Phase I safety and immunogenicity evaluation of MVA-CMDR, a multigenic, recombinant modified vaccinia Ankara-HIV-1 vaccine candidate

Abstract

Background: We conducted a Phase I randomized, dose-escalation, route-comparison trial of MVA-CMDR, a candidate HIV-1 vaccine based on a recombinant modified vaccinia Ankara viral vector expressing HIV-1 genes env/gag/pol. The HIV sequences were derived from circulating recombinant form CRF01_AE, which predominates in Thailand. The objective was to evaluate safety and immunogenicity of MVA-CMDR in human volunteers in the US and Thailand.

Methodology/principal findings: MVA-CMDR or placebo was administered intra-muscularly (IM; 10(7) or 10(8) pfu) or intradermally (ID; 10(6) or 10(7) pfu) at months 0, 1 and 3, to 48 healthy volunteers at low risk for HIV-1 infection. Twelve volunteers in each dosage group were randomized to receive MVA-CMDR or placebo (10∶2). Volunteers were actively monitored for local and systemic reactogenicity and adverse events post vaccination. Cellular immunogenicity was assessed by a validated IFNγ Elispot assay, an intracellular cytokine staining assay, lymphocyte proliferation and a (51)Cr-release assay. Humoral immunogenicity was assessed by ADCC for gp120 and binding antibody ELISAs for gp120 and p24. MVA-CMDR was safe and well tolerated with no vaccine related serious adverse events. Cell-mediated immune responses were: (i) moderate in magnitude (median IFNγ Elispot of 78 SFC/10(6) PBMC at 10(8) pfu IM), but high in response rate (70% (51)Cr-release positive; 90% Elispot positive; 100% ICS positive, at 10(8) pfu IM); (ii) predominantly HIV Env-specific CD4(+) T cells, with a high proliferative capacity and durable for at least 6 months (100% LPA response rate by the IM route); (iv) dose- and route-dependent with 10(8) pfu IM being the most immunogenic treatment. Binding antibodies against gp120 and p24 were detectable in all vaccination groups with ADCC capacity detectable at the highest dose (40% positive at 10(8) pfu IM).

Conclusions/significance: MVA-CMDR delivered both intramuscularly and intradermally was safe, well-tolerated and elicited durable cell-mediated and humoral immune responses.

Trial registration: ClinicalTrials.gov NCT00376090.

Figure 1. Consort clinical trial participant flow diagram (panel A).

Chronological schematic diagram showing all pre-enrollment, vaccination and blood collection visits for RV158 (panel B). Immunogenicity testing visits 3, 6, 8, 9 and 10 correspond to days 0, 42, 98, 168 and 252 post-vaccination initiation respectively.

Figure 2. Systemic and local vaccine related reactogenicity for each dose and route of vaccination.

The number and percent of subjects experiencing one or more local (panel A) or systemic (panel B) reactions is shown for each group after stratification by severity. The most severe reaction experienced by a volunteer determined the stratification into none, moderate, mild or severe categories. No serious or life threatening adverse events were reported.

Figure 3. Lymphocyte proliferation responses for each dose and route.

Lymphocyte proliferation responses against recombinant proteins (TH023 gp140 and LAI p24) are shown for all doses and routes of vaccination (panels A and B). HIV whole inactivated virus (WIV) antigens CM235_WIV (CRF01_AE vaccine matched isolate) and MN_WIV (subtype B heterologous isolate) are shown for all doses and routes of vaccination in panels C and D respectively. The Y-axis represents the LSI (scale = log₂) and the dotted line designates an LSI of 5 (cut-off for positive responses). Blue and red circles represent pre- and post-vaccination (day 0 and day 252) samples respectively.

Figure 4. Cumulative analysis of all qualitative cellular immune response assays.

The number of positive responders for HIV antigens (Env or Gag) in the ⁵¹Cr-release, Elispot, lymphocyte proliferation and whole blood ICS assays was tallied for all groups and compared with the placebo recipients. The figure graphically displays the summed cumulative positive responders for each of the 4 assay platforms. The total number of tests performed in each group is denoted below the dose and route. The top and bottom tables summarize the statistical analyses for Env and Gag respectively.

Figure 5. Multifunctional flow cytometry analysis for HIV Env-specific T cells.

Analysis was based on the cumulative positive cells in all Boolean subsets for all volunteers who were scored as positive by single cytokine analysis in the high-dose (10⁸ pfu) intra-muscular vaccine recipients ( Table 5 ). The legend shows the Pie Chart arcs representing each cytokine (or function). Pie Chart wedges show the relative sizes of the subsets of cells expressing the combination of functions represented in the surrounding Pie chart arcs.