ANTIBODIES TO LISTERIA-MONOCYTOGENES

Listeria monocytogenes is one of the leading foodborne pathogens and h as been implicated in numerous outbreaks in the last 2 decades. Immuno compromised populations are usually the most susceptible to Listeria i nfections. Although the pathogenic mechanism is a complex process, sig nificant progress has been made in unravelling the mechanism in recent years. It is now clear that numerous extracellular and cell-associate d proteins, such as internalin, listeriolysin, actin polymerization pr otein, phospholipase, metalloprotease, and possibly p60 proteins, are essential for L. monocytogenes entry into mammalian cells, survival in side the phagosome, escape into the cytoplasm, and cell-to-cell spread . Other proteins may be responsible for growth and physiology or to ma intain the structural integrity of the bacteria. Monoclonal and polycl onal antibodies have been developed against many of those antigens or their synthetic derivatives that have helped greatly to determine the structure and function of these antigens. The antibodies were also use d for the diagnosis and detection, immunocytochemical staining, and se rotyping of Listeria. Humoral immune response to live L. monocytogenes cells was examined in naturally or experimentally infected hosts. Stu dies revealed that only extracellular antigens induced the humoral res ponse, whereas cell-associated antigens had apparently no response. It is speculated that during the occasional bacteremic phase, L. monocyt ogenes releases extracellular antigens that are then processed by the immune system for antibody production. As L. monocytogenes is an intra cellular pathogen, the cell-associated antigens are not persistent in the blood circulation and thus fail to stimulate the humoral immune re sponse.