Background: There are 8 well-documented genotypes of hepatitis B virus (HBV) at this time point. Genotyping can be accomplished based on a partial sequence of hepatitis B virus (HBV) genome such as the pre-S or S gene. Several methods have been developed and used for HBV genotyping including direct sequencing, restriction fragment length polymorphism, line probe assay and enzyme-linked immunoassay. Recently, a novel, rapid and cost-effective genotyping method based on PCR amplification assay using type-specific primers that can identify all six major genotypes has been developed. This study was undertaken to characterise HBV genotypes and investigate the association between the prevalence of different genotypes and the severity of HBV-induced liver diseases.
Methods: Serum samples from carriers of HBV and patients with HBV-related liver diseases from Zhejiang Province were screened for viral serological markers using commercially available radioimmunoassay (RIA) and enzyme linked immunosorbent assay (ELISA) kits. Serum HBV DNA load was determined by real-time detection PCR. A type-specific primer based the nested-PCR method was employed in the HBV genotyping. The genotype results obtained were confirmed by direct sequencing of nested PCR amplicons of the pre-S region. Ten samples of each genotype (B and C) were sequenced.
Results: The survey on a cohort of 125 HBV carriers in and around Hangzhou City, Zhejiang Province showed the existence of HBV genotypes A (0.8%), B (48%), C (40.8%), D (0.8%), mixed B and C (9.6%) and an absence of E and F genotypes. Distribution of HBV genotypes in patients with liver diseases revealed a statistically insignificant higher prevalence of genotype B in mild chronic hepatitis (CH). Among the three genotypes B, C and mixed B/C infections 11 (73.3%), 3 (20%) and 1 (6.7%), (P<0.05), respectively in subjects with moderate CH, genotype B was significantly predominant. The infection patterns for genotypes B, C and B/C mixed in (i) liver cirrhosis (LC) 4 (23.5%), 10 (58.8%) and 3 (17.7%) and (ii) hepatocellular carcinoma (HCC) 2 (28.6%), 5 (71.4%) and 0 (0.0%) respectively revealed a marked association of C genotype with liver disease; however, the association was statistically insignificant (P>0.05). Differences in positive rate of HBeAg for the three genotypes B, 16 (30.8%), C, 27 (51.9%), and mixed B/C, 9 (17.3%) were significant (P<0.05), with genotype C showing predominance.
Conclusions: These findings show an interesting distribution of HBV A-D genotypes in Zhejiang Province. Furthermore, our results indicate a novel and markedly high prevalence of mixed B/C genotype infections in subjects with severe CH and LC, and a possible association of mixed B/C infections with the severity of liver diseases in this region of Mainland China.