POSITIVE EVIDENCE THAT ANTITOXOPLASMA GONDII IGA ANTIBODY EXISTS IN THE INTESTINAL-TRACT OF INFECTED CATS AND EXERTS PROTECTIVE ACTIVITY AGAINST THE INFECTION

The presence of anti-Toxoplasma gondii IgA antibody in the feces and i ntestinal tract of cats infected with this parasite was demonstrated u sing sn immunoblotting assay. Cats (n = 5) were inoculated orally with T. gondii cysts and supernatants of feces and washings of the intesti nal tract were assayed for secretory IgA specific for the parasite. Th e secretory IgA detected recognized tachyzoite antigens of m.w. 24, 34 , 38 and 43 kDa and one sporozoite antigen of m.w. 24 kDa. No reactivi ty was shown against bradyzoites or enteroepithelial stage parasites. Tachyzoites preincubated with washings of the intestinal tract of infe cted cats showed decreased activity in penetration of feline fibroblas t cells, as compared to tachyzoiter; preincubated with similar washing s derived from non-infected cats. The addition of either anti-cat IgA or anti-cat IgG to the washings had no effect on the inhibitory activi ty which reduced the parasite's cell-penetration activity. However, th e addition of both anti-cat IgA and anti-cat IgG to the washings dimin ished the inhibitory activity. These results suggest that anti-T. gond ii antibodies of both classes, secretory IgA and IgG, exist in the int estinal tract of infected cats and these may be capable of preventing infection. (C) 1997 Elsevier Science B.V.