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WEDNESDAY, March 3 (HealthDayNews) -- Researchers think they've confirmed the unlikely notion that a seemingly harmless viral infection helps people with HIV live longer.

The workings of the virus are far from clear, and scientists can't guarantee it's utterly benign. But study findings seem to suggest it somehow strengthens the immune systems of these patients.

"This puts the final nail in the coffin of people who doubted this effect because it's so odd," says Dr. Roger Pomerantz, director of the Center for Human Virology and Biodefense at Thomas Jefferson University in Philadephia. He wrote a commentary about the new study that appears in the March 4 issue of the New England Journal of Medicine.

Although it's apparently an ancient germ, GBV-C -- also known simply as "virus G" -- was only discovered in the mid-1990s. At first, scientists thought the virus was responsible for one of the potentially deadly liver diseases known as hepatitis. Later, they realized it didn't seem to cause any symptoms, even when the body's immune system failed to clear it away. But it still seems related to hepatitis.

Like hepatitis B, the virus is spread through exposure to blood and sexual contact. Research among healthy blood donors suggests it infects about 1.5 percent to 2 percent of the population, and about 13 percent have had it in the past, says study co-author Dr. Jack Stapleton, director of the University of Iowa HIV Program.

"The majority of healthy people who get this infection clear it and develop antibodies, much like many other viral infections like measles and hepatitis A," Stapleton says. Antibodies are the immune system's specialized soldiers in waiting, trained to attack certain kinds of germs.

Over the past several years, scientists have linked the presence of virus G to longer lifespans in those infected with HIV. In the new study, the most extensive of its kind, scientists examined the medical records of 271 men who became HIV-positive while they were taking part in a large American research project before the advent of powerful AIDS drugs nearly a decade ago.

Eighty-five percent of the men showed signs of virus G infection. And the men who didn't were 2.78 times more likely to die after five to six years than those who were persistently infected with the virus.

"If you have G virus, you're less likely to progress [to end-stage AIDS]," Pomerantz says. "It doesn't mean you won't progress. It means you'll be less likely to."

Those who had been infected with virus G but cleared it were even more likely to die, Stapleton says. This may be because HIV robbed the virus of immune cells to target.

So what's at work with virus G? The germ could somehow prime the immune system to effectively tackle the AIDS virus, Pomerantz says. Or perhaps something else, yet to be discovered, is at work, he adds.

However, Pomerantz doesn't think those infected with HIV should run out and try to get infected with virus G. "That's a real leap and asking for trouble, especially since we have no idea how it works," he says.

The next step: Figure out what's happening with virus G and, if possible, replicate it, Stapleton says. "If we could figure out a way to maintain [virus G] infection, then potentially we would have a disease-modifying treatment or vaccine."

More information

Virus G seems to be related to the various types of hepatitis; to learn more about hepatitis A, check with the U.S. Centers for Disease Control and Prevention. To get details about federal guidelines regarding AIDS treatment, visit AIDSinfo.

(SOURCES: Jack Stapleton, M.D., director, University of Iowa HIV Program, Iowa City; Roger Pomerantz, M.D., F.A.C.P., chief, Center for Human Virology and Biodefense, Thomas Jefferson University, Philadelphia; March 4, 2004, New England Journal of Medicine)

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