Hepatitis-G Virus May Stall HIV's Advance
Infection with mystery microbe improves odds
WEDNESDAY, Sept. 5, 2001 (HealthDayNews) -- An apparently toothless cousin of the deadly hepatitis C virus seems to retard the progress of another grave infection, HIV, in people carrying both organisms, new research says.
Scientists say people infected with both HIV, which causes AIDS, and a recently discovered and seemingly symptomless form of hepatitis called GB virus type C (GBV-C) are much less likely to die of AIDS in the short term than HIV patients not infected by the second virus.
The findings suggest that GBV-C might offer AIDS researchers a novel target for therapies to fight the disease. However, experts caution that the virus must be better understood before it can be exploited as a treatment.
"The fact that it was only first discovered in 1995, and there are plenty of diseases out there for which we really don't know the cause, leads us to be very conservative," says Dr. Daniel Diekema, an epidemiologist at the University of Iowa and a co-author of one of the studies, which appear this week in the New England Journal of Medicine. "It would be premature to infect people with this virus because we may find out there are adverse effects."
About 40 percent of HIV-positive people also carry GBV-C, which does not cause hepatitis or produce any other known symptoms. The organism is related to the flaviviruses that cause yellow and dengue fevers.
The first study, which was funded by the National Institute on Alcohol Abuse and Alcoholism, initially intended to look at the link between alcohol intake and liver damage in people with HIV and hepatitis. But it turned into something different when the scientists noticed the connection between co-infection with HIV and GBV-C, also known as hepatitis G.
Led by Dr. Jack Stapleton, the Iowa researchers tracked 362 HIV patients between 1988 and 2000, of whom 144 -- or roughly 40 percent -- also carried GBV-C. Those with only the AIDS virus were nearly 3.7 times more likely to die of the disease during the study period than those infected with both microbes, the group says.
Overall, 41 (28.5 percent) of the people with both viruses died during the study, compared with 123 (56 percent) of those carrying HIV only.
HIV's target is a form of white blood cell, called the CD4 T-cell, which is critical to a healthy immune response. But in the presence of GBV-C, HIV appears to have a much harder time infiltrating and replicating in T-cells, the researchers say.
Tests in the lab showed that cells infected with both viruses produced 30 percent to 40 percent less HIV, the study reports.
In the second study, a group of scientists led by Dr. Hans Tillmann of the Medical University in Hanover, Germany, found that HIV-positive people with genetic traces of GBV-C in their blood survived significantly longer with the fatal infection than those without the additional virus. They also had higher T-cell counts and lower concentrations of HIV in their blood.
Exactly how GBV-C might slow the spread of HIV isn't clear, the researchers say, adding that it could do so directly or by attracting immune molecules that battle the harmful virus when they reach the scene.
Whatever the case, the association between GBV-C infection and lower mortality from HIV "is very strong, and it appears to be real," Diekema says. "We made every attempt to control for what we thought were important co-factors, like baseline [T-cell] counts and receipt of appropriate anti-retroviral therapy" that might have skewed the results, he says.
Dr. Valentina Stosor, an infectious disease expert at Northwestern University Medical School in Chicago and co-author of an editorial accompanying the journal articles, says the studies about the role of this virus "should be looked at as an interesting phenomenon" that needs further study.
"This is a virus in search of a disease," Diekema agrees.
But until researchers can prove that GBV-C and HIV indeed interact, experts agree it's too soon to say if the new virus represents a potential target for AIDS treatment.
What To Do
More than 33 million people worldwide are infected with the AIDS virus. To learn more about the biology of HIV, visit the Web site of the University of California, San Francisco.
To learn more about flaviviruses, try Stanford University.