Effect of experimental trichinosis on intestinal secretion and on local antibody formation to cholera toxin.

The life cycle of Trichinella spiralis, a parasitic nematode, has three main stages: intestinal, migration and muscular stage. The present study was initiated to clarify the possible effects of the various stages of the infection on (a) enterotoxin induced intestinal secretion and (b) development of local immunity to cholera toxin. During the intestinal stage of trichinosis in mice challenge of ligated loops with cholera toxin gave rise to significantly greater fluid accumulation than was demonstrated in uninfected animals. In contrast, during migration and early muscular stage the secretory response was markedly reduced whereas in late muscular stage the fluid accumulation was normal. Absorption studies revealed that the intestinal fluid uptake was normal during the migration and muscular stages while it was markedly decreased during the intestinal stage which could probably explain the increased fluid accumulation in response to enterotoxin at this time. The normal absorption during the other stages suggests a true inhibition of the secretory process. To study the antibody response to cholera toxin during the various stages of T. spiralis infection the mice were given repeated peroral immunizations according to a schedule known to induce immunity to experimental cholera in mice. We found that T. spiralis infected mice, in which the immunization started ("priming") during the intestinal stage, had a significantly reduced IgA response in the small intestine. On the other hand T. spiralis infection had much less, if any effect on the IgA response to cholera toxin when immunization started before the infection and only the booster dose was given in the intestinal stage or when both priming and boosting were done after the intestinal stage.