Some people infected with the human immunodeficiency virus have remained healthy for as long as 15 years, leading some researchers attending the Tenth International Conference on AIDS to hypothesize that infection does not always mean death from AIDS.
"It is a ray of hope for the affected patients and the rest of the world that it is possible to co-exist with HIV without harm," said Dr. David Ho, director of the Aaron Diamond Cancer Research Center in New York City.Ho said there is a good chance that at least eight of 10 patients he has studied may never develop AIDS or an HIV-related illness. The patients, infected with HIV for 12 to 15 years, all have immune systems in the normal range and appear healthy.
Ho estimated that as many as 10 percent of people infected with HIV fall into the long-term, non-progressive or long-survivor category.
Dr. Susan Buchbinder, of the San Francisco Health Department, studied 601 HIV-infected men over a 15-year period and found that 7 percent had normal or near-normal immune systems.
"It is very clear that there is a group of people for whom it (HIV infection) is not a death sentence," Buchbinder said. "The encouraging news is that not everyone (infected with HIV) may develop AIDS."
Some scientists have hypothesized that so-called long-term survivors will eventually develop AIDS. But Buchbinder and Ho said there is no indication that will happen or that the immune system of these patients has been harmed.
That could mean bright news even for those who develop AIDS, because studies of long-term survivors may provide important information that could lead to effective treatment.
Ho said studies show that long-term survivors mount a stronger immune response against HIV than people who develop AIDS. Blood cells called CD8 appear to suppress growth of the virus. Ho said the survivors' cells do not seem more resistant to infection. Ho added, however, that some patients had a "pretty wimpy virus" that did not reproduce when grown in culture.
These findings "provide guideposts or targets to aim for in vaccine development," he said.
Ho's work dovetails with that of Dr. Jay Levy, an AIDS researcher at the University of California School of Medicine at San Francisco.
Levy, who has followed the same HIV-infected healthy man for 10 years, found that the patient's CD8 cells suppressed the reproduction of HIV. Levy identified a factor produced by the CD8 cells and said it appears to be a potent antiviral agent.
The action of this factor has been observed in the blood of many long-term survivors, Levy said.