NEOSPORA-CANINUM IN DOGS - DETECTION OF ANTIBODIES BY ELISA USING AN ISCOM ANTIGEN

An indirect enzyme linked immunosorbent assay (ELISA) for detection of antibodies to Neospora caninum in serum from dogs is described. Extra cted tachyzoite proteins incorporated into immunostimulating complexes (iscoms) were used as coating antigen. A mixture of a monoclonal anti body to dog immunoglobulin G and a horse radish peroxidase conjugated antibody to mouse Ig was used to detect bound antibody. When the iscom preparation was analysed by means of sodium dodecyl sulphate polyacry lamide gel electrophoresis it appeared to consist of a restricted numb er of proteins compared with whole parasite homogenates. In immunoblot analysis, using N. caninum positive sera from rabbits and dogs as pro bes, the major antigens recognized had approximate molecular weights b etween 30 and 45 and 17 to 19 kDa. Compared with an ELISA using a crud e solubilized tachyzoite antigen, the iscom ELISA substantially improv ed the sensitivity and specificity (to 97.6% and 95.6%, respectively, against an immunofluorescence test, IFAT, as indicator of true status) . There was a statistically significant positive correlation between I FAT titres and iscom ELISA OD450 values. The iscom ELISA absorbances ( and the IFAT titres) of dogs with proven clinical infections were not higher than those from non-clinically affected putatively infected dog s.