Scientists develop listeria vaccine: study

WASHINGTON (Reuters) - Scientists have developed a vaccine for the food-borne listeria that they hope to apply to more common illnesses like salmonella and tuberculosis, a researcher said on Monday.

Listeriosis caused by infection with the Listeria monocytogenes, which is common in wild and domesticated animals, and in soil and water. L. monocytogenes infection also a common cause of miscarriage and stillbirth. It commonly occurs as a food-borne contaminant.

The vaccine attacks the listeria bacteria inside a human or animal cell, but doesn't replicate the disease, said Darren Higgins, associate professor of microbiology at Harvard Medical School.

Listeria is potentially fatal and can cause high fever, severe headache and nausea. It is an intracellular bacterial pathogen, hiding and multiplying within the cell walls instead of attaching itself to the outside.

"We made a vaccine strain of listeria that can no longer replicate inside a host cell," Higgins said.

Instead, it stimulates T-cells, naturally occurring cells that can multiply to identify and kill infected cells, he said in an interview.

"It does not cause disease in the animal models that we tested. But it stimulates these T-cell responses, so, now, if we come back and challenge that mouse with a disease strain of listeria, that mouse does not get sick," said Higgins, whose study appeared Monday in the Proceedings of the National Academy of Sciences.

Higgins said he and H.G. Archie Bouwer, immunology research scientist at the Portland VA Medical Center, hope to apply the same method to salmonella and tuberculosis, which occur more frequently in the population.