Whilst suppression of HIV viral load is one of the immediate aims of anti-HIV therapy, the ultimate goal is to restore immune function and thereby prevent opportunistic disease and prolong life.

An immune-boosting treatment is one that improves the health of the immune system - the body's defence against infection. Such treatments typically aim to increase the number of CD4 T-cells and improve the immune system’s ability to recognise and fight infectious agents. Some immune therapies involve cytokines, chemical messages that enable communication among immune system cells. Interleukin-2, for example, has been studied as a way to increase CD4 cell counts. Directly stimulating the immune system can be a risky strategy, however, since it may encourage the production of new virus particles when infected resting immune cells are activated.

Combination antiretroviral therapy can produce dramatic and rapid increases in CD4 cell counts. Studies have shown that some people who take anti-HIV drugs can achieve nearly normal CD4 cell levels. But sometimes antiretroviral therapy leads to discordant virological and immunological responses, meaning that viral load decreases without an accompanying rise in CD4 cells, or vice versa.

Vaccines, which stimulate the immune system to prevent infection or control HIV replication once infected, have been studied since the beginning of the epidemic. While some studies have produced promising results, there is no proof yet that either antiretroviral drugs or vaccines can completely eradicate or control HIV without continuing treatment.

As effective treatment begins to restore immune function, problems may also arise as the recovering immune system begins to fight pre-existing pathogens. This phenomenon, known as immune reconstitution syndrome, can cause a variety of symptoms that may resemble worsening of the original condition.