Construction Of The Recombinant Streptococcus Suis Strains ST₁₇₁ΔhasB-Cap Of Expression Of Porcine Circovirus TypeⅡ Cap Antigen

Streptococcosis suis is a kind of zoonotic swine disease caused by a variety of pathogenic streptococcal infections,which has important public health significance.It is also one of the most important bacterial diseases that harm the pig industry and seriously restricts its development in worldwide.ST₁₇₁,the group C of Streptococcosis suis is a dedicated strain for producing live vaccine of Streptococcosis suis.The structural protein of Porcine Circovirus virusⅡtype（PCV2）,Cap protein,contains the main protective antigen epitope of the virus,stimulates the body to obtain a protective immune response,and is a target protein for vaccine and diagnostic reagents.PCV2 infection can cause immune suppression,and secondary or mixed infections can make Streptococcosis suis morbidity and mortality increased obviously.Immunization is an important measure to prevent porcine circovirus disease and Streptococcus suis disease.This study has constructed has B gene deletion strains ST₁₇₁Δhas B,which can inhibit ST₁₇₁ capsular polysaccharide secretion and make bacterial surface antigen protein is easy to be presented to the body’s immune cells to promote the immune response.ST₁₇₁Δhas B pathogenic has been preliminary evaluated.The research found that has B gene deletion mutation strains ST₁₇₁Δhas B virulence is reduced and its as weak poison vaccine strain will more safety.The ORF2 gene of PCV2has been cloned and The recombinant Streptococcus suis strains ST₁₇₁Δhas B-Cap of expression of PCV2 Cap antigen has been constructed.Quantitative Real-time PCR analysis and determine the transcriptional level of Cap and Szp are consistent between the gene recombinant mutant strain and its parent strain ST₁₇₁Δhas B.It proved that recombinant mutant strain can induce the production of Cap protein specific antibody is significantly higher than commercial PCV2 inactivated whole virus vaccine.In addition,it demonstrated that the ST₁₇₁Δhas B-Cap has the protective effect for Streptococcus equi subsp.zooepidemicus infection by the challenge test.This research has cloned the Cap gene of ORF2 of PCV2 and integrated into the Szp gene of ST171by homologous recombination technology to constructed the Cap protein expression of recombinant live carrier vaccine strains ST₁₇₁Δhas B-Cap,for application of PCV2 live bacteria carrier vaccine and ST₁₇₁ as living bacterium vaccine carrier provide candidate strains.