DETERMINATION OF ANTI-CRYPTOSPORIDIUM COPROANTIBODIES BY TIME-RESOLVED IMMUNOFLUOROMETRIC ASSAY

The role of the mucosal immune response against Cryptosporidium has be en suggested by studies on the therapeutic effects of hyperimmune colo strum. In order to study the intestinal response to this infection, we have developed a sandwich-type time-resolved immunofluorometric assay for the determination of anti-Cryptosporidium coproantibodies. This a ssay has the inherent sensitivity of an immunoassay without the proble ms due to background responses from other biological compounds, and is thus suitable for faecal samples. The intra-assay coefficients of var iation (5.1%, 4.6%, and 5.8% for immunoglobulins (Ig) A, M and G respe ctively), inter-assay coefficients of variation (9.4%; 10.5% and 12.2% for IgA, IgM and IgG, respectively) and specificity (100% for all 3 i sotypes) were all satisfactory. Using this assay to study 12 patients with the acquired immune deficiency syndrome (AIDS) who were infected with cryptosporidiosis, we found a marked elevation of anti-Cryptospor idium IgA and IgM coproantibody titres relative to 18 healthy control values, but no correlation with the gravity of the infection in terms of oocyst shedding. These results suggest that a non-protective mucosa l immune response develops to Cryptosporidium in AIDS patients.