Thimerosal increases risk of autism-like damage in autoimmune disease susceptible mice

Kofi kofi at anon.un
Sun Jun 20 23:30:20 EST 2004


   Molecular Psychiatry

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Thimerosal, Found In Childhood Vaccines, Can Increase The Risk Of 
Autism-like Damage In Mice

A new study indicates that postnatal exposure to thimerosal, a mercury 
preservative commonly used in a number of childhood vaccines, can lead 
to the development of autism-like damage in autoimmune disease 
susceptible mice. This animal model, the first to show that the 
administration of low-dose ethylmercury can lead to behavioral and 
neurological changes in the developing brain, reinforces previous 
studies showing that a genetic predisposition affects risk in 
combination with certain environmental triggers. The study was conducted 
by researchers at the Jerome L. and Dawn Greene Infectious Disease 
Laboratory at the Mailman School of Public Health, Columbia University.

Over the past 20 years, there has been a striking increase--at least 
ten-fold since 1985--in the number of children diagnosed with autism 
spectrum disorders. Genetic factors alone cannot account for this rise 
in prevalence. Researchers at the Mailman School, led by Dr. Mady 
Hornig, created an animal model to explore the relationship between 
thimerosal (ethylmercury) and autism, hypothesizing that the combination 
of genetic susceptibility and environmental exposure to mercury in 
childhood vaccines may cause neurotoxicity. Cumulative mercury burden 
through other sources, including in utero exposures to mercury in fish 
or vaccines, may also lead to damage in susceptible hosts. Timing and 
quantity of thimerosal dosing for the mouse model were developed using 
the U.S. immunization schedule for children, with doses calculated for 
mice based on 10th percentile weight of U.S. boys at age two, four, six, 
and twelve months. 

The researchers found the subset of autoimmune disease susceptible mice 
with thimerosal exposure to express many important aspects of the 
behavioral and neuropathologic features of autism spectrum disorders, 

* Abnormal response to novel environments; 

* Behavioral impoverishment (limited range of behaviors and decreased 
exploration of environment); 

* Significant abnormalities in brain architecture, affecting areas 
subserving emotion and cognition; 

* Increased brain size. 

These findings have relevance for identification of autism cases 
relating to environmental factors; design of treatment strategies; and 
development of rational immunization programs. The use of thimerosal in 
vaccines has been reduced over the past few years, although it is still 
present in some influenza vaccines. Identifying the connection between 
genetic susceptibility and an environmental trigger for autism--in this 
case thimerosal exposure--is important because it may promote discovery 
of effective interventions for and limit exposure in a specific 
population, stated the lead author Dr. Mady Hornig. Because the 
developing brain can be exposed to toxins that are long gone by the time 
symptoms appear, clues gathered in these animal models can then be 
evaluated through prospective human birth cohorts--providing a powerful 
to tool to dissect the interaction between genes and the environment 
over time. 


Citation source: Molecular Psychiatry 2004 Volume 9, advance on line 
publication doi:10.1038/sj.mp.4001529 

ARTICLE: "Neurotoxic effects of postnatal thimerosal are mouse 

M Hornig, D Chian, W. I. Lipkin 

Greene Infectious Disease Laboratory, Mailman School of Public Health, 
Columbia University, 722 W 168th St, New York, New York 10032 


Molecular Psychiatry is published by the Nature Publishing Group. 


This story has been adapted from a news release issued by Molecular 

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