Studies On The Target Schistosoma Japonicum Genes (Screened With Seara) Related To The Resistance Of Microtus Fortis

Schistosomasis is one of the word-wide spread parasitic zoonosis that causes serious healthy problem to both human and animals. It was reported that there are 40 species of mamals in the endemic area could be naturally infected with Schistosoma japonicum (S. japonicum),and Microtus fortis (M. fortis) is the only mamalian animals with native resistance to S. japonicum. Exploring the anti-schistosoma mechanism of M.fortis, screening the genes of M. fortis or target genes of S.japonicum that related to the resistance could provide some useful information for the development of anti-schistosomula vaccines and drugs.Ten positive clones were obtained in precious work of the liujinming`s group, by screening a adult worm phage display cDNA library from worms of S. japonicum with fresh sera of Microtus fortis. In order to find the candidate vaccine antigen encoding genes, we used 8 of positive clones alone or as cocktail vaccines, to vaccinate BALB/c mice and observe the preventive effects to schistosomiasis japanica. Compared with the blank control group, vaccination with clone 1 which displayed the ring zinc finger protein of S. japonicum induced reductions of 32.10% and 31.25% for mean worm burdens, 61.14% and 47.31% for liver egg burdens, and decreases of Paired worm ratios from 92.59% and 57.39% to 69.09% and 41.03%, respectively, over two independent trials. 8.02%-32.72% worm reductions and 40.19%-69.53% liver egg reductions were obtained from groups vaccinated with other clones in trial 1,but these could not be confirmed in trial 2.The full-length ORF sequence of the gene encoding a zinc finger protein (Here we named it Sjznf1) was obtained by RT-PCR from the mRNA of S.japonicum S.japonicum adult worm. The ORF is composed of 1014 nucleotides and encodes 195 amino-acid resides. Compared with the squences of zinc finger protein encoding gene of S. japonicum reported in GENEBANK with accession numbers AY222909 and EZ000159 , there were 99.7% and 99.4% identities in nucleotide sequence, and 99.4% and 98.5% identities in deduced amino acid sequence. There was a zinc finger protein domain (Ring-type or PHD-type) in the deduced amino acid sequence. After subcloning the cDNA of Sjznf1 into PGEX-4T-2 expression vector, the gene was expressed in E. coli BL21 when induced with IPTG. The expression product was a 63KDa fusion protein. The recombinant protein was used to vaccinate BALB/c mice, and 56.62% worm reduction and 75.39% liver egg reduction were obtained from the vaccinated group.It was the first reported that the phaged-displayed antigen and recombinant protein antigen of a ring zinc finger protein encoding gene from S. japonicum could induce high protective level in mice. The results revealed that this S. japonicum was worth further investigation on the development as a vaccicne.