Thoroughbred weanlings was monitored for three weeks following the second dose of primary vaccination (V2) by single radial haemolysis (SRH). The pattern of antibody response was similar for all vaccines. The antibody response of horses vaccinated with the inactivated whole virus vaccine (Duvaxyn IE-T Plus) was superior to that of the horses vaccinated with the ISCOM-matrix subunit (Equilis Prequenza Te) and canarypox recombinant (ProteqFlu-Te) vaccine. In this study 39% of weanlings failed to seroconvert following their first dose of primary vaccination (V1). Poor response to vaccination (H3N8) was observed among weanlings vaccinated with Equilis Prequenza Te and ProteqFlu-Te but not among those vaccinated with Duvaxyn IE-T Plus. PAXgene bloods were collected on days 0, 2, 7 and 14 following V1. Gene expression levels of IFN-γ, IL-1β (proinflammatory cytokine) and IL-4 (B cell stimulating cytokine) were measured using RT-PCR. Mean gene expression levels of IL-1β and IL-4 peaked on day 14 post vaccination. The increase in IL-4 gene expression by horses vaccinated with Equilis Prequenza Te was significantly greater to those vaccinated with the other two products. Vaccination with all three vaccines resulted in a significant increase in IFN-γ gene expression which peaked at 7 days post V1. Overall, there was no significant difference in IFN-γ gene expression by the horses vaccinated with the whole inactivated, the subunit and the canarypox recombinant vaccines included in this study.

ALVAC-HIV as a prophylactic and therapeutic vaccine: highlights from over a decade of clinical trials

ALVAC-HIV vaccines (vCP125, vCP205, vCP300, vCP1433, vCP1452 and vCP1521) are preparations of a modified recombinant canarypox virus designed to induce or augment CD8+ immune responses. As the focus of several Phase I–III trials, they have been the most extensively studied live vector-based HIV vaccines. Overall, ALVAC-HIV induces modest CD8+ T-cell responses in approximately 20–50% of recipients. The addition of IL-2, recombinant glycoprotein 120 or 160, Remune or LIPO-6T to ALVAC-HIV does not appear to enhance overall CD8+ T-cell immune responses. The ability of ALVAC-HIV to induce interclade immunity and immunogenicity in newborns with perinatal exposure to HIV has important implications for the control of HIV worldwide. Experience from clinical trials in over 10,000 HIV-infected and noninfected individuals has shown that ALVAC constructs are safe, with reactogenicity profiles similar to those reported for currently licensed vaccines. Despite seemingly modest immunogenicity at the present time, studies to date have set the stage for further exploration of the potential of ALVAC-HIV vaccines. This report highlights findings from clinical trials using ALVAC-HIV, alone and in combination with other agents, as both a prophylactic and a therapeutic vaccine.

A phase 1/2 comparative vaccine trial of the safety and immunogenicity of a CRF01_AE (subtype E) candidate vaccine: ALVAC-HIV (vCP1521) prime with oligomeric gp160 (92TH023/LAI-DID) or bivalent gp120 (CM235/SF2) boost

BACKGROUND

The development of an effective HIV-1 vaccine is critical to control the pandemic. A prime-boost HIV-1 vaccine trial assessing safety and immunogenicity was conducted in Thailand as part of an evaluation of candidate regimens for a phase 3 efficacy trial.

METHODS

ALVAC-HIV (vCP1521), expressing circulating recombinant form 01_AE (CRF01_AE) gp120/subtype B LAI and subtype B Gag/Protease boosted with recombinant envelope oligomeric CRF01_AE gp160 (ogp160) or bivalent CRF01_AE/subtype B gp120 CM235/SF2, was evaluated in a phase 1/II trial of 130 HIV-negative Thai adults.

RESULTS

One hundred forty volunteers were enrolled, and 130 completed all safety and immunogenicity visits. Reactogenicity was common but generally mild, and there was no significant difference in the adverse event rate between vaccine and placebo recipients (P = 0.26). There were 7 serious adverse events during the follow-up period, none of which were vaccine related. Cumulative HIV-specific, CD8-mediated, cytotoxic T-lymphocyte responses were observed in 11 (25%) of 44 subjects who received ALVAC boosted by bivalent gp120 and in 5 (11%) of 45 subjects who received ALVAC boosted by ogp160, but these differences were not statistically significant compared with those in placebo recipients (P = 0.62 and P = 0.37, respectively). HIV-specific lymphoproliferative responses were detected in 84% of subunit-boosted vaccine recipients and in 10% of placebo recipients. Neutralizing antibody responses to CRF01_AE and subtype B laboratory strains were seen in 95% of ogp160-boosted and 100% of gp120 B/E-boosted vaccinees, respectively.

CONCLUSIONS

These 2 different prime-boost regimens seem to be safe and displayed cell-mediated immune responses consistent with those in other trials of canarypox vectors.

