Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

David H. Francis


The objectives of this study were to identify the adhesive and immunogenic regions of the fimbrial adhesins of the three K88 fimbrial variants (ab, ac, and ad) of Escherichia coli. A panel of monoclonal antibodies (Mabs) specific for the conserved (-a) and variable (-b, -c, and -d) domains of the K88 variants, and anti-K88 unabsorbed (ab, ac, and ad) and absorbed subtype-specific (-b, -c, and -d specific) serum were used to investigate the role played by the conserved and variable domains of K88 adhesins in porcine colibacillosis. The adhesive region of the K88 adhesins was identified by the ability of certain Mabs to neutralize adherence of K88+ bacteria to porcine brush borders. An in vitro bacterial adherence assay showed that Mabs specific for the variable domains were able to completely neutralize adherence of the homologous variant of K88* E.coli, in a dose-dependent manner. The only neutralizing activity observed with the use of six -a specific (conserved) Mabs was partial neutralization by two of them of K88ad E.coli adherence to Phenotype C and D brush borders. Whole antibodies (Wabs) and Fab fragments (Fabs) of the variable domains behaved essentially identically in neutralizing adherence of K88* E.coli. Epitope mapping of antibodies to the variable domains showed that epitope to the adhesive region of K88 mapped partly in-band -c domains, and the entire -d domain of K88ab, K88ac, and K88ad adhesins, respectively. Our results indicate that the epi tapes to the adhesive region is mainly contained in the variable domain, however, the conserved domain may play a minor role. Anti-K88 serum developed to each of the three K88 variants was observed by immunodiffusion and seroagglutination assay to react against all the three K88 adhesins. Following cross absorption of whole anti-K88 serum with heterologous K88 variants to remove -a specific antibodies, the agglutination titer to the homologous variant decreased markedly, indicating that the main immune response was directed towards the conserved domain of the adhesins. Anti-K88 serum was able to inhibit the binding of Mabs to the homologous K88 variant, indicating that the Mabs share specificity with the anti-K88 serum for epitopes of the variable domains. Our results indicate that the majority of the immune response is directed at the conserved domain of E.coli K88 adhesins.

Library of Congress Subject Headings

Escherichia coli infections in swine
Swine -- Diseases




South Dakota State University



Rights Statement

In Copyright