Certain maternal infections during pregnancy have been previously linked to foetal damage and the risk of neural development disorders, including cytomegalovirus and rubella. Now, a team of microbiologists have speculated that infection with the HSV-2 strain of herpes may similarly contribute to the development of autism spectrum disorder (ASD) in male children.
The report, published in the journal for the American Society of Microbiologists, studied 442 mothers of children with ASD from 1999 to 2008, testing against a total of 464 frequently-matched controls. Blood tests were used to verify the presence of antibodies to five viruses that are known to damage foetuses - including rubella, HSV-1 and HSV-2.
Higher levels of HSV-2 antibodies during mid-pregnancy were found to be associated with a doubled risk that a male baby would be diagnosed with ASD. The same conclusion could not be drawn with female children as there were too few in the study. Read more: What is autism spectrum disorder? WIRED explains
The study argues that it is not the herpes virus itself that triggers autism, but the intense immune response it causes. The theory is that inflammatory molecules and antibodies generated by the mother's immune system can potentially cross the placenta and affect the development of the foetal brain.
However, these results were found in a group of women who were already genetically predisposed to ASD, meaning the pregnancies involved in the trial were a particularly vulnerable group. The lack of female children complicates the findings further. What's more, the scientists involved in the study said the presence of the active HSV-2 infection was merely one of a variety of environmental triggers that could potentially increase the likelihood of developing ASD.
Senior author Ian Lipkin claims HSV-2 is not “responsible for infecting the [foetal] brain and causing autism,” but it is one of many factors that could affect foetal development.
Peter Hotez, a vaccine scientist and pediatrician at Baylor College of Medicine in Houston, Texas, told Science magazine that "the changes in the architecture of the neocortex in the brains of kids with autism are so profound that it’s hard to imagine how an inflammatory response, even in utero, is going to cause that.”
The specific causes of autism are still unknown, but many believe a combination of genetic factors play a role. The condition occurs more often in people who have certain chromosomal conditions, such as fragile X syndrome or tuberous sclerosis, and is more common in men than in women. While the cause is still unknown, increased research into ASD in recent years is vital to understanding the condition and developing strategies to best help those affected.
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This article was originally published by WIRED UK
