Human immunodeficiency virus type 1 elite neutralizers: individuals with broad and potent neutralizing activity identified by using a high-throughput neutralization assay together with an analytical selection algorithm.

The development of a rapid and efficient system to identify human immunodeficiency virus type 1 (HIV-1)-infected individuals with broad and potent HIV-1-specific neutralizing antibody responses is an important step toward the discovery of critical neutralization targets for rational AIDS vaccine design. In this study, samples from HIV-1-infected volunteers from diverse epidemiological regions were screened for neutralization responses using pseudovirus panels composed of clades A, B, C, and D and circulating recombinant forms (CRFs). Initially, 463 serum and plasma samples from Australia, Rwanda, Uganda, the United Kingdom, and Zambia were screened to explore neutralization patterns and selection ranking algorithms. Samples were identified that neutralized representative isolates from at least four clade/CRF groups with titers above prespecified thresholds and ranked based on a weighted average of their log-transformed neutralization titers. Linear regression methods selected a five-pseudovirus subset, representing clades A, B, and C and one CRF01_AE, that could identify top-ranking samples with 50% inhibitory concentration (IC(50)) neutralization titers of >or=100 to multiple isolates within at least four clade groups. This reduced panel was then used to screen 1,234 new samples from the Ivory Coast, Kenya, South Africa, Thailand, and the United States, and 1% were identified as elite neutralizers. Elite activity is defined as the ability to neutralize, on average, more than one pseudovirus at an IC(50) titer of 300 within a clade group and across at least four clade groups. These elite neutralizers provide promising starting material for the isolation of broadly neutralizing monoclonal antibodies to assist in HIV-1 vaccine design.

A phase I double blind, placebo-controlled, randomized study of a multigenic HIV-1 adenovirus subtype 35 vector vaccine in healthy uninfected adults.

BACKGROUND: We conducted a phase I, randomized, double-blind, placebo-controlled trial to assess the safety and immunogenicity of escalating doses of two recombinant replication defective adenovirus serotype 35 (Ad35) vectors containing gag, reverse transcriptase, integrase and nef (Ad35-GRIN) and env (Ad35-ENV), both derived from HIV-1 subtype A isolates. The trial enrolled 56 healthy HIV-uninfected adults. METHODS: Ad35-GRIN/ENV (Ad35-GRIN and Ad35-ENV mixed in the same vial in equal proportions) or Ad35-GRIN was administered intramuscularly at 0 and 6 months. Participants were randomized to receive either vaccine or placebo (10/4 per group, respectively) within one of four dosage groups: Ad35-GRIN/ENV 2×10(9) (A), 2×10(10) (B), 2×10(11) (C), or Ad35-GRIN 1×10(10) (D) viral particles. RESULTS: No vaccine-related serious adverse event was reported. Reactogenicity events reported were dose-dependent, mostly mild or moderate, some severe in Group C volunteers, all transient and resolving spontaneously. IFN-γ ELISPOT responses to any vaccine antigen were detected in 50, 56, 70 and 90% after the first vaccination, and in 75, 100, 88 and 86% of Groups A-D vaccine recipients after the second vaccination, respectively. The median spot forming cells (SFC) per 10(6) PBMC to any antigen was 78-139 across Groups A-C and 158-174 in Group D, after each of the vaccinations with a maximum of 2991 SFC. Four to five HIV proteins were commonly recognized across all the groups and over multiple timepoints. CD4+ and CD8+ T-cell responses were polyfunctional. Env antibodies were detected in all Group A-C vaccinees and Gag antibodies in most vaccinees after the second immunization. Ad35 neutralizing titers remained low after the second vaccination. CONCLUSION/SIGNIFICANCE: Ad35-GRIN/ENV reactogenicity was dose-related. HIV-specific cellular and humoral responses were seen in the majority of volunteers immunized with Ad35-GRIN/ENV or Ad35-GRIN and increased after the second vaccination. T-cell responses were broad and polyfunctional. TRIAL REGISTRATION: ClinicalTrials.gov NCT00851383.

In vivo electroporation enhances the immunogenicity of an HIV-1 DNA vaccine candidate in healthy volunteers.

