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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. The carboxy-terminal portion of intimino157 of E. coli 0157:147 is being used as the immunogen for such a vaccine because: i.) antibodies against this portion of the outer membrane protein adhesin block adherence of the microbe to tissue culture cells and in a mouse model of colonization, ii.) this portion of intimino157 has been plant optimized to increase expression of the protein in plant expression systems.
The project was briefly delayed when it was discovered that the carboxy-terminal portion of intimino157 was being glycosylated in the plant cell system. In E. coli 0157:147, intimino157 is not glycosylated. The gylcosylation of the protein was the result of an aberrant immune response that was unable to block colonization of E. coli 0157:147. This problem has been remedied and a new plant cell clone expressing an unglycosylated carboxy-terminal portion of intimino157 is currently being characterized. In collaboration with Dr. Wayne Curtis of Penn State University, production of the plant cell clone expressing the plant-optimized carboxy-terminal portion of intimino 157 is being scaled-up. Previous studies have shown that mice fed plant cells expressing intimino157 make an antibody response that blocks adherence of E. coli 0157:147 to tissue culture cells. In addition, lab results have shown that mice immunized intraperitoneally with purified carboxy-terminal portion of intimino 157 are not colonized to the same extent as non-immunized mice. These results suggest that an orally-delivered vaccine comprised of the carboxy-terminal portion of intimino 157 can function in blocking adherence of E. coli 0157:147 in the mouse model of E. coli 0157:147 colonization.