CD4 and infection: A cross-sectional study of 41 untreated subjects with acute and chronic HIV infection, including elite controllers of viremia with HIV persistently lower than 50 RNA copies per ml plasma, viremic controllers with HIV levels at 50–2000 copiers per ml plasma, and patients with progressive infection showed that higher levels of CTLA-4 expression on HIV-specific CD4+ T cells positively correlated with the levels of HIV viremia and progression of infection, as well as reduced IL-2 production (141).