Scientists have been grappling with the puzzle of the origins of autism for decades – now a study suggests that a bad cold or flu during pregnancy could be a cause.
They have shown that when the mother’s immune system is boosted in response to a viral infection, it can hinder the developing baby’s brain development.
Female embryos appeared to be protected from these effects, but according to research on mice, a third of male embryos were affected to some extent.
This is consistent with autism being more common in boys than girls, according to the team from Cold Spring Harbor Laboratory (CSHL) in New York.
Researchers have discovered that autism can develop while a fetus is in the womb. When a pregnant woman gets a bad cold or flu, her immune response can trigger a neurological reaction in the baby’s brain
Researchers simulated a viral infection in mice and monitored the fetus’s response to how the mother’s immune system responded to a cold or flu virus, known as maternal immune activation (MIA).
MIA is activated when the immune system kicks into high gear, increasing levels of cytokines and chemokines that can cross the placenta and the baby’s blood-brain barrier.
Chemokines fight the flu by moving other immune cells, such as cytokines, to the site of the infection.
Cytokines are small immune cells that fight harmful pathogens by summoning other immune cells to create symptoms such as fever, runny nose and body aches.
Because a fetus’s brain is so sensitive to environmental cues in the womb, this response can cause a wide range of behavioral problems, including social disabilities such as autism spectrum disorder.
Irene Sanchez Martin, a postgraduate student at CSHL, said her recent experiments with mice showed that when the mother contracted a virus, the embryo’s brain development slowed.
‘The difference in my work is that I monitor what has happened to the fetus 24 hours after exposure to the maternal inflammation, rather than analyzing the behavior of the offspring as adults.’
Sanchez Martin focused on how prenatal inflammation caused by a cold or flu affected the brain of the developing fetus.
Prenatal inflammation has been linked to causing dysfunction in the brain of the growing fetus and may affect the way it organizes the neural networks that connect cells and synapses.
If these are disrupted, the number of neurons and synapses in the brain can decrease, which has been linked to the development of autism in humans.
One of the most important breakthroughs showed that although female embryos appeared to be protected from the MIA, about a third of male embryos showed signs of brain development deficits consistent with autism.
Additional research needs to be done to unravel the link between the immune system’s response to a virus and its impact on the fetus.
More than 5.4 million people in the US are currently diagnosed with autism and 40 to 80 percent are likely related to genetics, but that still means 20 to 60 percent are caused by other factors.
Early diagnosis is crucial in autism because there are currently no treatments and it takes years to test and diagnose the disorder.
Sanchez Martin said her research is still in the early stages and more work needs to be done to definitively link cold and flu viruses to autism.
However, she is hopeful that future findings can help doctors recognize the early warning signs of autism before a child is born.