Study On Pneumococcal Histidine Triad ProteinD(PhtD) And Pneumococcal Choline-binding Protein A(PcpA) As Vaccine Candidates

Streptococcus Streptococcus pneumoniae spreads in the atmosphere,they first adsorption on the nose pharynx ministry,bronchial or lungs,then invade and infect the body.Invasive pneumococcal disease includes many diseases,IPD has higher morbidity and mortality to high-risk groups like the baby,and the old.In recent years,the application of vaccines to precaution invasive pneumococcal disease becomes more and more popular.Now commonly used pneumonia vaccine is pneumonia polysaccharide-protein conjugate vaccine and pneumococcal capsular polysaccharide vaccine worldwide.Current vaccine research mainly focused on the protein vaccine with broad spectrum,in order to improve the protection to elderly and children,which can overcome complex preparation technology,expensive price,overcome vaccine application limitation on a variety of serotype of streptococcus pneumoniae meanwhile.In the research,we expressed and the prepared the PhtD and PcpA protein via prokaryotic expression system,and evaluated their immunogenicity and immune protection as potential vaccine.In this paper,the choice of pneumococcal cholesterol-binding protein A(Pneumococcal Choline-binding Protein A,PcpA)N terminal truncated protein of 377 amino acids and Streptococcus pneumoniae pneumococcal histidine triad protein(Pneumococcal Histidine Triad ProteinD,PhtD)and 210 amino acids at the end of the truncated protein as protein vaccine candidate,named PcpAN377,PhtD and PhtD N210,PcpAN377.PhtDN210 and PhtD gene sequence were designed to plasmid pET20b-PcpAN377,pET20b-PhtD,pET20b-PhtDN210,then expressed in BL21.we used PcpAN377,PhtD and PhtDN210 protein immune animal(mice and rabbits).Then we obtained polyclonal antibody serum,we demonstrated that PcpAN377,PhtD and PhtDN210 had high immunogenicity via detection of the antibody of the serum.We detected protective rate of PcpAN377,PhtD and PhtDN210,the result showed that the protective rate of PcpAN377 and PhtD were more than 50%?Animal model demonstrated that PcpAN377,PhtD and PhtDN210 protein has immunogenicity and immune protection,they has great potential to be protein vaccine.There are three steps in the early stage of streptococcus pneumonia infection,adhere,colony and invasion.Adsorption process which is mainly composed of the surface protein adsorption to the epithelial cells is the most important step,because it have a crucial effect in the subsequent infection of streptococcus pneumoniae,It is also called adhesive,adjust the streptococcus pneumoniae attached to the host cell surface.In addition,we have confirmed that PcpAN377 protein is the surface protein of streptococcus pneumonia through flow cytometry.We carried cell adhesion experiment to evaluate the antagonism between PcpAN377 protein immune antibodies and streptococcus pneumonia adhesion.At last,we proved the feasibility of pcpAN377 protein serve as immunogenic.