Friendly Gut Bacteria Aid Immune System in Fighting off Infection

Research published by scientists at UT Southwestern Medical Center has found that bacteria present in the human gut help initiate the body’s defense mechanisms against Toxoplasma gondii, a nasty parasite responsible for toxoplasmosis. While generally considered to be mild, a T gondi infection can have serious and potentially fatal effects in pregnant women, their fetuses and anyone else with a weakened immune system.

How it is that the body first senses the presence of this parasite has been somewhat of a mystery for a long time. But in this new UT Southwestern study (appearing online and in the Aug. 20 issue of Cell Host & Microbe), researchers suggest that instead of activating receptors directly, T gondii’s first interaction in the human gut is with the helpful bacteria that live inside us. Those bacteria then release signaling molecules, alerting the human host to the invader.

What an important role this is for those friendly, probiotic gut bacteria that we need to have living inside of us! This is why it is a travesty that antibiotics are so overprescribed and that we so often casually knock out our entire flora for no good reason at all.

“While this is very early data, our results suggest that looking at the bacteria present in each patient’s gut could help physicians understand their susceptibility to infectious diseases,” said Dr. Felix Yarovinsky, assistant professor of immunology at UT Southwestern and senior author of the paper. “It also suggests the possibility of developing novel probiotic strategies for treating parasitic infections."

T gondii affects more than 1 billion people worldwide. The protozoan parasite can infect most warm-blooded animals, but the primary host is the house cat. Animals are generally infected with T gondii by ingesting contaminated meat, water or the feces of a cat that has recently been infected; however, the parasite also can be passed from mother to fetus.

Toxoplasmosis is often passed to humans through contaminated cat feces; therefore, pregnant women are encouraged to keep all house cats indoors and recruit someone who is not pregnant to clean the litter box daily. Once a person is infected, the parasite penetrates the intestine and spreads throughout all organs.

Dave