<OL> <LI> Investigate the role of p60 and serotype 4b specific surface antigens in the ability of L. monocytogenes to colonize and grow on RTE meat products (effort to be led by Dr. Luchansky and Dr. Kathariou). <LI>Evaluate the interaction between P-glycoprotein and these surface antigenic determinants in the ability of L. monocytogenes to attach to, invade, and multiply in human intestinal epithelial cells (coordinated amongst the Kathariou, Neudeck and Czuprynski laboratories). <LI>Investigate whether these determinants are required for virulence in the gastrointestinal tract using a mouse model, and whether the administration of specific antibodies, or the generation of such antibodies during immunization or infection, might protect against gastrointestinal infection with L. monocytogenes (coordinated by the Kathariou and Czuprynski laboratories).
APPROACH: To investigate the role of target molecules in attachment to RTE meats, both wild-type and mutant strains of L. monocytogenes deficient in p60 or in the serotype 4b-associated antigens will be inoculated into packages of frankfurters. Isogenic mutant strains have already been constructed. Packages will be stored at refrigeration and abuse temperatures and sampled throughout the shelf life of the product for viable listeriae. Next, isogenic mutants deficient in serotype 4b-associated surface antigens will be used in cell culture assays with fully differentiated Caco-2 cells to assess their potential for adherence, invasion, and intracellular growth. The mutants deficient in serotype 4b surface antigens will also be used to intragastrically inoculate genetically susceptible A/J mice to assess their ability to cause infecetion. For both the cell line and mouse challenge studies, the experiments will be performed in the presence and absence of monoclonal antibodies specific for the surface antigens.