Multidrug Resistance Conferred by Novel DNA Polymerase Mutations in Human Cytomegalovirus Isolates

Abstract

The emergence of antiviral-resistant cytomegalovirus (CMV) strains is a continuing clinical problem, with increased numbers of immunocompromised patients given longer-duration antiviral prophylaxis. Two previously unrecognized CMV DNA polymerase mutations (N408K and A834P) identified separately and together in at-risk lung and kidney transplant recipients and a third mutation (L737M) identified in a liver transplant recipient were characterized by marker transfer to antiviral-sensitive laboratory strains AD169 and Towne. Subsequent phenotypic analyses of recombinant strains demonstrated the ability of mutation N408K to confer ganciclovir (GCV) and cidofovir (CDV) resistance and of mutation A834P to confer GCV, foscarnet, and CDV resistance. Mutation L737M did not confer resistance to any of the antiviral agents tested. A recombinant strain containing both N408K and A834P demonstrated increased GCV and CDV resistance compared to the levels of resistance of the virus containing only the A834P mutation. The addition of mutation N408K in combination with A834P also partially reconstituted the replication impairment of recombinant virus containing only A834P. This suggests that perturbation of both DNA polymerization (A834P) and exonuclease (N408K) activities contributes to antiviral resistance and altered replication kinetics in these mutant strains. The identification of these multidrug-resistant CMV strains in at-risk seronegative recipients of organs from seropositive donors suggests that improved prophylactic and treatment strategies are required. The additive effect of multiple mutations on antiviral susceptibility suggests that increasing antiviral-resistant phenotypes can result from different virus-antiviral interactions.

The Novel Anticytomegalovirus Compound AIC246 (Letermovir) Inhibits Human Cytomegalovirus Replication through a Specific Antiviral Mechanism That Involves the Viral Terminase

“…Worryingly, GCV resistance in HCMV infections appears to have been increasing during recent years, and the emergence of cross-resistance to either or both second-line agents (FOS and CDV) is encountered in all forms of transplantation (42). Mechanistically, the latter is explained by the fact that all licensed drugs used for the systemic treatment of HCMV share a common target molecule, the viral DNA polymerase pUL54 (15,35,(42)(43)(44). In light of these facts, there is an urgent medical need for new anti-HCMV drugs that do not have the limitations associated with the existing therapeutics and that combine efficacy with a novel mode of action, thus excluding cross-resistance to the available anti-HCMV agents.…”

Characterization of Multiple Cytomegalovirus Drug Resistance Mutations Detected in a Hematopoietic Stem Cell Transplant Recipient by Recombinant Phenotyping

“…Resistance mutations are detected most often in the UL97 gene and confer resistance to GCV alone (5). In general, UL54 mutations emerge after prolonged GCV exposure and thereby increase the level of GCV resistance conferred by mutations already present in the UL97 gene (6)(7)(8)(9). Infections with multidrug-resistant CMV isolates that contain several mutations in the UL97 and/or UL54 genes were reported in immunocompromised patients (10)(11)(12).…”

Recombinant Phenotyping of Cytomegalovirus UL54 Mutations That Emerged during Cell Passages in the Presence of either Ganciclovir or Foscarnet

“…In this view, bacterial artificial chromosome (BAC) technology has become the method of choice for the generation of recombinant HCMVs in order to study antiviral drug resistance (11,12,14,17,(40)(41)(42). In addition, an effect between UL54 mutations and specific genetic backgrounds on antiviral resistance has been reported by a few groups (11,15,17,43,48).…”