Immunogenicity of a novel Clade B HIV-1 vaccine combination: Results of phase 1 randomized placebo controlled trial of an HIV-1 GM-CSF-expressing DNA prime with a modified vaccinia Ankara vaccine boost in healthy HIV-1 uninfected adults

Abstract

Background: A phase 1 trial of a clade B HIV vaccine in HIV-uninfected adults evaluated the safety and immunogenicity of a DNA prime co-expressing GM-CSF (Dg) followed by different numbers and intervals of modified vaccinia Ankara Boosts (M). Both vaccines produce virus-like particles presenting membrane-bound Env.

Methods: Four US sites randomized 48 participants to receiving 1/10th the DNA dose as DgDgMMM given at 0, 2, 4, 6 and 8 months, or full dose DgDgM_M or DgDgMM_M regimens, given at 0, 2, 4, and 8 months, and 0, 2, 4, 6, and 10 months, respectively. Peak immunogenicity was measured 2 weeks post-last vaccination.

Results: All regimens were well tolerated and safe. Full dose DgDgM_M and DgDgMM_M regimens generated Env-specific IgG to HIV-1 Env in >90%, IgG3 in >80%, and IgA in <20% of participants. Responses to gp140 and gp41 targets were more common and of higher magnitude than to gp120 and V1V2. The gp41 antibody included reactivity to the conserved immunodominant region with specificities known to mediate virus capture and phagocytosis and did not cross-react with a panel of intestinal flora antigens. The 3rd dose of MVA increased the avidity of elicited antibody (7.5% to 39%), the ADCC response to Bal gp120 (14% to 64%), and the one-year durability of the IgG3 responses to gp41 by 4-fold (13% vs. 3.5% retention of peak response). The co-expressed GM-CSF did not enhance responses over those in trials testing this vaccine without GM-CSF.

Conclusion: This DNA/MVA prime-boost regimen induced durable, functional humoral responses that included ADCC, high antibody avidity, and Env IgG1 and IgG3 binding responses to the immunodominant region of gp41. The third, spaced MVA boost improved the overall quality of the antibody response. These products without co-expressed GM-CSF but combined with protein boosts will be considered for efficacy evaluation.

Trial registration: ClinicalTrials.gov NCT01571960.

Fig 1. CONSORT flow diagram.

Allocation, follow-up, and analysis for HIV Vaccine Trials Network (HVTN) study 094. Abbreviations: 1/10 DgDgMMM, treatment arm receiving two 1/10 doses of DNA followed by three doses of MVA at 0, 2, 4, 6 and 8 months; DgDgMM_M, treatment arm receiving two full doses of DNA followed by three doses of MVA given at 0, 2, 4, 6, and 10 months; DgDgM_M, treatment arm receiving two full doses of DNA followed by two doses of MVA at 0, 2, 4, and 8 months; ADCC, antibody dependent cellular cytotoxicity.

Fig 2. Summary immune responses.

Overall peak binding antibody and ICS response rates among vaccine recipients at two weeks after the 2nd and 3rd MVA in the DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. A positive response to IgG Env or IgA Env indicates positive responses to at least one ENV antigens measured by the BAMA binding antibody assay; a positive response to ANY CD4+ or ANY CD8+ indicates positive responses to any least one peptide pool and/or cytokine measured by the ICS assay.

Fig 3. Peak IgG and IgG3 response rates and magnitudes.

(A) Peak IgG binding antibody response rates. (B) Peak IgG binding response magnitudes. (C) Peak IgG3 binding antibody response rates. (D) Peak IgG3 binding antibody response magnitudes. Responses are to individual antigens at two weeks after the 2nd and 3rd MVA or placebo in the Placebo, DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. Shown are total IgG binding antibody response rates to HIV-1 Env gp140 (ConS gp140), HIV-1 Env gp120 (Con 6 gp120 B), the V1V2 loop, gp41 and the gp41 immunodominant region (IDR).

Fig 4. IgG and IgG3 response rates and magnitudes over time.

(A) Total IgG and IgG3 binding antibody response rates. (B) Total IgG and IgG3 binding antibody response median magnitudes and inter-quartile range (IQR) responses. Responses among vaccine recipients over time at two weeks, 6 months, 9 months, and 12 months after the last vaccination in the DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. For the comparison of two visits within an arm, McNemar’s and Wilcoxon signed rank tests were used to compare the response rates (A) and magnitudes (B) among responders, respectively.

Fig 5. Antibody avidity.

Distribution of binding antibody avidity response magnitude among vaccine recipients at two weeks and 6 months after the 2nd and 3rd MVA in the DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. Avidity Index (AI) was calculated for the ID epitope tetramer for those with a positive binding response to the ID epitope tetramer and only for samples not saturated (MFI < 23000). Wilcoxon signed rank tests were used to compare AI values among positive responders.

Fig 6. A. ADCC response rate (GTL). B. ADCC response magnitude.

(A) Peak ADCC response rates. (B) Peak ADCC response magnitudes. Responses are to individual antigens at two weeks after the 2nd and 3rd MVA or placebo in the Placebo, DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. For the DgDgM_M arm, only peak percent Granzyme B activity for BaL gp120 was measured. Positive responses are shown as filled circles and negative responses are shown as open circles (B). Box-plots represent the distribution for the positive responders only. Response rates were compared using Fisher’s exact test (A); response magnitudes among responders across treatment arms were compared using Wilcoxon Rank Sum test (B).

Fig 7. Cellular immune responses measured by intracellular cytokine staining (ICS).

(A) CD4+ response rates. (B) CD4+ response magnitude. (C) CD8+ response rate. (D) CD8+ response magnitudes. Peak ICS response rates and response magnitude to Gag, Env and Pol in the CD4+ (Panels A & B) and CD8+ (Panels C & D) T-cell subsets at two weeks after the 2nd and 3rd MVA or placebo in the Placebo, DgDgM_M and DgDgMM_M groups. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively. Shown are response rates (A, C) and response magnitudes (B, D) for the sum of individual antigen responses, reported as % of CD4+ or CD8+ T cells producing IFN-gamma and/or IL-2. Positive responses are shown as filled circles and negative responses are shown as open circles (B, D). Box-plots represent the distribution for the positive responders only. Response rates were compared using Fisher’s exact test (A, C); response magnitudes among responders across treatment arms were compared using Wilcoxon Rank Sum test (B, D).

Fig 8. Radar plot of peak antibody-mediated and cellular immune responses by vaccine regimen.

(A) Response rates of each assay readout. (B) Response magnitudes of each assay readout. DgDgM_M refers to immune responses after the last MVA in the DgDgM_M group; DgDgMM and DgDgMM_M refer to immune responses after the 2nd and 3rd MVA in DgDgMM_M group, respectively.