Prevalence of S gene mutations within the major hydrophilic region of hepatitis B virus in patients in Dongguan, southern China.

HBsAg point mutations within the major hydrophilic region (MHR) have frequently been reported to be associated with diagnostic failure, vaccine escape and immunotherapy escape. However, the prevalence of escape mutations in chronic hepatitis B (CHB) patients has not been systematically studied in patients from southern China within the past decade. This study aimed to determine the prevalence of escape mutations within the MHR of hepatitis B virus in patients in Dongguan, southern China. Between June 2015 and May 2016, 391 patients who were chronically infected with HBV were enrolled in the study, including 240 patients with the genotype B strain and 151 with the genotype C strain. The most frequent mutated position was s126 (4.3%), followed by s100 (3.3%), s101 (2.8%), s133 (2.8%), s145 (2.3%), s120 (2.0%) and s129 (1.8%). Furthermore, the mutations sY100C, sQ101R/K, sS114A, sP120T, sT/I126A/N/S, sQ129R, sM133L/T/S and sG145R/A were prevalent in at least one genotype, with a frequency higher than 1%, which indicated that these mutations were relatively common. In addition, sQ101K/R was found only in genotype C isolates (P < 0.05), and sT126A was only discovered in genotype B isolates (P = 0.047), indicating that such mutations were genotype-associated mutations. Notably, combinations of escape mutations within the MHR were also frequently discovered in genotypes B (5.0%) and C (6.6%), with no significant difference (P = 0.498). These results indicated that we should increase the surveillance HBsAg mutations among HBV-infected patients in China.