Invasion of a Body Snatcher
New research by French scientists has revealed how Listeria monocytogenes can activate the cellular transport machinery that transports viruses and small molecules and proteins and use it to invade cells and hide from the body's immune system. Once the microbe has safely entered a cell it can replicate and continue the infection process. The harmful Listeria monocytogenes pathogen can be found in foods such as soft cheese and processed meat products, notably in those kept refrigerated for a long period where the pathogen can grow at low temperatures. Cooking destroys most of the cells that can grow at refrigeration temperature but the problem lies in that consumers do not always cook ready-to-eat products such as fermented sausages and smoked fish before consumption. The body usually protects itself from bacteria and other foreign microbes thanks to a process called phagocytosis. A second process known as endocytosis is used by the cells against smaller molecules and viruses. Pascale Cossart at the Howard Hughes Medical Institute in Massachusetts and her colleague Esteban Veiga at the Pasteur Institute in Paris observed that Listeria - which is 20 times the size of the largest particle scientists believed a cell could absorb by endocytosis - could invade non-phagocytic cells. By manipulating the gene expression of the cells Listeria was invading, they established that specific molecules proven to be involved in endocytosis were essential for successful invasion by Listeria. According to Cossart, Listeria's use of receptor-mediated endocytosis to infect hosts suggests that other bacteria may make use of the same mechanism to gain entry into non-phagocytic cells.