Fasciola hepatica procathepsin L3 protein expressed by a baculovirus recombinant can partly protect rats against fasciolosis.

Fasciola hepatica juveniles express immunodominant cathepsin L proteins, which are mainly found in their immature, procathepsin form. A gene encoding such a procathepsin L (FheCL3) was expressed by a baculovirus recombinant and by Saccharomyces cerevisiae. The glycosylated FheCL3 proteins obtained by both systems were used in a vaccination/challenge experiment in rats. Both antigens evoked similar antibody responses, but only the baculovirus expressed FheCL3 caused a significant protection against the number of liver flukes (52% protection, P=0.01), whereas the S. cerevisiae expressed FheCL3 did not. In a second experiment in rats, deglycosylated versions of both antigens were used, but this did not improve their efficacies.