Some men infected with the virus that causes AIDS apparently get help from an unexpected source--another virus. The second virus appears to delay the progression of the disease, according to new research. The result may eventually help scientists develop novel treatments for the affliction.
Because people infected with HIV have compromised immune systems, other viruses are usually bad news. But about 5 years ago, scientists discovered that a common virus called GB virus C appeared to prolong the lives of men infected with HIV. On its own, GB virus C, which infects about 85% of the general population, does no harm. The research was controversial, however, because other studies found no benefit. To put the matter to rest, epidemiologist Jack Stapleton of the University of Iowa, Iowa City, and colleagues turned to the Multicenter AIDS Cohort Study, which has been collecting blood samples from 5622 homosexual men every 6 months since 1984. Some of the men became infected with HIV during the course of the study.
The team tested blood samples of 271 men with HIV, some of whom had GB virus C before catching HIV, and others of whom didn't. GB virus C does offer a survival advantage, the researchers report in the 4 March issue of The New England Journal of Medicine, but the effect can only be seen in men who have carried both viruses for a long time. Men who were infected with both viruses for a year and a half had the same survival rate 5 years later as men with HIV alone. However, men who carried both viruses for 5 years were almost three times as likely to be alive as those with HIV alone. After 11 years they were almost twice as likely to be alive. On the other hand, men who were infected with GB virus C but cleared the helper virus fared worse than those who never had it.
The study suggests that GB virus C had a protective effect in some studies but not others because the studies may have been following patients who had carried one or both viruses for different amounts of time. "This paper puts that controversy to rest," says virologist Donald Mosier of The Scripps Research Institute in La Jolla, California. More importantly, this "provocative observation ... leads to big questions as to why [the virus] is protective." Retrovirologist Roger Pomerantz of Thomas Jefferson University in Philadelphia says, "the bottom line is, we don't know." Once they do, the next step is to develop a therapy that mimics the GB virus C's beneficial effect.