Hepatitis C subtyping assay failure in UK patients born in Sub-Saharan Africa: implications for global treatment and elimination

The newly developed direct-acting antivirals (DAAs) have revolutionised the treatment of chronic hepatitis C virus (HCV), where cohort studies have shown that cure rates as high as 98% can be achieved. Whilst genome sequencing has demonstrated that some subtypes of HCV naturally harbour drug resistance associated substitutions (RAS), these have not been considered important as previous molecular epidemiological studies have suggested that such difficult-to-treat subtypes are rare. Therefore, to optimise and streamline molecular detection and sequence-based typing of diverse RAS-containing subtypes, a novel panel of single round PCR assays was applied to HCV derived from 146 individuals, whose likely source of infection was from regions of sub-Saharan Africa (SSA). Partial NS5A and NS5B sequences were obtained from 135 HCV-positive patients born in 19 different countries from SSA but attending clinics in the UK. Virus subtype assignments were determined by pairwise-distance analysis and compared to both diagnostic laboratory assignments and free-to-use online typing tools. We determined that routine clinical diagnostic methods incorrectly subtyped 59.0% of samples, with a further 6.8% incorrectly genotyped. Of five commonly used online tools, Geno2Pheno performed most effectively in determining a subtype in agreement with pairwise distance analysis. Considering the estimated number of HCV infections to have occurred in across Africa, this study provides a simple low-cost pathway to guide regional therapeutic choice and assist global eradication programmes.