Evaluation of Echinococcus multilocularis tetraspanins as vaccine candidates against primary alveolar echinococcosis

Echinococcus multilocularis causes an important zoonotic cestode disease. The metacestode stage proliferates in the liver of intermediate hosts including human and rodents and forms multiple cysts. Recently, members of a transmembrane protein tetraspanin (TSP) family have been used as vaccines against schistosomosis, or as diagnostic antigens for cysticercosis. In this study, seven tetraspanins of E. multilocularis, designated as TSP1 to TSP7, were evaluated for their protective potential against primary alveolar echinococcosis. The large extracellular loop (LEL) region of these tetraspanins was cloned from a full-length enriched cDNA library of E. multilocularis metacestodes and expressed in Escherichia coli as a fusion protein with thioredoxin. Recombinant TSPs were applied as vaccines against an E. multilocularis primary experimental infection in BALB/c mice. Cyst lesions in the livers of vaccinated and non-vaccinated mice were counted. The cyst lesion reduction rates induced by the seven tetraspanins in vaccinated vis-à-vis non-vaccinated mice were: 87.9%, 65.8%, 85.1%, 66.9%, 73.7%, 72.9% and 37.6%. Vaccination conferred protective rates to mice ranging from 0% (TSP5, 6, 7) to maximally 33% (TSP1, 3). The results indicated that recombinant tetraspanins have varying protective effects against primary alveolar echinococcosis and could be used in vaccine development.