Common Virus Is Said to Slow HIV, Help Combat Infections
New studies confirm that an innocuous and relatively common virus can prolong the survival of AIDS patients, researchers said here Thursday.
People who had HIV, the virus that causes AIDS, and were co-infected with the virus, called GBV-C, were 2.5 times more likely to survive than those who were not co-infected during an 11-year evaluation period, epidemiologist Carolyn Williams of the National Institute of Allergy and Infectious Diseases told the 10th Conference on Retroviruses and Opportunistic Infections.
The time is nearing when physicians will deliberately infect HIV and AIDS patients with the virus to determine how beneficial it really is, said Jack Stapleton of the University of Iowa.
The discovery could also lead to new drug treatments for HIV infections, he said.
Recent studies have shown that GBV-C has infected humans for millions of years, but the virus was not actually identified until 1995, when two teams of molecular biologists isolated it.
The Abbott team called the new virus GB virus C because it was genetically similar to the hepatitis C virus, while Genelabs called it hepatitis G. Although both names are now used, GBV-C is now used more commonly because the virus does not seem to infect the liver or cause any other adverse symptoms in humans. It is transmitted sexually, through blood products and from mother to infant at birth.
Between 1% and 2% of U.S. blood donors are actively infected with GBV-C, and another 13% to 18% have antibodies indicating a previous infection. As many as 40% of HIV-positive individuals have an active infection, however.
Stapleton reported in September 2001 that co-infection with GBV-C increased survival of HIV-positive individuals by about 50%, but subsequent studies have given less encouraging results.
To examine the problem more carefully, a team headed by Williams examined stored blood serum samples collected in the ongoing Multi-center AIDS Cohort Study. The group tested samples from 271 men collected an average of 12 to 18 months after an HIV diagnosis and found that 39% of them had an active GBV-C infection.
An initial examination of medical records coming about 11 years after the initial diagnosis had indicated no survival benefit from the co-infection.
Puzzled, they tested serum samples collected six years after the initial diagnosis and found that 12 of the men who were originally infected with GBV-C had cleared the infection. Ten of those 12 had died by 11 years after diagnosis.
When the team reanalyzed the data, they found that 75% of those who were persistently infected by GBV-C were still alive after 11 years, compared with only 39% of those who were not persistently infected.
“That’s a pretty strong beneficial effect,” Williams said.
But she cautioned that researchers should not rush into deliberate infections because of the experience with the 12 people who cleared the infection, who were more likely to die than those who had never been infected by GBV-C. Stapleton, meanwhile, studied the virus in the test tube to try to understand how it works. He reported here that the virus binds to the CCR-5 receptor on the surface of white blood cells called T-cells, the same receptor that is used by HIV to enter the cells. That binding limits the amount of HIV that can enter the cell.
GBV-C “doesn’t prevent infection by HIV, but it slows replication,” he said. The GBV-C infection also increases the production of various chemokines, proteins that mobilize and activate white blood cells to fight infections. “There are multiple mechanisms by which it helps the HIV-positive,” he concluded.
