CD4 and HIV-1 infection: Life-long persistence of HIV-1 infection is primarily due to small numbers of virally infected, long-lasting memory CD4+ T cells that harbor chromosomally integrated HIV-1 DNA as a “provirus.”1,2 Within these cells, HIV-1 frequently remains in a transcriptionally silent (latent) state, which shields the virus from host immune responses and reduces viral cytopathic effects.3