FOUR HIV-positive people who have mysteriously avoided developing AIDS could have a primitive and overlooked branch of the immune system to thank.
Behind the immune system鈥檚 sophisticated armoury of antibodies and cells tuned to recognise specific foreign proteins lies its frequently neglected evolutionary forerunner. This is the innate immune system, which triggers non-specific defences when microbes invade.
According to Jay Levy of the University of California, San Fransisco, it is probably the innate immune system that is saving the lives of four HIV-infected people who have turned down anti-HIV drugs for the past six to eight years. Levy told the AIDS conference in Barcelona last week (see 鈥淲orld waits for a breakthrough鈥�) that even though these people have dangerously low levels of immune cells, they are not developing pneumonia and the other opportunistic infections that are the deadly hallmarks of AIDS.
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While the numbers of their immune cells are plummeting overall, a tiny population of cells has remained intact. These survivors churn out interferon, a potent chemical that switches on immune defences when they spot any virus 鈥� including HIV, Levy has shown.
Why these cells have escaped the ravages of HIV in these four individuals is still unknown. But boosting numbers of the cells in other patients could help them fight off opportunistic infections. And doctors already know of two drugs that do exactly that. 鈥淭his could be an alternative defence mechanism,鈥� Levy says.