Cellular immune responses induced with dose-sparing intradermal administration of HIV vaccine to HIV-uninfected volunteers in the ANRS VAC16 trial

Abstract

Objective: The objective was to compare the safety and cellular immunogenicity of intradermal versus intramuscular immunization with an HIV-lipopeptide candidate vaccine (LIPO-4) in healthy volunteers.

Methodology: A randomized, open-label trial with 24 weeks of follow-up was conducted in France at six HIV-vaccine trial sites. Sixty-eight healthy 21- to 55-year-old HIV-uninfected subjects were randomized to receive the LIPO-4 vaccine (four HIV lipopeptides linked to a T-helper-stimulating epitope of tetanus-toxin protein) at weeks 0, 4 and 12, either intradermally (0.1 ml, 100 microg of each peptide) or intramuscularly (0.5 ml, 500 microg of each peptide). Comparative safety of both routes was evaluated. CD8+ T-cell immune responses to HIV epitopes (ELISpot interferon-gamma assay) and tetanus toxin-specific CD4+ T-cell responses (lymphoproliferation) were assessed at baseline, two weeks after each injection, and at week 24.

Results and conclusion: No severe, serious or life-threatening adverse events were observed. Local pain was significantly more frequent after intramuscular injection, but local inflammatory reactions were more frequent after intradermal immunization. At weeks 2, 6, 14 and 24, the respective cumulative percentages of induced CD8+ T-cell responses to at least one HIV peptide were 9, 33, 39 and 52 (intradermal group) or 14, 20, 26 and 37 (intramuscular group), and induced tetanus toxin-specific CD4+ T-cell responses were 6, 27, 33 and 39 (intradermal), or 9, 46, 54 and 63 (intramuscular). In conclusion, intradermal LIPO-4 immunization was well tolerated, required one-fifth of the intramuscular dose, and induced similar HIV-specific CD8+ T-cell responses. Moreover, the immunization route influenced which antigen-specific T-cells (CD4+ or CD8+) were induced.

Trial registration: ClinicalTrials.gov NCT00121121.

Figure 1. Composition of the LIPO-4 vaccine.

The amino acid sequences correspond to the four antigenic segments of HIV proteins (red) covalently linked to the T-helper–stimulating epitope of tetanus toxin (TT, black) and linker residues (green). The lines under the HIV sequences represent 12 previously reported CD8⁺ T-cell–stimulating epitopes (peptide numbers in brown); the HLA class-I molecules (A or B in blue) restricting the T-cell responses are also indicated.

Figure 2. ANRS VAC16 Participant flow chart.

Figure 3. CD8⁺ T-cell responses (ELISpot IFNγ) to HIV peptides as a function of vaccination route, expressed as individual response.

Panel A, all responders (N = 68), and Panel B, responders given 3 injections (N = 44°. For each responder, the magnitude of the response against individual HIV peptides, expressed as the total spot-forming units per million peripheral blood mononuclear cells (SFU/10⁶ PBMC), evaluated at times 1–4 corresponding to weeks 2, 6, 14 and 24.

Figure 4. CD8⁺ T-cell responses (ELISpot IFNγ) to HIV peptides as a function of vaccination route, expressed as cumulative percentages.

Panel A, all volunteers (N = 68), and Panel B, volunteers who received 3 injections (N = 44). The numbers of volunteers who had mounted responses to at least one HIV peptide at weeks 2, 6, 14, 24 are given above the columns: after intradermal (ID, crosshatched) or intramuscular (IM, empty) injections.

Figure 5. Summary of responses induced in vaccinated volunteers after 1, 2 or 3 intradermal (Panel A, N = 33) or intramuscular (Panel B, N = 35) injections.

Responses were evaluated at weeks 2, 6, 14 and 24 as follows: CD8⁺ T-cell responses to HIV peptides, assessed with ELISpot IFNγ (total SFU/10⁶ PBMC defined as total SFU of positive responses minus the background: nonresponder empty; <100 crosshatched; 100–<500 solid squares; 500+ dotted); CD4⁺ T-cell proliferation against TT peptide (stimulation index: <3 empty; 3–<5 crosshatched; 5–<10 dotted; >10 solid) and induration present 48–72 hours postinjection (diameter (mm): none open; <5 crosshatched; 5–<10 dotted; >10 solid). Subjects in each panel are ordered as follows: CD8⁺ T-cell nonresponders (ELISpot IFNγ), CD4⁺ T-cell responders (proliferation) and, finally, CD4⁺ T-cell responders. Injections were given at weeks 0 and 4 to all 68 subjects and also at week 12 to 44 subjects ND, not done; NA, not applicable.