The aim of this study was investigation of variation(s) in the Hepatitis B virus (HBV) reverse transcriptase domain. 120 patients with chronic HBV infection recruited. 104 patients were received nucleos(t)ide analogs treatments. DNA extractions were done from plasma samples. Direct sequencing and alignment of Polymerase Chain Reaction products were applied for further analysis. HBV genotypes determined by NCBI's Genotyping Tool. Polymorphism(s) were detected by using DnaSP software. Of 120 samples, 98 were sequenced. All of products were HBV genotype D. 13/98 (13.27%) of patients had M539I/V substitutions corresponding to YMDD motif. FLLAQ to FLMAQ was observed among 22/98 (22.98) patients. Two substitutions N459Y and L515M were significantly correlated (R2 = 0.486 and R2 = 0.941 respectively) with FLLAQ motif variation. Mutation ratio among treatment-received patients to treatment-naïve patients was 0.2-0.6. Drug resistance conferring substitutions (DRCSs) were rtL180M (22/98), rtA194V (11/98), rtM204V (1/98), and rtM204I (11/98). Furthermore, six variants were observed among all patients. Appearance of DRCSs in HBV polymerase is a major obstacle to the virus treatments. In the present study, it was shown that DRCSs are more prevalent among treated patients. Therefore, replacement of current anti-viral regimen with novel anti-HBV drugs is warranted in the future.
Keywords: Chronic hepatitis B virus; Drug resistance conferring substitution; HBV reverse transcriptase; Hepatitis B virus polymerase; Nucleotide analogues resistance mutation.