乙型肝炎病毒S基因“a”决定簇基因序列的多态性

Analysis for the variability of HBsAg “a”determinant

用聚合酶链反应（ＰＣＲ）产物直接序列分析，测定３０例乙型肝炎表面抗原（ＨＢｓＡｇ）阳性中国人感染的乙型肝炎病毒Ｓ基因“ａ”决定簇序列，其中ａｄｗ２１例，ａｄｒ８例，ａｙｗ１例。在１２１到１４７共２７个氨基酸中，１２１，１２３～１２５，１２７～１２８，１３０～１３３，１３５～１４２，１４４～１４５和１４７高度保守，而第１２６位可为丙氨酸、异亮氨酸或苏氨酸，１４３位可为丙氨酸、天冬酰胺或苏氨酸，１２９为谷氨酸，１３６为酪氨酸各１例。２例ＨＢｓＡｇ阴性病人在第１２３～１２４间插入２～３个氨基酸，可能是用现行试剂不能检出血清中ＨＢｓＡｇ的原因。研究结果说明了中国人感染的ＨＢＶ“ａ”决定簇序列的多态性，可为进一步研究ＨＢＶ的Ｓ基因变异提供参照。

The gene encoding “a ” determinant of “ S” antigen from HBsAg positive patients with chronic illness and /or hepatocarcinoma in China was amplified and sequenced directly for its molecular characterization Amino acid residues 122 to 147 of HBsAg were predicated by sequencing the corresponding part of the S gene of HBV DNA in 30 HBsAg-positive sera . Residues were found to be highly-conservative , except at five positions. These were at positions 126. (Ala or Ile or Thr) , 143 (Thr or Ala ) , 129(Glu or Gln),and 136(Ser to Tyr).However ,Sequencing of isolate from two HBsAg negative patients with chronic liver disease revealed insertion mutationts. lnserted sequences introduced 2 or 3 amino acids between codons 122 to 1 2 4 immediately upstream of the ' a ' determinant. Our data might be useful for development of vaccines and diagnostic HBsAg immunoassays,