Besides the central nervous system and genital tract, other HIV reservoirs include certain immune cells other than CD4T-cells, the lymph nodes, the thymus and lymphoid tissue in the gut. Anti-HIV drugs vary in their capacity to reduce viral replication in these locations.

Effective combination antiretroviral therapy appears to reduce the amount of HIV in the lymph nodes ^[1]. But the virus often remains detectable in lymph node tissue despite prolonged suppression of blood viral load. In the Merck 035 study, which looked at combination therapy with indinavir, patients with sustained undetectable blood viral load for two years did not show evolution of HIV RNA sequences in their lymph nodes, suggesting that viral replication was minimised even though HIV was not eliminated completely^[2].

HIV is also found in the ocular fluid of the eye. Although not all antiretroviral drugs penetrate well into the eye, a small study of patients with ocular manifestations of AIDS-defining illnesses found that most had undetectable HIV in their aqueous humour (fluid in the front of the eyeball) within four to eight months of starting HAART^[3].

More recently, researchers demonstrated that HIV continues to replicate in lymphoid tissue in the gut despite antiretroviral therapy that effectively suppresses viral load in the blood ^[4]. They also found that patients who had been infected with HIV longer and had more inflammation were less likely to achieve viral suppression in the gut.

The difficulty in eliminating HIV from lymph tissues and other ‘sanctuary sites’ represents the main barrier to full eradication. For further information, see Can HIV be eradicated?