Gut worms protect babies' brains from inflammation

http://www.eurekalert.org/pub_releases/2015-07/du-gwp072015.php

Public Release: 20-Jul-2015
Duke University

A Duke University study in rats finds that gut worms can protect babies' brains from long-term learning and memory problems caused by newborn infections.

Baby rats with tapeworms avoided the brain inflammation that plagued worm-free rats after exposure to immune triggers in adulthood.

What's more, the benefits began early, while still in the womb. Expectant mother rats with tapeworms passed similar protection on to their worm-free pups, the researchers found.

The findings could point to new ways to treat or prevent the chronic brain inflammation linked to cognitive disorders like Alzheimer's disease, autism and depression.

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Previous studies by Duke neuroscientist Staci Bilbo and colleagues showed that when rats get bacterial infections at a very early age, even elsewhere in the body, immune cells in their brains become hypersensitive to subsequent infections and pump out a continuous stream of messenger molecules called cytokines that can cause cognitive problems later in life.

But for Bilbo, who is an associate professor of psychology and neuroscience and a member of the Duke Institute for Brain Sciences, something didn't quite add up. Given how frequently bacterial infections strike, it was still unclear why a single infection at the wrong time would send the brain's immune cells into permanent overdrive.

"We have faced bacterial infections throughout our entire evolutionary history, presumably also during the neonatal period," Bilbo said. "It always seemed kind of strange that the immune system would have evolved to overreact like that."

That got Bilbo thinking. "Maybe this isn't how the immune system evolved to work," she said.

According to what scientists call the "Biome Depletion Theory," some autoimmune and inflammation-related diseases may be the result of too few of the life forms that once lived in and on the body -- particularly gut worms -- rather than too many.

Tapeworms, roundworms and other wormy companions have inhabited the warm wet folds of animal intestines for more than 100 million years, bathing in a constant supply of food and nutrients.

Over millions of years of co-existence, the theory goes, the immune system learned to tolerate these live-in guests, and eventually adapted to work with worms in mind.

The theory is that now, with worms gone from our guts, the body's natural defenses can spiral out of control.

"Our bodies are essentially an ecosystem," said Duke immunologist and study co-author William Parker.

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