Science Scene: In midst of ice cream recall, researchers work to improve gut health with listeria

Ellen Airhart

The bacteria listeria caused one of the worst events on campus in 2015 — the removal of Blue Bell ice cream from UT shelves. However, not everyone is avoiding the bacteria. Researchers at the UT Health Science Center at San Antonio are using listeria to make breakthroughs in colon cancer research.

Listeria monocytogenes is the species of bacteria found in the contaminated Blue Bell ice cream. Listeria monocytogenes triggers the foodborne illness listeriosis, which can lead to diarrhea and other stomach problems, and then fever and muscle aches. The most dangerous symptom of listeriosis is sepsis, an infection throughout the entire body, and meningitis, the swelling of the membranes around the brain and spinal cord. Pregnant women are about 20 times more likely than other healthy adults to get listeriosis. About a third of the babies who had mothers with listeriosis die. 

 But the presence of listeria in the intestines is not a death sentence. The symptoms of listeriosis only show if the immune system fails to stop the bacteria from reaching the blood and nervous system. About 70 percent of adults have listeria as part of their microbiome — the natural community of tiny organisms that live on and in the body. In the gut microbiome, there are trillions of bacteria with more than 3 million different genes.

Listeria flourishes in the gut, making it useful to researchers dealing with problems relating to the intestines. Tyrel Curiel and Peter Dube, researchers at the UT Health Science Center in San Antonio, received a grant to research how listeria could fight diseases such as colitis and colon cancer.

Curiel’s research focuses on B7 homologue 1 (B7-H1), a molecule that modulates, or influences, the microbiome. Curiel and his team were researching the effect of B7-H1 on mice tumors when they realized mice lacking B7-H1 were more likely to develop colon cancer. 

Dobe said when B7-H1 is not expressed in the human gut, patients suffer from an imbalance of the microorganisms that live there. This microbiome imbalance is
called dysbiosis.

“Gut bacteria affects your health generally,” Curiel said. “Good gut health could make you potentially age more slowly as well as help you fight Alzheimer’s and dementia.”

Curiel and Dobe have joined forces to create listeria, which carries genes that express molecules that interact with B7-H1 in order to maximize its effectiveness.

“The idea is to see whether we can improve gut health by modulating B7-H1 levels,” Dobe said. 

Scientists have devoted many resources to studying the human microbiome in recent years. In the Human Microbiome Project, a five-year initiative the U.S. National Institutes of Health launched in 2008, scientists tested how changes in the human microbiome relate to human health. 

Dobe said the modified listeria would not lead to listeriosis. Ironically, Curiel and Dobe plan to put the modified listeria in ice cream for easy and delicious patient consumption.

“These strains of listeria have proved safe in a variety of trials, so they would be safe to use on people,” Dobe said. 

Blue Bell removed its ice cream from shelves because listeriosis is a miserable and, at worst, deadly disease. With this research, there is hope that the same bacteria will someday help, rather than harm, the human body.