Indian Veterinary Research Institute, Eastern Regional Station, 37-Belgachia Road, 700037 WestBengal, Kolkata, India.
Mol Biol Rep. 2011 Mar;38(3):2067-73. doi: 10.1007/s11033-010-0332-7. Epub 2010 Sep 18.
Echinococcus granulosus is a parasitic helminth which affects both man and animals. During infection with larval stage of the organism secretory and membrane-bound (S/M) proteins play a meaningful role for evasion of immune system. Antigen B (AgB) is one of them. Present investigation has defined sequence diversity of AgB2 subunit of cattle and buffalo isolates of the organism. A total of 55 isolates were screened by polymerase chain reaction based single stranded conformation polymorphism (PCR-SSCP). Subsequently, six conformers could be detected. Based on predicted amino acid sequences of 90 amino acid residues, three clusters could be deduced. Sequence information of two buffalo isolates was homologous to AgB4 indicating gene switching phenomenon in between closely related isoforms. Numerical value of Tajima's D test proved negative selection pressure. Using artificial neural network (ANN), B cell linear epitope and stretches of agretope were predicted. Three clusters could be defined on the basis of B cell linear epitope. Out of three clusters, two showed more than 50% binding propensity with same MHCII alleles whereas, cluster 3 exhibited binding propensity with other MHCII alleles (DRB1_1501, DRB1_1502). Relative expression of AgB2 was more in active cysts (1.636 ± 0.092) followed by degenerating (0.449 ± 0.037) and calcified (0.255 ± 0.008). This result suggested that relative expression of AgB2 declines with progression of the disease. Using recombinant AgB2 sensitivity, specificity and accuracy of the ELISA test was 96.7, 94.7 and 95.9%, respectively. No cross reactivity was found with common cestode and trematode infected cattle and buffalo because cross reactive antigen was expressed intracellularly. Finally, this was concluded that AgB2 is the suitable immunological marker for detection, diagnosis and progression of the disease.
细粒棘球蚴是一种寄生性蠕虫，会感染人和动物。在感染幼虫阶段时，该生物体的分泌型和膜结合型（S/M）蛋白在逃避免疫系统方面发挥着重要作用。抗原 B（AgB）就是其中之一。本研究定义了牛和水牛感染细粒棘球蚴的 AgB2 亚基的序列多样性。使用聚合酶链反应基于单链构象多态性（PCR-SSCP）对总共 55 个分离株进行了筛选。随后，检测到了 6 种构象。基于 90 个氨基酸残基的预测氨基酸序列，可以推断出 3 个簇。两个水牛分离株的序列信息与 AgB4 同源，表明在密切相关的同工型之间存在基因转换现象。 Tajima 的 D 测试的数值证明了负选择压力。使用人工神经网络（ANN）预测 B 细胞线性表位和抗原决定簇。基于 B 细胞线性表位可以定义 3 个簇。在这 3 个簇中，有 2 个簇与相同的 MHCII 等位基因的结合倾向性超过 50%，而簇 3 则与其他 MHCII 等位基因（DRB1_1501、DRB1_1502）表现出结合倾向性。在活性包囊中 AgB2 的相对表达水平更高（1.636 ± 0.092），其次是退化（0.449 ± 0.037）和钙化（0.255 ± 0.008）。这一结果表明，随着疾病的进展，AgB2 的相对表达水平下降。使用重组 AgB2，ELISA 检测的灵敏度、特异性和准确性分别为 96.7%、94.7%和 95.9%。与感染常见的带绦虫和吸虫的牛和水牛没有交叉反应，因为交叉反应抗原是在细胞内表达的。最后得出结论，AgB2 是用于检测、诊断和疾病进展的合适免疫标志物。
