Detection of Hepatitis B Virus Genome with Mutations Outside the Major Hydrophilic Region in the Surface Antigen Isolated from Patients with Coexisting HBsAg and Anti-HBs

Background: The leading cause of mutations in the hepatitis B virus (HBV) genome is the high rate of nucleotide misincorporation during reverse transcription. Most mutations were found within the “a” determinant of the S gene’s major hydrophilic region (MHR). They resulted in escape mutants due to amino acid changes in the MHR. However, mutations outside the MHR can also trigger escape mutants. Objectives: This study focused on further molecular studies on the MHR of genotype D of HBV DNA isolated from patients with chronic HBV infection, together with the coexistence of hepatitis B surface antigen (HBsAg) and hepatitis B surface antibodies (anti-HBs) in their serum samples. Methods: In this study, serum samples from 83 patients with chronic HBV infection were analyzed by serological and immunological tests for the concurrence of HBsAg and anti-HBs. In addition, the mutation in the HBV DNA was assessed by nucleotide sequencing of S genes within, upstream, and downstream of the MHR. Results: Among 83 patients with chronic HBV infection, the coexistence of HBsAg and anti-HBs were detected in 11 (13.25%) individuals. Mutations in eight amino acids of seven samples analyzed for nucleotide sequencing were observed at 27 different sites in three locations, namely upstream, within, and downstream of the MHR. The mutations affected the structure of the epitope and the appearance of an escape mutant. Conclusions: The results indicated that mutations downstream and upstream of the MHR play a role in the coexistence of HBsAg and anti-HBs in patients with chronic HBV infection.