engleski

Hepatitis B virus: molecular genotypes and S gene mutants among end stage chronic hepatitis B patients

Hepatitis B virus (HBV) infection is an infectious inflammatory liver disease that affects more than 2 billion people in the world. Genotypically, HBV genomes have been classified into ten groups ; designated A-J, based on an intergroup divergence of approximately 8% based on S gene sequence. The S gene encodes for the hepatitis B surface antigen (HBsAg), which indicates current hepatitis B infection. It is well known that the genotypes vary geographically and that certain genotypes results in higher rates of chronicity, severity of disease clinical course, and different anti-viral drug response. Twelve serum samples obtained from end stage chronic hepatitis B patients immediately before liver transplantation were studied. Patients were selected based on their clinical and serology data, and the stage of the disease. The aim of the study was to determine molecular genotypes of HBV in the selected patients and to identify mutations in HBV S gene, which afford HBV variants a distinct survival advantage, permitting the mutant virus to escape from the immune system. S gene mutations affect HBsAg immunogenicity, and are often induced under immunosupression (vaccines or hepatitis B immune globulin therapy, HBIg. They are also responsible for reactivation of the disease, diagnostic assay failure and occult hepatitis B infection. Amplification of target HBV-DNA region were carried out by nested polymerase chain reaction (PCR) using selected primers, corresponded to the conserved regions among the different genotypes, allowing the distinction of HBV genotypes. The products of nested PCR were sequenced, using the second-round primers. The obtained sequences were then submitted to the Blast program in order to determine their similarity to other HBV strains deposited in GenBank. Genotypes of HBV were found to be type D (8 patients) and type A (4 patients). Twenty one point mutations detected in the S gene of HBV affect 'a' determinant, located on the major hydrophilic region (MHR) of HBsAg. Changes in that region disrupt the antigenicity of HBsAg in multiple ways and have impact on the severity of the disease. Five of detected mutations (G102N, F127L, C147Y, G159A and G159R) were identified to be the new ones.

Hepatitis B virus; genotypes; S gene mutants; end stage chronic hepatitis B patients

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