1. Using novel cell culture systems to establish the role of hepatitis C virus NS5A resistance in the era of direct-acting antiviral therapy
- Author
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Jones, Christopher Robert and Cooke, Graham
- Abstract
Hepatitis C virus (HCV) is an enveloped, single-stranded, positive-sense, ribonucleic acid (RNA) virus. The discovery of direct-acting antivirals (DAAs) has revolutionised the management of hepatitis C. Several highly efficacious combination regimens are now available and offer high cure rates (>95%). The presence of baseline or treatment-emergent resistance-associated substitutions (RASs), particularly NS5A RASs, complicate therapy and reduce cure rates for some patients. A better understanding of NS5A RASs is required to guide treatment strategies. This study used established and novel cell culture systems to investigate the role of NS5A resistance testing in the DAA treatment era. Competition assays were performed using Jc1 reporter viruses with and without the L31V NS5A RAS in Huh7.5 cells to investigate the mechanism behind long-term persistence of NS5A RASs following treatment failure. A phenotypic resistance assay for clinical isolates was developed using the recently described Huh7.5-SEC14L2 cell culture system. A systematic review investigated the relevance of treatment optimisation strategies, including resistance-optimisation strategies, in the DAA era. This study found no evidence to support trans-complementation of NS5A as a mechanism to explain the long-term persistence of NS5A RASs. Enhanced propagation of the L31V-containing Jc1 virus in an infection system, despite reduced infectivity and replication capacity, suggests increased cell-to-cell spread as an alternative mechanism, which requires further study. In the Huh7.5-SEC14L2 system, genotype 1a clinical isolates possess a similar Ledipasvir resistance phenotype compared to replicon data. A Y93H-containing clinical isolate conferred a 3-4x fold-change in EC50, lower than the >1000x described in replicon studies. This discrepancy is related to the proportion of RAS present within the viral population and the EC90 value is a more accurate indicator of resistance phenotype. Real-world studies testing resistance-optimised treatment strategies are emerging. Despite an increasing emphasis on simplified treatment strategies, NS5A RASs will remain of relevance for some patients in the pangenotypic DAA treatment era.
- Published
- 2020
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