THE F41 ADHESIN OF ENTEROTOXIGENIC ESCHERICHIA-COLI - INHIBITION OF ADHESION BY MONOCLONAL ANTI BODIES

The anti-adhesive properties of 23 specific monoclonal antibodies (MAb s) against the F41 adhesive fimbrial antigen of enterotoxigenic Escher ichia coli (ETEC) were studied in brush border adhesion inhibition tes ts and haemagglutination inhibition tests with four F41-positive E. co li strains and purified F41 antigen. These MAbs recognize five epitope clusters, F41-1 to F41-5. It was proven that these epitope clusters w ere located on the 29 kDa F41 major fimbrial subunits. All nine MAbs a gainst epitope cluster I inhibited the adhesion of F41-positive strain s to brush border preparations of calf and pig intestines and the haem agglutination of sheep and guinea pig erythrocytes by the F41-positive strains and purified F41 antigen. The fourteen MAbs against the other four epitope clusters showed very little to no blocking of adhesion a nd haemagglutination. The results indicate that the adhesion of F41 to intestinal epithelial cells is mediated by the same domain of the 29 kDa F41 major fimbrial subunit(s) as the adhesion of F41 to erythrocyt es. Irrespective of their epitope specificity F41 MAbs protected infan t mice against a challenge with F41-positive ETEC. MAbs against all ep itope clusters partly protected piglets against challenge with F41-pos itive ETEC in a similar way. Therefore, we conclude that direct blocki ng of the receptor binding site located on the major fimbrial subunit is not the main mechanism how antibodies protect against ETEC infectio n.