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These studies will improve the knowledge concerning the immune responses of cattle to E. coli O157:H7, and will determine the suitability of the Tir protein as a vaccine strategy.
Escherichia coli O157:H7 is a common cause of bloody diarrhea and life-threatening illness. Infection often results from the ingestion of undercooked groundbeef, which becomes contaminated at slaughter through contact of bovine feces with carcass surfaces. E. coli O157:H7 is highly prevalent in the feces of U.S. beef cattle. Strategies to reduce the prevalence of this organism are needed. One strategy is to vaccinate cattle with E. coli O157:H7 proteins that mediate bacterial attachment to cells that line the intestines of cattle;however, no studies have been done to determine whether these proteins actually mediate intestinal colonization in adult cattle (the main source of ground beef) or elicit protective immunity. This study will address both questions. The length of fecal shedding of E. coli O157:H7 bacterial strains that differ only by the ability to produce the translocated intimin receptor (Tir) protein will be studied in adult cattle. The study will also determine whether the levels of antibody to Tir are correlated with protection of adult cattle against E. coli O157:H7, and whether Tir immunization with or without prior recent infection will boost immunity and further reduce E. coli O157:H7 fecal shedding.