Preliminary Study On The Mechanism Of Irradiation-induced Activation Of Host Dendritic Cells By Schistosoma Japonicum

Schistosomiasis japonicum is a serious and widely distributed zoonotic parasitic disease,which causes serious harm to human health and social development.The pathogenicity of schistosomiasis is mainly caused by chronic infection of the liver.Therefore,the interaction between parasites and host immune system is particularly important in the prevention and control of schistosomiasis japonicum.The most effective drug for the treatment of the disease is praziquantel.Although praziquantel is relatively effective,it has been used for many years to treat schistosomiasis,thus increasing the risk of developing drug resistance in schistosomiasis.Although no resistant geographic strains have been found,the possibility of drug resistance cannot be ignored.Therefore,it is necessary to find new effective treatment methods,especially to develop a safe and effective vaccine.Previous studies in our laboratory have found that radiation-attenuated schistosomula vaccine can well induce host protective immune response,and has great prospects for development as a vaccine.However,the mechanism of host protective immune response induced by radiation-attenuated schistosomula is not clear.Dendritic cells as specialized antigen presenting cells play an important role in the interaction between Schistosoma japonicum and host immune system.We speculate that there are differences between the death patterns of radiation-attenuated schistosomula and normal schistosomula,also the differences in the activation of host dendritic cells and the expression of surface marker molecules between radiation-attenuated schistosomula and normal schistosomula.To verify this hypothesis,we have carried out studies on the mechanism of activated dendritic cells(DCs)of the radiation-attenuated schistosomula.Firstly,we co-cultured RA schistosomula and normal schistosomula with DC cells for 24 h after cultured for 4 d,7 d,10 d and 14 d,respectively.Flow cytometry was used to detect the expression of CD40,CD80,CD86,MHC-?,the surface marker of Schistosoma japonicum.It was found that the CD40,CD80,CD86 expression levels of MHC-? and costimulatory molecules on the surface of BMDC cells induced by irradiation were higher than those of normal schistosomula at 4 and 10 days(P < 0.05).On the 7th and 14 th day,the CD80,CD86 expression level of MHC-? and costimulatory molecules on the surface of BMDC cells in the radiation-attenuatedschistosomula group was higher than that in the normal schistosomula group(P < 0.05),but there was no significant difference in the expression of CD40 in the radiation-attenuated schistosomula group.Results the expression of DC surface marker molecule CD40,CD80,CD86,MHC-?was up-regulated in irradiated parasites,which indicated that irradiated parasites had stronger ability to stimulate the maturation of DC phenotypes in mice than normal ones.Secondly,in order to further explore the effect of RA schistosomula on DC functional maturation,we used ELISA method to co-culture Schistosoma cercariae or schistosomula cells with DC cells for 24 h after cultured in vitro for 4 days,7 days,10 days and 14 days,respectively.The expression of cytokines IL-12,IFN-?,IL-4 and TNF-? in the supernatant of co-culture was detected.Results the expression of cytokines IL-12,IFN-?,IL-4 and TNF-? were up-regulated in irradiated parasites,which indicated that radiation-attenuated schistosomula and its ability to activate DC function matured more effectively than normal schistosomula.Finally,in order to further explore whether there are differences in cell death patterns between radiation-attenuated schistosomula and normal schistosomula,We cultured radiation-attenuated schistosomula and normal schistosomula in vitro for 4days,7 days,10 days,14 days,and then cultured in vitro for 4 days,7 days and 10 days by gene chip hybridization,respectively.The expression of Schistosoma cercariae or schistosomula genes in normal group and irradiation group were detected and analyzed on the 14 th day,and the differentially expressed genes were compared between the two groups.This study has made a meaningful exploration on the mechanism of high protective immunity induced by irradiation and laid a foundation for further experiments.