Monoclonal antibodies against colonization factor antigen I pili from enterotoxigenic Escherichia coli

Analysis of colonization factor antigen I, an adhesin of enterotoxigenic Escherichia coli O78:H11: fimbrial morphology and location of the receptor-binding site

Colonization factor antigen I (CFA/I) of enterotoxigenic Escherichia coli was dissociated into one type of subunit (15 kDa). The dissociation was achieved either by heating CFA/I in sodium dodecyl sulfate at 100 degrees C or by heating it for 20 min in water. Heating in water to 100 degrees C yielded only in the 15-kDa subunit, but heating to 85 degree C yielded small amounts of oligomers in addition. The monomeric subunits obtained after heating in water are stable, as demonstrated by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis without heating prior to the electrophoretic run. These subunits inhibited CFA/I-induced hemagglutination, indicating that they had maintained their receptor-binding properties. When the hybridoma technique was used, two types of monoclonal anti-CFA/I antibodies were obtained. Antibodies obtained by immunization with the purified subunits were more reactive with subunits than with fimbriae, as shown by enzyme-linked immunosorbent assay. These antibodies strongly inhibited CFA/I-induced hemagglutination. When examined by immunoelectron microscopy, these antibodies seemed to label the fimbrial tips. A similar labeling pattern was obtained with gold particles modified with the receptor ganglioside GM2. Antibodies obtained by immunization with fimbriae reacted in enzyme-linked immunosorbent assays equally well with fimbriae and subunits. They inhibited CFA/I-induced hemagglutination only slightly. Immunoelectron microscopy revealed that these antibodies labeled the fimbriae densely and regularly over their entire lengths. In a coagglutination experiment with Staphylococcus aureus and monoclonal antibodies, the subunits retained their receptor-binding properties. From these results, we conclude that CFA/I fimbriae consist entirely of one type of adhesive subunit, of which only the one at the tip is accessible to the receptor.

Isolation and characterization of monoclonal antibodies directed against different epitopes of type-1-like fimbriae from a multifimbriated E. coli strain

Monoclonal antibodies (MAbs) were raised against purified fimbriae isolated from the uropathogenic E. coli strain WF96 (O7:K1:H6:F11rel,F10). This strain expresses at least four different types of fimbriae. 11 MAbs were selected for further characterization. They are directed against epitopes of a fimbrial type which is composed of 19.5 kDa subunits. It resembles type 1 fimbriae with regard to its high resistance to disruption by SDS. The MAbs were tested for crossreactivity to type 1 fimbriae and other fimbriae with known F-serotypes by ELISA. Two of these MAbs, Pili III 2F7 and Pili III 68C5, were directed against an epitope which was also found on MS fimbriae (type 1). Thus type 1 like fimbriae of E. coli WF96 share at least one epitope with MS fimbriae. Nevertheless, the antigenic properties of these two fimbrial types were found not to be completely identical, since all the other 9 MAbs were not crossreactive. The MAbs were not able to inhibit haemagglutination of erythrocytes of different species and thus not directed against adhesive sites of the fimbriae. All the epitopes detected by MAbs were accessible on native fimbriae; some of them were also detectable on denatured fimbrial subunits. Electron micrographs revealed that these epitopes were evenly distributed on the fimbrial organelle.

Adherence pili of avian strains of Escherichia coli O78

Avian colisepticemia starts with the invasion of the trachea by virulent strains of Escherichia coli, with strains of serotype O78 responsible for about 50% of the cases. Several O78 strains isolated from poultry with colisepticemia produced pili with a subunit of molecular weight of 18,000 that mediated adherence to avian epithelial tissues in vitro and in vivo.

Examination of enterotoxigenic Escherichia coli H10407 (colonization factor antigen I+) by scanning electron microscopy with conductive staining

We have used the scanning electron microscope to examine enterotoxigenic Escherichia coli H10407, which expresses colonization factor antigen I pili. The use of low accelerating voltages and conductive staining procedures allowed us to obtain images of colonization factor antigen I pili and other structural details which were obscured by conventional gold-coating techniques.

