Identification of a fibrinolytic enzyme in Schistosoma mansoni eggs and modulated blood fibrinogen metabolism in S. mansoni-infected mice

Aqueous extracts of Schistosoma mansoni eggs have been shown to have fibrinolytic activity inhibitable by a serine protease inhibitor. Fibrinolytic activity was not present in extracts of either adult worms or cercariae. A 27 kDa enzyme that was proteolytically active on fibrinogen in zymography and that degraded fibrinogen in a pattern similar to that of plasmin, is presumed to be responsible for the schistosome egg fibrinolytic activity. Anti-human fibrinogen antisera were shown to have antibodies that cross-reacted with mouse fibrinogen in Western immunoblots. Electroblotted sera from S. mansoni-infected and control uninfected mice displayed different antigenic profiles when probed with the cross-reactive anti-human fibrinogen antibodies, suggesting an alteration in mouse host fibrinogen metabolism as a result of the parasitic infection. We discuss the possibility that modulation of fibrinogen metabolism is a factor in a recently discovered anti-atherogenic effect exerted by schistosomes.