New HIV Subtype May Be Tougher to Treat: CDC

CDC researchers have identified a new class of HIV that could give rise to infections that are resistant to AZT and potentially thwart the effectiveness of antiretroviral therapy in some patients. HIV's ability to mutate and become resistant to a patient's treatment is a growing concern worldwide. But the new HIV subtype was found in newly diagnosed patients who had not yet started therapy.

The scientists analyzed viral samples from 603 patients before the patients began drug therapy. Slightly more than 3 percent of the patients had mutations in a particular region of an HIV gene that gives the virus a high potential to become drug-resistant, according to J. Gerardo Garcia-Lerma and colleagues. These patients had mutations that differed from mutations in the same gene that are already known to make HIV resistant to AZT. But experiments showed that HIV with these new mutations carried a significant potential for developing resistance to AZT (zidovudine) and possibly to stavudine.

According to the researchers, "a close monitoring of treatment responses in patients infected with these viruses is prudent," as the mutations have a "higher potential . . . to compromise the efficacy of antiretroviral therapy."

Studies have shown that in patients treated with AZT, AZT resistance does not necessarily blunt the effectiveness of HIV drug combinations that include a protease inhibitor, noted an editorial by Dr. Daniel R. Kuritzkes of the University of Colorado Health Sciences Center in Denver. However, these drug regimens may not be as effective in patients who have AZT resistance before ever starting therapy. The article, "Increased Ability for Selection of Zidovudine Resistance in a Distinct Class of Wild-Type HIV-1 from Drug-Naive Persons," appears in the Proceedings of the National Academy of Sciences early online edition at www.pnas.org.

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