Prokaryotic Expression Of Two Surface Antigens Of Streptococcus Equi Subsp. Zooepidemicus And Immune Protection In Mice

Swine streptococcosis disease is a kind of bacterial disease that severely restricts the development of the pig industry in China.With the rapid development of large-scale breeding enterprises in China,the harm caused by the disease has become increasingly prominent.At the same time,the disease is also an important zoonotic disease.Swine streptococcus disease mainly causes swine meningitis,joint swelling,sepsis,endocarditis,etc.The disease has become one of the most important swine diseases in China’s pig industry.The main pathogens of the disease include Streptococcus suis type 2 and Streptococcus equi subsp.zooepidemicus.The prevention and treatment of bacterial diseases mostly depend on the use of antibiotics,but the widespread use of antibiotics has led to increasing resistance of Streptococcus equi subsp.zooepidemicus and increased drug residues in the animal byproducts.In order to reduce the use of antibiotics and the cost of drug,the use of vaccines is particularly important.Based on the previous research results in our laboratory,the purpose of this study was to clone and express some of the genes that may have good immunoreactivity through deep mining of relevant data.The two proteins expressed in this study,Sec＿205 and MAP,showed good immunoreactivity in Western blot,and the results of immunological challenge in mice showed that both proteins can protect some mice from lethal dose attack of C55138 strain.The previous data analysis speculates that the two proteins expressed in this study are cell surface anchoring proteins,and this speculation was verified by the results of flow cytometry.After immunizing the two proteins,mice produced relatively high antibody responses.Based on the detection of antibody subtypes,these two proteins were mainly to stimulat the production of Ig G1 antibodies.In the passive immune protection assay,the immune sera of both proteins could provide good passive immune protection for mice,indicating that antibody-mediated immune protection plays a vital role in preventing mice from being attacked by lethal doses attack of C55138 strains.Through real-time quantitative PCR,it was found that the two genes in Streptococcus equi subsp.zooepidemicus isolated from the spleen of infected mice were up-regulated to varying degrees compared with that cultured in the medium,indicating that these two proteins may be important virulence factors of the strain.And bacterial adhesion inhibition experiments showed that these two proteins may play an adhesion role when the Streptococcus equi subsp.zooepidemicus invades the host.The above experiments showed that the two surface antigens of Streptococcus equi subsp.zooepidemicus expressed in this study have good immunogenicity and can provide good immune protection for mice in challenge study.These results further strengthen the understanding of Streptococcus equi subsp.zooepidemicus and also laid the foundation for the development of a new subunit vaccine fight against swine streptococcal disease.