Phase 1 safety and immunogenicity testing of DNA and recombinant modified vaccinia Ankara vaccines expressing HIV-1 virus-like particles

Abstract

Background: Recombinant DNA and modified vaccinia virus Ankara (rMVA) vaccines represent a promising approach to an HIV/AIDS vaccine. This Phase 1 clinical trial compared the safety and immunogenicity of a rMVA vaccine administered with and without DNA vaccine priming

Methods: GeoVax pGA2/JS7 DNA (D) and MVA/HIV62 (M) vaccines encode noninfectious virus-like particles. Intramuscular needle injections were used to deliver placebo, 2 doses of DNA followed by 2 doses of rMVA (DDMM), one dose of DNA followed by 2 doses of rMVA (DMM), or 3 doses of rMVA (MMM) to HIV-seronegative participants.

Results: Local and systemic symptoms were mild or moderate. Immune response rates for CD4 + and CD8 + T cells were highest in the DDMM group and lowest in the MMM group (77% vs 43% CD4 + and 42% vs 17% CD8 +). In contrast, response rates for Env binding and neutralizing Ab were highest in the MMM group. The DMM group had intermediate response rates. A 1/10th-dose DDMM regimen induced similar T cell but reduced Ab response rates compared with the full-dose DDMM.

Conclusions: MVA62 was well tolerated and elicited different patterns of T cell and Ab responses when administered alone or in combination with the JS7 DNA vaccine.

Figure 1.

Schematic representations of the HIV-1 vaccines and study design. A, Schematics for DNA and recombinant MVA immunogens. B, HVTN 065 trial schema. CMVIE, CMV immediate early promoter; gag, HIV-1 gene encoding group-specific antigens; PR and RT, protease and reverse transcriptase encoding regions of HIV-1 pol; tat, vpu, and rev, HIV-1 regulatory genes; gp120 and gp41, surface and transmembrane subunit-encoding regions of HIV-1 env; gp41tr, gp41 with a 115 amino acid C-terminal truncation; BGHpA, bovine growth hormone polyadenylation sequence; x, presence of inactivating point mutations in packaging sequences for viral RNA in Gag and the protease, reverse transcriptase, strand transfer, and RNase H activities of Pol [9]; PmH5, the modified H5 early/late vaccinia promoter; deletions II and III, naturally occurring deletions in MVA.

Figure 2.

Reactogenicity of study vaccine regimens. The percentage of participants with local pain and/or tenderness (A) or any systemic symptom (B) following each vaccine dose is shown. Reactions were graded as none, mild, moderate, or severe. The vaccine groups are given at the top of the schematics, and the immunization status of groups, at the bottom. D, DNA; M, MVA; P, placebo. The number of Ds and Ms indicates the number of immunizations; for example, DDM means 2 DNA and one MVA immunization. For more details, see Subjects, Materials, and Methods.

Figure 3.

Immune response rates determined in end point assays. Response rates for CD4⁺ T cells (A), CD8⁺ T cells (B), and anti-Env Ab (C). Responses for CD4⁺ and CD8⁺ T cells are for responses to Gag, Env, or Pol measured as IFN-γ– or IL-2–producing cells scored using intracellular cytokine staining (ICS) following stimulation with potential T cell epitope peptide pools. Response rates for anti-Env Ab were measured using an ELISA for the SP400 peptide, a peptide representing the immunodominant region of gp41. Lymphocytes and serum for determining response rates were harvested at 2 weeks following immunizations. Significant differences between groups are indicated where appropriate. All assays were performed in HVTN laboratories on frozen samples. Letters at the bottom of schematics indicate group and the immunization status of groups. See Subjects, Materials, and Methods for more details.

Figure 4.

