TCR avidity determines the efficacy of HIV suppression by CD8⁺ T cells. (A) HLA-B*2705⁺ CD4⁺ T cells infected with wt (HIV_NL4-3) or ΔNef (HIV_NL4-3ΔNef) viruses were assayed for HLA-B*27 expression by flow cytometry. Surface expression of HLA-B*27 is shown for infected p24⁺ cells (gray) and uninfected p24⁻ cells (black). (B) Representative flow cytometry plots showing p24 expression in CD4⁺ T cells infected with titrated amounts of wt or ΔNef viruses after 3 days of coculture with high- or low-avidity CD8⁺ T-cell clones. Percentages of p24⁺ cells and E:T ratios are indicated. (C) Fold decrease in the percentage of p24⁺ CD4⁺ T cells infected with titrated amounts of wt or ΔNef viruses after 3 days of coculture with higher (n = 4) or lower (n = 4) avidity CD8⁺ T-cell clones at E:T ratios of 1:1. The Wilcoxon signed-rank test was used to compare suppression of wt versus ΔNef viruses. **P < .01.