AIDS virus outsmarts drugs

Brigham Young University researchers have demonstrated that the AIDS virus is evolving so fast in some patients that it has become immune to the heralded "AIDS cocktail," a commonly prescribed multi-drug therapy.

"Combination drug therapies are clearly extending lives and improving the quality of lives of HIV-infected patients, and some scientists have purported the cocktail to be a cure," said Keith A. Crandall, assistant professor of zoology at BYU. "But our study shows that a cure is further away than we thought. The virus is still evolving, and the HIV population is acquiring drug-resistant mutations."

In a paper in the Mar. 1999 issue of Molecular Biology and Evolution, Crandall reported how he, in collaboration with the National Institutes of Health and the National Cancer Institute, analyzed the DNA sequences of certain genes taken from eight patients who had been taking combined drug therapies for at least two years during the study.

He found significant evolution of the virus over the course of one to two years, even in the three patients who had only small traces of HIV in their systems.

In five of the patients, the virus changed so much that it was no longer affected by the drugs -- in scientific parlance, the virus "escaped" drug therapy.

Yet, even given this news -- a clear indication of the futility of drug therapy for AIDS -- the researchers maintained that drugs were the answer to the disease. Since the HIV mutations appeared to evolve in the same way for each patient, Crandall said, "Hopefully new drugs can catch up to this elusive virus."

Crandall noted, however, that he was concerned not only with HIV's drug resistance, but also with other viruses and bacteria. Physicians have over-prescribed antibiotics and anti-viral agents, inadvertently strengthening germs, he said.

In addition to the doctors, patients have to shoulder some of the blame for the current situation. Too often, they demand antibiotics for colds or the flu, which are not affected by the drugs. Also, as Crandall explained, they frequently stop taking antibiotics before they have completed the full dosage. This leaves a small amount of bacteria that is strong enough to resist the drugs in the patient's system -- bacteria that then may be passed on to others.

"We now have superstrains of bacteria that are resistant to any antibiotics we can throw at them," he said. "The problem is serious and will continue to get worse until physicians have a better understanding of evolutionary biology and patients follow their doctors' instructions."