Abstract: 　Objective To search for the gene encoding specific antigen of Ancylostoma caninum that induces host′s protective immunity. Methods A lambda ZAPⅡ cDNA library of A.canium was screened with sera from dogs immunized subcutaneously with hookworm larvae(L3). After sequencing, insert gene (AcAg) from positive clones was ligated into PUC18 and PET28C. Recombinant pET28C plasmid was induced to expressed protein in the E.coli BL21. The characteristic of recombinant protein is analyzed by SDS-PAGE and Western bloting assay. Results Five positive clones were obtained, and proved to be the same. The insert gene (AcAg) in pET28C vector expressed a recombinant protein of about 43 kDa. Using Western bloting assay, this protein was recognized by the sera from dog immunized with Ancylostoma caninum third stage infected larvae and used for screening library. Conclusion The AcAg, which exhibits 35% homologous to Caenorhabditis elegans gene unc-89, is a novel specific antigen of A.caninum. Its ability to elicit the protective immunity and the probability of the recombinant protein as a vaccine need to be further evaluated.

Key words: hookworm antigen, cloning and expression