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In high-income countries and regions, such as Australia, Canada, Western Europe and the United States, highly active antiretroviral therapy (HAART) is widely available because of subsidized access. As a result, AIDS-related infections and deaths have greatly decreased. This effect of HAART is so immense that researchers expect that some HIV-positive people who can adhere to therapy and who have minimal co-existing complications can live near-normal life spans.
A consequence of many viral infections is that the immune system is activated. This is a normal procedure that enables the immune system to go into a heightened state of alert and mobilize its forces against invading germs. Once an infection has been brought under control and the invading germs wiped out, the immune system then dampens down activation to a more normal state.
HIV infection activates the immune system very early in the course of infection. This activation appears to cause dysfunction within the immune system, also very early in the course of infection. Some researchers theorize that prolonged activation of the immune system due to HIV infection leads to increasingly dysfunctional behaviour by the immune system and, eventually, if treatment is not started, to the development of AIDS.
Although HAART is very good at suppressing HIV in the blood, infected cells continue to produce low levels of HIV in the body. And although the immune system continues to experience activation, albeit at a reduced level because of HAART, this continued activation over many years may gradually degrade organ-systems such as the heart and blood vessels, kidneys, bones, and so on.
Experiments conducted on monkeys infected with the AIDS-causing virus SIV and those in people taking HAART over the long-term confirm the presence of low-level activation. Because of the potential for continuous activation of the immune system to accelerate the ageing process, research teams in high-income countries are beginning to focus on this aspect of HIV infection. Their efforts are aimed at gaining a better understanding of why this activation occurs in the presence of HAART and developing ways to safely lessen it.