A model system for the study of antigen secretion by adult Schistosoma mansoni in vivo.

Schistosoma mansoni (6 weeks old) were surgically transferred from donor C57BI/6 mice to the hepatic portal veins of naive recipients of the same inbred strain. Between 70% and 100% of the parasites were alive 15 days later, and egg deposition was observed after transfer of worm pairs. The physiological status of the parasites was monitored by measuring the levels of a schistosome gut antigen, circulating anodic antigen (CAA), in the serum of the recipients. When only male worms were transferred, serum CAA levels increased slowly to a peak 9 days later, which was followed by a rapid decline. When worm pairs were transferred, there was an early peak in serum CAA levels followed by a gradual decline, but these levels were always higher than those recorded after male-only transfer; in two mice the pattern was similar to that observed following receipt of male worms. More CAA and eggs were produced after transfer of paired versus separated worms. It was concluded that although worm pairs can be successfully transferred, their physiological status may be sub-optimal. In contrast, male worms survive consistently well, and their transfer to a naive recipient provides a convenient model with which to study the release of antigens by schistosomes in vivo.