BACKGROUND: Immune senescence can occur in untreated HIV infection and is partially reversible with effective antiretroviral therapy (ART). Here, we investigated the differences in immune senescence of T cell subsets among Chinese men who have sex with men (MSM) living with HIV virologically suppressed on ART compared to those ART-naive. METHODS: A cohort of MSM living with HIV with different disease courses was included, untreated viral non-controllers (n = 26) and those on ART (n = 30). The percentages of naive, central memory (TCM), effector memory (TEM), and terminally differentiated memory (TemRA) subsets of CD4 and CD8 T cells were studied, along with markers of senescence (CD28-CD57+) and activation (HLA-DR). Telomere length of naive and memory CD8 T cells was quantified by real-time PCR. The correlation between senescent CD4 and CD8 T cell subsets and CD4 and CD8 cell counts was analyzed with the Spearman rank correlation. RESULTS: Compared with the ART-naive group, the percentage of senescent cells (CD28- CD57+) in total CD8 T cells was significantly lower in the ART group (P <
0.01). Significant differences were observed among CD8 T cell subsets, but not in CD4 T cell subsets (P <
0.05). In the ART group, the percentage of senescent cells (CD28-CD57+) in TN and TCM subsets of both CD4 and CD8 T cells was lower (all P <
0.05). HLA-DR expression was significantly lower in all CD4 and CD8 T cell subsets except TEMRA subset (P <
0.05). The telomere length of CD8 T cell subsets did not differ significantly between the two groups. The percentage of senescent naive CD4 T cells was inversely correlated with CD4 T cell counts (r = -0.42, P = 0.0343), while the percentage of senescent naive CD8 T cells was positively correlated with CD8 T cell counts (r = 0.47, P = 0.0161) in the ART-naive group, but not in the ART group. CONCLUSIONS: Virologically suppressed MSM living with HIV exhibit lower immune senescence of T cell subsets, which is more pronounced for CD8 cell subsets. The percentage of senescent naive T cells is significantly correlated with clinical immunity based on CD4 and CD8 T cell counts.