Surface Membrane Protein Annexin Of Schistosoma Japonicum Gene Cloning, Expression And Evaluation Of Immune Protection

Schistosomiasis japonicum caused by infection with schistosome, is the most harmful parasitic zoonosis in china. The current control efforts rely primarily on snail killing and praziquantel chemotherapy. However, it is difficult to eliminate snails ( in termediate host) completely and praziquantel, the sole wide-spread efficient drug for schistosomasis, can't avoid high rates of re-infection after mass treatment.Moreover, the development of resistance to praziquantel limits strategies based on chemotherapy. Therefore, it is necessary to develop an efficient safe vaccine and new anthelmintic drugs against schistosome. The schistosome can survive in the hostile host environment for decades and must therefore display effective strategies to evade the host immune responses; the surface of the adult worm is covered by a living syncytial layer, the tegument bounded by a complex multilaminate surface, and it is directly attacked by the host immune responses. The reason that schistosome has a strong self-protection is closely related to its surface membrane, so in-depth study of schistosome surface membrane antigen protein is to study the composition and changes in the interaction between Schistosoma japonicum and host, immune evasion mechanisms revealed Schistosoma key. One gene encoding surface membrane proteins,Annexin of Schis tosoma japonicum,have been cloned,and also the studies on the gene expression and biological function was carried out preliminarily in this paper.Using the gene sequence of the surface membrane protein Annexin of Schistosoma mansoni,one EST(GeneBank accession NO.AY812989)was searched in the schistosoma japonicum EST bank.With PCR technique,one surface membrane protein encoding genes Annexin were cloned.Sequential analysis showed that the ORF of Sjan contains 1023 nucleotides,and encodes 341 amino acids with a molecular weight of 39.4KD.The Sjan cDNA fragment was subcloned into expression vector to construct prokaryotic expression plasmids Sjan/pET28a,and transformed to E.coli BL21(DE3),with the molecular weight of 42.9KD,The purified rSjan protein induced 23.27% worm burden reduction and 35.04% liver egg reduction in model of BALB/c mice.In conclusion,the Annexin gene of Schistosoma japonicum were cloned and expressed in E.coli as a fusion protein which seems to be an effective vaccine antigen candidate for schistosomiasis.The studies also provided the background to investigate the mechanism of evading the host immune responses about Schistosoma japonicum, and the new idea for the development of efficient and safe anti-schistosomiasis vac- cine and new drugs.