ABSTRACT
Two recombinant plasmids pVAX/Sj23 and pVAX/mIL-18 containing Schistosoma japonicum 23 000 membrane protein (Sj23) and murine IL-18 were evaluated for their ability to induce immune responses and to protect against S. japonicum challenge in mice. All animals vaccinated with pVAX/Sj23 alone or plus pVAX/mIL-18 developed specific anti-SWAP (soluble worm antigen preparation) ELISA antibody and splenocyte proliferation response,and co-injection of pVAX/mIL-18 significantly increased the production of IFN-γ and IL-2 compared with pVAX/Sj23 alone, indicating that IL-18 enhances the Th1-dominant immune response. The challenge experiment showed that worm reduction rates in pVAX/Sj23 group compared with control group (pVAX1) was 26.5% and in the pVAX/Sj23 plus pVAX/mIL-18 group was 41.9% ,and the hepatic egg reduction rates were 42.7 and 49.6%,respectively. These results indicated that co-injection of an IL-18 plasmid with Sj23 DNA vaccine efficiently improves the protective effect against S. japonicum infection.