An ancient virus that has tagged along harmlessly through human evolution appears to improve people's chances of surviving AIDS by blocking HIV's ability to infect blood cells, new research shows. Several recent studies have found that people who are infected with GB virus C are substantially less likely to die of AIDS complications than people who are uninfected. Experts now theorize that GBV-C thwarts HIV's ability to attach itself to T cells by blocking CCR5 receptors--one of the "doors" on the surface of T cells that HIV must lock onto before infecting the cells. HIV is harmless until it can enter a T cell and begin making copies of itself.
"There is not a way for the virus to get into the cells. The doors are gone," said Carolyn Williams of the National Institute of Allergy and Infectious Diseases. Williams studied 271 men who were diagnosed with HIV infection in 1985. After 11 years, 75% those also infected with GBV-C were still alive compared with 39% who never had the virus.
Researchers at the University of Iowa are planning to test the effectiveness of deliberately giving the virus to HIV-positive people who are resistant to all standard anti-HIV drugs. GBV-C was discovered in 1995. It was at first mistakenly thought to be a hepatitis virus and called hepatitis G. Now, however, scientists say that while the virus is closely related to hepatitis C, it causes no disease that they can find. GBV-C, like HIV, is transmitted mainly through blood or sexual contact. The virus is believed to have existed since the earliest humans.