Monoclonal antibodies against different epitopes on colonization factor antigen I of enterotoxin-producing Escherichia coli

Hybridoma-secreting monoclonal antibodies (MAbs) against colonization factor antigen I (CFA/I) were produced by the fusion of spleen cells from immunized BALB/c mice with F/O myeloma cells. The 25 MAbs with the highest antibody titer against CFA/I, as determined by an enzyme-linked immunosorbent assay, were studied for specificity and the capacity to agglutinate CFA/I-carrying bacteria. Most of the MAbs agglutinated a majority of 16 CFA/I-positive strains tested but not any of a number of CFA-deficient mutants or strains carrying other colonization factors (CFA/II and CFA/IV). One MAb that agglutinated all the CFA/I-positive strains and one MAb that did not agglutinate any of these strains were compared for their reactivities with different preparations of CFA/I. Whereas both MAbs bound to or could be inhibited by isolated CFA/I fimbriae as well as the subunit protein, only the agglutinating MAb bound to CFA/I, as expressed on whole bacteria. The nonagglutinating MAb, on the other hand, bound considerably better than the agglutinating MAb to a peptide corresponding to the 46 N-terminal amino acid residues of the CFA/I subunit protein. These results suggest that the two MAbs are directed against different epitopes on CFA/I.

Identification of a human erythrocyte receptor for colonization factor antigen I pili expressed by H10407 enterotoxigenic Escherichia coli

We have identified a receptor for colonization factor antigen I (CFA/I) pili in human erythrocyte membranes. Erythrocyte binding assays, using whole organisms, suggested that the CFA/I receptor was a glycoprotein containing important sialic acid moieties. Subsequently, human erythrocyte membranes were extracted with lithium diiodosalicylate to obtain a soluble glycoprotein fraction from which to isolate receptors. The extracted material caused agglutination of the CFA/I+ but not the CFA/I- organisms at a protein concentration of 0.5 mg/ml. The CFA/I receptor was identified in iodinated extract by an affinity isolation procedure, using whole bacterial cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of the washed, extract-coated H10407 CFA/I+ organisms revealed a band with an apparent molecular weight of 26,000 which was present in the original extract but was not observed on extract-coated H10407 CFA/I- bacteria. The addition of purified CFA/I pili reduced binding of the 26,000-molecular-weight receptor to CFA/I+ bacteria. The CFA/I-specific receptor species also bound to wheat germ agglutinin-agarose. This observation supported the suggestion that the CFA/I receptor identified in this report is a sialoglycoprotein.

Isolation and characterization of monoclonal antibodies against pili of Corynebacterium renale and Corynebacterium pilosum

Five monoclonal antibodies against pili of Corynebacterium renale 115 P+ (piliated clone) and two monoclonal antibodies against pili of C. pilosum 92 P+ (piliated clone) were produced. These antibodies bound to pili of the homologous strain in in enzyme-linked immunosorbent assay (ELISA) and agglutinated P+ but not P- (non-piliated clone) of each homologous strain. The five monoclonal antibodies against C. renale 115 P+ pili were divided into 2 groups, comprising 16/5, 160/1 and 32/6 and 13/4 and B20/3, based on the results of a competitive binding assay. The results may indicate the presence of at least 2 distinct antigenic areas on the pilus of C. renale 115 P+. The monoclonal antibodies of the first group inhibited adhesion of C. renale 115 P+ bacteria to the epithelial cells of bovine vulva, while the second group did not. Two monoclonal antibodies against C. pilosum 92 P+ pili recognized the same area on the pilus of C. pilosum 92 P+, and inhibited the adhesion of C. pilosum 92 P+ bacteria to the epithelial cells of bovine vulva. The adhesion of these bacteria was inhibited by the monoclonal antibodies in the form of IgG as well as by the Fab fragment. The strains of C. renale and C. pilosum which reacted with each of the anti-C. renale 115 P+ pili and anti-C. pilosum 92 P+ pili monoclonal antibodies were small in number and of restricted distribution.

Monoclonal antibodies against the K99 antigen of Escherichia coli for diagnostic purposes

Hybridomas secreting monoclonal antibodies against the K99 antigen of Escherichia coli were produced by the fusion of spleen cells from immunized BALB/c mice with P3/X63-Ag8.653 myeloma cells. The seven hybridomas which produced the highest antibody titers in vitro, as detected by enzyme-linked immunosorbent assay (ELISA) and Perma slide agglutination test (PSAT), were chosen for antibody production in vivo. No cross reaction was observed with K88ab, F41 and P987 antigens in the ELISA. The titer of each ascitic fluid was established by the ELISA and the slide agglutination (SAT) tests. The two ascitic fluids with the highest titer in the SAT were incorporated into the set of antisera used for serotyping at our laboratory. The results were satisfactory both in terms of stability and specificity.