Regulatory T cells generated during cytomegalovirus in vitro stimulation of mononuclear cells from HIV-infected individuals on HAART correlate with decreased lymphocyte proliferation

HIV-infected patients fail to fully recover cell-mediated immunity despite HAART. To identify regulatory factors, we studied the phenotype and function of in vitro cytomegalovirus (CMV)-stimulated T cells from HAART recipients. CFSE-measured proliferation showed CD4+ and CD8+ cells dividing in CMV-stimulated cultures. Compared with healthy controls, CMV-stimulated lymphocytes from HAART recipients had lower 3H-thymidine incorporation; lower IFNγ and TNFα production; higher CD4+CD27-CD28- and CD8+CD27-CD28- frequencies; lower CD4+CD25hi; and higher FoxP3 expression in CD8+CD25hi cells. CMV-specific proliferation correlated with higher IFNγ, TNFα and IL10 levels and higher CD4+perforin+ and CD8+perforin+ frequencies. Decreased proliferation correlated with higher CD4+CD27-CD28- frequencies and TGFβ1 production, which also correlated with each other. Anti-TGFβ1 neutralizing antibodies restored CMV-specific proliferation in a dose-dependent fashion. In HIV-infected subjects, decreased proliferation correlated with higher CMV-stimulated CD8+CD25hi frequencies and their FoxP3 expression. These data indicate that FoxP3- and TGFβ1-expressing regulatory T cells contribute to decreased immunity in HAART recipients