Key reports from the XV International HIV Drug Resistance Workshop 2006.

The XV International HIV Drug Resistance Workshop recorded advances in basic and clinical science of HIV resistance to antiretrovirals as well as new findings on resistance by hepatitis B virus (HBV) and hepatitis C virus (HCV). In the clinical arena, attendees learned of four cases of resistance to lopinavir/ritonavir monotherapy, correlation between low-frequency pretreatment mutations and failure of a first antiretroviral regimen, emergence of non-nucleoside-related mutations in 20% of patients interrupting a suppressive nonnucleoside regimen, and evolution of mutations conferring resistance to an HIV entry inhibitor that is being studied as a vaginal microbicide. New data reported from the POWER 1, 2 and 3 salvage trials suggested that there is a close correlation between darunavir (TMC114) phenotypic susceptibility, the number of baseline protease inhibitor-related resistance mutations and virological response. Scientists exploring the mechanisms of resistance reported of mutations in the carboxy-terminal domain of reverse transcriptase that may further resistance to zidovudine, novel mutations that may contribute to resistance of both nucleoside and non-nucleoside reverse transcriptase inhibitors, and a mechanism that HCV and HIV may share to resist antiviral therapy.