SUMMARYProteins associated with the schistosome tegument are of great importance for the development of new intervention strategies since they may be exposed on the surface of the parasite. Herein, we have isolated a cDNA clone encoding for theSchistosoma mansoniSmIg and its recombinant protein was tested as a potential vaccine candidate. Initially, its amino acid sequence was analysed by bioinformatics and shown to possess an N-terminal signal peptide, a C-terminal transmembrane helix, 4 glycosylation sites, an immunoglobulin conserved domain and 73% similarity with a hypotheticalS. japonicumprotein of unknown function. SmIg was produced byE. colias a recombinant protein (rSmIg) and its protective effectiveness was evaluated againstS. mansoniinfection with 100 cercariae in a murine model. Mice immunized with rSmIg induced an immune response characterized by dominant IgG1 isotype and significant levels of IFN-γ, TNF-α, IL-10 and IL-4. Although immunogenic, the recombinant vaccine failed to induce worm burden reduction when compared to the infected control group. However, rSmIg-immunized mice had significant reductions of liver granuloma volume and fibrosis content by 31·8% and 49%, respectively. In conclusion, SmIg is a new tegument protein fromS. mansonithat plays an important role in reducing pathology induced by parasite infection.