UC Davis researchers believe they have discovered the cause of as much as 23 percent of autism cases, pinpointing antibodies in some mothers that attack proteins needed for fetal brain development.
Mothers of some children with autism were more than 21 times as likely to have the specific antibodies in their blood as mothers who did not have autism, according to the study, published online Tuesday by the journal Translational Psychiatry.
The discovery could lead to a diagnostic test for women considering pregnancy that could predict a child’s chance of developing what the researchers are calling “maternal autoantibody-related” (MAR) autism.
Such a test could lead to more accurate diagnosis of children with autism and to the development of a drug capable of blocking the antibodies, protecting the brain of a fetus.
“We hope that, one day, we can tell a mother more precisely what her antibody profile means for her child, then target interventions more effectively,” principal investigator Judy Van de Water of the MIND Institute said in a news release.
A separate, related study, also published Tuesday by the same journal, found that exposure to the maternal antibodies affected the behavior and development of rhesus monkeys.
In 2008, Van de Water’s team identified antibodies in women that increased the risk of having a child with autism. Genetic factors and prenatal viral infections are among the other known causes of autism spectrum disorders.
The team’s new work revealed the mothers’ antibodies targeted seven antigens, all substances that play roles in neurodevelopment. Mothers with antibodies reacting to any of the seven were found to be more than three times more likely to have a child with autism.
The researchers used blood samples from 246 Northern California mothers of children with autism and a control group 149 mothers of typically developing children.
Some combinations of antibodies were not found in any of the mothers in the control group.
As early as 13 weeks, maternal antibodies can be detected in a fetus. If they act against the body’s own tissue, rather than to ward off bacteria or viruses, they are called autoantibodies.
“It is important to note that women have no control over whether or not they develop these autoantibodies, much like any other autoimmune disorder,” Van de Water said. “And, like other autoimmune disorders, we do not know what the initial trigger is that leads to their production.”
UCD has patented the test technology and licensed development rights to Pediatric Bioscience Inc. of Sacramento.
The study’s other authors are: Daniel Braunschweig, Paula Krakowiak, Paul Duncanson, Robert Boyce, Robin Hansen, Paul Ashwood and Irva Hertz-Picciotto, all of UCD.
For the monkey study, groups of pregnant monkeys were injected with specific antibodies from mothers of children with MAR autism or antibodies from mothers of children without autism.
A team led by Melissa Bauman, a MIND Institute faculty member, evaluated the behavioral development of the monkeys’ offspring and conducted magnetic resonance imagining of their brains during their first two years.
They found the monkey mothers treated with the autism-related antibodies were more protective of their young when other monkeys were pregnant, indicating the mothers perhaps sensed a greater risk to their young, Bauman said in a news release.
Such offspring more often approached other infants in their rearing group and, later, made approaches to unfamiliar peers — “highly unusual and potentially dangerous for young rhesus monkeys.”
Though they approached their peers more often, their peers groomed them less often.
“It is possible that there were subtleties in the demeanor of the (offspring of treated mothers) that dissuaded their peers from interacting with them,” Bauman said.
MRI analysis of their brains revealed that brain growth was faster in the males among them, compared to control offspring. Total brain volume of the males also was greater than normal.
UCD researchers have found similar abnormal brain development in male children of mothers with the autism-related antibodies.
Other study authors were Van de Water, Braunschweig, Aaron Lee, Cynthia Schumann and David Amaral of UCD.
— Reach Cory Golden at firstname.lastname@example.org or 530-747-8046. Follow him on Twitter at @cory_golden