March 3, 2004 -- An apparently harmless virus may allow some men with HIV to live longer, healthier lives. But researchers say those benefits only emerge after many years of being infected with both viruses.
A new study found men infected with both HIV and GB virus type C (GBV-C), previously known as hepatitis G, for at least five years were three times less likely to die than HIV-positive men who did not have GBV-C.
GBV-C is a virus that infects white blood cells, but is not known to cause any disease in humans. People with the virus can carry it for up to 40 years, and the virus is transmitted through blood and blood products.
Researchers say six previous studies have also found a survival advantage for HIV-positive men who had GBV-C, but three others showed no benefit, and the relationship between the two viruses is controversial.
But researchers say this new study, published in the March 4 issue of the New England Journal of Medicine, is the first to take into account the duration of infection with GBV-C and its effect on the progression of HIV disease.
"We found strong evidence that HIV-positive men who have persistent GBV-C infection survive longer than those who do not have GBV-C," says researcher Jack Stapleton, MD, of the University of Iowa, in a news release. "The survival advantage is large and depends on how long the GBV-C infection persists."
2 Viruses Better Than 1 for HIV Survival?
In the study, researchers compared two separate sets of blood samples taken from men who were infected with HIV. The first set consisted of 271 samples that were taken within 18 months of when the patient was infected with HIV. The second set of 138 samples was drawn from the men five to six years later.
The study showed that men who had GBV-C infection in both sets of samples taken at least five years apart lived the longest. Eleven years after contracting HIV, 75% of the men who had GBV-C in both samples were alive compared with only 39% of the men who did not have GBV-C in either sample.
The men who had GBV-C in their first blood sample but not in the second had the highest risk of dying, and only 16% of these men were still alive after 11 years.
In an editorial that accompanies the study, Roger J. Pomerantz, MD, and Giuseppe Nunnari, MD, of Thomas Jefferson University in Philadelphia, say there has been much controversy about the interactions of GBV-C and HIV. But this well-done study may settle certain aspects of this question.
They say there is a long history of interactions between viruses whereby one virus lessens the impact of another, and future HIV therapies may benefit from a greater understanding of the relationship between GBV-C and HIV.
For example, some research suggests that GBV-C may inhibit HIV from growing in human cells. They say more research is needed to understand the role of GBV-C in HIV progression and to determine why some men in the study cleared the GBV-C virus from their system.