Evaluation Protective Efficacy Of Difference Serotype Of Streptococcus Suis And Screening Immunogenic Protein Antigens

Streptococcus suis is a gram-positive facultative anaerobic bacteria, according to thecharacteristics of capsular polysaccharide differences, S. suis can be divided into35serotypes,named1-34and1/2. S. suis serotype2is the most popular and widely serotype, however, it isnot the only S. suis type2have pathogenic, type7and type9were often separated in pigfarms. At present, Whole-cell inactivated vaccine is a hotspot of research, but it only provideprotection for the same serotype and the other serotype can’t get the better immune protection.some subunit vaccines for virulence factors already development, but the immune effect is noteffective enough because of the vaccine was lacked certain immunogenicity.Therefore, in order to prevent and control S. suis disease, a wide protection vaccinecandidate molecules were screened. All mice were immunized inactivated S. suis type2GDisolate, S. suis type7WH isolate, S. suis type9ZD isolate with3×108CFU dose3timesrespectively, and one week later, all mice were challenged with homologous strain. Screeningimmunogenicity isolate through detection of antibody levels; test bacteria titer of blood, tissueand organs; observation Pathology and analysis survival rate for the next test, namelyimmunogenicity protein screening. Animal experiment results showed that the three S. suisisolates all can stimulate the body to produce higher levels antibody after immune mice, andthe control group did not produce antibodies in mice; protection rate were62.5%,87.5%, and75%respectively against homologous isolate; bacteria titer in blood and tissue of mice inimmunized group were significantly less than the control group, and bacteria levels reachedthe highest on3dpi (day post infection), and after falling rapidly; pathological observationresults shown that no obvious pathological changes in the immune group mince, and thecontrol group of mice present a typical meningitis, and endocarditis. Summing up the aboveresults, S. suis type7WH inactivated whole cell vaccine provide the highest protection rateafter immunization of mice. Therefore, application method of two-dimensionalelectrophoresis combined with Western blot to screen immunogenic proteins of this strain.Predicting for protein structure of screening after mass spectrometry, as well as prokaryoticexpression to validate their reactogenicity.The two-dimensional gel electrophoresis (2-DE) for S. suis type7WH proteomeseparation was established and followed by western blot identification for immune-relatedproteins of S. suis WH strain. Three proteins were recognized by S. suis positive serum, theywere identified as L-lactate dehydrogenase (LDH) by mass spectrometry analysis. Analysis ofthe predicted protein indicated that the molecular mass was35420u, PI was5.05, there waretwo transmembrane regions, which were located10-28and110-129, and three-dimensional structure of the protein was successfully simulated according to the forecast analysis. Afterprokaryotic expression of LDH, there was a significant band in40000u, verificationreactogenicity combined with Western blot method, lactate dehydrogenase showed goodreactogenicity, it could be used as an effective vaccine candidate molecules for the preventionof S. suis.