金黄色葡萄球菌FnbpA的CD4+T细胞表位鉴定

摘要

Fibronectin-binding protein A (FnbpA) is a crucial surface protein of Staphylococcus aureus,which is able to adhere on host cells to induce a strong Th1 and Th17 responses in early stage of S.aureus infection.To identify the CD4+ T cell epitopesin S.aureus FnbpA,the seven predicted peptides in FnbpA were synthesized according to analysis of the binding affinity between MHC class Ⅱ molecules and the CD4+ T-cell epitopes in S.aureus FnbpA by related bioinformatics softwares.Then,the lymphocyte collected from spleen of FnbpA immunized C57BL/6 (H-2b) mice were stimulated with the 7 synthesized peptides,respectively,and the ability to induce T-cell proliferation and cytokines response were detected to validate the activity of the peptides.The results showed that the peptides of F5 (FnbpA488-505) induced significantly higher cell proliferation and higher levels of IFN-γ and IL-17A responses than that of other peptides.These data demonstrate the pepfide F5 of FnbpA488-505 is one of the T-cell epitopes in FnbpA of S.aureus to elicit immune responses in C57BL/6 mice.Inconclusion,our study provides important data for the further design of the FnBPA epitope peptide-based S.aureus vaccines.%金黄色葡萄球菌(S.aureus)表达的菌体表面纤连蛋白结合蛋白A(FnbpA)在感染早期与宿主细胞粘附过程中起关键作用,将其免疫小鼠后能够诱导机体产生强烈的Th1和Th17反应.但FnbpA诱导Th1和Th17反应的CD4+T细胞表位尚不清楚.本研究根据FnbpA二级结构及其与MHC IⅡ分子的结合能力对CD4+T细胞表位进行预测与分析,选择并合成7个候选CD4+T细胞表位肽.将每个表位肽分别对FnbpA免疫的C57BL/6小鼠CD4+T细胞进行体外刺激,通过检测CD4+T细胞增殖及其分泌的细胞因子水平对免疫优势表位进行初步鉴定.再以初步鉴定的优势表位肽段免疫小鼠,并检测其诱导的特异性细胞免疫应答水平.结果表明,表位肽F5(FnbpA488-505)能够显著诱导CD4+T细胞增殖并分泌高水平IFN-γ和IL-17A,而且F5在不同S.aureus菌株中高度保守.表明FnbpA488-505是诱导CD4+T细胞分化为Th1/Th17的T细胞表位.本研究为S.aureus的FnbpA表位肽疫苗的进一步设计提供了实验依据.