Abstract
Background
HCV genotype 1a (HCV g1a) followed by HCV g1b, –g2, and –g3 are the most common etiologic agents in the ~3 million current HCV-infections in the US. To achieve effective therapy, antiviral drug resistance testing is often essential but not fully available. Knowledge of both the genotype and the presence of HCV mutations in the genes of the major drug targets (NS3, NS5A and NS5B) can assist in optimal treatment selection.
Methods
The HCV genotype of 1000 HCV positive clinical plasmas and sera was determined (HCVg Direct, GenMark). Ten independent Sanger sequencing assays detecting antiviral drug resistance mutations in the genes encoding NS3, NS5a, and NS5b were developed. Six of these assays address mutations in all three genes in the two most common genotypes (HCV g1a and g1b). In addition, four more assays address mutations in NS5a and NS5b of HCV g2 and g3. These mutations are resistance determinants against 11 anti-HCV drugs as shown in Figure 1. A streamlined workflow employs conventional reverse transcriptase PCR, gel electrophoresis, spectrophotometry, bi-directional Sanger sequencing and reporting. The assays were designed to cover hot spot regions and capturing all known resistance mutations in NS3, NS5a and NS5b.
Results
Consistent with previous US HCV incidence reports, g1a, g1b, g2, and g3 comprised 99% of 1000 sequentially tested HCV patient specimens (62%, 12%, 11%, and 14%, respectively). Testing of more than 20 clinical samples each for g1a, g1b, g2, and g3 resulted in successful detection of NS3, NS5a, and NS5b mutations that confer drug resistance. The design successfully permitted detection of relevant mutations known to date for all 11 drugs. The number of reportable mutations range from 20 ‒ 36, 9 ‒ 49, and 10 ‒ 29 for the NS3, NS5a, and NS5b inhibitors, respectively (Figure 1).
Conclusion
These assays provide the most comprehensive commercially available antiviral drug resistance information to date for mutations in HCV NS3, NS5A, and NS5B. This testing will assist physicians in deciding on the most appropriate treatment options for their patients.
Disclosures
J. Nutt, Viracor Eurofins Laboratories: Employee, Salary; 
J. Grantham, Viracor Eurofins Laboratories: Employee, Salary; M. Smith, Viracor Eurofins Laboratories: Employee, Salary; E. Smith, Viracor Eurofins Laboratories: Employee, Salary; A. Wedin, Viracor Eurofins Laboratories: Employee, Salary; 
A. Tyler, Viracor Eurofins Laboratories: Employee, Salary; M. Miralles, Viracor Eurofins Laboratories: Employee, Salary; S. Kleiboeker, Viracor Eurofins Laboratories: Employee, Salary; M. Wissel, Viracor Eurofins Laboratories: Employee, Salary
Interstrain Variation in the Human Cytomegalovirus DNA Polymerase Sequence and Its Effect on Genotypic Diagnosis of Antiviral Drug Resistance
