Abnormal brain growth and function are features of autism, an increasingly common developmental disorder that now affects 1 in 60 boys in the US. Now researchers from the University of Pittsburgh and Thoughtful House Center for Children in Austin, Texas, have found remarkably similar brain changes to those seen in autism in infant monkeys receiving the vaccine schedule used in the 1990’s that contained the mercury-based preservative thimerosal.
The group’s findings were published yesterday in the journal Acta Neurobiologiae Experimentalis. They used scanning techniques that assessed both brain growth and brain function in the same animals over time. The research team was able to see differences in the way the brains of vaccinated and unvaccinated animals developed. Scans were performed before and after the administration of primary MMR and DTaP/Hib boosters that were given at the human equivalent of 12 months of age.
Throughout the study period, vaccinated animals showed an increase in total brain volume – a feature of the brain in many young children with autism - when compared with unvaccinated animals. However, a specific part of the brain associated with emotional responses that is thought to be important in autism, the amygdala, did not show abnormalities until after the 12-month vaccines had been given. In addition, after the 12-month vaccines only, the functional brain scans showed significant differences between vaccinated and unvaccinated groups. These functional scans looked at the activity of receptors for morphine-like compounds (opioids) that may play a role in the brain of children affected by autism. Vaccine administration was associated with an increase in opioid binding activity in the amygdala compared with a decrease in the unvaccinated group.
The results indicate that multiple vaccine exposures during the previous 3-4 months may have had a significant impact on brain growth and development in ways that are consistent with the published data on autism. For the amygdala, the novel findings of abnormal growth and function appear to be a function of more recent vaccine exposures - the 12-month primary MMR vaccine and the DTaP and Hib boosters.
In an accompanying editorial Dr. Kris Turlejski, the Editor-in-Chief, described the findings as “alarming”, “support[ing] the possibility that there is a link between early immunization and the etiology of autism.”
In the same primate model, the research team has already identified delayed acquisition of vital brainstem reflexes in infants exposed to the thimerosal-containing hepatitis B vaccine on the first day of life, compared with unvaccinated animals. A larger, second phase study is currently underway to see if these findings can be replicated.
Dr. Andrew Wakefield, who is not a listed author but whose support in the design of the study is acknowledged, said “I hope the model will not only provide important insights into the origins of autism, but also ways of safely testing possible new autism treatments and vaccines.”
References:
Laura Hewitson, Brian J. Lopresti, Carol Stott, N. Scott Mason, and Jaime Tomko. Influence of pediatric vaccines on amygdala growth and opioid ligand binding in rhesus macaque infants: A pilot study. Acta Neurobiol Exp 2010. 70: 147–164
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