Changes in the surface antigen profile ofSchistosoma mansoniduring maturation from cercaria to adult worm

Abstract

Antigenic proteins on the surfaces of different developmental stages ofSchistosoma mansoniwere radio-iodinated by the lodogen-catalysed method and identified by immunoprecipitation with a panel of antisera. The sera comprised specific immune serum from mice harbouring a chronic schistosome infection or vaccinated with γ-irradiated cercariae; serum from rabbits immunized with adult schistosome tegumental outer membranes or a partially purified Mr32K glycoprotein from adult worm membranes; and a monoclonal antibody recognizing an Mr20 K antigen on the surface of schistosomula. The Mr38–32 K glycoproteins were the major antigens identified in surface-labelled cercariae and their probable association with the glycocalyx is discussed. Schistosomula transformed from cercariae either mechanically or by penetration of host skinin vitro, expressed a similar pattern of surface antigens to that identified for cercariae, but low molecular weight antigens of Mr20, 17 and 15 K were also detected. The Mr38–32 K glycoproteins, although present on newly transformed schistoso mula, were progressively replaced with time, by a single dominant glycoprotein (Mr32 K) expressing identical epitopes to those on the Mr 38–32 K complex. Moreover, the data confirm that the Mr32 K glycoprotein persists on the tegument afterin vivomaturation and is conserved, together with Mr20 and 15 K antigens, through to the adult stage. New antigens (Mr97 and 25 K) were also detected duringin vivomaturation and were present in late-stage schistosomes recovered from infected hosts. In addition, the enzyme alkaline phosphatase is expressed on the surfaces of 3-week-old liver worms as a dominant antigen (Mr65 K); this feature may be related to nutritional and/or physiological processes in the tegument of this metabolically active stage of development.