囊虫抗原模拟表位的筛选和序列分析

Immunoscreening of the antigen mimic epitope of Cysticercosis from the phage peptide library screened by anti lumbricus immunoglobulin

目的探讨能否从与兔抗蚯蚓血清免疫球蛋白(EIg)结合后的噬菌体12肽库中筛选囊虫抗原模拟表位。方法噬菌体12肽库经过EIg筛选1轮后,再以囊虫病患者血清免疫球蛋白(CIg)作为靶分子进行3轮吸附-洗脱-扩增,随机挑取24个蓝色噬菌斑扩增;分析其抗原性及诊断囊虫病的价值;并测定核苷酸序列分析同源性。结果24个克隆中有17个克隆可与囊虫病患者混合血清发生免疫反应,其中6个A491值较高的克隆ELISA和囊虫抗原DotELISA的抗体阳性率无显著性差异(P>0.05);与其它寄生虫病的交叉反应率明显低于囊虫抗原(P<0.05),说明所获克隆具有诊断囊虫病的潜在价值。挑选其中2个克隆(C3、C5)测定核苷酸序列,结果显示这两个抗原模拟表位的氨基酸序列具有结构同源性。结论将EIg结合后的肽库作为源肽库经过3轮筛选,得到对囊虫病具有较高潜在诊断价值的抗原模拟表位。

To obtain the mimic epitope of specific and sensitive diagnostic antigen of Cysticercosis from phage 12 mer peptide library screened with anti lumbricus immunoglobulin (E Ig )of rabbits. The phage mer 12 peptide library was immunoscreened with specific E Ig purified from sera of rabbits in the first round,and the specific C Ig,purified from sera of patients with Cysticercosis, was used to immunoscreen the phage peptide library from the second to the forth round. After 4 rounds of panning, 24 positive plaques were selected and amplified. The reactivity of each clone was examined by ELISA. The positive clones were confirmed by the examination of sera from different patients with parasitie infections. Two specific clones were sequenced and their amino acid sequences were compared with each other. Results showed that 17 of 24 phage clones could bind to the mixed sera of cysticercosis patients, while 6 clones had a same sensitivity in ELISA as the antigen of cysticercus cellulosae performed in Dot～ELISA, but they showed higher specificity than the antigen of cysticercus cellulosae. The amino acid sequences of two clones showed high homology. It indicates that the mimic epitopes play a better role in serodiagnosis of cysticercosis, and the amino acid sequences of two epitopes are the same.