Study On The Pneumococcal Surface Protein A Mucosal Vaccine Delivered By Bacterium-like Particle

Streptococcus pneumoniae is a major cause of invasive pneumococcal disease,septicemia and meningitis in worldwide,predominantly affecting young children,elderly and the immune compromised person.Current vaccines against invasive pneumococcal disease are based on the polysaccharide capsules of the most clinically relevant serotypes.Due to serotype replacement,non-vaccine serotypes of pneumoniea have become more clinically relevant.It is necessary to develop a protein-based pneumococcal vaccine as an alternative vaccine to prevent pneumococcal infection diseases.Various pathogenic organisms infect human through mucosal tissues,the induction of protective immunity at mucosal tissues is a primary strategy to prevent infectious diseases.Injection-based vaccines induce only systemic immune response,but mucosal vaccines induce both systemic and mucosal immune responses.Therefore,mucosal vaccine has been considered as an ideal form for prevention of and protection from infectious diseases.The novel antigen delivery systems targeting mucosal microfold epithelial cells(M cells)and dendritic cells(DC cells)facilitate the induction of effective mucosal and systemic immunities.Moreover,secretory IgA is the major player in the mucosal immune system.Recently,a bacterium-like particles(BLP)-based vaccine delivery system was developed for nasal vaccination.BLP mimics bacterial shape,which is suitable for uptake by M cells and DC cells.And studies show BLP could activate innate immune system and acts as potent immune-stimulant for mucosal vaccine.We utilized BLP as a novel antigen delivery system to display pneumococcal surface protein A(PspA).PspA is the important virulent factor of pneumoniae,it interferes component C3 deposition on bacterial surface thereby inhibits the host defense system from opsonization and phagocytosis.Here,we fused PspA(family 2,clade 4)with a protein anchor(PA),which detrived from the C-terminl of Lactococcus lactis AcmA cell-wall hydrolase.PspA4-PAprotein was expressed in E.coli BL21(DE3)strain,then anchored at BLP surface.Though Application with BLPs/PspA4-PA as a nasal vaccine to mice,we found BLPs/PspA4-PA efficiently induced PspA4-specific IgG in the serum and PspA4-specific S-IgA in mucosal washes.Furthermore,this mucosal vaccine led to sufficient protections against homologous and heterologous PspA family pneumococcal infections.In conclusion,PspA4-based pneumococcal vaccine deliveried by BLP has the potential to become a new generation of nasal vaccine to prevent pneumococcal dieases.Moreover,these events emphasize the need to evaluate the potential for pneumococcal cross-reactive proteins to contribute to future vaccines.WHO recommend a multiplex opsonophagocytosis assay(MOPA)to evaluate the pneumococcal capsular polysaccharides antibody of the pneumococcal conjugated vaccines.Here we expored a modified OPKA to identify protective antibodies against PspA.This assay successfully monitored the pneumococcal capsular polysaccharides antibody of the PPV23,but not efficiently detected protective antibody to PspA.This OPKA still need to improve.