用核酸序列分析鉴别甲肝病毒疫苗株与野毒株

Nucleotide sequence analysis used in distinguishing vaccine strain from wild strain of HAV

目的鉴别在接种甲肝减毒活疫苗（Ｈ２株）后２３天发生的一例甲型肝炎，其病原体是疫苗株还是野毒株。方法用细胞培养、ＩＥＭ等确认病原体，接种普通狨猴检定病毒毒力，测定核苷酸序列分析病毒基因型。结果甲型肝炎的确诊依据有：抗ＩｇＭ（＋），双份血清ＨＡＶ总抗体效价１６倍增长以及粪便排出ＨＡＶ（郑株）。该粪便悬液攻击普通狨猴后，肝脏呈现持续性组织病理改变，证明郑株是强毒ＨＡＶ。郑株的３个片段共１３７７个核苷酸序列分析表明，与１９８８年上海甲肝流行株合－５２的同源性高达（９８．３０～９９．４０）％，判定为ＩＡ基因亚型，与Ｈ２株疫苗病毒的基因亚型不同。结论该例甲型肝炎是接种甲肝减毒活疫苗中交叉感染野毒株引发的偶合病例。

Objective To distinguish whether the etiologic agent was the vaccine strain or wild strain of HAV for vaccine Zheng who suffered from hepatitis A on day 23 after inoculation with the live attenuated hepatitis A vaccine, H2 strain. Methods Cell cultivation and IEM were used for confirming the etiologic agent, common marmosets were challenged for identifying the virulence of HAV and nucleotide sequence was determined for analyzing the genotype of HAV. Results The evidences for diagnosis of hepatitis A were: anti HAV IgM(+), 16 fold rise of anti HAV titer in paired sera and HAV (Zheng strain) shedding in feces. The liver of common marmosets challenged with the positive fecal suspension revealed persistent histo pathologic changes, Thus the virulence of Zheng strain was demonstrated. Three fragments of 1377 nucleotides, of which 467 bases (47-513) at the 5' end of genome and 910 bases (2447-3356) including 168 bases (3024-3191) at the joint site of P1 and P2 genus for genotyping have been sequenced for Zheng strain. The homology rate of Zheng strain with He 52 strain, a wild HAV strain recovered during Shanghai epidemic of hepatitis A in 1988, was significantly higher (98.3-99.4)% than with H2 vaccine viruses (90-94.9)%. Zheng strain was classified into IA subgenotype which was different from the subgenotype IB of H2 vaccine viruses. Conclusions The hepatitis A of Zheng was a coincidental case not related to vaccination but caused by cross infection with wild strain of HAV during inoculation of live attenuated hepatitis A vaccine.