The cDNA fragments of interest were amplified using \%Sj\%λ ZipLox library as the templates by PCR and then cloned into a eukaryotic expression vector p\|CMV\|GH; A small number of DNA fragments inserted in the recombinants was identified by restriction cleavage, EST sequencing and bioinformatical analysis; mice were injected intramuscularly with the expression library(L\|CMV\|SjR) or sublibraries(L\|CMV\|SjR 1,L\|CMV\|SjR 2 and L\|CMV\|SjR 3), immunized mice were challenged with \%Schistosoma japonicum\% cercariae on day 35, the levels of IgG antibodies in sera from the immunized mice were detected by ELISA. The results demonstrated that a partial cDNA expression library of \%S.j,\% with～10\+5 transformants, was constructed, most of the recombinants contained the insert DNA fragments of interest, and these fragments had the features of protein\|coding sequences for \%Schistosome.\% There were no significant differences for the levels of IgG antibodies in sera from all of the immunized groups. Mice immunized with L\|CMV\|SjR, L\|CMV\|SjR 1 and L\|CMV\|SjR 2 developed significant protective effect against \%Sj\% infection compared to control mice injected with the empty plasmid, the rate of worm reduction was about 30%.
This paper was about the study on the mechanism of Microtus fortis against Schistosoma japonicum. Firstly, we confirmed that Microtus fortis came from epidemic region (Dongting Lake beaches) and non epidemic region (Qingtong Gorge in Ningxia province) were both resistant to Schistosoma japonicum infection after re infection tests for several times. It seemed that their resistant ability was inheritable rather than acquired. Secondly, it was demonstrated by in vivo check up and in vitro killing assay that there were some native antibodies of IgG3 subclass specifically to the schistosomula and adult worm of Schistosoma japonicum in Microtus fortis, which probably played an important role in resisting Schistosoma japonicum associated with complement. It was shown that macrophages and eosinophils in abdominal cavity of Microtus fortis had native ability of adhering to the schistosomula of Schistosoma japonicum. Then, the adult worm cDNA library of Schistosoma japonicum was screened with sera from Microtus fortis . Five positive clones were obtained, four of which were identified as new genes. Full length cDNA of the two new genes were isolated by RACE. DNA vaccine was constructed with one named EST mfs 3. After the Kunming mice immunized with this vaccine, the worm reduction rate and the egg reduction rate were 28.4% and 21.73% compared with that in control group respectively. This kind of DNA based EST mfs 3 vaccine was highly expressed in E.coli and induecd strong immune response in challenged group. Finally, two groups of cDNA probes prepared from liver and lung of Microtus fortis with or without Schistosoma japonicum infection were hybridized to the cDNA chip prepared from rat respectively. 156 and 332 genes revealed differential expression in infectious group compared with normal group. In conclusion, there would be many factors contribute to the mechanism of Microtus fortis against Schistosoma japonicum. We should stress the essentials and make further research on how to take advantage of them to defend us from
