Ajduvant Effect Of Pachymaran In Klebsiella Pneumoniae Fimbriae Adhesion Protein On Mucosal Immunity

Klebsiella pneumoniais an important opportunistic pathogen which can causeserious respiratory and digestive disease in both human and animal. Fimbriae is animportant pathogenic factor of Klebsiella pneumonia，adhesion of the bacteria to hostmucosal surfaces by the adhesion of fimbriae is generally considered an essential stepin the development of infection.Mucosa is the first immune line of body defence against pathogens.Mucosalimmunization can induce local and systemic immune responses effectively. But thevast majority of antigen can not produce effective immune responses when suppliedby mucosal because of its weak immunogenicity and short response time. Therefore, amucosal adjuvant which is efficient, safe and without side effects is important formucosal immunity.Polysaccharide is an important component of living organisms with a variety ofbiological functions, which the most important is the immunomodulatory effects.Intestinal mucosa is the main venues where polysaccharide through oral route exertimmunomodulatory effects on the local and systemic immunity. It has a very broadapplication prospects to develop polysaccharide as a new mucosal adjuvant because ofits low side effect and low immunologic tolerance.In this study, we successfully expressed adhesion proteins K of Klebsiellapneumoniae Type1Fimbriae (fimK) in E. coli BL21Codon Plus (DE3), and preparepolyclonal antibodies of fimK as antigens.Then we explored the immune enhancement and intestinal mucosaimmunomodulatory effects of Pachymaran and Lycium barbarum polysaccharides onimmunosuppressive model mice. The results showed that the two polysaccharidescould improve the spleen index of immunosuppressive model mice, enhancedintraperitoneal macrophage phagocytosis, regulated theratio of CD4+/CD8+cellsubsets in spleen and the ratio of T, B lymphocyte in intestinal Peyer’s and the levels of IL-12, IL-4, IFN-γ cytokine in both serum and intestinal tissue. Pachymaran andLycium barbarum polysaccharides were proved to enhance the immunity ofimmunosuppressive model mice. Furthermore, both of them had the immunomodulatoryeffects on intestinal mucosal immune system, and Pachymaran was better than Lyciumbarbarum polysaccharides on immunomodulatory effects significantly.Furthermore, the purpose of this study was to explore the effect ofpolysaccharide adjuvant on mucosal immunity. In this study, PLGA microsphereswrapped fimK was prepared as immunization antigen through oral and Pachymaranwas prepared as mucosal adjuvant for immunization. Safety of the vaccine wasevaluated by protection test against Klebsiella pneumoniae challenge. The resultsshowed that polysaccharide adjuvant could enhance the level of serum-specific IgGand intestinal mucosa-specific IgA significantly, indicating that polysaccharideadjuvant can enhance the humoral immune response significantly. Then the ratio oflymphocyte CD3+CD4+/CD3+CD8+in spleen and intestine Peyer’s and the level ofserum and intestinal tissues of IFN-γ and IL-4cytokine levels were detected. Theresults showed that the ratio of lymphocyte CD3+CD4+/CD3+CD8+increasedsignificantly, indicating that immune response was under the regulation of CD4+phenotype T cell mainly. The level of cytokines IL-4was increased significantly,indicating that the immune response induced by Pachymaran tend to Th2type. Inaddition, Pachymaran could protect immunosuppressive model mice against fatalKlebsiella pneumonia.In this study, the adjuvant effect of Pachymaran on mucosal immunity ofKlebsiella pneumoniae TypeⅠFimbriae adhesion was investigated. The study showedthat Pachymaran could enhance local and systemic mucosal immune responses inmice, and could also protect immunosuppressive model mice against fatal Klebsiellapneumonia, indicating that Pachymaran, an immune enhancer, has potential todevelope to mucosal adjuvant.