Comparison of two strains of Schistosoma mansoni with respect to the sites and kinetics of immune elimination in irradiated cercaria-immunized mice.

A comparison was made of the sites of elimination of NMRI and Mill Hill strains of Schistosoma mansoni in C57BL/6J mice previously immunized with 50 krad gamma-irradiated cercariae of the homologous strain. In the first experiment, the fate of percutaneous challenge infections with 75Se-labeled cercariae was evaluated by autoradiography of tissue squashes and hepatic portal perfusion. For both strains of parasite, migration from skin to lungs was delayed but not reduced in immunized mice relative to controls, with immune elimination taking place at some point after migration to the lungs. In a second experiment, resistance to the Mill Hill strain of S. mansoni was compared in mice challenged by percutaneous infection with cercariae and by intravenous injection with lung schistosomula. Both types of challenge were shown to be vulnerable to immune elimination. We conclude that under the conditions employed in this study, there is no significant difference between the NMRI and Mill Hill strains of S. mansoni in the patterns of migration and elimination, with most or all elimination in both control and immunized mice taking place after migration from the skin.