Contrasting effects on ganciclovir susceptibility and replicative capacity of two mutations at codon 466 of the human cytomegalovirus UL97 gene

Background: Human cytomegalovirus (HCMV) infections cause significant morbidity in immunocompromised hosts. Resistance to ganciclovir is predominantly associated with alterations in the HCMV UL97 kinase and, more occasionally, with mutations in the HCMV DNA polymerase gene. Objectives: The aim of this study was to investigate the impact of two different mutations found at the same UL97 codon on drug susceptibility and viral replicative capacity. Mutation V466G was observed in a solid organ transplant recipient whereas mutation V466M was observed in a patient with AIDS. Study design: Two HCMV UL97 mutations, V466M and V466G, were transferred to recombinant viruses using a bacterial artificial chromosome system. Susceptibility testing of the recombinant wild-type and mutant viruses was performed using a standard plaque reduction assay. Replication kinetics of recombinant viruses was investigated using a yield assay. Results: Mutant V466G was resistant to ganciclovir and had significant replicative defect whereas mutant V466M was drug susceptible and had unaltered replication kinetics. Furthermore, mutant V466G formed small viral plaques with intracellular inclusions. Conclusions: To our knowledge, this is the first report of such contrasting phenotypes for drug susceptibility and replicative capacity for HCMV mutations found at the same codon of the UL97 gene. (C) 2010 Elsevier B.V. All rights reserved.