CD4 and HIV-1 infection: In the case of HIV-1 infection, LTNP and EC may control viral replication with the help of cytotoxic CD4 T lymphocytes specific for p24 (31, 32), and characteristically have CD4 T cells that vigorously proliferate in response to HIV-1 antigens, compared to non-proliferative CD4 T cells from subjects with progressive disease (24).