Schistosoma japonicum reveals distinct reactivity with antisera directed to proteases mediating host infection and invasion by cercariae of S. mansoni or S. haematobium.

Serine proteases released from the acetabular glands of cercariae, also known as cercarial elastases, are key enzymes in the penetration process of schistosomes through the skin of the final host. Antisera against these enzymes secreted from Schistosoma mansoni or S. haematobium reveal differences in the patterns of elastase expression among schistosome species and among different developmental stages of the larvae. Immunolocalization studies showed that antisera raised against the enzyme s28 protease react with S. mansoni, S. haematobium and also S. japonicum, in developing as well as mature cercariae and in both pre- and post-acetabular glands. Antisera against the enzyme SmCE detect the respective antigen solely in the pre-acetabular glands. Remarkably, the SmCE-1a isoform is detectable with DNA-vaccinated mouse sera in S. mansoni and S. haematobium only, but is apparently absent from the acetabular glands of S. japonicum. These differences in immunoreactivity of cercarial enzymes may be related to the distinct infection process of S. japonicum.