BACKGROUND: DNA-based vaccines have been safe but weakly immunogenic in humans to date. METHODS AND FINDINGS: We sought to determine the safety, tolerability, and immunogenicity of ADVAX, a multigenic HIV-1 DNA vaccine candidate, injected intramuscularly by in vivo electroporation (EP) in a Phase-1, double-blind, randomized placebo-controlled trial in healthy volunteers. Eight volunteers each received 0.2 mg, 1 mg, or 4 mg ADVAX or saline placebo via EP, or 4 mg ADVAX via standard intramuscular injection at weeks 0 and 8. A third vaccination was administered to eleven volunteers at week 36. EP was safe, well-tolerated and considered acceptable for a prophylactic vaccine. EP delivery of ADVAX increased the magnitude of HIV-1-specific cell mediated immunity by up to 70-fold over IM injection, as measured by gamma interferon ELISpot. The number of antigens to which the response was detected improved with EP and increasing dosage. Intracellular cytokine staining analysis of ELISpot responders revealed both CD4+ and CD8+ T cell responses, with co-secretion of multiple cytokines. CONCLUSIONS: This is the first demonstration in healthy volunteers that EP is safe, tolerable, and effective in improving the magnitude, breadth and durability of cellular immune responses to a DNA vaccine candidate. TRIAL REGISTRATION: ClinicalTrials.gov NCT00545987.

Vaccination with a modified vaccinia virus Ankara (MVA)-vectored HIV-1 immunogen induces modest vector-specific T cell responses in human subjects.

We investigated whether vaccination of healthy HIV-seronegative and HIV-1-seropositive antiretroviral therapy-treated subjects with recombinant modified vaccinia virus Ankara expressing an HIV-1 immunogen (MVA.HIVA) induced MVA-specific T cell responses. Using IFN-γ Elispot assays, we observed new or increased responses to MVA virus in 52% of HIV-seronegative subjects and 93% HIV-1 seropositive subjects; MVA-specific T cell frequencies were generally low and correlated poorly with T cell responses to the HIV-1 immunogen. In two vaccinees, responses were mapped to CD8+ T cell epitopes present in replication-competent vaccinia virus. These data support further evaluation of MVA as a viral vector for HIV-1 immunogens.

Equivalence of ELISpot assays demonstrated between major HIV network laboratories.

BACKGROUND: The Comprehensive T Cell Vaccine Immune Monitoring Consortium (CTC-VIMC) was created to provide standardized immunogenicity monitoring services for HIV vaccine trials. The ex vivo interferon-gamma (IFN-γ) ELISpot is used extensively as a primary immunogenicity assay to assess T cell-based vaccine candidates in trials for infectious diseases and cancer. Two independent, GCLP-accredited central laboratories of CTC-VIMC routinely use their own standard operating procedures (SOPs) for ELISpot within two major networks of HIV vaccine trials. Studies are imperatively needed to assess the comparability of ELISpot measurements across laboratories to benefit optimal advancement of vaccine candidates. METHODS: We describe an equivalence study of the two independently qualified IFN-g ELISpot SOPs. The study design, data collection and subsequent analysis were managed by independent statisticians to avoid subjectivity. The equivalence of both response rates and positivity calls to a given stimulus was assessed based on pre-specified acceptance criteria derived from a separate pilot study. FINDINGS: Detection of positive responses was found to be equivalent between both laboratories. The 95% C.I. on the difference in response rates, for CMV (-1.5%, 1.5%) and CEF (-0.4%, 7.8%) responses, were both contained in the pre-specified equivalence margin of interval [-15%, 15%]. The lower bound of the 95% C.I. on the proportion of concordant positivity calls for CMV (97.2%) and CEF (89.5%) were both greater than the pre-specified margin of 70%. A third CTC-VIMC central laboratory already using one of the two SOPs also showed comparability when tested in a smaller sub-study. INTERPRETATION: The described study procedure provides a prototypical example for the comparison of bioanalytical methods in HIV vaccine and other disease fields. This study also provides valuable and unprecedented information for future vaccine candidate evaluations on the comparison and pooling of ELISpot results generated by the CTC-VIMC central core laboratories.

