Important note: Information in this article was accurate in March 1999. The state of the art may have changed since the publication date.AIDSWEEKLY Plus; Monday, March 15, 1999
Daniel J. DeNoon, Senior Editor
Two separate studies confirm that even before they begin treatment, a surprisingly high number of people already harbor drug- resistant virus. Both reports were made in late-breaker sessions at the 6th Conference on Retroviruses and Opportunistic Infections, held January 31-February 4, 1999, in Chicago, Illinois.
The findings may necessitate a major - and expensive - change in how doctors begin treating HIV infected patients.
"The transmission of multi-drug-resistant HIV has occurred in multiple cities across the U.S.," said University of California, San Diego researcher Susan Little. "Proactive resistance testing in all cases of primary HIV infection may be crucial for selecting appropriate antiretroviral regimens."
Little and colleagues tested HIV isolates obtained at a mean 79 days after infection from patients in five U.S. cities: Boston, Dallas, Denver, Los Angeles, and San Diego. All of the isolates were taken from the patients no fewer than seven days before they began taking anti-HIV drugs.
An astonishing 28 percent of these patients carried virus with reduced susceptibility (2.5- to 10-fold) to one or more components of current highly active antiretroviral therapy (HAART) regimens. Overall, 13 percent of the patients had reduced susceptibility to protease inhibitors.
Major resistance (10- to 1000-fold) to at least one antiretroviral - a level of resistance so high that the drug likely would be virtually ineffective - was seen in 4 percent of the patients. This largely was due to protease inhibitors: overall, 3 percent of patients had virus with major resistance to these potent new drugs.
Corroboration of these findings came from a report by S. Wegner of the U.S. Military HIV Research Program, Rockville, Maryland. Wegner and colleagues evaluated HIV isolated from 95 active-duty U.S. military personnel with documented seroconversion within three years - and no prior anti-HIV therapy whatever.
Overall, Wegner's team found that 21 percent of these recent infections resisted at least one anti-HIV drug. Most disturbing was the finding that genotypic and phenotypic tests showed respectively that 3.2 and 2.2 percent of the patients had virus resistant to two different classes of drug. And resistance to three classes of drug - nucleoside and nonnucleoside RT inhibitors and protease inhibitors - was seen in 2.1 percent of patients by genotypic tests and in 3.3 percent of patients by phenotypic tests.
"The substantial prevalence of drug resistance in this therapy- naive cohort suggests resistance testing prior to starting treatment may be useful to optimize initial therapy," Wegner said.
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