High Prevalence of Q80K Among NS3 Resistance-Associated Substitutions in Subtype 1a Patients with Chronic Hepatitis C Prior to Treatment with Direct Acting Antivirals: The Croatian Data

Therapy for chronic hepatitis C is based on direct-acting antiviral drugs (DAA) that include protease inhibitors, polymerase inhibitors, as well as inhibitors of NS5A protein. Resistance-associated substitutions (RAS) can be associated with inadequate treatment outcomes with DAA. People with HCV subtype 1a infection carrying Q80K polymorphism could have a reduced treatment response to a protease inhibitor simeprevir. The data on the prevalence of Q80K polymorphism and other RAS worldwide are quite variable.
The study goal was to analyze the frequency of Q80K polymorphism and other substitutions associated with HCV resistance to NS3 inhibitors in patients previously not treated with simeprevir infected with HCV subtype 1a from Croatia.
The study included 136 people with chronic hepatitis C and infected with HCV subtype 1a receiving clinical care at the department of viral hepatitis of the University hospital for infectious diseases, Zagreb and Croatian reference center for viral hepatitis from July 2015 to April 2016. All participants were not previously treated with simeprevir and not co-infected with HIV. Detection of Q80K polymorphism and other substitutions associated with resistance to NS3 inhibitors was performed by population-based sequencing on ABI PRISM® 3100 genetic analyzer. Phylogenetic tree was constructed using the Maximum Likelihood method and supported with a bootstrap test of 1000 replicates. Geno2Pheno algorithm was used for the interpretation of sequences, detection of resistance associated substitutions and determination of the clade of the sequence.
The prevalence of Q80K polymorphism was observed in 42.6% of patients while resistance to simeprevir (mediated by other RAS as well) was detected in 46.3% of patients. Phylogenetic analysis of subtype 1a sequences showed the separation into 2 clades and Q80K polymorphism was exclusively present in clade I isolates. Other RAS detected in the patients included V36L, T54S, V55A, S122R, and I170T.
In conclusion, the prevalence of Q80K polymorphism was found to be rather high in patients with chronic hepatitis C infected with clade I subtype 1a while other substitutions associated with resistance to protease inhibitors were rarely found in Croatian cohort. The results of this study confirm the need for pre-treatment screening for Q80K in subtype 1a patients considered for simeprevir treatment.