The introduction of antiretroviral therapy (ART) for HIV infection in the mid 1990s has transformed a lethal disease into a chronic disease. But despite the success of ART in controlling infection, ART has not been able to eliminate all traces of virus from the body. If treatment is discontinued, viral loads rebound, and treatment also can fail even in the most adherent patients.
The main obstacle to wiping out HIV with ART is the reservoir of latent virus found mainly in long-lived resting memory CD4 T cells. Because these cells aren't actively replicating, the virus is both hidden from the immune system and invulnerable to ART.
Friedrich MJ. Scientists Investigate Routing Latent HIV From Its Reservoirs to Achieve a Cure. JAMA. 2012;308(4):325-327. doi:10.1001/jama.2012.8466