Proteases of liver fluke - enzymatic characterisation and prospects for vaccination against fasciolosis

Liver flukes produce cathepsin B and cathepsin L in their excretory-secretory material.Cathepsin B is predominately released in the juvenile stage of the life-cycle, while different cathepsin L’s are released throughout the cycle. Phylogenetic analysis of the mature proteins shows that cathepsin L’s and B form distinct clades, as expected. Cathepsin L proteases also form clades that reflect their predicted enzymatic activity, and their temporal expression. We have expressed examples of both these cathepsins in yeast, and purified them for both enzymatic analysis and for use as vaccines. Recently, a vaccination experiment was performed combining cathepsins B and L as immunogens, demonstrating that a multivalentvaccine may be optimal.