Schistosoma Japonicum: Cloning, Expression Of SjIR₃ And Immune Protection In Mice Induced By RSjIR₃

Schistosomiasis is one of the worldwide parasitic diseases that threaten the health of human and livestock. The recent strategy of controlling schistosomiasis is mass chemotherapy to human and livestock synchronously and elimination of oncomelania snails in transmission focuses. But control of this disease has been hampared by frequent reinfection and high cost of chemotherapy. One complementary approach for controlling schistosomiasis is immunoprophylaris of the parasite. SjIR₃ was obtained by screening Schistosoma japonicum(S.j) cDNA library with infected rabbit sera by S.j. To test the probility of rSjIR₃ as vaccine candidate, we subcloned it into pET32a(+), and obtained recombinant SjIR₃(rSjIR₃)expressed in E.coli. Then tested the immune protective efficiency in mice immunized with rSjIR₃.SjIR₃ was obtained from S.j adult cDNA library by PCR, Then analysed its secondary structures and epitopes by bioformatics. By routine methods, It was subcloned into pET32a(+). The rSjIR₃ expressed in E. coll BL₂₁ was obtained after induced by IPTG. and identificated by SDS-PAGE and western-blot. Mice for experiments were immunized into intramuscularly with rSjIR₃ or rSjIR₃+FCA at 0-2-4-6 wk. The control groups with PBS or FCA. The mice were challenged with 40+1 S.j cercariae per mouse after the final vaccination. Forty-five days later, mice were sacrificed and perfused. The adult worms and eggs were counted. Immune protection was evaluated. Serium samples were collected before every immunization and the challenge infection. The IgG level in sera were delected by ELISA.The SjIR.3 has 100% identities with that in GenBank(AY251481). It was a soluble protein with 32.11% α-helix , 18.73% extended strand and 49.16% random coil in secondary structure, and two domains PS50204 and SSF69572 belongs to Activating Enzyme of the ubiqutin-like proteins E₁. rSjIR₃ has 51 kDa molecular weight and good antigenicity. The level of IgG in sera increared after immunization with rSjIR₃ and rSjIR₃+FCA. The worm reducation rate and the egg reducation rate were 26.63%, 34.79% and 26.38%, 44.09% respectively.SjIR₃ could be expressed in E.coli. rSjIR₃ has good antigenicity and can induce partial immune protective efficiency in mice against the challenge infection.