Anti-invasive activity of bovine lactoferrin against Listeria monocytogenes

We have investigated the possible role of bovine lactoferrin in protecting the intestinal epithelium from bacterial infections, using as an in vitro model enterocyte-like cell lines HT-39 and Caco-2 infected with a food-borne pathogen, Listeria monocytogenes. When infection occurred in the presence of 1 mg/ml of bovine lactoferrin, in the form of apolactoferrin or iron- or manganese-saturated forms, the adhesion of bacteria to eukaryotic cells was unaffected, but the number of internalized bacteria was reduced by 42- to 125-fold. The possibility of a toxic effect of lactoferrin was excluded, because bovine lactoferrin was used at nonbactericidal and noncytotoxic concentrations.