Regulatory T-lymphocyte subsets in patients with HIV-infection receiving highly active antiretroviral therapy

Background. The reason why HIV-infected patients receiving highly active antiretroviral therapy (HAART) suffer from the increased immune activation remains elusive. Regulatory T-cells (Treg) are able to control immune activation, but their quantity may vary due to the infection. The aim of this work was to estimate the number and subsets of Tregs in HIV-positive patients receiving virologically effective HAART. Materials and methods. The CD4+ T-lymphocyte (CD3+CD4+) and Treg (CD3+CD4+FOXP3+) quantities were determined by flow cytometry. Treg subsets were assessed based on the FOXP3 expression level. The state of T-cell activation was established according to the simultaneous expression of CD38 and HLA-DR molecules. Results. It was shown that HIV-positive patients compared to healthy people have reduced CD4+ T-lymphocyte counts despite virologically effective HAART. At the same time in HIV-infected people, Treg absolute numbers were only slightly decreased. Moreover, the major part of Treg pool in their blood consisted of lymphocytes with a high level of FOXP3 expression that corresponded to the phenotype of cells with the highest suppressor activity. However, an increased relative amount of activated CD4+ T-lymphocytes was retained in the HIV-infected individuals’ blood. Conclusion. In HIV-infected patients who received HAART in time and whose treatment resulted in an effective HIV viral load suppression and a satisfactory CD4+ T-cell counts increase, a relatively large pool of peripheral Tregs is maintained. However, these lymphocytes are not enough to fully control immune activation that develops against the background of chronic lentivirus infection.