The detection and measurement of coproantibodies to Nippostrongylus brasiliensis in rats following a primary infection.

Investigations were initiated to study the possible detection and measurement of coproantibodies in animals infected with a gastrointestinal nematode parasite. Faecal extracts, extracts of small intestinal mucosa and sera of rats infected with intestinal nematode Nippostrongylus brasiliensis were examined for total IgA, IgM and IgG levels and haemagglutinating and precipitating antibodies specific to parasite antigens over a 30-day-period following infection. It was found that in both faecal and mucosal extracts immunoglobulin concentrations increased after a primary infection. In faecal extracts there was a seven-fold increase of IgA, a three to six-fold increase of IgG and about a fifty-fold increase of IgM. Haemagglutinins in faecal extracts detected by adult worm excretory-secretory (ES) products and adult worm and infective larvae somatic extracts were observed from 3 days after infection (DAI). Haemagglutinins detected by ES products reached their highest titres on 11-12 DAI while those reacting with adult worm somatic extracts showed the highest level between 15 and 19 DAI. A similar pattern of response was found in the antibody levels of the intestinal mucosa. Haemagglutinins detected in faeces during the first 12 DAI reacted with the same antigens as antibodies present in the sera at that time but coproantibodies from 18, 24 and 30 DAI were different from those circulating in sera at that stage of the infection. The results suggest that measurement of coproantibody levels may provide a convenient and useful index of local immune responses to gastrointestinal helminths.