srtBCD菌毛基因簇在猪链球菌黏附及跨宿主传播中的作用研究

Streptococcus suis (SS) is an important pathogen of pig and human and the pathogenesis is unclear，including 33 serotypes. In our previous research, we found that srtBCD pilus gene cluster was associated with pathogenicity with the ability of expression, although its coding gene of a key structural protein Sbp2 was divided into two fragments of sbp2'and sbp2" and was reported as pseudogenes with no function. On the other hand, we found that in Streptococcus suis, srtBCD pilus gene cluster only existed in the SS2 virulent strains and SS14 strains which showed pathogenicity for man but didn’t exist in SS2 avirulent strains and other SS7 and SS9 virulent strains that only showed pathogenicity for pig by analysis of genome alignment and animal experiments. The previous research indicated that the gene cluster could be associated with the pathogenicity of SS, and may be associated with the phenomenon of crossing species barrier. In this study, methods of gene deletion, prokaryotic expression, immunology and surface expression of foreign genes in E. coli would be performed to clarify the formation of the pilus surface structure and their interaction with the host receptors which were involved in the pathogenic process based on the previous research.

猪链球菌(Streptococcus suis)是重要的人兽共患病病原，分33个血清型，其致病机理尚不清晰。对其毒力因子的研究，有利于深入了解其机制。申请者前期研究发现，srtBCD菌毛基因簇并非原来报道的没有功能的假基因，其关键蛋白基因sbp2虽然被分隔为sbp2’和sbp2”两个片段，但前者仍可表达，并与细菌的致病性相关；另一方面通过基因组比对和动物实验发现，猪链球菌的srtBCD菌毛基因簇仅出现在对人有致病性的猪链球菌2型强毒株和14型中，在2型弱毒株及其它仅对猪致病的7型及9型中并不存在。提示该基因簇与SS的致病性相关，并可能参与猪链球菌的跨宿主传播。本申请在前期研究的基础上，拟利用基因缺失、细胞微生物学和外源基因的大肠杆菌表面表达等方法，系统阐明该基因簇的表达产物是如何形成相关表面结构，又如何与宿主蛋白相互作用进而参与致病过程的，并探究它是否为猪链球菌跨宿主传染给人的关键分子。

猪链球菌（Streptococcus suis）是重要的人畜共患病原，其中以血清型2型致病力最强，并且能够造成人的感染。申请者在前期研究中发现了一个主要在猪链球菌2型分布的srtBCD菌毛基因簇，该基因簇一直以来被认为是假基因因而没有被研究，本研究中，申请者发现该基因簇可以表达，并且通过一系列实验证实了该基因簇与猪链球菌跨宿主传播相关。首先通过基因组学方法证实了srtBCD菌毛基因簇为猪链球菌强毒2型特有，并且能够作为猪链球菌2型的毒力靶标；随后通过实验证实了srtBCD菌毛基因簇各组分能够参与到猪链球菌的黏附、侵袭与毒力中，并且其中的主要菌毛蛋白SBP2’发挥了主要作用。SBP2’能够与FN结合参与到猪链球菌感染过程当中。通过实验证实了SBP2’能够在主动和被动两种层面对猪链球菌起到保护作用，能够作为猪链球菌的亚单位疫苗候选分子。另外，通过实验证实了猪链球菌SBP2’是更好的猪链球菌感染人菌株的靶标。综上，对猪链球菌srtBCD菌毛基因簇参与猪链球菌跨宿主传播及毒力的作用进行了详细的阐释。以第一资助发表SCI论文6篇，其它资助发表4篇。