 Memory CD4 cells may provide a reservoir of latent HIV that cannot be completely eliminated using currently available anti-HIV medications. The overall goal of this observational study is to develop new strategies to eliminate the latent HIV reservoir in HIV infected individuals. CD4-cell subsets, cellular anti-HIV factors, and cellular drug transporters will be observed to determine which resting memory cells hide latent HIV and to determine the mechanisms responsible for the persistence of the latent HIV reservoir. 