An update on HIV-1 antiretroviral resistance

Purpose of review Emergence of antiretroviral drug resistance limits the benefit of antiretroviral therapy for many patients. Despite considerable progress, much remains to be learned about drug resistance. Studies published over the last year have contributed significantly to the understanding of HIV-1 drug resistance. Recent findings The prevalence of antiretroviral drug resistance is rising among persons newly infected with HIV-1 in the US and Europe. In this setting, resistance testing prior to starting antiretroviral therapy has been shown to be cost-effective. Immunologic stability despite emergence of drug resistance on a failing antiretroviral regimen may be due to lower levels of immune activation by drug-resistant virus. Recent studies show that continued use of lamivudine contributes to partial viral suppression despite the presence of lamivudine resistance. New, more sensitive assays for detecting drug resistance mutations highlight the problem of resistance to nonnucleoside reverse transcriptase inhibitors following use of single-dose nevirapine for prevention of mother-to-child transmission. Data from laboratory and clinical studies provide a more complete understanding of resistance to the protease inhibitor atazanavir and to the fusion inhibitor enfuvirtide. Summary New data on HIV-1 drug resistance continue to improve our understanding of the epidemiology, pathogenesis and management of antiretroviral drug resistance.