The prevalence of mutations in the major hydrophilic region of the surface antigen of hepatitis B virus varies with subgenotype.

Mutations in the major hydrophilic region (MHR) of the surface antigen of hepatitis B virus (HBV) may result in vaccine escape, failure of immunotherapy and antiviral resistance. These mutants may be transmitted and constitute a public health threat. We aimed to determine the prevalence of MHR mutations of HBV in areas of high endemicity in Guangxi, China. HBV surface gene was analysed from 278 HBsAg-positive asymptomatic individuals recruited from Guangxi using cluster sampling. Three genotypes, B, C and I, were identified. The overall prevalence of MHR mutations is 17.6%. The prevalence of MHR mutations in genotype B (15.1%) is not significantly different from that in genotype C (16.4%). However, the prevalence in subgenotype C5 (31.1%) is significantly higher than in subgenotype C2 (13.0%) (chi(2) = 6.997, P < 0.05). The prevalence of escape mutations and overlapping polymerase substitutions in subgenotype C5 is significantly higher than in subgenotypes B2 and C2. In total, 7.9% of MHR mutants are escape mutations and 72.1% of MHR mutations produced amino-acid changes in the overlapping polymerase, including resistance mutations to entecavir. Our results suggest that the prevalence of MHR mutations varies with subgenotype. The prevalence of escape mutations and polymerase mutations may be associated with subgenotype.