Fine-mapping of immunodominant linear B-cell epitopes of the Staphylococcus aureus SEB antigen using short overlapping peptides.
Fine-mapping of immunodominant linear B-cell epitopes of the Staphylococcus aureus SEB antigen using short overlapping peptides.
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DOI：
10.1371/journal.pone.0090445
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Wu C
中科院分区：
文献类型：
--
作者：
Zhao Z;Li B;Sun HQ;Zhang JY;Wang YL;Chen L;Hu J;He YF;Zeng H;Zou QM;Wu C
金黄色葡萄球菌肠毒素B（SE B）是金黄色葡萄球菌最强的外毒素之一。SEB序列保守，结构稳定，是MRSA疫苗的候选抗原。尽管对SEB的细胞免疫应答被充分表征，但关于SEB特异性体液免疫应答，特别是关于详细的表位作图，知之甚少。本研究利用SEB的重组无毒突变体（rSEB）和AlPO 4佐剂免疫BALB/c小鼠，证实rSEB能诱导高水平的抗体和有效的抗MRSA感染的免疫保护作用。接着，收集免疫小鼠的抗血清，并使用一系列重叠的合成肽精细地定位SE B内的线性B细胞表位。通过ELISA方法筛选出3个SE B的免疫显性B细胞表位，包括一个新的表位SEB 205 -222和两个已知的表位SEB 97 -114和SEB 247 -261。使用截短的肽，用肽-KLH抗血清进行ELISA，并且三个免疫显性B细胞表位的核心序列被验证为SEB 97 -112、SEB 207 -222和SEB 247 -257。在体外实验中，SEB 97 -112、SEB 207 -222和SEB 247 -257抗血清均能抑制SEB诱导的BALB/c小鼠脾淋巴细胞的T细胞有丝分裂和细胞因子产生。同源性分析表明，SEB 97 -112和SEB 207 -222在不同的金黄色葡萄球菌菌株中具有较好的保守性。SEB的三维晶体结构表明，SEB 97 -112位于SEB内部的环状区域，而SEB 207 -222和SEB 247 -257位于SEB外部的β切片区域。总之，本研究中SEB抗原线性B细胞表位的精细定位将有助于进一步了解针对MRSA感染的抗SEB免疫，并有助于优化基于SEB抗原的MRSA疫苗设计。
Staphylococcal enterotoxin B (SEB) is one of the most potent Staphylococcus aureus exotoxins (SEs). Due to its conserved sequence and stable structure, SEB might be a good candidate antigen for MRSA vaccines. Although cellular immune responses to SEB are well-characterized, much less is known regarding SEB-specific humoral immune responses, particularly regarding detailed epitope mapping. In this study, we utilized a recombinant nontoxic mutant of SEB (rSEB) and an AlPO4 adjuvant to immunize BALB/c mice and confirmed that rSEB can induce a high antibody level and effective immune protection against MRSA infection. Next, the antisera of immunized mice were collected, and linear B cell epitopes within SEB were finely mapped using a series of overlapping synthetic peptides. Three immunodominant B cell epitopes of SEB were screened by ELISA, including a novel epitope, SEB205-222, and two known epitopes, SEB97–114 and SEB247-261. Using truncated peptides, an ELISA was performed with peptide-KLH antisera, and the core sequence of the three immunodominant B cell epitopes were verified as SEB97-112, SEB207-222, and SEB247-257. In vitro, all of the immunodominant epitope-specific antisera (anti-SEB97-112, anti-SEB207-222 and anti-SEB247-257) were observed to inhibit SEB-induced T cell mitogenesis and cytokine production from splenic lymphocytes of BALB/c mice. The homology analysis indicated that SEB97–112 and SEB207-222 were well-conserved among different Staphylococcus aureus strains. The 3D crystal structure of SEB indicated that SEB97–112 was in the loop region inside SEB, whereas SEB207-222 and SEB247-257 were in the β-slice region outside SEB. In summary, the fine-mapping of linear B-cell epitopes of the SEB antigen in this study will be useful to understand anti-SEB immunity against MRSA infection further and will be helpful to optimize MRSA vaccine designs that are based on the SEB antigen.
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