Potent cocktails of anti-HIV drugs can pound the AIDS virus down to undetectable levels in the blood. But a pair of papers in tomorrow's Science (pp. 1291  and 1295 ), report that the virus can survive the shelling in a small number of T cells, immune cells that are HIV's primary target. Viruses in this hidden reservoir, moreover, can be woken from their shell shock and induced to reproduce, at least in the test tube. Either current drug regimens may take many years to totally rid the body of HIV, experts say, or they are not powerful enough to do so
Although HIV had already been caught lurking in immune cells after drug treatment, some scientists had speculated that the virus might exist in a damaged, powerless form. To check out that prospect, two research teams--one led by immunologist Robert Siliciano at the Johns Hopkins University School of Medicine in Baltimore, and the other by virologist Douglas Richman of the University of California, San Diego, School of Medicine in La Jolla--looked for HIV in so-called memory T cells, which help lead the attack when the immune system encounters microbial invaders it has seen before.
The researchers took blood cells, including memory T cells, from HIV-positive patients who were on a strict regimen of multiple-drug therapy and cultured them with cells from uninfected people. As soon as the researchers triggered the memory T cells to become activated, the virus started replicating and infecting the HIV-negative cells--even though viral levels in the HIV-positive cells were minuscule. Although the results appear to confirm that HIV weathers a multidrug attack, the researchers did find some good news: There was no evidence that the surviving virus had mutated, which suggests that it had not become resistant to the drugs.
AIDS researchers aren't surprised by the viral comeback. "We knew that patients over this time frame would become virus positive if treatment is removed," says retrovirologist John Coffin of Tufts University in Medford, Massachusetts. "The virus has to still be somewhere." Indeed, the findings "should not have any impact on what we recommend to patients," says Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. "We are reaping enormous benefits for patients by keeping the virus as low as possible for as long as possible."