用合成多肽分析细粒棘球蚴AgB抗原亚单位的反应性表位

Reactive Epitope Analysis of AgB Subunit Antigens of Echinococcus granulosus by Using Synthetic Peptides

目的通过合成多肽分析细粒棘球蚴AgB1、AgB2和AgB4等3个亚单位抗原的主要反应性表位区域。方法用ELISA法分析来源于细粒棘球蚴AgB1、AgB2和AgB4亚单位基因序列的5个人工合成多肽KK36、RK30、B4-1、B4-2和B4-3,及上述3个亚单位重组抗原在血清抗体检测中的反应性,共检测细粒棘球蚴病(115例)、多房棘球蚴病(54例)、囊尾蚴病(22例)患者和健康人(18例)血清209份。用受试者工作特征(ROC)曲线分析合成多肽和重组抗原在血清检测中的诊断效率。结果多肽KK36和RK30诊断细粒棘球蚴病的敏感性分别为89.2%和85.0%,特异性为62.5%和59.4%,诊断效率分别为84.8%和80.4%,与AgB1(84.5%)和AgB2(81.2%)抗原诊断效率相近,拟合AgB1和AgB2重组抗原的ROC曲线。来源于AgB4抗原的3个多肽B4-1、B4-2和B4-3检测细粒棘球蚴病患者血清的诊断效率分别为49.4%、57.9%和77.4%。其中,B4-3的反应性最佳,B4-2也有一定的反应性。结论 KK36和RK30完整地包含了AgB1和AgB2抗原的反应性表位区域。B4-2和B4-3多肽均含有AgB4抗原的部分表位区域,推测AgB4抗原的表位区域位于序列的中后段。

Objective To analyze reactive epitope of three subunit antigens AgB1, AgB2 and AgB4 of Echinococcus granulosus by using synthetic peptides. Methods Five synthetic peptides, KK36, RK30, B4-1, B4-2, and B4-3, derived from the sequences of AgB1, AgB2, and AgB4 subunit of E. granulosus, and the three recombinant subunits were used for the detection of serum antibodies by ELISA. A panel of 209 serum samples from patients with cystic echinococcosis （115）, alveolar echinococcosis （54）, cysticercosis （22）, and healthy persons （18） was used in the study. The diagnostic efficiency of the recombinant subunits and peptides for serum detection was estimated and compared using receiver-operating characteristics （ROC） curve. Results The sensitivity and specificity of peptides KK36 and RK30 in patients with cystic echinococcosis were 89.2% and 62.5%, 85.0% and 59.4%, respectively. Their diag- nostic efficiency （84.8% and 80.4%） was similar to AgB1 and AgB2 antigen （84.5% and 81.2%）. The ROC curves of peptides KK36 and RK30 were well fitted by that of recombinant subunit AgB1 and AgB2. For the three peptides de- rived from AgB4 subunit, serum detection indicated that the diagnostic efficiency of B4-1, B4-2 and B4-3 were 49.4%, 57.9%, and 77.4%, respectively. Peptides B4-3 showed best reactivity and B4-2 also showed certain reactivity to the sera from patients with cystic echinoeoccosis. Conclusion Peptides KK36 and RK30 contain the reactive epitope re- gion of AgB1 and AgB2 subunits. B4-2 and B4-3 contain partial region of the reactive epitope of AgB4. The epitope re- gion of AgB4 may be in the central and back part.