The role of mucus in antibody-mediated rapid expulsion of Trichinella spiralis in suckling rats

Rat pups suckling dams parasitized by Trichinella spiralis express rapid expulsion, a protective response that is associated with the entrapment of infectious muscle larvae in intestinal mucus. Immunofluorescent studies revealed that antibodies were bound to the surfaces of the entrapped larvae. Mucus binding and rapid expulsion occurred in normal pups dosed with larvae coated with antibodies prepared from infected rat serum. Subsequent experiments revealed that entrapped larvae escaped from mucus after 2 hr in vitro incubation in saline. Escape correlated with the loss of the surface-bound antibodies, suggesting that mucus entrapment was reversible and dependent on antibody coating. Finally, when protective antibodies were injected 1, 2 or 6 hr after larvae were administered to pups, the parasites were forced to leave their epithelial niche and became enveloped in mucus. The above findings suggest that mucus trapping of T. spiralis larvae is dependent upon the coating of larvae by antibody, but that trapping is reversible, and is not in itself the pivotal event in rapid expulsion. The primary mechanism of rapid expulsion appears to be antibody-mediated inhibition of processes required for the parasite to maintain itself in the epithelium.