HIV can linger years with no antibodies.

HIV can linger years with no antibodies

The AIDS-causing virus, HIV, can reside in individuals for three years without triggering production of the antibodies doctors use as evidence of AIDS infection, new research indicates.

The findings, which suggest that prolonged viral latency in HIV-infected people may be more common than previously recognized, add a dark cloud to an already bleak AIDS horizon. But a potential silver lining emerges as well, researchers say. On the one hand, the study suggests that many people who test negative for HIV antibodies may in fact be infected. If these people can infect others via sexual contact or blood transfusion -- something researchers stress remains uncertain in these individuals -- then the likelihood of inadvertent disease transmission may be substantially increased. On the other hand, the research suggests some infected individuals can suppress viral activity so effectively that for years they may show no antibody response, let alone symptoms of disease. This provides hope that scientists may eventually develop drugs or other treatment approaches that could delay disease onset indefinitely in infected individuals.

David T. Imagawa of the University of California, Los Angeles, School of Medicine and his colleagues followed 133 homosexual men who at six-month intervals repeatedly tested negative for HIV antibodies despite continued high-risk sexual activity. Using sensitive viral culture techniques, the researchers detected HIV in 31 (23 percent) of these men, 27 of whom have remained without detectable antibodies for up to 36 months after infection.

Previous studies had hinted at the possibility of such long latencies in apparently infected individuals with extremely low antibody levels, says William A. Haseltine of the Dana-Farber Cancer Institute in Boston. But methodological uncertainties and the possibilities of contamination clouded interpretation of these studies. "In the present study, the presence of infection is clear," he says in an editorial accompanying the research report in the June 1 NEW ENGLAND JOURNAL OF MEDICINE. The finding, he adds, "raises the sobering possibility that HIV infections may be transmitted by blood and organ donors who are silently infected."

However, Imagawa told SCIENCE NEWS, "you must also remember that [high-risk] individuals should know they shouldn't be donating blood. So the added risk there may not be as large as we think." Moreover, he says, the study population of antibody-negative individuals engaged in high-risk behaviors may not be representative of the population at large. These individuals may have mechanisms of suppressing viral activation or may be infected with mutant viruses incapable of replicating.

Indeed, Imagawa adds, the research provides preliminary evidence that a subpopulation of white blood cells called CD8 cells may play a heretofore unrecognized role in suppressing viral activity in some infected individuals. Researchers may learn to manipulate such natural mechanisms to forestall disease progression after HIV infection.