Characterization of CD31 expression in CD4+ and CD8+T cell subpopulations in chronic untreated HIV infection.

Abstract Background The platelet endothelial cell adhesion molecule-1 (PECAM-1) or CD31 has been involved in regulation of T-cell tolerance, activation, survival and homing in mice cells. However, there is limited knowledge about the expression pattern and role of this molecule in human T cells, particularly in conditions of chronic immune activation. Objectives We explored CD31 expression in T cell differentiation subsets of individuals with untreated HIV infection and in non-HIV-infected controls. We also assessed phenotypic differences between CD31+ and CD31- subsets in memory and terminally differentiated (TEMRA) CD4+ and CD8 + T cells. Methods Forty-one individuals with untreated HIV infection and 34 non-HIV-infected controls were included in the study. We compared the expression of CD31 in CD4+ and CD8 + T cells across stages of differentiation in the two study groups by flow cytometry. We also analyzed the expression of CD57 (a marker of senescence), Ki67 (a marker of cycling cells), PD-1 (a marker of exhaustion), and CD38/HLADR (a marker of immune activation) on memory and TEMRA CD31+ and CD31- T cells. Results CD31 expression was significantly higher in CD8 + T cells than in CD4 + T cells, measured as frequency, absolute numbers and median fluorescence intensity (MFI), in both study groups (p  Conclusion In the context of HIV-associated chronic immune activation, specifically on memory CD8 + T cells, CD31 expression was associated with higher PD-1 and CD38/HLADR co-expression, suggesting that CD31 expression may result from an insufficient attempt to contain T cell exhaustion and activation. CD31-targeted therapies may contribute to modulate these cellular responses.