Yu Simiao, Zhang Hua, Yao Di, Liu Wei, Wang Xintong, Chen Xiaoting, Wei Yuhua, Zhang Zhenghai, Wang Jiannan, Yu Liquan, Sun Hunan, Wu Zhijun, Yu Yongzhong, Song Baifen, Ma Jinzhu, Tong Chunyu, Cui Yudong
College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China.
College of Animal Science and Veterinary Medicine, HeiLongJiang BaYi Agricultural University, Daqing 163319, China.
Microb Pathog. 2015 Dec;89:108-13. doi: 10.1016/j.micpath.2015.09.006. Epub 2015 Sep 28.
Iron-regulated surface determinant B (IsdB) of Staphylococcus aureus (S. aureus) is a highly conserved surface protein that can induce protective CD4(+) T-cell immune response. A pivotal role of CD4(+) T-cells in effective immunity against S. aureus infection has been proved, but CD4(+) T-cell epitopes on the S. aureus IsdB have not been well identified. In this study, MHC binding assay was firstly used to predict CD4(+) T-cell epitopes on S. aureus IsdB protein, and six peptides were synthesized to validate the probable epitopes. Two novel IsdB CD4(+) T-cell epitopes, P1 (residues 159-178) and P4 (residues 287-306), were for the first time identified using CD4(+) T-cells obtained from IsdB-immunized C57BL/6 (H-2(b)) and BALB/c (H-2(d)) mice spleen based on cell proliferation and cytokines response. The results showed that P1 and P4 emulsified in Freund's adjuvant (FA) induced much higher cell proliferation compared with PBS emulsified in FA. CD4(+) T-cells stimulated with peptides P1 and P4 secreted significantly higher levels of IFN-γ and IL-17A. However, the level of the cytokine IL-4 almost remained unchanged, suggesting that P1 and P4 preferentially elicited polarized Th1-type responses. In addition, BALB/c mice just respond to P4 not P1, while C57BL/6 mice respond to P1 not P4, implying that epitope P1 and P4 were determined as H-2(b) and H-2(d) restricted epitope, respectively. Taken together, our data may provide an explanation of the IsdB-induced protection against S. aureus and highlight the possibility of developing the epitope-based vaccine against the S. aureus.
金黄色葡萄球菌的铁调节表面决定簇B（IsdB）是一种高度保守的表面蛋白，可诱导保护性CD4(+) T细胞免疫反应。CD4(+) T细胞在抗金黄色葡萄球菌感染的有效免疫中起关键作用已得到证实，但金黄色葡萄球菌IsdB上的CD4(+) T细胞表位尚未得到很好的鉴定。在本研究中，首先使用MHC结合试验预测金黄色葡萄球菌IsdB蛋白上的CD4(+) T细胞表位，并合成了六种肽以验证可能的表位。基于细胞增殖和细胞因子反应，首次使用从经IsdB免疫的C57BL/6（H-2(b)）和BALB/c（H-2(d)）小鼠脾脏中获得的CD4(+) T细胞鉴定出两个新的IsdB CD4(+) T细胞表位，即P1（第159 - 178位氨基酸残基）和P4（第287 - 306位氨基酸残基）。结果表明，与弗氏佐剂（FA）乳化的PBS相比，弗氏佐剂乳化的P1和P4诱导了更高的细胞增殖。用肽P1和P4刺激的CD4(+) T细胞分泌的IFN-γ和IL-17A水平显著更高。然而，细胞因子IL-4的水平几乎保持不变，表明P1和P4优先引发极化的Th1型反应。此外，BALB/c小鼠仅对P4有反应而对P1无反应，而C57BL/6小鼠对P1有反应而对P4无反应，这意味着表位P1和P4分别被确定为H-2(b)和H-2(d)限制性表位。综上所述，我们的数据可能为IsdB诱导的抗金黄色葡萄球菌保护作用提供解释，并突出了开发基于表位的抗金黄色葡萄球菌疫苗的可能性。
