Optimizing the immunogenicity of HIV prime-boost DNA-MVA-rgp140/GLA vaccines in a phase II randomized factorial trial design

Abstract

Background: We evaluated the safety and immunogenicity of (i) an intradermal HIV-DNA regimen given with/without intradermal electroporation (EP) as prime and (ii) the impact of boosting with modified vaccinia virus Ankara (HIV-MVA) administered with or without subtype C CN54rgp140 envelope protein adjuvanted with Glucopyranosyl Lipid A (GLA-AF) in volunteers from Tanzania and Mozambique.

Methods: Healthy HIV-uninfected adults (N = 191) were randomized twice; first to one of three HIV-DNA intradermal priming regimens by needle-free ZetaJet device at weeks 0, 4 and 12 (Group I: 2x0.1mL [3mg/mL], Group II: 2x0.1mL [3mg/mL] plus EP, Group III: 1x0.1mL [6mg/mL] plus EP). Second the same volunteers received 108 pfu HIV-MVA twice, alone or combined with CN54rgp140/GLA-AF, intramuscularly by syringe, 16 weeks apart. Additionally, 20 volunteers received saline placebo.

Results: Vaccinations and electroporation did not raise safety concerns. After the last vaccination, the overall IFN-γ ELISpot response rate to either Gag or Env was 97%. Intradermal electroporation significantly increased ELISpot response rates to HIV-DNA-specific Gag (66% group I vs. 86% group II, p = 0.026), but not to the HIV-MVA vaccine-specific Gag or Env peptide pools nor the magnitude of responses. Co-administration of rgp140/GLA-AF with HIV-MVA did not impact the frequency of binding antibody responses against subtype B gp160, C gp140 or E gp120 antigens (95%, 99%, 79%, respectively), but significantly enhanced the magnitude against subtype B gp160 (2700 versus 300, p<0.001) and subtype C gp140 (24300 versus 2700, p<0.001) Env protein. At relatively low titers, neutralizing antibody responses using the TZM-bl assay were more frequent in vaccinees given adjuvanted protein boost.

Conclusion: Intradermal electroporation increased DNA-induced Gag response rates but did not show an impact on Env-specific responses nor on the magnitude of responses. Co-administration of HIV-MVA with rgp140/GLA-AF significantly enhanced antibody responses.

Fig 1. The number of individuals screened, randomized, allocated and withdrawn from the trial and the number of samples analyzed.

Fig 2. IFN-γ ELISpot responses.

(A) the DNA vaccine-specific Gag Smi peptide pool and, (B) the HIV-MVA vaccine-specific Gag CMDR, (C) Env CMDR peptide pools by the first randomization, to (D) Gag CMDR and (E) Env CMDR peptide pool stimulation by the second randomization in samples collected two weeks after the final vaccination in vaccine recipients only. Responders and non-responders are shown by filled and open circles, respectively. Median values in responders are given in brackets.

Fig 3. Binding antibody responses.

(A) subtype B gp160, (B) subtype C gp140 and (C) subtype E gp120 antigen by the second randomization, in samples collected four weeks after the final vaccination in vaccine recipients only. Responders are shown by filled circles and non-responders are shown by open circles. The Wilcoxon rank-sum test was used for comparisons.