Alterations of CD4+CD25+Foxp3+ regulatory T cells in HIV-infected slow progressors of former blood donors in China

Our objective was to study the alterations of CD4+CD25+Foxp3+ Tregs in HIV-infected SPs and to examine the role of Tregs in the disease progression of HIV. The proportion of CD4+CD25+Foxp3+ Tregs in peripheral blood of 24 SPs, 30 asymptomatic HIV-infected patients, 20 AIDS patients, and 16 non-infected controls was quantified using flow cytometry. HIV Gag peptide mix-induced IFN-γ expression in CD8+ T cells in whole and CD25-depleted PBMCs was examined to evaluate the function of Tregs. The expression of CTLA-4 in Tregs was also detected to measure the suppressive effect of Tregs. HLA-DR and CD38 expression were measured to study the relationship between the frequency of Tregs and immune activation of HIV-infected patients. The frequency of CD4+CD25+Foxp3+ regulatory T cells in SPs was lower than in asymptomatic HIV-infected patients, AIDS patients, and normal controls (P < 0.05). Tregs in SPs showed lower intracellular CTLA-4 expression than those of asymptomatic HIV-infected patients and AIDS patients (P < 0.05). The frequency of Tregs significantly correlated with the percentage of CD38 expression on CD4+ and CD8+ T cells (P < 0.05). Multivariate regression analysis showed that the CD4+ T cell count was the strongest independent factor correlated with the absolute count of Tregs, while viral load had the strongest predictive strength on the proportion of Tregs. We conclude that a lower frequency of Tregs and intracellular CTLA-4 expression of Tregs was one of the characteristics of SPs that may have important clinical impacts for the prediction of the clinical progress of HIV infection.