|Highly active retroviral therapies (HAART) suppress circulating HIV levels below the limits of detection and restore immune function. The early promise of such therapies, that they might eliminate HIV infection from the body within a few years treatment, has been tempered because the virus is able to persist silently in infected CD4+ cells in patients undergoing HAART.
Infection of CD4+ cells with HIV leads to activation and up-regulation of cell surface proteins that further facilitate HIV entry, usually culminating in cell death through apoptosis. However, some activated cells survive and return to their resting state with HIV integrated into their genome and remain as a reservoir capable of HIV replication, and commonly persist even after intensive HAART. (Draining HIV reservoirs)