Scientists at Purdue university have revealed a detailed mechanism that allows the interaction of Listera with a cell-surface protein, or receptor, on intestinal cells.
'Knowing the entryway into the cell will allow us in the future to develop a method to prevent that interaction," said Arun Bhunia in the department of food scientist at the university.
Jennifer Wampler, a postdoctoral student and lead author of the study, added : "Listeria is often implicated in patients with weakened immune systems, so we think that this research could also give us clues as to how other diseases work."
Bacteria have proteins, called ligands, that 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.
Listeria, with a 20 per cent fatality rate, is considered to be one the most deadly foodborne diseases and is responsible for about 2,500 recorded foodborne illnesses annually in the US alone.
The Purdue 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 are also found on cell surfaces and act as receptors, they will begin investigating how to control the infection process.
For the study - published in the February issue of Infection and Immunity - the Purdue researchers 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."
The Purdue researchers plan to study whether the Hsp60 is more abundant in the intestine and also in people most at risk from Listeria-caused foodborne disease, such as pregnant women or HIV patients.