[Mutation of hepatitis B virus S gene in children with hepatitis B virus-associated glomerulonephritis].

Objective: Hepatitis B virus-associated glomerulonephritis (HBV-GN) is an immune complex-mediated glomerulonephritis. The present study was conducted to identify HBV S gene mutation in children with HBV-GN.

Methods: Serum HBV DNA was extracted in 53 children, including 30 with HBV-GN, 5 with HBV-carrying nephrosis (control group 1), and 18 HBV carriers (control group 2). HBV S gene sequence was amplified by polymerase chain reaction (PCR). The PCR products were sequenced directly and compared with AY167097.1, an epidemic HBV strain in China.

Results: (1) The adw serotype of HBV was found in all the 30 cases with HBV-GN, 5 cases with HBV-carrying nephrosis and 17 HBV carriers except for 1, in whom adr serotype was identified. (2) HBV genotype B was found in 29 children with HBV-GN, 5 cases with HBV-carrying nephrosis and 17 HBV carriers, genotype E was found in a child with HBV-GN, and genotype C in an HBV carrier. (3) A total of 17 kinds of different single nucleotide change in HBV S gene were identified in 21 of 30 (70%) HBV-GN patients. Among them, 16 of 21 (76.2%) nucleotide mutations resulted in amino acid substitution. It was interesting that most (11/16, 68.8%) amino acid substitutions involved threonine, serine and tyrosine, the potential phosphorylation sites of mitogen-activated protein kinase (MAPK) and protein tyrosine kinase (PTK) in HBV protein. Single nucleotide changes which didn not result in amino acid substitution were found in 2 HBV-carrying nephrosis patients, 2 HBV carriers and 5 cases with HBV-GN.

Conclusion: Single nucleotide changes in HBV S gene were found in most children with HBV-GN. Most mutations in HBsAg resulted in amino acid substitutions involving threonine, serine and tyrosine, which may play a role in the pathogenesis of HBV-GN.