Drug-Resistant Viruses Have Different Transmission Risks

Spanish researchers report that there is a wide variation in how easily drug-resistant strains of HIV can be transmitted, with a fivefold difference in transmission risks seen between some drug-resistant variants of the virus. Writing in the October 15 edition of the journal Clinical Infectious Diseases, the researchers say HIV with the T215Y genetic mutation, which conveys resistance to AZT and Zerit, is five times easier to transmit than virus with the K103N mutation, which conveys cross-resistance to all three available nonnucleoside reverse transcriptase inhibitors. The researchers say the study did not examine actual transmission events related to each genetic variation of the virus, only how easily they may be transmitted in relation to each other by how often the mutation appears in a group of HIV-positive adults studied. But they do note that their findings help explain why nonnuke resistance appears far less frequently in the general public than does resistance to nucleoside analogs and protease inhibitors. The study also examined several other common mutations conveying resistance to one or more protease inhibitors and other nucleoside drugs. The researchers say the T215Y and M41L mutations'the latter linked with nucleoside reverse transcriptase inhibitor drugs'were the most transmissable, appearing in about 20% of both recent HIV seroconverters and of those with long-term infections and detectable viral loads. The least transmissible mutations, appearing in only about 4% to 6% of the study subjects, were the M184V mutation. linked with Epivir and Emtriva resistance. and the K103N mutation. which conveys resistance to all nonnucleoside analogs.