Interactions of the bacterial pathogen Listeria monocytogenes with mammalian cells: bacterial factors, cellular ligands, and signaling.

Listeria monocytogenes is a food borne pathogen which has the very unique property of crossing three barriers during infection eliciting meningitis, meningo-encephalitis and abortions with a mortality rate of about 30%. Indeed, after crossing the intestinal barrier, Listeria disseminates via the lymph and the blood, to the brain and/or the placenta after crossing the brain-blood barrier and/or the placental barrier. During disease, this organism infects a variety of tissues and cell types in which it is mostly intracellular due to its capacity to induce its own phagocytosis into cells which are normally nonphagocytic. The strategies used by Listeria to enter cells are different from those used by other well known invasive pathogens. Listeria thus appears as a fine model to study the molecular and cellular basis of bacterial invasion. In addition, not only during entry into cells but also during intra- and intercellular movement, Listeria exploits mammalian cell functions and is thus a novel tool for elucidating some unsolved fundamental aspects of cell biology, such as ligand receptor signaling and actin cytoskeleton rearrangements. In this review, the molecular and cellular basis of entry of Listeria into cells and of its intracellular motility will be discussed.