Schistosoma mansoni: Adhesion of mannan-binding lectin to surface glycoproteins of cercariae and adult worms

Schistosoma mansoni is a blood-dwelling trematode which can persist for sev eral years in the vessels of the human host. The schistosomal surface has b een extensively characterized by lectin binding studies, revealing the carb ohydrate composition of the worm's tegument. Using fluorescent and scanning electron microscopy we demonstrate that the surface carbohydrates of cerca riae and adult worms are the binding ligands for mannan-binding lectin (MBL ), a serum protein that is part of the innate immune system. An in vitro co mplement activation assay with Clq-deficient complement suggests that MEL, in association with the serine proteases MASP-1 and MASP-2, is capable of f ixing complement components on the schistosomal tegument and activating the complement cascade via the "MBL pathway." MBL is constitutively expressed by hepatocytes and present in the blood at a stable level. Since it is also a weak acute-phase protein and therefore upregulated in an acute-phase res ponse we investigated the serum MBL levels in patients infected with Schist osoma sp. and in healthy control persons. An enzyme-linked immunosorbent as say indicated no differences between the two groups. Although our results s uggest an involvement of MBL activated complement in vitro, its role in viv o remains to be clarified. (C) 2000 Academic Press.