Longitudinal T-Cell Phenotypic Dynamics During Sustained Antiretroviral Therapy in People With HIV.

Background: Antiretroviral therapy (ART) suppresses HIV replication and partially restores immune function, but immunologic abnormalities often persist. Methods: We performed longitudinal multiparametric flow cytometry on peripheral blood mononuclear cells from 79 people with HIV-1 (51 women, 28 men) who were virologically suppressed and followed over a median 6 years of ART. We assessed T-cell counts and expression of activation (CD38⁺HLA-DR⁺), cycling (Ki67⁺), exhaustion (TIGIT⁺PD-1⁺), cytotoxicity (CD107a⁺), and regulatory (FoxP3⁺CD25⁺) markers across memory subsets, and we examined associations with sex and HIV reservoir size and activity. Results: CD4⁺ T-cell counts increased and CD8⁺ T-cell counts declined over time, improving CD4/CD8 ratios. Immune activation and cycling markers decreased in both T-cell compartments. TIGIT/PD-1 expression declined significantly in CD4⁺ memory subsets but not in CD8⁺ T cells, while CD107a expression remained elevated in effector memory CD8⁺ and CD4⁺ T cells. Regulatory CD4⁺ T cells declined over time, and no significant associations were observed between T-cell phenotypes and HIV reservoir measures or between sexes. Conclusions: Long-term ART promotes partial immune normalization, including reduced activation and reversal of CD4⁺ T-cell exhaustion. However, persistent expression of CD8⁺ T-cell surrogate markers of exhaustion and stable cytotoxic profiles suggest ongoing antigenic stimulation, potentially driven by HIV or chronic coinfections.