Suppression of HIV-1 infection in vitro by HIV-specific CD8⁺ T-cell clones. (A) Primary CD4⁺ T cells isolated from a HLA B*2705⁺ healthy donor and blasted with PHA were infected with the replicative HIV-1 strain NL4.3 (MOI = 10^−1.8) in the presence or absence of KK10-specific CD8⁺ T-cell clones with distinct levels of antigen sensitivity (highest, C2A; intermediate, H10G; lowest, D8B) or a control NV9-specific CD8⁺ T-cell clone; E:T ratio 1:10. After 3 days, HIV-1 infection levels were measured using intracellular p24 staining. Numbers show the percentages of p24⁺ cells in the cultures. (B) Inverse correlation between CD8⁺ T-cell antigen sensitivity and HIV-1 infection in vitro (% of p24⁺ cells) determined using Spearman rank test (each dot represents 1 clone). (C) Assessment of suppressive activity (fold decrease of p24⁺ cells compared with infected CD4⁺ T-cell controls in the absence of CD8⁺ T cells) for CD8⁺ T-cell clones at different E:T ratios. (D) Measurement of p24⁺ cells at decreasing MOI (10^−1.8, 10^−2.2, 10^−3.3) and different E:T ratios for CD8⁺ T-cell clones with highest (●), intermediate (□), or lowest (◇) levels of antigen sensitivity. CD8^neg cells were gated for the analyses. (E) Plasma viral loads and CD4 counts in 21 untreated HIV-infected donors grouped according to the antigen sensitivity (lower ● or higher ○) of their individual immunodominant CD8⁺ T-cell response, determined in peptide titration IFN-γ ELISPOT assays conducted ex vivo. Immunodominant responses (including HLA-A2 Nef PL10, A3 Gag RY10, A3 Nef QK10, A24 RW8, A26 Gag EL9, B7 Gag GL9, B7 Nef TL10, B8 Gag GI9, B8 Nef FL8, B8 Gag DL10, B27 Gag KK10, and B51 Env RL9) were screened using a panel of 49 optimized cytotoxic T lymphocyte epitopes.