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⁺CD25^hi; and higher FoxP3 expression in CD8⁺CD25^hi 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⁺CD25^hi frequencies and their FoxP3 expression. These data indicate that FoxP3- and TGFβ1-expressing regulatory T cells contribute to decreased immunity in HAART recipients.