Human immunodeficiency virus type 1 (HIV-1)-specific CD8+-T-cell responses for groups of HIV-1-infected individuals with different HLA-B*35 genotypes

Abstract

Human immunodeficiency virus type 1 (HIV-1)-infected individuals with HLA-B*35 allelic variants B*3502/3503/3504/5301 (B*35-Px) progress more rapidly to AIDS than do those with B*3501 (B*35-PY). The mechanisms responsible for this phenomenon are not clear. To examine whether cellular immune responses may differ according to HLA-B*35 genotype, we quantified HIV-1-specific CD8(+)-T-cell (CTL) responses using an intracellular cytokine-staining assay with specimens from 32 HIV-1-positive individuals who have B*35 alleles. Among them, 75% had CTL responses to Pol, 69% had CTL responses to Gag, 50% had CTL responses to Nef, and 41% had CTL responses to Env. The overall magnitude of CTL responses did not differ between patients bearing B*35-Px genotypes and those bearing B*35-PY genotypes. A higher percentage of Gag-specific CTL was associated with lower HIV-1 RNA levels (P = 0.009) in individuals with B*35-PY. A negative association between CTL activity for each of the four HIV antigens and viral load was observed among individuals with B*35-PY, and the association reached significance for Gag. No significant relationship between CTL activity and viral load was observed in the B*35-Px group. The relationship between total CTL activity and HIV RNA among B*35-Px carriers differed significantly from that among B*35-PY carriers (P < 0.05). The data are consistent with the hypothesis that higher levels of virus-specific CTL contribute to protection against HIV disease progression in infected individuals with B*35-PY, but not in those with B*35-Px.

FIG. 1.

Survival analysis of B*35-Px- and B*35-PY-positive individuals free of AIDS. Data for 16 B*35-Px individuals were compared with data for 16 B*35-PY individuals. RH and P were calculated by Cox model analyses.

FIG. 2.

Quantifying HIV-1-specific CD8⁺ T cells by intracellular cytokine staining. Aliquots of PBMC from one HIV-1-infected individual were stimulated by recombinant vaccinia virus expressing negative control Eco, HIV-1 antigens (Env, Gag, Pol, and Nef), and positive control SEB first, followed by staining with anti-CD3, -CD4, -CD8, and -IFN-γ antibodies. The antigen-specific CD8⁺ T cells were enumerated and expressed as a percentage, shown on the upper right quadrant of each plot. FITC, fluorescein isothiocyanate.

FIG. 3.

Broadly reactive antigen-specific CD8⁺ T cells were detected in both B*35-Px and -PY groups. The percentage of IFN-γ-producing CD8⁺ T cells specific for HIV-1-antigens Env, Gag, Pol, and Nef in each patient was expressed as one open circle. Data for 16 B*35-Px individuals and 16 B*35-PY individuals were included in each plot.

FIG. 4.

Association between viral loads and HIV-1-specific CTL numbers at the time of blood draw. Plots on the upper row are correlations between viremia (log₁₀) levels and Env, Pol, Gag, and Nef specific CTL numbers in the B*35-PY group of patients; those on the lower row are the same correlations for the B*35-Px group of patients. Each open circle represents one patient. There is a significant inverse correlation between Gag-specific CTL and viral load in the B*35-PY group (r = −0.614; P = 0.009).