Poxvirus-based vaccine candidates for HIV: two decades of experience with special emphasis on canarypox vectors

Poxvirus vectors have emerged as important vectors for licensed veterinary vaccines and candidate vaccines for humans. Vaccinia, highly-attenuated vaccinia strains and avipoxviruses have been assessed extensively in preclinical models, as well as in humans, to determine their immunogenicity and protective efficacy against HIV. The attenuated vaccinia strains and avipoxviruses have been shown to be safe and able to carry HIV genes and express their proteins to induce both antibodies and cellular immune responses. Preclinical studies show protection against HIV challenge. When using a live attenuated vector system, one must be cognizant of the potential for immune dampening because of vector-specific immunity. In this regard, avipoxviruses, such as canarypox, appear free of the inhibitory effects of vector immunity and repeated use. Unlike vaccinia-based vectors derived from classical vaccine strains, NYVAC and modified vaccinia Ankara may be less susceptible to this effect. In the coming 5 to 10 years, we will certainly know whether this class of vaccine candidates, either alone or in a prime-boost format with other vectors or proteins, will contribute to HIV disease management either from a preventive or therapeutic perspective. Additional Phase I and II studies, as well as human efficacy trials will provide new information. Furthermore, it is hoped that this body of data will contribute to a better understanding of the relevance of specific immunogenicity end points to protection and the predictive value of available animal models in HIV vaccine development.

Strategies for designing vaccines eliciting Th1 responses in humans

There is currently a major interest in designing vaccines capable of eliciting strong cellular immune responses. The induction of cytotoxic and Th1 helper cellular responses is for example highly desirable for vaccines targeting either chronic infectious diseases or cancers (therapeutic vaccines). Similarly, Th1 vaccines would be useful in redirecting inappropriate antigen-specific immune responses in patients with autoimmune diseases and allergies. Importantly, emerging technologies and a better understanding of the physiology of immune responses offer new avenues to rationally design such vaccines. Approaches based on the identification and selection of immunogens containing T cell epitopes can be used, together with epitope-enhancement strategies, to increase binding to MHC, or to improve recognition by T cell receptor complexes. Optimized immunogens can subsequently be presented to the immune system with appropriate vectors allowing to target professional antigen-presenting cells, such as dendritic cells. Such antigen presentation platforms can be used alone or in association, as part of mixed immunization regimens (heterologous prime-boosts), in order to elicit broad immune responses. The rational design of Th1 adjuvants can also benefit from our better understanding of the nature of proinflammatory signals leading to the initiation of both innate and adaptive immune effector mechanisms. Candidate Th1 vaccines (or components such as vectors or adjuvants) will have to be tested in exploratory clinical studies, implying a need for new assays and methods allowing to assess in a qualitative and quantitative manner low-frequency T cell responses in humans.

Rational development of prophylactic HIV vaccines based on structural and regulatory proteins

The severity of the AIDS epidemic clearly emphasises the urgent need to expedite HIV vaccine candidates into clinical trials. Prophylactic HIV vaccine candidates have been evaluated in non-human primates. Based on specific proof of principle studies the first phase III clinical studies have recently begun in humans. However, a truly effective HIV vaccine is not yet at hand and many problems related to specific properties of the virus remain to be overcome. Previously proven empirical approaches have largely failed and now rational thinking based on an understanding of immunity to lentiviral infections is needed. This review addresses the scientific problems and complications facing the development of an HIV vaccine as well as the possible strategies currently available to overcome these problems. Recent attention has focussed on identifying the immune correlates and mechanisms of protection from either HIV infection or protection from disease progression. Based on these observations, the logic and rational behind the development of multiple component vaccine strategies are highlighted.

HIV type 1 vaccine-induced T cell memory and cytotoxic T lymphocyte responses in HIV type 1-uninfected volunteers

T cell memory to human immunodeficiency virus type 1 (HIV-1) antigens and anti-HIV-1 cytotoxic T lymphocyte (CTL) activity were assessed after administration of live canarypox virus (ALVAC) expressing HIV-1 env, gag, and protease (vCP205) vaccine given alone, vCP205 given with SF-2 recombinant gp120 (rgp120) vaccine, and placebos at 0, 1, 3, and 6 months. Healthy, HIV-1-uninfected subjects reporting high-risk and low-risk behavior for HIV-1 were enrolled. Anti-HIV-1 Env CD8(+) CTLs (HIV-1(MN) and/or HIV-1 subtype B and C primary isolate sequences) were detected in 12 (60%) and anti-HIV-1 Gag CD8(+) CTLs in 7 (35%) of the 20 vCP205 vaccine recipients tested by CTL assay 3.5 months after the final immunization. Fourteen days after the fourth immunization, lymphocyte proliferation in response to HIV-1 Gag antigen was detected in 14 (48%) of 29 vCP205 vaccine recipients, but secreted cytokine levels to HIV-1 Gag antigen were not above unstimulated levels. Coadministration of SF-2 rgp120 vaccine with vCP205 vaccine enhanced lymphocyte proliferation in response to HIV-1 envelope glycoprotein and broadened the envelope-stimulated cytokine secretion pattern, so that it consisted of both Th1 and Th2 cytokines compared with only interferon gamma (IFN-gamma) after vCP205 vaccine given alone. There was a possible association between HIV-1 envelope glycoprotein-stimulated interleukin 2 secretion and CD8(+) CTLs against HIV-1 envelope glycoprotein, and an inverse relation between lymphocyte proliferation and CTLs against HIV-1 Gag antigens. Thus, a durable anti-HIV-1 CD8(+) CTL response was detected after immunization with the live canarypox virus vaccine and preexisting helper T cell memory responses did not necessarily predict later CD8(+) CTL activity.

Vaccines for the prevention of HIV-1 disease

Clinical investigation in humans and experimental lentivirus infection in nonhuman primates have advanced our understanding of immune responses that control HIV-1 disease. Recently, immunization approaches in macaques have shown that the immune response can control viremia and improve clinical outcome. When such vaccine strategies are formulated to be similarly immunogenic in humans, they could form the basis for the development of candidate AIDS vaccines that would prevent infection, suppress progression to disease or reduce HIV-1 transmission in humans.