Toxocara Cati as a Target for Feline IgA

Toxocara cati is a common intestinal parasite of cats globally. On the mucous membranes, the host’s immune system defends itself against​ invading pathogens, such as parasites, with immunoglobulin A (IgA) among other mechanisms. The precise role of IgA in T. cati infections is not yet understood. We determined the total IgA levels from serum ( n = 8) and feces ( n = 10) of T. cati -infected cats before and after anthelmintic treatment with a commercial ELISA. These results were compared with IgA levels of nonparasitic cats (serum n = 8, feces n = 6). We also visualized the binding of feline IgA to​ adult T. cati worms with immunohistochemistry and analyzed the IgA-reactive antigens with Western blot. Five antigenic bands were further analyzed with mass spectrometry. We found no consistency between total IgA levels in serum or feces and T. cati infection. In immunohistochemistry, the intestines, reproductive tracts, excretory canals, and muscle cell bodies of T. cati were the most immunoreactive parts when processed with either Toxocara -positive cat sera or pathogen-free cat serum. When comparing T. cati -infected and pathogen-free cat serum as IgA source in Western blot, most bands showed nonspecific IgA immunoreactivity independent of the host’s Toxocara status. In mass spectrometry, the most prevalent proteins in the selected antigenic bands were two uncharacterized proteins, intermediate filament proteins, endoplasmin, paramyosin, actins, and glutamate dehydrogenase. The combined findings of this study suggest that IgA has mainly nonspecific actions against T. cati .