HIV-specific humoral responses benefit from stronger prime in phase Ib clinical trial

Abstract

BACKGROUND. Vector prime-boost immunization strategies induce strong cellular and humoral immune responses. We examined the priming dose and administration order of heterologous vectors in HIV Vaccine Trials Network 078 (HVTN 078), a randomized, double-blind phase Ib clinical trial to evaluate the safety and immunogenicity of heterologous prime-boost regimens, with a New York vaccinia HIV clade B (NYVAC-B) vaccine and a recombinant adenovirus 5-vectored (rAd5-vectored) vaccine. METHODS. NYVAC-B included HIV-1 clade B Gag-Pol-Nef and gp120, while rAd5 included HIV-1 clade B Gag-Pol and clades A, B, and C gp140. Eighty Ad5-seronegative subjects were randomized to receive 2 × NYVAC-B followed by 1 × 1010 PFU rAd5 (NYVAC/Ad5hi); 1 × 108 PFU rAd5 followed by 2 × NYVAC-B (Ad5lo/NYVAC); 1 × 109 PFU rAd5 followed by 2 × NYVAC-B (Ad5med/NYVAC); 1 × 1010 PFU rAd5 followed by 2 × NYVAC-B (Ad5hi/NYVAC); or placebo. Immune responses were assessed 2 weeks after the final vaccination. Intracellular cytokine staining measured T cells producing IFN-γ and/or IL-2; cross-clade and epitope-specific binding antibodies were determined; and neutralizing antibodies (nAbs) were assessed with 6 tier 1 viruses. RESULTS. CD4+ T cell response rates ranged from 42.9% to 93.3%. NYVAC/Ad5hi response rates (P ≤ 0.01) and magnitudes (P ≤ 0.03) were significantly lower than those of other groups. CD8+ T cell response rates ranged from 65.5% to 85.7%. NYVAC/Ad5hi magnitudes were significantly lower than those of other groups (P ≤ 0.04). IgG response rates to the group M consensus gp140 were 89.7% for NYVAC/Ad5hi and 21.4%, 84.6%, and 100% for Ad5lo/NYVAC, Ad5med/NYVAC, and Ad5hi/NYVAC, respectively, and were similar for other vaccine proteins. Overall nAb responses were low, but aggregate responses appeared stronger for Ad5med/NYVAC and Ad5hi/NYVAC than for NYVAC/Ad5hi. CONCLUSIONS. rAd5 prime followed by NYVAC boost is superior to the reverse regimen for both vaccine-induced cellular and humoral immune responses. Higher Ad5 priming doses significantly increased binding and nAbs. These data provide a basis for optimizing the design of future clinical trials testing vector-based heterologous prime-boost strategies. TRIAL REGISTRATION. ClinicalTrials.gov NCT00961883. FUNDING. NIAID, NIH UM1AI068618, AI068635, AI068614, and AI069443.

Figures

Figure 9. Polyfunctionality of Gag-specific T cell responses elicited in HVTN 078.

CD4+ (A) and CD8+ (B) T cell responses to Gag were measured 2 weeks after the final vaccination by ICS and reported as the percentage of CD4+ or CD8+ T cells with 1, 2, 3, or 4 functions (top panels) or the percentage of CD4+ or CD8+ T cells within a functional subset that expressed a given combination of markers as specified by “+” or “–” below the bottom panels.

Figure 8. T cell responses elicited in HVTN 078.

CD4+ (A) and CD8+ (B) T cell responses were measured 2 weeks after the final vaccination by ICS and reported as the percentage of CD4+ or CD8+ T cells producing IFN-γ and/or IL-2 for placebo recipients (combined for groups 1–4) and vaccinees in each treatment group. Positive responses are shown in red symbols and negative responses in blue. Boxes and whiskers represent positive responders only (see Methods). N, NYVAC-B; P, placebo; Ad, rAd5; Lo, 108 rAd5 PFU; Med, 109 rAd5 PFU; Hi, 1010 rAd5 PFU.

Figure 7. VISR elicited in HVTN 078.

Sera were tested at the end of the study (1 year after enrollment) using 3 commercially available EIA kits: Abbott Architect HIV Ag/Ab Combo, Bio-Rad Genetic Systems HIV 1/2 Plus O EIA, and Bio-Rad Multispot HIV-1/HIV-2 Rapid Test. The percentage of reactive samples for any test (left) or each of the individual tests is shown. T1, NYVAC/Ad5hi (white bars); T2, Ad5lo/NYVAC (light gray bars); T3, Ad5med/NYVAC (dark gray bars); T4, Ad5hi/NYVAC (black bars).

Figure 6. Longevity of nAb responses in HVTN 078.

The tier 1 Env-pseudotyped virus MN.3 was tested in the TZM-bl neutralization assay 2 weeks (visit 10) and 6 months (visit 13) after the final vaccination. nAb titers are shown for placebo and vaccine recipients. Positive responses are shown in red symbols and negative responses in blue.

Figure 5. MB of nAb responses elicited in HVTN 078.

Five tier 1 Env-pseudotyped viruses (BaL.26, Bx08.16, MW965.26, SF162.LS, and MN.3) were tested in the TZM-bl neutralization assay 2 weeks after the final vaccination. Data are represented as MB curves, where the x axis represents nAb titers, and the y axis represents the fraction of viruses neutralized. Dashed lines represent subject-specific responses. Solid lines represent group averages.

Figure 4. Strain-specific nAb responses elicited in HVTN 078.

Six tier 1 Env-pseudotyped viruses (MN.3, SF162.LS, BaL.26, MW965.26, NP03.13, and Bx08.16) were tested in the TZM-bl neutralization assay 2 weeks after the final vaccination. nAb titers are shown for placebo and vaccine recipients. Positive responses are shown in red symbols and negative responses in blue. P, placebo; T1, NYVAC/Ad5hi; T2, Ad5lo/NYVAC; T3, Ad5med/NYVAC; T4, Ad5hi/NYVAC.

Figure 3. V1-V2–specific IgG and gp140-specific IgA elicited in HVTN 078 two weeks after the final vaccination.

IgG responses to (A) clade B case_A gp70 V1-V2, (B) clade C 1086 V1-V2 tags, and (C) clade AE A244_293F V1-V2 tags were measured as MFI (see Methods). (D) IgA responses to consensus clade B Env gp140 were measured as MFI. Positive responses are shown in red symbols and negative responses in blue. Boxes and whiskers represent the positive responders only (see Methods).

Figure 2. Binding IgG responses elicited in HVTN 078 two weeks after the final vaccination.

IgG titers against consensus clade A Env (ConA) gp140 (A), clade B Env (ConB) gp140 (B), clade C Env (ConC) gp140 (C), and ConS gp140 (D) were calculated for positive responders using AUC (1:50 dilution, 5-fold titration series). Positive responses are shown in red symbols and negative responses in blue. Boxes and whiskers represent the positive responders only (see Methods).

Figure 1. CONSORT statement 2010 flow diagram.

The number of participants enrolled, randomized, followed up, and analyzed is shown for placebo and treatment groups. Two of 12 early terminations occurred prior to the primary immunogenicity visit (visit 10) due to lack of time and commitment to the study. The remaining 7 early terminations due to participants’ refusal resulted predominantly from an extension of the study with version 2 of the protocol; these participants did not consent to the additional visit scheduled in version 2.