The human antibody response to infection with Verocytotoxin-producing Escherichia coli.

Jenkins, Claire (2000). The human antibody response to infection with Verocytotoxin-producing Escherichia coli.. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f982

Abstract

Strains of Verocytotoxin-producmg Escherichia coli (VTEC) are inportant food and water-borne pathogens causing gastroenteritis, and in more severe cases, haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS), Hie antibody response of patients infected with VTEC 0157 to the lipopo lysaccharide (EPS) of this organism has been well-characterised, however, the antibody response to other putative pathogenicity factors expressed by VTEC is poorly understood. The aim of this research was to characterise a range of bacterial components, including Verocytotoxin (VT), EPS, enterohaemolysm, H7 flagella antigen, fimbriae and proteins encoded by the locus of enterocyte effacement (LEE) pathogenicity island, and to assess the humoral antibody response to these components. Antibodies to VT could not be detected in patients infected with VTEC using immunoblotting, and patients could not be distinguished from healthy blood donors using a VT-based ELISA. Patients infected with different serogroups of VTEC produced antibodies to the homologous EPS, but sera from healthy blood donors were also found to contain antibodies to the EPS of two common VTEC serogroups. The detection of antibodies to the EPS of VTEC 0157 in saliva demonstrated the possibility of developing a non-invasive diagnostic technique. Most patients infected with VTEC produced antibodies to the LEE-encoded proteins expressed by strains of VTEC 0157 and other VTEC strains associated with human infection. The antibody response of patients infected with VTEC to the LEE-encoded proteins contributed towards our understanding of the role of each protein in the pathogenicity of strains with the AE phenotype. Certain strains produced a haemolysin under specific growth conditions, termed enterohaemolysin. The haemolysin phenotype varied between strains of VTEC and certain strains may produce other haemolysins in addition to enterohaemolysin. Few patients produced antibodies to enterohaemolysin or the H7 flagella antigens. Strains of VTEC 0157 did not express fimbriae, and all but one strain of VTEC other than 0157 expressed type 1 fimbriae. Variations in haemolysin expression and the types of fimbriae produced reflect the diversity of the VTEC group. The antibody response of patients infected with VTEC appears to be mainly directed at EPS and certain LEE-encoded proteins. Detection of these antibodies in patients’ sera would provide good evidence of VTEC infection.

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