Maternal Infection, Autism and the Bacterial Microbiome

I posted a news story about the latest autism/microbiome findings a couple of weeks ago, but saw this article[i] today in Spectrum magazine and thought it worth writing about as it really is important research.  I’m sure too it has implications beyond autism.

Ultimately – from 4 major pieces of research – we now know how maternal immune activation may lead to autism in children.  (We already knew, from epidemiological studies, that autism risk increases by 37% in cases of maternal infection.)

1. In 2014, a study showed that children with autism have patches of immature neurons in the cortex of their brains.
2. In 2016, researchers found this same “anatomical oddity” in mouse pups who’d been exposed to infections while in utero.
3. The latest study shows that these neurons are over-active, potentially causing autism-like behaviors in the mice. (This confirms too one of the main theories of autism:  “…too much excitation in brain signals relative to inhibition.”)
4. A 2^nd paper, in the same issue of Nature, showed that these brain patches and subsequent behavioral problems could be prevented by giving the pregnant mice vancomycin, an antibiotic.

“This finding implicates gut bacteria in the effects of maternal inflammation on the developing brain.”

HOLY COW.

More on #3 above:  Pregnant mice were essentially infected with a virus. The researchers then measured the amount of time their pups spent burying marbles and interacting with unfamiliar mice, both of which are good equivalents to the repetitive behaviors and social issues seen in autism.  They also looked at the pups’ brains for a protein called parvalbumin, which is a marker for a class of neurons that inhibit brain activity.  In the pups born of infected mothers, patches of neurons lacked paravalbumin.  And those pups with large patches in a part of the brain that processes touch, temperature and pain spent more time burying marbles and interacting with other mice.

When the pregnant mice were given vancomycin, which kills a certain kind of gut bacteria, the pups were normal at birth.  These bacteria stimulate the production of immune cells that produce interleukin-17A (IL17-A).  There are equivalent types of bacteria in humans.  Says the lead research on the #4 article, “Gut bacteria in maternal intestines play a critical role in shaping brain development in fetuses when mothers are exposed to inflammation.”

I remember well picking up a really bad cold in my 3^rd trimester of pregnancy with Alex. And I’ve suffered IBS my entire life too, after a childhood filled with antibiotics.  I’ve always felt that my gut health (or lack thereof), led to my own autoimmune illnesses, and was tied in to Alex’s autism.  (Thus, my obsession with what grows in our gut – and thus, this blog.) Finally, I feel like there has been some major progress on the environmental cause of this autism epidemic.  Not that this is the complete answer, of course. I mean, women have always had infections during pregnancy.  The big question that remains is….what is causing this alteration in gut bacteria in moms that leads to changes in brain development in our babies?  Still, this I just a huge step in the right direction.

Now if only we knew how to treat those parvalbumin-free patches AFTER birth.

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[i] https://spectrumnews.org/news/maternal-infection-may-trigger-autism-traits-via-neuronal-patches/