Safety and immunogenicity study of Multiclade HIV-1 adenoviral vector vaccine alone or as boost following a multiclade HIV-1 DNA vaccine in Africa.

BACKGROUND: We conducted a double-blind, randomized, placebo-controlled Phase I study of a recombinant replication-defective adenovirus type 5 (rAd5) vector expressing HIV-1 Gag and Pol from subtype B and Env from subtypes A, B and C, given alone or as boost following a DNA plasmid vaccine expressing the same HIV-1 proteins plus Nef, in 114 healthy HIV-uninfected African adults. METHODOLOGY/PRINCIPAL FINDINGS: Volunteers were randomized to 4 groups receiving the rAd5 vaccine intramuscularly at dosage levels of 1×10(10) or 1×10(11) particle units (PU) either alone or as boost following 3 injections of the DNA vaccine given at 4 mg/dose intramuscularly by needle-free injection using Biojector® 2000. Safety and immunogenicity were evaluated for 12 months. Both vaccines were well-tolerated. Overall, 62% and 86% of vaccine recipients in the rAd5 alone and DNA prime - rAd5 boost groups, respectively, responded to the HIV-1 proteins by an interferon-gamma (IFN-γ) ELISPOT. The frequency of immune responses was independent of rAd5 dosage levels. The highest frequency of responses after rAd5 alone was detected at 6 weeks; after DNA prime - rAd5 boost, at 6 months (end of study). At baseline, neutralizing antibodies against Ad5 were present in 81% of volunteers; the distribution was similar across the 4 groups. Pre-existing immunity to Ad5 did not appear to have a significant impact on reactogenicity or immune response rates to HIV antigens by IFN-γ ELISPOT. Binding antibodies against Env were detected in up to 100% recipients of DNA prime - rAd5 boost. One volunteer acquired HIV infection after the study ended, two years after receipt of rAd5 alone. CONCLUSIONS/SIGNIFICANCE: The HIV-1 rAd5 vaccine, either alone or as a boost following HIV-1 DNA vaccine, was well-tolerated and immunogenic in African adults. DNA priming increased the frequency and magnitude of cellular and humoral immune responses, but there was no effect of rAd5 dosage on immunogenicity endpoints. TRIAL REGISTRATION: ClinicalTrials.gov NCT00124007.

A Phase 1 study to evaluate the safety and immunogenicity of a recombinant HIV type 1 subtype C-modified vaccinia Ankara virus vaccine candidate in Indian volunteers.

A recombinant modified vaccinia Ankara virus vaccine candidate (TBC-M4) expressing HIV-1 subtype C env, gag, tat-rev, and nef-RT genes was tested in a randomized, double-blind, dose escalation Phase I trial in 32 HIV-uninfected healthy volunteers who received three intramuscular injections of TBC-M4 at 0, 1, and 6 months of 5 x 10(7) plaque-forming units (pfu) (low dosage, LD) (n = 12) or 2.5 x 10(8) pfu (high dosage, HD) (n = 12) or placebo (n = 8). Local and systemic reactogenicity was experienced by approximately 67% and 83% of vaccine recipients, respectively. The reactogenicity events were mostly mild in severity. Severe but transient systemic reactogenicity was seen in one volunteer of the HD group. No vaccine-related serious adverse events or events suggesting perimyocarditis were seen. A higher frequency of local reactogenicity events was observed in the HD group. Cumulative HIV-specific IFN-gamma ELISPOT responses were detected in frozen PBMCs from 9/11 (82%), 12/12 (100%), and 1/8 (13%) volunteers after the third injection of the LD, HD, and placebo groups, respectively. Most of the responses were to gag and env proteins (maximum of 430 SFU/10(6) PBMCs) persisting across multiple time points. HIV-specific ELISA antibody responses were detected in 10/11, 12/12, and 0/8 volunteers post-third vaccination, in the LD, HD, and placebo groups, respectively. No neutralizing activity against HIV-1 subtype C isolates was detected. TBC-M4 appears to be generally safe and well-tolerated. The immune response detected was dose dependent, modest in magnitude, and directed mostly to env and gag proteins, suggesting further evaluation of this vaccine in a prime-boost regimen.