Study On The Infection Model And Pathogenic Mechanism Of Rhodococcus Equi

As an important pathogen,Rhodococcus equi(R.equi)seriously impedes the development of equine breeding industry by its high mortality rate on infected foals,causing significant economic losses of breeding farm.The bacteria can also infect human,threatening the public health.C urrently underlying mechanisms of its pathogenic is unclear.Usages of foals for stud ies of R.equi infection have multiple issues,such as its high cost and against animal welfare.There had been no effective infection models for R.equi infection studies yet.Therefore,in this study,we constructed a mouse model for R.equi infection by exploring ways and doses of R.equi infection to support further study and to compare pathogenicity of pathogenic and non-pathogenic R.equi and immune responses of infected mice.The R.equi infected mouse model was conducted by infected SPF BALB/c mice with high,medium and low dose of R.equi via were infected with pathogenic and non-pathogenic R.equi,different bacterial quantities(10~6,10~7,10~8 CFU/mL)and different infection patterns(Intratracheal injection IT、Caudal vein injection IV).And to explore the pathogenesis of R.equi.by detection the changes of the bacterial contents in the lung,liver and spleen of mice were observed.The pathological changes of lung,liver and spleen The expression of Jagged 1,Delta 4,Arginase 1 and iNOS mRNA in the alveolar lavage fluid(BAL),The expression of the mRNA on the inflammatory cytokines of TNF-α,IFN-γ,IL-10,IL-4,and the presence or absence of antibodies in the sera of infected miceThe amount of Rhodococcus equi replication in lung indicates that the model of IT infection in mice model is more effective than IV infection,the replication capacity in vivo means that Pathogenicity of R.equi is stronger than non-pathogenic R.equi,and increas with increasing dose.The amount of R.equi replication in spleen indicates the same that Pathogenicity of R.equi is stronger than non-pathogenic R.equi.After infect high-dose pathogenic R.equi in mice,the severity of lesion in Pathologic histology.In the immune response,compare with non-pathogenic R.equi,the pathogenicity R.equi can be long-term survival in infected mice and can not be cleared.Pathogenic R.equi infection can not stimulate the express ion of iNOS and Delta 4 in BAL cells of mice,and thus can not stimulate Th1 cells’s immune response in vivo to clear R.equi.High dose pathogenicity R.equi infection,promoting the express of Jagged 1 in BAL cells,activating the express of IL-10 in lymphocyte,inhibiting Th1’s cell immunity,but can not effectively kill R.equi.In this study,the experimental model of mice infected with Rhizoctonia solani was established,and the pathogenesis of Rhizoctonia solani was studied,which provided the basis for further study of R.equi.The mechanism of pathogenicity R.equi infection could not stimulate the immune response of Th1 cells to remove R.equi,thus promote Th2humoral immune enhancement,But it can not effectively remove R.equi.Due to the number of experimental mice and individual differences and other reasons,to expand the sample size to further study confirmed.