Schistosoma japonicum scFv-IL18 fusion DNA ameliorates hepatic fibrosis in schistosomiasis-infected mice via improving local concentration of IL-18 in liver.

The pathogenesis of chronic schistosomiasis is caused by irritation of the schistosome eggs trapped in liver that induce delayed hypersensitive reactions from the surrounding tissues, leading to the formation of inflammatory granuloma and subsequent fibrosis. A Schistosoma japonicum (S. japonicum) single-chain fragment variable (SjscFv) which specifically binds to the S. japonicum soluble immature egg antigen (SIEA) can be used as a target to deliver specific cytokine towards the site of hepatic fibrosis. To test this hypothesis, a novel recombinant plasmid, pVAX1/SjscFv-IL18, was constructed by fusing SjscFv to IL-18 gene with a 45bp glycine-rich linker. Furthermore, experiments on mice showed that pVAX1/SjscFv-IL18 could effectively express IL-18 in the liver and in serum. Hepatic contents of IL-2 and IFN-γ (Th1-type) in S. japonicum-infected mice vaccinated with pVAX1/SjscFv-IL18 increased significantly but those of their IL-4 and IL-10 (Th2-type) decreased as compared to the analyzed results of 4 cytokines in the liver cells of control mice vccinated with pVAX1/IL18. Consistent with the levels of Th1 and Th2 cytokines, mice vaccinated with pVAX1/SjscFv-IL18 developed much less hepatic fibrosis 20weeks after infection, which was evaluated by average volumn of granuloma and collagen contents. These data suggested that the linkage of IL-18 to the target-specific SjscFv molecule appears to be a potentially promising trial route of therapy, the hepatic fibrosis in S. japonicum-infected mice may be ameliorated through effective expression of IL18 in liver.

Characterization and vaccination of two novel Schistosoma japonicum genes screened from a cercaria cDNA library.

Two novel genes, SJCWL05 and SJCWL06, were harvested from screening of Schistosoma japonicum (S. japonicum) cercaria cDNA library by using pig sera vaccinated (VPS) with S. japonicum immature egg ws-vaccine (S. japonicum iEw). Prokaryotic recombinant plasmids pGEX-4T-1/SJCWL05 and pGEX-4T-1/SJCWL06 were constructed to analyze their immunogenicity, which was confirmed by SDS-PAGE and Western blotting. Two eukaryotic recombinant plasmids, pcDNA3/SJCWL05 and pcDNA3/SJCWL06, were constructed, and their ability to protect mice against challenge of S. japonicum was evaluated. All mice vaccinated with pcDNA3/SJCWL05 or pcDNA3/SJCWL06 developed ELISA-specific anti-S. japonicum SIEA (S. japonicum soluble immature egg antigens) antibody. Immunoprotection experiments showed that worms and liver eggs reduced 34.64% and 39.14% in the pcDNA3/SJCWL05 group and those reduced 27.17% and 27.95% in the pcDNA3/SJCWL06 group, respectively. The reduction rates of intestine and uterine eggs in female worms of both groups reached 39.45% and 38.5% as well as 30.02% and 28.7%, respectively. Results of our study suggest that novel genes, SJCWL05 and SJCWL06, are potential vaccine candidates against schistosomiasis japonica.

Artificial preparation, indoor passage, and nature breed of Oncomelania hupensis infected with Schistosoma Japonicum.

OBJECTIVE: To prepare the infected Oncomelania hupensis by artificial method for the research on the activity, vaccine, and genetic variation of Schistosoma Japonicum (S. Japonicum). METHODS: The mature eggs of S. Japonicum were collected by Nylon silk method and the miracidia were incubated under appropriate conditions. Negative snails were infected with miracidia in different proportion by means of individual or collective infection to seek the best method and proportion of infection between miracidia and snails. Infected snails were divided into 12 groups in total. I-VI groups were for individual infection and VII-XII groups were for collective infection. There were 200 snails in each group. The infection ratios between snails and miracidia in Group I-VI or VII-XII were 1:0,1:5,1:10,1:15,1:20,1:25, respectively. The infected snails were screened, numbered, and reared singly. The amount of cercariae was calculated once every 10 days until the infected snails died. Then cercariae shedding quantity, infection quantity, and mortality of infected snails in every group were compared to find the best infection method and the best infection proportion between miracidia and snails. The cercariae were collected from the first generation of infected snails and were used to infect experimental animals. The mature eggs of S. Japonicum were saved from the infected experimental animals and incubated to get miracidia. The snails were artificially infected by miracidium to get the second generation of infected snails. The developmental rates of adult worms, the egg density in fecal and liver were compared between artificially and naturally infected snails. Results In individual infection Group I-VI,the average infection value of snails were 0 ± 0,22.7 ± 4.2,31.7 ± 4.5,53.0 ± 5.3,39.3 ± 5.9,32.7 ± 4.7,the average fatality of snails were 21.7 ± 3.1,25.0 ± 3.6,31.3 ± 4.9,44.7 ± 6.5,78.3 ± 9.5,89.7 ± 13.6, and the average value of cercariae shedding from infected snails were 0.0 ± 0.0,308.0 ± 96.6,428.1 ± 146.2,527.0 ± 171.1,571.4 ± 148.9,602.9 ± 356.3, respectively. In collective infection Group VII-XII,the average infection value of snails were 0 ± 0,12.3 ± 2.5,18.7 ± 4.7,28.3 ± 4.2,33.3 ± 4.7,29.3 ± 5.5,and the average fatality of snails were 22.7 ± 3.8,23.7 ± 4.5,28.3 ± 5.5,47.0 ± 9.5,75.7 ± 8.5,86.3 ± 12.2, and the average value of cercariae shedding from infected snails were 0 ± 0,244.5 ± 57.3,292.3 ± 74.8,347.1 ± 100.8,477.2 ± 142.1,447.3 ± 161.4, respectively. The second generation of artificially infected snails was obtained successfully. The average infection rate and fatality rate for the second generation of artificially infected snails were 24.65% and 24.50%, both of which were not obviously different from that of the first generation of artificially infected snails (P>0.05). In the animal experiment, the worm growth rate for the naturally infected snails, the first or second generation of artificially infected snails were 68.50%,73.50% or 71.00%. There was no obvious difference among them (P>0.05). The fecal (or liver) eggs per gram for the naturally infected snails, the first or the second generation of artificially infected snails were 1 503 ± 269,1 683 ± 233, or 1 541 ± 117 (or 6 641 ± 1 819,6 272 ± 1 419, or 7 263 ± 1 643). There was no significant difference among the 3 groups (P>0.05). CONCLUSION: Infected snails can be obtained through the artificial method by using S. Japonicum miracidia to infect snails. Individual infection has the advantage over collective infection. The optimal proportion of infection between snails and miracidia is 1:15. There was no significant difference between the first and the second generation of artificially infected snails in the average of cercariae shedding, infection, and fatality average of snails. There was no significant difference between artificially and naturally infected snails in the developmental rate of adult worms, fecal and liver eggs per gram.