Immunisation with Salmonella typhimurium-delivered glyceraldehyde-3-phosphate dehydrogenase protects mice against challenge infection with Echinococcus multilocularis eggs.

Recombinant glyceraldehyde-3-phosphate dehydrogenase of the cestode parasite Echinococcus multilocularis was expressed in Escherichia coli and in Salmonella typhimurium. The potential of different forms of the recombinant antigen to protect BALB/c mice against oral challenge infections with E. multilocularis eggs was evaluated. Oral or intraperitoneal immunisation with live attenuated S. typhimurium as a carrier for recombinant glyceraldehyde-3-phosphate dehydrogenase of the E. multilocularis resulted in significant protection, reducing the number of developing metacestodes up to 79.8%. The sera of protected animals did not contain detectable amounts of antibody against glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis. By contrast, although anti-glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis antibodies were detectable in the sera, immunisation with E. coli-expressed recombinant glutathione-S-transferase-fusion protein or with glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis fused to a 6HIS-tag failed to protect the animals against oral challenge infections. These data emphasise that antigen delivery systems play a critical role in vaccination and the induction of protective immunity against helminth parasites.