Predominant amino acid substitutions in NS5B gene of hepatitis C virus in blood donors and treatment-naïve hepatitis and HIV patients in Nigeria

Background: Hepatitis C virus (HCV) genome undergoes high rate of mutation, which results in generation of genetically diverse HCV isolates. There is paucity of data on mutations in the nonstructural 5b (NS5b) gene of circulating HCV and their implications in the Nigerian population. Here, we identified clinically-important mutations in HCV isolates, which may influence response to therapy and disease prognosis. Methodology: HCV RNA was extracted from a total of 301 blood samples collected from 99 symptomatic treatment-naïve hepatitis patients, 125 HIV-infected individuals and 77 asymptomatic blood donors in Ibadan, Nigeria. The RNA was reverse–transcribed to complimentary DNA and HCV NS5B gene amplified by nested PCR. The amplified products of 42 HCV were sequenced and sequences were aligned with those from GenBank and HCV databases in MEGA 7.0. Nucleotide sequences were translated to amino acids while substitutions in the amino acids were analyzed with reference to H77 prototype strain of HCV. Results: A total of 10 amino acid polymorphisms were observed from the 42 sequenced NS5B gene, with the major clinically-important amino acid mutations being S15G in 28 (66.7%) participants, T7N (24, 57.1%), G61R (23, 54.8%), S54L (22, 52.4%), G89E (14, 33.3%), T79M (12, 28.6%), and T711 (11, 26.2%). Others were Q67R (7, 16.7%), Q47H (7, 16.7%) and S84F (2, 4.8%). S15G/A/V mutations were more predominant in patients with HIV (76.9%, 10/13) followed by patients with clinical hepatitis (75.0%, 12/16) and blood donors (46.1%, 6/13). Q67R and T71I mutations were not predominant in patients with clinical hepatitis as they were detected in only 31.3% (5/16) and 43.8% (7/16) participants respectively, compared to S15G (75.0%, 12/16), S54L (68.8%, 11/16), G61R/E (68.8%, 11/16) and T7N/S (56.3%, 9/16). There was no statistically significant difference in the distribution of each of the 10 amino acid polymorphisms detected within patients with symptomatic clinical hepatitis (x2=9.311, p=0.409), HIV-infected patients (x2=13.431, p=0.1440) and asymp- tomatic blood donors (x2=3.775, p=0.9256). Similarly, there was no significant difference in the distribution between the 3 categories of the study participants except for T79M mutation, which was significantly higher in HIV-infected patients (61.5%, 8/13) compared to patients with clinical hepatitis (18.8%, 3/16) and asymp- tomatic blood donors (7.7%, 1/13) (x2=10.456, p=0.0054). Conclusion: Mutations in the NS5B gene could be associated with worse prognosis of the disease or antiviral failure due to viral resistance in patients undergoing therapy. The absence of Q47H mutations in majority of the study participants in our study implies that they will not respond well to daprevir and mericitabine. Screening of patients for pre-existing resistant mutations before commencement of therapy and monitoring during and after therapy are recommended.