"This research reveals a detailed mechanism that allows interaction of Listeria with a cell-surface protein, or receptor, on intestinal cells," said microbiologist Arun Bhunia. "Knowing the entryway into the cell will allow us in the future to develop a method to prevent that interaction."
Bacteria have proteins, called ligands, which bind with a protein molecule, or receptor, on cells in the body, which is like placing a key in a lock. This interaction opens the door that leads to a complicated series of biochemical reactions. These reactions allow the pathogen to enter cells, in this case in the intestine, and then move on into the liver, spleen, brain or placenta, causing illness and possibly death.
The research team placed a Listeria protein known to bind with human host cells in a laboratory dish with human intestinal cells. They found that the bacteria's ligand bound with an intestinal cell surface protein, which they identified as heat shock protein 60 (Hsp60).Heat shock proteins are found in most cells. They are called chaperone proteins because they help other proteins stay organised when cells face any type of stress. Until recently, it was believed these proteins were only found in the mitochondria, the cells' engines.
Now that researchers know that these proteins also are found on cell surfaces and act as receptors, they will begin investigating how to control the infection process. The scientists used an anti-Hsp60 antibody, a built-in disease-fighting antibody that reduced Listeria's ability to bind with intestinal cells by 74 per cent.
"If interaction of these two molecules is the beginning of the infection's intestinal phase pathway that leads to illness, then we need to block them," Bhunia said. "Our focus now is to determine when and under what conditions the bacterium moves from intestinal cells into the system.
"If we understand the mechanism of how bacteria interacts with cells before causing damage and producing systemic illness, this may allow us to formulate a vaccination strategy to prevent the infection."
Listeria is responsible for about 2,500 recorded food-borne illnesses annually in the United States and is the deadliest food-borne disease, according to the Centers for Disease Control and Prevention. The study of the bacteria, conducted by researchers at Purdue University, was published in the February issue of the journal Infection and Immunity.