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目的 分析HBsAg和抗-HBs双阳性乙型肝炎患者HBV S基因"a"决定簇序列特征.方法 巢式PCR法扩增4例HBsAg和抗-HBs双阳性乙型肝炎患者HBV S基因,PCR扩增产物直接进行测序和克隆后测序,对获得的"a"决定簇序列进行比对分析.结果 PCR扩增产物直接测序表明,4例患者HBV"a"决定簇低保守区各有1个氨基酸位点显示多态性.PCR产物克隆后测序表明,病例1 S基因"a"决定簇126位点(s126)氨基酸可为苏氨酸(T)、异亮氨酸(I)和丝氨酸(S),s134氨基酸可为苯丙氨酸(F)和丝氨酸(S);病例2 s126氨基酸可为丙氨酸(A)和苏氨酸(T);病例3 s126氨基酸可为异亮氨酸(I)和天冬酰胺(N);病例4未发现多态性位点.结论 HBV S基因"a"决定簇序列的多态性可能是引起乙型肝炎患者HBsAg和抗-HBs双阳性的原因之一.

Objective To identify the sequence of hepatitis B virus S gene"a"determinant in patients with positive HBsAg and anti-HBs.Methods Nested-PCR Was used to amplify the HBV S gene in 4 patients with positive HBsAg and anti-HBs,and the PCR products were sequenced directly or after cloning.The sequences of"a" determinants were then analyzed by sequence alignment.Results Direct sequencing of PCR products showed that there was one amino acid (aa)residue in"a"determinant less conserved region emerging polymorphism in all 4 patients.Clone sequencing showed that aa residue at 126 of "a"determinant in patient 1 miSht be Thr,Ile and Set,at 134 might be Phe and Set;the aa at 126 in patient 2 misht be Ala and Thr.and in patient 3 might be Ile and Asn;aa polymorphism was not found in patient 4.Conclusion The polymorphism of"a"determinant in HBV S gene might be associated with positivity of both HBsAg and anti-HBs in hepatitis B patients.