San Francisco Chronicle - Sunday, July 7, 2002
Sabin Russell, Chronicle Medical Writer

A five-year study of new HIV infections in the city -- released here on the eve of the 14th International AIDS Conference -- also found:

-- In 1996, only 2.5 percent of those tested were infected by a virus resistant to two different classes of drugs. That number rose to 13 percent by 2000.

-- Resistance had developed quickly to the newest class of AIDS drugs, top- of-the-line medications known as non-nucleoside reverse transcriptase inhibitors.

-- The mutated viruses are being spread by patients currently under treatment, in whom the virus is evolving ways to sidestep medicines targeted against it. The troubling findings are based on a UCSF study of the genetic fingerprints of virus from blood samples of patients known to be infected within one year of the test.

S.F. RESULTS SIGNAL TREND

Dr. Frederick Hecht, co-author of the study, said the research is important because patterns detected among the city's closely studied population of HIV- infected men are early indicators of how the epidemic will evolve elsewhere. "Some people are becoming infected with virus that is much more difficult to treat," said Hecht, a San Francisco General Hospital AIDS specialist, at a press conference.

It remains unclear, however, just how dangerous the trend may be. The number of patients initially infected by the drug-resistant strains remains small, and there is some evidence the mutant viruses are less lethal than their "wild" counterparts.

Patients initially infected with the newer viral strains showed a higher level of disease-fighting white blood cells than those carrying the nonmutant virus. In theory, the mutant strains may be so battered by antiviral drugs that they are evolving into a less dangerous bug.

But Hecht cautioned that the differences in blood cell counts were not large, and further studies are needed to determine whether the new viruses are "less fit," and therefore less of a menace. It can take 10 years for an untreated HIV infection, which slowly erodes the immune system, to progress into a deadly case of AIDS.

DIFFICULT TO TREAT

In the short term, a new infection by a mutant strain is more problematic to treat.

Not used widely until 1999, the non-nucleoside inhibitors are popular because they have worked well, are easier to take and have fewer side effects than other AIDS drugs.

The difficulty for patients who pick up the drug-resistant strains is that they will have to start their treatment with drugs of last resort, so-called "salvage regimes" normally reserved for those who have failed all prior treatments.

Results of the study will be published in Wednesday's issue of the Journal of the American Medical Association.

E-mail Sabin Russell at srussell@sfchronicle.com.
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