Studies On Protection And Immune Mechanism Of The EgG1Y162-1 And EgG1Y162-2 Against Echinococcus Granulosus In Mice

Objective:To identify vaccine candidate character of egG1 Y162-1 and egG1 Y162-2 against hydatidosis,through detecting the immunoprotection and its mechanism.Methods:Four groups of female mice were used,and grouped them as A,B,C and D,we prepared the vaccine by egGlY162-1 and egGlY162-2 with complete/incomplete Freund's adjuvant for immunization or booster as A and B.Freund's complete adjuvant(FCA)in NS as C,which were immunized NS as D.All mice were immunized once Per 2 weeks for 2 months.The mice in all groups were challenged intraperitoneally with Eg protoscoleces(1000 protoscoleces per mouse)on the 8 week(after the last vaccination)and sacrified on the 30 week after vaccination.Immunoprotection was computed by formula:reduction in cyst load=1-(average of cysts in test group/average of cysts in control group)×100%.Serum antibody titers of IgG,IgG1,IgG2a,IgG2b and IgE were respectively detected by ELISA.We researched the change of serum level of cytokines(1L-2?IFN-??TNF-??IL-4 and IL-10)by ELISA.The counts of CD4+?CD8+?CD4+CD25+T reg?CD4+CD25+Foxp3+ Treg subsets of splenocytes were detected by FCM.The proliferation of splenocytes was measured by CCK-8 method and the apoptotic rates of splenocytes with or without ConA stimulation were examined by Annexin V-FITC Kits.Result:Mice immunized with egG1Y162-1 and egG1Y162-2 produced effective immunity protection.The dynamic observation showed that in the oral immunization group,the antibody titers of IgG,IgG1,IgG2a,IgG2b and IgE of group A and B increased significantly from week 2 to week 8,respectively the antibody titers of IgG,IgG2a,IgG2b and IgE were peaking on week 8,with IgGl peaking on 30week.The levels of IL-2 and TNF-? of group A and B increased on week 8,then decreased on week 30;while IFN-??IL-4 and IL-10 of group A and B increased on week 8,and peaking on week 30.The percentages of the CD4+and CD8+subsets increased significantly on week 30.The percentages of the CD4+CD25+T reg and CD4+CD25+Foxp3+Treg subsets decreased significantly on week 30.The splenocytes proliferation of group A and B increased significantly.The splenocytes apoptotic rate of group A and B decreased significantly.No obvious difference could be found about the result between group C and D.Conclusion:egG1Y162-1 and egG1Y162-2 were identified as a vaccine candidate for its effective protection,egGlY162-1 and egGlY162-2 showed a effectively protective immunity,which may attribute to:(1)IgGs and IgE-mediated humoral immune response.(2)cell-mediated immunity(especially Thl cell marked by IL-2)was associated with this high immunoprotection.(2)Humoral immune and cytoimmunity complement and influence each other,IL-4 assists to stimulate type transformation of IgE which plays an important role in Eosinophils-related anti-parasite immunity.It's concluded that CD+4 and CD+8 T cells may play an important role in the protection induced by egG1Yl62-1 and egG1 Y162-2 vaccine of Eg.Apoptosis of splenocytes may be inhibited in mice by immunization with the egGlY162-1 and egGl Y162-2 vaccine.Splenocytes proliferation and Thl response can be induced in the mice against the challenge of Eg protoscoleces.CD4+T cell and the specific antibody(IgG,IgG2b and IgE)may play important roles in the protection induced by the vaccine.