A phase IIA randomized clinical trial of a multiclade HIV-1 DNA prime followed by a multiclade rAd5 HIV-1 vaccine boost in healthy adults (HVTN204)

Abstract

Background: The safety and immunogenicity of a vaccine regimen consisting of a 6-plasmid HIV-1 DNA prime (envA, envB, envC, gagB, polB, nefB) boosted by a recombinant adenovirus serotype-5 (rAd5) HIV-1 with matching inserts was evaluated in HIV-seronegative participants from South Africa, United States, Latin America and the Caribbean.

Methods: 480 participants were evenly randomized to receive either: DNA (4 mg i.m. by Biojector) at 0, 1 and 2 months, followed by rAd5 (10(10) PU i.m. by needle/syringe) at 6 months; or placebo. Participants were monitored for reactogenicity and adverse events throughout the 12-month study. Peak and duration of HIV-specific humoral and cellular immune responses were evaluated after the prime and boost.

Results: The vaccine was well tolerated and safe. T-cell responses, detected by interferon-γ (IFN-γ) ELISpot to global potential T-cell epitopes (PTEs) were observed in 70.8% (136/192) of vaccine recipients overall, most frequently to Gag (54.7%) and to Env (54.2%). In U.S. vaccine recipients T-cell responses were less frequent in Ad5 sero-positive versus sero-negative vaccine recipients (62.5% versus 85.7% respectively, p = 0.035). The frequency of HIV-specific CD4+ and CD8+ T-cell responses detected by intracellular cytokine staining were similar (41.8% and 47.2% respectively) and most secreted ≥2 cytokines. The vaccine induced a high frequency (83.7%-94.6%) of binding antibody responses to consensus Group M, and Clades A, B and C gp140 Env oligomers. Antibody responses to Gag were elicited in 46% of vaccine recipients.

Conclusion: The vaccine regimen was well-tolerated and induced polyfunctional CD4+ and CD8+ T-cells and multi-clade anti-Env binding antibodies.

Trial registration: ClinicalTrials.gov NCT00125970.

Figure 1. Number of individuals enrolled, randomized to vaccine or placebo, followed-up and analyzed.

ICS = Intracellular cytokine staining, Ad5 = Adenovirus serotype 5.

Figure 2. Maximal local and systemic reactogenicity after each vaccination.

Frequency of local (A) and systemic (B) reactions occurring within three days following each DNA and rAd5 vaccination. Local injection site reactions included pain, tenderness, erythema and induration. Systemic reactions included malaise/fatigue, headache, chills, myalgia, arthralgia or increased body temperature. P = Placebo, V = Vaccine.

Figure 3. Magnitude of T-cell responses recognizing global PTEs 6 weeks after the Ad5 boost in all participants and by Ad5 titer in US participants.

Shown are the magnitude of T-cell responses as measured by IFN-γ ELISpot responses (A) and percentage of CD4+ (B) and CD8+ (C) T-cells producing interferon-γ and/or interleukin-2 in response to Env, Gag, Pol or Nef six weeks after rAd5 boost in all participants (left) and in United States participants stratified by adenovirus serotype-5 titer (<12, ≥12, right). Only the Ad5 data for US participants is shown as they had the highest proportion of participants who were Ad5 negative at baseline. Positive responders are shown in red and negative responders in blue. The boxplots show the distribution of responses in positive responders only. The box indicates the median and inter-quartile range; whiskers extend to 1.5 times the inter-quartile range from the upper or lower quartile. The numbers above the graphs indicate the number positive relative to the total number examined and the corresponding percentage positive.

Figure 4. Polyfunctional CD4+ and CD8+ T-cell IFN-γ, TNF-α and IL2 cytokine responses.

The left graphs show the percentage of the HIV-specific CD4+ (upper panel) or CD8+ (lower panel) T-cells that are producing one, two or three cytokines in the vaccine recipients. Intracellular cytokine staining analyses were done on PBMC obtained six weeks after the rAd5 boost. The right graphs depict the percentage of cells producing interferon-γ, interleukin-2 or tumor necrosis factor-α in those cells producing one cytokine (middle panels), and the percentage of cells co-producing two cytokines (panels on the right). The boxplots show the distribution of responses in positive responders only. The box indicated the median and inter-quartile range; whiskers extend to 1.5 times the inter-quartile range from the upper or lower quartile.

Figure 5. Magnitude of CD4+ and CD8+ T cell ICS responses to empty Ad5 vector.

Percentage of CD4+ (top panels) and CD8+ T cells (bottom panels) producing interferon-γ and/or interleukin 2, or both, by intracellular cytokine staining, in response to Ad5 empty vector stimulation in all (left panels) or US only (right panels) placebo and vaccine recipients 6 weeks after the Ad5 boost. Positive responders are shown in red and negative responders in blue. The box plots and numbers above the graphs are as in Figure 2.

Figure 6. Neutralizing antibody responses to Tier 1 viruses.

Positive responders are shown in red and negative responders in blue. The boxplots show the distribution of responses in positive responders only. The box indicates the median and inter-quartile range; whiskers extend to 1.5 times the inter-quartile range from the upper or lower quartile.