Streptococcus suis is an emerging swine and human pathogen causing severe infections and sudden death. During infection, complement C3a and C5a were reported to induce immune cells towards infection and injury sites via their corresponding receptors C3aR and C5aR. However, how S. suis evade immune surveillance mediated by C3aR and C5aR remains unclear. In this study, we analyze and construct an S. suis bacterial two-hybrid prey library containing 39 LPXTG motif anchored proteins and 18 secreted proteins. Two highly possible C3aR-binding proteins: thiol-activated toxin Suilysin, putative RTX family exoprotein A gene and three highly possible C5aR-binding proteins: thiol-activated toxin Suilysin, putative 5'-nucleotidase and subtilisin-like serine protease are identified through bacterial two-hybrid assay. Far-western blot assay confirms that a cholesterol-binding cytolysin Suilysin can interact with both C3aR and C5aR. Chemotaxis assays demonstrate that recombinant and natural Suilysin can inhibit monocyte chemotaxis mediated by C3a and C5a. These findings enlarge our knowledge of suilysin biological significance and provide a new perspective on S. suis complement evasion.

中文翻译：

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猪链球菌的互补C3aR / C5aR结合蛋白Suilysin有助于单核细胞趋化性。

猪链球菌是一种正在出现的猪和人类病原体，可导致严重感染和猝死。在感染期间，据报道补体C3a和C5a通过其相应的受体C3aR和C5aR诱导免疫细胞向感染和损伤部位发展。但是，猪链球菌如何逃避C3aR和C5aR介导的免疫监视尚不清楚。在这项研究中，我们分析和构建了一个猪链球菌细菌两杂种猎物文库，其中包含39个LPXTG基序锚定蛋白和18个分泌蛋白。通过细菌鉴定出两种高度可能的C3aR结合蛋白：硫醇激活的毒素水溶蛋白，假定的RTX家族外蛋白A基因和三种高度可能的C5aR结合蛋白：硫醇激活的毒素水溶蛋白，推定的5'-核苷酸酶和枯草杆菌蛋白酶样丝氨酸蛋白酶。二杂交试验。远西方印迹测定法证实胆固醇结合的溶血素溶血素可以同时与C3aR和C5aR相互作用。趋化性测定表明重组和天然的溶血素可以抑制C3a和C5a介导的单核细胞趋化性。这些发现扩大了我们对水溶蛋白的生物学意义的认识，并为猪链球菌补体逃避提供了新的视角。