Research On The Adherence And Cytotoxicity Of Streptococcus Suis Serotype 2 And Virulence Factors With Cell Line Hep-2

Streptococcus suis (S. suis) is a common pathogenic microorganism and can cause a variety of clinical diseases in human and swine. Based on the CPS antigens of S. suis, 35 serotypes or capsular types have been characterized. S. suis serotype 2 (SS2) is most commonly associated with severe disease and is the serotype most frequently isolated from pigs.When infected with Streptococcus suis in humans, it can cause meningitis, endocarditis, septicemia, Septic Shock, Streptococcal toxic shock syndrome and so on. Recently, there is still a lack of adequate understanding of the spread in vivo of S. suis. And the role of virulence factors is poorly understood, too. Research mainly focused on the mechanism of swine meningitis caused by SS2. To understand the pathogenesis of S. suis infection contributes to develop strategies for prevention or therapy. The interactions between pathogenic microorganism and host cells may play an important role in its pathogenicity. Study the interaction of pathogenesis and host cells, can provide theoretical basis for drug screening and vaccines design.In this study, Hep-2 was used as a cell model, and used 8 different phenotypes SS2: 1, 6, 9, 21, A3, A38, A40, SC19 for research. Virulence factors MRPA, SLY and IMPDH were cloned, expressed and purified. These proteins were also used to do the adherence assay, invasion assay, SS2 cell injury assay and protein cell injury assay. These tests tried to describe the characters of the infection of S. suis and those virulence factors' role in infection.The results showed that SS2 strain SC19, A 40, 21 can adherent to Hep-2 cells, p=0.0001, while 6 and A3 can't adherent to them. In the Invasion Assays, most SS2 can not invade into Hep-2 cells. The results of Adherence inhibition Assays showed that protein SLY, MRPA, IMPDH, HSP60, and HSP70 all can inhibit SS2 adherent to Hep-2, Significant differences, p < 0.0001. Except strain 1, all the other strains can do injury to Hep-2 cells, p < 0.05, and these toxicities varied with the change of numbers of SS2. But when bacteria number reached 105, the toxicity of strain 6, A3, A 40, SC19 reached a little peak. Protein SLY, MRPA, IMPDH, HSP60, HSP70 all have toxicity to Hep-2 cells, significantly different (p > 0.005), but there is no significant trend with the change of concentration (p>0.05). Conclusions are EF,SLY,MRP are not necessary in the adherence of streptococcus suis to Hep-2 cells. SS2 can adherent to Hep-2 but can not invade into it. SS2 have significant cytotoxicity to Hep-2 cells. Protein SLY, MRPA, IMPDH, HSP60and HSP70 all has toxicity to Hep-2 cells, and can all inhibit the adherence to Hep-2 cells.