Protease Inhibitor–Resistant Hepatitis C Virus Mutants With Reduced Fitness From Impaired Production of Infectious Virus

Division of Infectious Diseases, Department of Medicine, Inflammatory Diseases Institute, and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Gastroenterology (Impact Factor: 16.72). 11/2010; 140(2):667-75. DOI: 10.1053/j.gastro.2010.10.056
Source: PubMed


Several small molecule inhibitors of the hepatitis C virus (HCV) nonstructural protein (NS) 3/4A 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.
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.
Most PI-resistance mutations resulted in moderate loss of replication competence, although several (V36A/L/M, R109K, and D168E) showed 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 with decreased yields of infectious virus for most mutations, a subset of mutants (Q41R, F43S, R155T, A156S, and I170A/T) showed greater impairment in their ability to produce virus than predicted from reductions in RNA replication capacity. Detailed examination of the I170A mutant showed no defect in release of virus from cells and no significant difference in specific infectivity of extracellular virus particles.
Replicon-based assays might underestimate the loss of fitness caused by PI-resistance mutations, because some mutations in the NS3 protease domain specifically impair late steps in the viral life cycle that involve intracellular assembly of infectious virus.

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Available from: David Mcgivern, Aug 13, 2014
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    • "Together with the (sub)genomic replicon, this HCVcc system has been the working horse for screening and identification of new antiviral drugs [17]. Since only recently alternative full-length isolates have been described that efficiently propagate in cell culture [18] [19] [20] [21] [22], this system has long been restricted to one specific viral isolate, designated JFH1, and intra-or inter-genotypic chimeric derivatives thereof [23]. In addition, hepatoma cells that support robust replication of HCVcc have characteristics that differ significantly from those of primary human hepatocytes, e.g., continuous proliferation, impaired innate immunity and reduced metabolic activity [24] [25]. "
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    • "Some variations appeared under the selective pressure of drugs or other factors whereas the others such as R155K are preexistent before the treatment (Colson et al., 2008; Rong et al., 2010). NS3/4A mutations were reported to impair the fitness of HCV replicons (Shimakami et al., 2011). But the drug resistant mechanisms for many mutations have not been fully understood, so there is a crucial need to explore the drug resistant mechanism, which may help to develop drug candidates effective not only to the wild-type (WT) NS3/4A protease but also to its variants. "
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