Construction And Expression Of DNA Vaccine PIRES-Sj97-Sj14-Sj26 And Study On Its Immunogenicity In Mice

Objective To construct DNA vaccine pIRES-Sj97-Sj14-Sj26 and study on its immunogenicity in mice in order to find a new strategy to protect Schistosoma japonica disease .Methods Construct plasmid pIRES-Sj97-Sj14-Sj26 that contains fatty binding protein(Sj14),GST(Sj26) and paramyocin (Sj97) genes,which can be expressed on the membrane. The plasmid was transfected into Hela cells. RT-PCR was used to detect the expression of Sj14mRNA, Sj26 mRNA and Sj97mRNA in the Hela cells, the indirect immunofluorescent test detected the expression of trans-membrane Sj26. Fifty BALB/c mice were randomly divided into 5 equal groups to be injected with pIRES-Sj97-Sj14-Sj26 plasmid DNA, pIRES-Sj14-Sj26 plasmid DNA , pIRES-Sj26 plasmid DNA, pIRES blank vector ,and normal saline respectively into the quadriceps muscles of thigh. 8 weeks after the immunization the mice were killed and total IgG in serum was detected by ELISA. Single splenocyte suspension was prepared to detect the level of IFN-γby ELISA and the lymphocyte stimulating index(SI) by MTT method .FCM was used to analyse the the subgroups of splenocyte.Results 48 hours after the transfection, RT-PCR showed the expression of Sj14 mRNA. Sj26 mRNA and Sj97 mRNA, indirect immunofluorescence test proved the expression of Sj26 protein. High level IgG(P<0.01,P<0.05) in the pIRES-Sj97-Sj14- Sj26 group was detected in the serum of BALB/c mice after they were immunized 8 weeks by ELISA. SI of the pIRES-Sj97-Sj14-Sj26 group is significant higher than other groups(P<0.01), while the IFN-γlevel is significant higher than pIRES blank vector and normal saline groups(P<0.01),but shows no significant difference when compared with pIRES-Sj14-Sj26 and pIRES-Sj26 groups. FCM showed the percentages of CD4+ and CD8+ T cells rose much higher in the pIRES-Sj97-Sj14-Sj26 group(P<0.01,P<0.05) . Conclusion pIRES-Sj97-Sj14-Sj26 vaccine may induce stronger immune response in BALB/c mice, which paves the way for the study on its protective effect on mice after the infection with cercaria.