猪链球菌2型Orf207基因缺失菌株的构建及其生物学特性检测

Construction of Orf207 gene mutant strain of Streptococcus suis type 2 and detection of its biological characterization

【背景】猪链球菌2型(streptococcus suis type 2, SS2)可引起人、猪的脑膜炎、关节炎及败血症等,不仅给养猪业带来巨大的经济损失,同时严重威胁公共卫生安全。本团队前期通过噬菌体展示文库技术发现Orf207编码蛋白可能参与SS2诱导的脑膜炎发生,然而其在SS2致病过程中的具体作用尚不清楚。【目的】探究Orf207基因对SS2致病性的影响。【方法】采用温敏性自杀质粒介导的同源重组系统,构建SC19 Orf207基因缺失菌株ΔOrf207及其回补菌株CΔOrf207,系统比较缺失菌株与野生株间在生长特性、形态、组织定殖能力、毒力情况、细胞黏附与侵袭及抗巨噬细胞吞噬能力等生物学特性方面的差异。【结果】与野生株相比,缺失菌株链长变短,生长速度略慢;而且Orf207缺失显著增加了小鼠的存活率,降低了细菌在血液、心脏、肝脏、脾脏、肺脏、肾脏、脑组织的定殖能力和对肺组织的病理损伤并显著减弱SS2对HeLa细胞的黏附与侵袭能力及抗巨噬细胞吞噬能力。【结论】Orf207基因可以显著降低SS2对宿主的致病能力,本研究结果不仅丰富了SS2的致病机制,也为SS2疫苗等研发提供了新靶点。

[Background]Streptococcus suis type 2(SS2)may cause meningitis,arthritis,and sepsis in humans and pigs,which not only brings great economic damage to the pig industry but also seriously threatens public health safety.In the previous study,using the phage display library technique,this team found that the protein encoded by Orf207 may be involved in SS2-induced meningitis;however,its specific role in the pathogenesis of SS2 is still unclear.[Objective]To explore the effect of the Orf207 gene on SS2 pathogenicity.[Methods]In this study,the homologous recombination system mediated by the thermosensitive suicide plasmid was used to construct the SC19 Orf207 gene deletion strainΔOrf207 and its complementing strain CΔOrf207,after which the differences in biological characteristics such as growth characteristics,colony morphology,tissue colonization capacity,virulence,cell adhesion and invasion,and anti-macrophage phagocytosis between the deletion strain and the wild strain were systematically compared.[Results]Compared to wild strains,the deletion strain had shorter chain length and slower growth rate.Moreover,Orf207 deficiency significantly increased the survival rate of mice and reduced the colonization of bacteria in the blood,heart,liver,spleen,lung,kidney and brain,alleviating pathological damage to lung tissues.It also remarkably reduced the adhesion and invasion ability of SS2 to Hale cells and its anti-macrophage phagocytosis.[Conclusion]The above results indicate that gene Orf207 can significantly reduce the pathogenicity of SS2 to the host.The findings of this study enrich the pathogenesis of SS2 and provide a new target for the development of SS2 vaccine.