ObjectivesMicroRNA-155 (miR-155) regulates T-cell differentiation and activation. It has also been associated with HIV infection. However, it remains unclear whether miR-155 is related to the T-cell response in HIV-infected individuals (e.g. T-cell activation and exhaustion). MethodsWe performed a cross-sectional study involving 121 HIV-1-infected patients on highly active antiretroviral therapy (HAART) and 43 HAART-naive patients. MiR-155 levels in the peripheral blood were determined by quantitative reverse transcription-polymerase chain reaction (PCR). T-cell immune activation, exhaustion, and homeostasis were measured by determining the expression of CD38, programmed death 1 (PD-1) and CD127 via flow cytometry. ResultsThe levels of miR-155 in total peripheral blood mononuclear cells, CD4 T cells and CD8 T cells from HIV-1-infected patients were increased (P < 0.01). Nonresponders and HAART-naive patients also exhibited a higher percentage of CD8(+)CD38(+) T cells and a lower percentage of CD4(+)CD127(+) and CD8(+)CD127(+) T cells (P < 0.05). We also found higher levels of PD-1 expression on the CD4(+) and CD8(+) T cells of HIV-1-infected patients (P < 0.05). ConclusionsOur findings suggest that miR-155 levels in the peripheral blood of HIV-1-infected patients are increased and associated with T-cell activation. Therefore, miR-155 is a potential biomarker of the immune response following HIV-1 infection.