Fibrinogen Binding Sites P336 and Y338 of Clumping Factor A Are Crucial for Staphylococcus aureus Virulence
Fibrinogen Binding Sites P336 and Y338 of Clumping Factor A Are Crucial for Staphylococcus aureus Virulence
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DOI：
10.1371/journal.pone.0002206
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发表时间：
2008-05-21
期刊：
影响因子：
3.7
通讯作者：
Tarkowski, Andrej
中科院分区：
文献类型：
--
作者：
Josefsson, Elisabet;Higgins, Judy;Tarkowski, Andrej
我们早些时候已经证明，凝集因子A(ClfA)是金黄色葡萄球菌的一种纤维蛋白原结合表面蛋白，是感染性关节炎的重要毒力因子。当ClfA分子中的两个氨基酸P-336和Y-338分别改变为丝氨酸和丙氨酸时，纤维蛋白原的结合性能就会丧失。在两株强毒金黄色葡萄球菌Newman和LS-1中构建了ClfAP(336)Y(338)突变体。这项研究的目的是分析这两个对ClfA的纤维蛋白原结合至关重要的氨基酸是否对金黄色葡萄球菌的致病能力具有重要意义。通过静脉接种细菌诱导小鼠感染性关节炎或败血症。在严重程度和频率方面，clfAP(336)Y(338)突变体引起的关节炎明显低于野生型菌株。突变感染的小鼠的全身炎症也要温和得多，指标包括死亡率、体重减轻、肾脏细菌生长和IL-6水平降低。用第二个突变体验证了数据，其中clfAP(336)和Y-338分别被改变为丙氨酸和丝氨酸。当较大的细菌接种量诱导脓毒症时，clfAP(336)Y(338)突变体导致的败血症死亡显著减少。重要的是，用ClfAP(336)SY(338)A突变体的重组A结构域免疫，而不用重组ClfA免疫，可防止败血症死亡。我们的数据有力地表明，ClfA的纤维蛋白原结合活性对于金黄色葡萄球菌引起疾病表现的能力是至关重要的，并且重组ClfA通过去除其结合纤维蛋白原的能力而提高了疫苗潜力。
We have earlier shown that clumping factor A (ClfA), a fibrinogen binding surface protein of Staphylococcus aureus, is an important virulence factor in septic arthritis. When two amino acids in the ClfA molecule, P-336 and Y-338, were changed to serine and alanine, respectively, the fibrinogen binding property was lost. ClfAP(336)Y(338) mutants have been constructed in two virulent S. aureus strains Newman and LS-1. The aim of this study was to analyze if these two amino acids which are vital for the fibrinogen binding of ClfA are of importance for the ability of S. aureus to generate disease. Septic arthritis or sepsis were induced in mice by intravenous inoculation of bacteria. The clfAP(336)Y(338) mutant induced significantly less arthritis than the wild type strain, both with respect to severity and frequency. The mutant infected mice developed also a much milder systemic inflammation, measured as lower mortality, weight loss, bacterial growth in kidneys and lower IL-6 levels. The data were verified with a second mutant where clfAP(336) and Y-338 were changed to alanine and serine respectively. When sepsis was induced by a larger bacterial inoculum, the clfAP(336)Y(338) mutants induced significantly less septic death. Importantly, immunization with the recombinant A domain of ClfAP(336)SY(338)A mutant but not with recombinant ClfA, protected against septic death. Our data strongly suggest that the fibrinogen binding activity of ClfA is crucial for the ability of S. aureus to provoke disease manifestations, and that the vaccine potential of recombinant ClfA is improved by removing its ability to bind fibrinogen.