The Role of Infections in Autism

Summary:

We already know that inflammation causes damage to the DNA and to the brain, but inflammation does not occur for no reason. The most common trigger for inflammation that may affect children from every country, from big cities, and from small villages, children of very young and old parents, now and 40 years ago - is an infection. Infections may be of different types: very short bacterial infections, severe influenza virus infections and life long infections caused by latent herpes viruses. The common characteristic is that they all trigger inflammation. 

There are hundreds of published articles that show the association between maternal infection of any type during pregnancy and autism in children. There were experiments showing that laboratory animals that were infected with viruses during pregnancy give birth to mice with autistic phenotype. It is an infection that triggers this complex mechanism starting with inflammation and leading to a cascade of events: damage and alteration of genes, brain alterations, immune system aberration, and gastrointestinal problems. 

 

The Role of Infections in Autism

An overwhelming number of publications show a wide range of infectious agents that are suspected to play a role in the initiation and development of ASD:

In a Swedish study of 2019, involving 1.8 million children, it was proved that any viral infection during pregnancy significantly increases the likelihood of autism in a child.


In a Danish study that analyzed all children born in Denmark from 1980 to 2005, it was found that hospitalization due to viral infection in the mother in the first trimester and bacterial infection in the mother in the second trimester were associated with a subsequent diagnosis of ASD in a child. 


In another large Israel study of 1996, it was found that there is a positive correlation between the birth of autistic children and the epidemics of measles and viral meningitis in the mother.

 

 

Apart from this, genetic changes in mouse brain cells, similar to those in ASD and schizophrenia, have been shown to be a result of maternal immune activation (mIA) due to inflammation caused by a viral infection. In a study involving monkeys, monkeys manifested autistic behavior if their mothers experienced immune activation during pregnancy.


In another study, it was shown that newborn rats inoculated with a disease virus inside the brain showed an autistic phenotype and had similar changes in blood levels with elevated levels of TNF-alpha, IL-1 alpha and IL-1 beta.

Moreover, viral infections have the ability to directly damage DNA. 

In one study, a mechanism, that showed the direct effect of viral infection on enhancing the activity of 21 genes and suppressing the activity of 18 genes in the brain, was shown. According to this study, these gene changes led to patterns of autism and schizophrenia.


Due to the fact that their genome is similar to the human one, DNA viruses (such as herpesviruses) are able to embed fragments of their DNA into the carrier’s DNA, thereby disrupting the immune system, so that it does not react to the presence of the virus.

 

However, such micro changes, in turn, affect the expression of genes responsible for other functions. In particular, if the virus infected the brain, then by inserting its DNA into the brain cells DNA, the virus directly affects brain formation and functioning.

Some viruses, such as herpesviruses or rubella virus cannot be completely treated, they only can be suppressed. Since not much attention is paid to these viruses in children with autism, they are not controlled. 

As a result, chronic infections create "a vicious circle", in which the virus constantly causes inflammation, inflammation constantly affects genes and brain, while the weakened immune system cannot suppress the virus and this cycle of events continues year after year.

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