CD4 and HIV-1 infection: The outcome of HIV-1 infection is categorized into three groups: (a) long-term non-progressors (LTNPs), who can be subdivided into elite controllers (those with CD4+ T cell counts >500/mm3, undetectable viral load [VL], and spontaneous control of HIV-1 without antiretroviral therapy [ART] for more than 7 years and virus controllers (those who establish and retain effective control of HIV-1 for <7 years); (b) typical progressors (TPs); and (c) rapid progressors (RPs).