Magnitude and persistence of vaccine-induced T cell responses. The magnitudes of CD4⁺ (A) and CD8⁺ (B) T cell responses following full-dose DDMM and MMM vaccine regimens are shown. Data represent responses directed against Gag and Env as measured by IFN-γ and/or IL-2 production of CD4⁺ and CD8⁺ T cells in an intracellular cytokine staining (ICS) assay (for more details, see Subjects, Materials, and Methods). Box plots represent the median and 25th and 75th percentiles for positive data (indicated by red points); blue points indicate negative data. Response rates are shown below the schematics as the number of participants who tested positive out of the total number of participants tested, with the percentage of responders given immediately below. Pre&P, prebleed at baseline and placebos; +2wk, samples harvested at 2 weeks after an injection; +3mo and + 6mo, samples harvested at 3 or 6 months after the last injection. Letters at the bottom of the schematics indicate the group and the immunization status of the groups. D, DNA; M, MVA; P, placebo. The number of Ds and Ms indicates the number of immunizations; for example, DDM means 2 DNA and one MVA immunization . *P < .05 for CD4⁺ T cell response frequency when compared with the +2-week time point following the final vaccination in the DDMM regimen; **P < .05 for CD8⁺ T cell response frequency when compared with that seen after the first MVA boost in the DDMM regimen or DMM. C–F, Polyfunctionality of the positive responses for IFN-γ, IL-2, and TNF-α production measured using multicolor flow cytometry and Boolean analyses. Shown are the percentages of CD4⁺ (C) and CD8⁺ (D) T cells producing single cytokines and the degree of polyfunctionality for the CD4⁺ (E) and CD8⁺ (F) responses. 1, the percent of responding cells producing a single cytokine; 2, the percent producing 2 cytokines; 3, the percent producing 3 cytokines. The numbers (n) in panels C–F represent the number of participants in each group with positive CD4⁺ or CD8⁺ T cell responses to any gene as measured by IFN-γ and/or IL-2 production.

Figure 5.

Breadth/depth and magnitude of T cell responses to Gag and Env. A, Percent responders, median magnitudes, and total number of recognized peptide pools for the 4 vaccine regimens. The total number of recognized pools represents the sum of all of the peptide pools recognized in assays successfully completed for a group normalized to the maximum number of individuals tested for CD4⁺ and CD8⁺ T cell responses in that group. Note that this normalization was largest for the low-dose DDMM group that had only 10 participants compared to the 30 participants in the other groups. B–C, Percent of responders with CD4⁺ or CD8⁺ T cells, respectively, recognizing different numbers of peptide pools. The numbers in the graph are the median number of peptide pools recognized by responders to a particular regimen. D, DNA; M, MVA; P, placebo. The number of Ds and Ms indicates the number of immunizations; for example, DDM means 2 DNA and one MVA immunization. Note that the numbers represent the breadth and/or depth of induced T cells as defined elsewhere [17]. Potential T cell epitope pools are grouped depending on the frequency of HIV-1 epitope variants, so variants of the same epitope may be in different peptide pools [15].

Figure 6.

Magnitudes and response rates of Env binding and neutralizing antibodies. A, Binding Ab for SP400, a peptide representing the immunodominant region of gp41. B, Binding Ab for ADA gp120. C, Neutralizing Ab for HIV-1_MN. Designations below schematics indicate groups and response rates (see legend to Figure 4 for details). The box plots show median and 25th and 75th percentiles for positive data (indicated by red points); blue points indicate negative data. Data for determining P values include only positive data. D, Percent of positive MN neutralization responses also neutralizing other tier 1 isolates. Seventeen of the samples demonstrating neutralization against HIV-1_MN were evaluated further. The tier 1 isolates are shown including HIV-1_SF162, HIV-1_W61D (T cell laboratory-adapted strain), and HIV-1_BAL.

Figure 7.

Vector-specific T cells. The percentage of MVA-specific CD4⁺ or CD8⁺ T cells producing IFN-γ by ICS assay is shown for samples analyzed at 1 week following the first or second MVA boost for the DDMM and MMM vaccine regimens. The percentage of participants with vector-specific T cell responses (response rate) is given below the schematic.