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The ultimate goal of this investigation is to develop an inexpensive, effective, easily administered vaccine to prevent cattle from becoming infected with E. coli 0157:147 so as to block transmission of these organisms to humans. Intimin is an outer membrane protein of E. coli O 157:147 that is required for colonization of neonatal calves. Therefore, it is hypothesized that an intimin-based vaccination strategy in calves might reduce colonization of cattle with E. coli 0157:147. To test this concept in a small animal model, transge nic tobacco plant cells that expressed the cell-binding domain of E. coli 0157:147 intimin were developed and then immunized mice parenterally with intimin expressed from the plant cells, or fed mice the transgenic plant cells, or both.
Status: It was previously shown that mice not only generate an intimin-specific mucosal immune response when primed parenterally and boosted orally with transgenic plant cell expressed intimin but also exhibit a statistically significant reduced duration of E. coli 0157: H7 fecal shedding after challenge.
Two lots of freeze-dried, intimin expressing NT-1 cells (the C34 clone) were shipped for verification of the antigen content (by Western) and then used for immunogenicity studies in calves.
Six calves (two in a fast group and four in a second) were fed the freeze-dried material in a milk replacer. Preliminary results indicate that all six animals had a detectable anti-intimin IgA response in their feces as measured by ELISA. (Please note: Results are being investigated to determine whether or not the fecal immune responses to intimin are only IgA or are IgA and IgG 1). The serum antibody responses to intimin in the orally vaccinated animals were minimal compared to the serum responses of calves immunized parentally with the
antigen. However, the latter animals had a minimal fecal antibody response.