Study Finds Weakening of AIDS Virus

 Comparing HIV samples from 1986-89 to recent samples, an international team of scientists says the virus that causes AIDS has substantially weakened since the onset of the pandemic two decades ago. 



 Reporting Friday in the journal AIDS, researchers from Case Western Reserve University in Cleveland and the Institute of Tropical Medicine in Antwerp theorized that the virus potentially could stop causing disease within 60 years. 



 Even in light of such a dramatic prediction, the team insists that HIV, the pathogen that leads to AIDS, remains an aggressive and lethal microbe. 



 Dr. Eric Arts, the U.S. collaborator from Cleveland, wrote with his Belgian colleagues that the findings suggest that HIV's ability to replicate ``may have decreased in the human population since the start of the pandemic.'' In short, the robust capacity of the virus to reproduce itself inside human cells has declined over the years. 



 The scientist drew this sweeping conclusion by comparing 12 HIV samples from 1986 to 1989 to 12 samples of the virus from 2002 to 2003. Samples from both eras were from different patients, but closely matched genetically, scientists said, and were studied in Petri dishes, where they replicated in a medium of white blood cells, their preferred targets in real-life infection. 



 Seventy-five percent of the recent samples were weaker on all counts, suggesting they would be less likely to spread in an infected individual or be transmitted to someone else. 



 The team of scientists theorize the virus could be weakening as a way to better survive in the host, rather than causing death immediately, it has weakened to persist longer. Among other infectious agents that have shown similar weakening over time, scientists have pinpointed a trend toward ``equilibrium.'' 



 World Health Organization statistics show that nearly 40 million people are infected with HIV globally and that 3 million people worldwide died of viral complications last year. 



 As compelling as the new laboratory study may seem, infectious disease experts said the findings are not definitive. 



 Dr. Charles Gonzalez, an infectious disease expert at New York University in Manhattan, said he is not convinced the world is anywhere near seeing a generalized ``weakening'' of HIV strains. 



 ``This is too quick,'' he said in terms of viral evolution. Two decades is not enough time for such an aggressive pathogen to be already on a path toward extinction, he said. Gonzalez cited another recent HIV study finding that even a virus that does not spread quickly in an individual still can be lethal. 



 Gonzalez also questioned culturing methods, saying it was difficult to make proper samples of the virus two decades ago. ``I know that because I was doing sampling then, and I am doing sampling now.'' 



 Dr. Gary Leonardi, chief of virology at Nassau University Medical Center in East Meadow, N.Y., questioned the small number of samples. ``It's an interesting finding, but 12 samples are not enough,'' he said. 



 Leonardi added that the study size leaves too many open questions concerning differences in viruses in various parts of the world. He also pointed out that drug-resistant strains of HIV exist and those viruses tend to be more lethal. 



 ``When you expose the virus to (drugs) from the point of evolution, you are telling the virus to mutate or die,'' Leonardi said. ``What we've mostly seen is that the virus has chosen to mutate. It's what is called survival of the fittest.'' 



 Nevertheless, the team that found HIV to be weakening said such loss of potency has been detected with other killer pathogens, such as the smallpox virus and the bacteria that cause tuberculosis or syphilis. With that in mind, they say, continued weakening of HIV could bode well for the future.