Monoclonal antibodies to K88ab, K88ac and K88ad fimbriae from enterotoxigenic Escherichia coli

Abstract

K88ab, K88ac and K88ad fimbriae derived from enterotoxigenic Escherichia coli strains involved in porcine colibacillosis were used to immunize BALB/c mice. Several hybridomas secreting monoclonal antibodies (MAbs) against the three intact K88 fimbriae subtypes were produced by fusion of spleen cells from these mice with P3-X63-Ag8.653 myeloma cells. Hybridomas producing MAbs with affinity for all 3 E. coli K88 subtypes proved to be the most frequent (248/303), but subtype-specific monoclonals (39/303) as well as MAbs reacting with two but not with the third subtype (16/303) were also produced. The antibody-containing culture supernatants from 71 selected hybridomas were characterized by enzyme-linked immunosorbent assay (ELISA) titrations, ELISA inhibition experiments and further examined by immunoblotting. Derivation of several MAbs specific for one of the E. coli fimbrial antigens, K88ab, K88ac or K88ad, was of interest in view of the extensive sequence homology in their primary structures. Specific binding of the MAbs to fimbriae on the surface of K88-positive E. coli strains was indicated by agglutination tests and visualized by immuno gold labeling and electron microscopy. The present MAbs against K88 fimbriae have potential veterinary applications for diagnosis and treatment of porcine colibacillosis. Preliminary results indicate the therapeutic value of oral administration of murine ascitic fluid containing anti-K88 MAbs to piglets experimentally infected with E. coli K88.