Sept. 22, 1999 (Seattle) -- Rising numbers of gay men in the U.S. are being infected with variations of the AIDS virus that are able to resist drug treatment, according to research in the current issue of the Journal of the American Medical Association.
Scientists from New York and San Diego reported that drug-resistant forms of HIV -- almost never seen in newly infected individuals just five years ago -- now account for up to a quarter of new infections among gay men who live in major cities. But the researchers say that in most cases the level of resistance is low, meaning existing drugs will probably continue to work.
"What we're seeing is like what happened with tuberculosis," Roger Pomerantz, MD, tells WebMD. "It got a little resistant, then a little more resistant, and now we have a fair amount of tuberculosis that is quite resistant to several drugs. I'm predicting that is what will happen with HIV," says Pomerantz, a professor of medicine at Thomas Jefferson University and a contributor to this issue of JAMA.
Pomerantz says that when viruses and bacteria develop resistance to common drugs, doctors must use larger doses or switch to new medications. Doctors now test many tuberculosis patients for resistance before deciding which drugs to use, he says. But he says that's not yet warranted for people found to have HIV.
In one of the studies, researchers from the University of California, San Diego, looked at samples of HIV taken from 141 gay men from San Diego, Los Angeles, Dallas, Denver, and Boston. The samples were collected before the men were treated, which meant that any drug resistance was present at the time of infection.
The scientists tested the samples in the laboratory to see how much of each HIV drug was necessary to keep the virus from multiplying. Then they compared the results with tests on normal HIV samples.
Susan Little, MD, an assistant adjunct professor at UCSD and one of the study's authors, tells WebMD that only 2% of the samples contained a form of the virus that had more than 10 times the normal resistance to at least one HIV drug. "That's the good news," she says, "because it tells us that highly resistant HIV is still quite rare."
The bad news, she says, is that 26% of the samples had more than 2.5 times the normal resistance to at least one HIV drug. She says it's not clear whether that level of resistance is likely to prevent the usual treatments from working in people.
The other study was done by scientists from the Aaron Diamond AIDS Research Center at Rockefeller University in New York. They looked at HIV samples from 80 gay men, most of whom were from New York and Los Angeles.
Genetic testing of virus samples from the men found that 16% had mutations known to be associated with drug resistance. However, lab tests found that only 2% of the men had HIV that was highly resistant to drugs.
Pomerantz says even resistant versions of HIV usually can't withstand the standard treatment for HIV, which involves a "cocktail" of several drugs. But the incidence of so-called multidrug-resistant HIV is increasing, he says, which means scientists will have to continue developing new drugs in order to stay one step ahead of the evolving virus.
Both studies were funded in part by a grant from the National Institutes of Health.