November 14, 2010

Protease Inhibitor-Resistant Hepatitis C Virus Mutants with Reduced Fitness from Impaired Production of Infectious Virus

Gastroenterology. 2010 Nov 3. [Epub ahead of print]

Shimakami T, Welsch C, Yamane D, McGivern D, Yi M, Zeuzem S, Lemon SM.

Division of Infectious Diseases, Department of Medicine, Inflammatory Diseases Institute, and the Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.


BACKGROUND & AIMS: Several small molecule inhibitors of the hepatitis C virus (HCV) NS3/4A protease have advanced successfully to clinical trials. However, the selection of drug-resistant mutants is a significant issue with protease inhibitors (PIs). A variety of amino acid substitutions in the protease domain of NS3 can lead to PI resistance. Many of these significantly impair the replication fitness of HCV RNA replicons. However, it is not known whether these mutations also adversely affect infectious virus assembly and release, processes in which NS3 also participates.

METHODS: We studied the impact of 25 previously identified PI-resistance mutations on the capacity of genotype 1a H77S RNA to replicate in cell culture and produce infectious virus.

RESULTS: Most PI-resistance mutations resulted in moderate loss of replication competence, although several (V36A/L/M, R109K, and D168E) demonstrated fitness comparable to wild type, whereas others (S138T and A156V) were severely impaired both in RNA replication and infectious virus production. Although reductions in RNA replication capacity correlated well with decreased yields of infectious virus for most mutations, a subset of mutants (Q41R, F43S, R155T, A156S, and I170A/T) reproducibly demonstrated greater impairment in their ability to produce virus than predicted from reductions in RNA replication capacity. More detailed examination of the I170A mutant demonstrated no defect in release of virus from cells, and no significant difference in specific infectivity of extracellular virus particles.

CONCLUSIONS: Replicon-based assays might underestimate the loss of fitness caused by PI-resistance mutations, as some mutations in the NS3 protease domain specifically impair late steps in the viral lifecycle that involve intracellular assembly of infectious virus. All studies published in Gastroenterology are embargoed until 3PM ET of the day they are published as corrected proofs on-line. Studies cannot be publicized as accepted manuscripts or uncorrected proofs.

Copyright © 2010 AGA Institute. Published by Elsevier Inc. All rights reserved.

PMID: 21056040 [PubMed - as supplied by publisher]


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