Methioninc aminopcptidasc 2 (MAP2) is an sscntial enzyme that is involved in protein maturation. It plays a key role in the removal of the initiating methionine residuefrom nascent polypeptide chains. In the present study, a geneencoding methionine aminopeptidase 2 of Schistosoma japonicum (SjMAP2) was cloned and characterized. Real-time RT-PCR and Western blot analysis revealed that this wasexpressed in each testing developmental stage in S. japonicum, but more highly expressed at 42 days in male adultworm, suggesting this gene as male differentially expressed.The results also showed that the gene was differentiallyexpressed in worms from three different host species. It washighly expressed in worms from the schistosome-susceptiblemouse, expressed at a lower level in worms from the lesssusceptible rat, and at an even lower level in worms from thenon-permissive host Microtus frtis. The expression of thegene was affected significantly when the hosts were treatedwith praziquantel： Expression was down-regulated by92.17％and 49.01%, respectively, in treated male and femaleadult worms in comparison with untreated worms. Animmuno-experiment in mice indicated that vaccination withrecombinant SjMAP2 could induce partial protective efficacyagainst schistosome infection. The data presented heresuggest that SjMAP2 is an important molecule in thedevelopment of the schistosome and that it may be a potentialnew drug target or vaccine candidate for schistosomiasis.