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

Antiretroviral therapy (ART) suppresses HIV replication and partially restores immune function, but immunologic abnormalities often persist.

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.

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.

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.