Novel DNA polymerase mutations conferring cytomegalovirus resistance: Input of BAC-recombinant phenotyping and 3D model

► CMV clinical isolates with new polymerase mutations in two transplant patients. ► Mutations conferring low-level resistance to ganciclovir and high level resistance to cidofovir. ► Analyzed using BAC recombinant technology. ► Input of 3D model in resistance mechanism analysis. Long-term exposure to antiviral therapy in immunocompromised patients favors emergence of human cytomegalovirus (HCMV) resistance mutations. Two new UL54 DNA polymerase mutations (deletion of codon 524 and N408S substitution) identified in a kidney recipient and a bone marrow recipient respectively were characterized. Marker transfer experiment through recombination into a HCMV AD169 BAC demonstrated del524 and mutation N408S confer GCV and CDV resistance. These results suggest continued mutation of UL54 under selective antiviral pressure. Characterization of each new mutation is thus required to inform genotypic assays and to better understand the functional regions of UL54 for the development of novel antivirals.