Background:  Cytotoxic T lymphocyte (CTL) activity is a critical factor involved in viral replication control in HIV-1 infection. We wanted to know whether the administration of an HIV-1 immunogen (Remune) in combination with ART could influence the generation of CD8⁺-specific responses in HIV-1 patients.

Methods:  Every 3 months for 36 months, we evaluated 54 patients participating in a randomized, double blind, placebo-controlled study (STIR-2102), receiving ART in combination with either Remune (n = 27) or placebo (n = 27). Precursor frequencies and percentages of proliferating CD4⁺ and CD8⁺ HIV-1-specific T cells were determined by 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) incorporation assays; specific cytotoxicity was analyzed by ⁵¹Cr release assay and interferon-g (IFN-γ) production was measured by ELISpot.

Results:  We found significantly increased lymphoproliferative responses specific for HIV-1 antigens, at month 36 post-immunization, in the Remune group (n = 11) as compared to the placebo group (n = 10), for CD8⁺ T cells (5.7±8.4 vs 1±1.1% CD3⁺CD8⁺CFSE^low; p = 0.034) and for CD4⁺ T cells (5.7±5.6 vs 1.7±1.9% CD3⁺CD4⁺CFSE^low; p = 0.053). HIV-specific T-cell precursor frequencies were also increased in Remune group as compared to placebo (p = 0.031 for CD8⁺ and p = 0.05 for CD4⁺). There was a significantly negative correlation between viral load, T cell HIV-specific precursor frequencies (r = –0.649; p = 0.042) and lymphoproliferative responses (r = –0.696; p = 0.025 for CD3⁺CFSE^low) in the Remune group, but not in the placebo group. Increased numbers of IFN-g-producing CD4⁺ and CD8⁺ T cells to HIV-1 antigens (460±262 spot-forming cells [SFC] vs 65±40 SFC/10⁶ cells; p = 0.005) and of IFN-g-producing CD8⁺ T cells to gag (854±872 vs 369±576/10⁶ cells; p = 0.024) were observed in the Remune group (n = 15) compared to the placebo group (n = 13). ⁵¹Cr release assays showed only in the Remune group a significant increment of gag/pol-specific CTL (n = 20):  baseline, 2.3±1 lytic units/10⁶ PBMC; Remune, 20.2±10.1 lytic units/10⁶ PBMC; placebo, 4.3±2.6 lytic units/10⁶ PBMC (p <0.05). For gag/pol-specific memory CTL precursors (n = 23) results showed:  baseline, 171±152 CTLp/10⁶ PBMC; Remune, 1963±672 CTLp/10⁶ PBMC; placebo, 185±48 CTLp/10⁶ PBMC (p <0.05. There was a strong negative correlation between CTLp frequency for gag/pol and viral load only in the Remune group (r = –0.783; p = 0.003).

Conclusions:  Long-term therapeutic vaccination with Remune induces CD8⁺ HIV-specific cytotoxic responses that correlated negatively with viral load in patients with chronic HIV-1 infection.