Listeria monocytogenes(Listeria) is an invasive pathogen among dairy cattle and can cause infection of multiple organs resulting in abortion or mortality. Interestingly, Listeria also colonizes many adult cattle without causing clinical symptoms. It is completely unknown what bacterial or bovine factors keep Listeria infection in check, and what factors drive the progression from asymptomatic to lethal infection. The overall goal of our project is to understand how Listeria colonizes the bovine gut, since it is a determinant of infection outcomes. Specifically, we will:i)investigateListeriareplication in the bovine gut and and dissemination in the gut tissue, and ii) determinethe bovine immune responses to Listeria infection. Our experimental infection model will examine Listeria strains that have been collected from dairy cattle.