Construction And Immunogenicity Of Multivalent DNA Vaccine For Schistosoma Japonicum

Schistosomiasis japonicun is one of the most serious parasitic diseases that threaten the health of human and livestock.The comprehensive control measure based on the chemotherapy of praziquantel has made great achievements for the control of Schistosomiasis in China.However,drug treatment does not block up the transmission of the disease.Therefore,it is necessary to develop other strategies to complement existing control measures.Since schistosomes do not multiply within the final host,a vaccine,which induces even a partial reduction in worm burdens,could considerably reduce pathology,limit parasite transmission and be less expensive than repetitive drug treatment,making it an essential component for the long-term control of schistosomiasis.In this study,DNA vaccines including pVAX-GST,pVAX-GST-FABP and pIRESneo-GST-FABP-Sj23 were constructed.And mouse IL-18 was cloned and the eukaryotic expression vector pVAX-IL-18 was constructed.Therafter the immune protection against Schistosoma japonicum challenge was evaluated in mice.Construction of eukaryotic expression vectors The Sj23;SjGST and SjFABP genes were amplified by polymerase chain reaction and cloned into pMD18-T vector and sequenced.And the gene fragments were inserted into eukaryotic expression vector pVAX and pIRESneo,respectively,generating recombinant plasmids pVAX-GST,pVAX-GST-FABP and pIRESneo-GST-FABP-Sj23. Construction of eukaryotic expression vector of IL-18 The mouse IL-18 coding gene was amplified from total RNA of mouse spleen lymphocytes by RT-PCR,and cloned into eukaryotic expression vector (pVAX) to construct the recombinant plasmids pVAX-IL-18.Immunization experiment The recombinant DNA vaccine was extracted,purified and inoculated into BALB/c mice by intramuscular injection.After two times injections,mice were challenged by Schistosoma japonicum cercariae.The infected mice were killed and the number of the adult worm was counted after 42 days post-challenge.The results indicated all the recombinant vaccines could induce high IgG antibody to Schistosoma japonicum,pIRESneo-GST-FABP-Sj23+IL-18 could induce the highest IgG;and IL-18 connected group could produce higher levels of IFN-γin mice,compared with the others group.The three recombinat DNA vaccines was successfully constructed which had some immunoprotection.The recombinant DNA vaccine had immunoprotection highly,such as pIRESneo-GST-FABP-Sj23 and pIRESneo-GST-FABP-Sj23+IL-18 reached 45.0%,69.8%eggs reduction rate and 40.0%,47.5%worms reduction rate respectivly.These results indicated that multivalent DNA vaccine can provide better immune protection against parasites challenge and IL-18 is an adjuvant molecule for genetic immunization against schistosomiasis japonica.