单纯乙型肝炎疫苗免疫后表面抗原携带者“a”决定簇基因变异的分子流行病学特征

目的　了解单纯乙型肝炎疫苗免疫失败后表面抗原 ( HBs Ag)携带者和未免疫携带者 HBs Ag基因变异的流行特点及乙型肝炎病毒 ( HBV)基因型和血清亚型的分布特点。　方法　应用直接测序和基因序列特异固相聚合酶链反应( SS- SPPCR)方法 ,分别检测 69例单纯乙型肝炎疫苗免疫后携带者和 83例未免疫携带者 ,乙型肝炎病毒 HBs Ag“a”决定簇氨基酸的变异及 HBV基因型和血清亚型的分布。　结果　 HBV基因型 B、C和 D均存在 ,其中 B和 C为优势基因型 ;血清亚型 adr、adw2、avr、ayw1、ayw2和 ayw3均存在 ,其中 adr和 adw2为优势血清亚型。直接测序检测的乙型肝炎疫苗免疫后携带者 HBs Ag“a”决定簇氨基酸变异率明显高于未免疫携带者对照 ,变异率分别为 3 1.9% ( 2 2 / 69)和 8.4 % ( 7/ 83 )。14 5、12 6和 13 3位是最常见的氨基酸变异点。应用更为敏感的 SS- SPPCR法分别检测 14 5和 12 6位氨基酸点突变的变异率 ,各组间差别不明显。经直接测序法检测 ,免疫后携带者基因变异危险度 ( OR)是未免疫携带者的 5 .1倍。按基因型和血清亚型分层分析 ,基因型 B和 adw2血清亚型携带者受免疫后出现基因变异的危险度明显高于未免疫携带者 ,分别为3 1.7和 2 8.9。　结论　接种乙型肝炎疫苗者可引起表面抗原基因的免疫逃避

Molecular Epidemiology Characteristic of Mutation in "a" Determinant Region of Hepatitis B Surface Antigen of Chinese Carriers after Hepatitis B Vaccination

Objective To understand the feature of hepatits B surface antigen(HBsAg)mutations in "a" determinant region among carrier children who developed chronic hepatitis B virus(HBV) infection and were with or without immunoprophylaxis. Methods HBsAg mutations,HBV genotypes and subtypes were determined by PCR directed sequencing and sequence-specific solid-phases PCR analysis(SS-SPPCR) for 69 Chinese carrier cases after hepatitis B vaccination and 83 population-based children carriers as control. Results Genotypes B,C and D were detected in this region. Genotypes B and C were the majority genotypes of HBV, Adr?adw2?ayr?ayw1?ayw2 and ayw3 subtypes were determined among these carriers. Adr and adw2 were theleading subtypes.Prevalence of amino acid substitutions as detected by direct sequencing among immunized cases and children control group were 31.9% and 8.4% respectively.The most frequent amino acid substitutions observed were at residues 145, 126 and 133. However,there was no difference in the prevalence of 145 and 126 amino acid mutants as detected by a sensitive SS-SPPCR method between carrier cases and controls. The total odds(OR) was 5.1 for mutants detected by direct sequencing. Odds ratio were 31.7 and 28.9 among genotype B and adw2 subtype subjects for mutants detected by direct sequencing respectively. Conclusions The hepatitis B virus mutants in the "a" determinant are fairly consistent observed with HB vaccine immunization. HBV variant strains may pre-existent as minor quasi-species in carrier children without immunizaion.The risk of mutation is related to HBV subtypes and genotypes.