Submitted to: International Symposium and Workshop on Shiga Toxin ... Escherichia coli
Publication Type: Abstract Only
Publication Acceptance Date: June 26, 1997
Publication Date: N/A
Technical Abstract: We are exploring the bovine immune response to Escherichia coli O157:H7 in order to develop vaccination strategies to reduce fecal shedding of this pathogen in cattle. Three groups of calves were studied. One group was orally vaccinated with an E. coli O157:H7 variant that does not express Shiga-like toxins (SLT) I or II, a second group with wild-type (wt) E. coli iO157:H7 (SLT II**+), and a third group with a nonpathogenic strain of E. coli. All calves were subsequently challenged with wt O157:H7 three weeks after a second vaccination. Prior exposure to wt 0157:H7 or the SLT**- variant did not reduce fecal shedding of wt O157:H7 upon challenge. All calves developed antibodies to O-antigen. Peripheral blood mononuclear cells (PBMCs) isolated from the calves vaccinated with the SLT**- strain proliferated in response to heat-killed O157:H7, while PBMCs from calves vaccinated with wt O157:H7 or control strain did not. These findings support the hypothesis that SLT II has an immunosuppressive effect which future vaccination efforts will need to address.