Maternal Immune Activation (MIA)

While we know that most psychiatric disorders have a strong genetic component, we equally know that none are purely determined by genetic factors alone. Studies in monozygotic (identical twins) show that if one half of the twin has a mental disorder, the other has a chance of about 40 to 60% of also developing the disorder. While this is much higher than the risk in the general population it is also much less than 100% even though both twins share all of their genes. This clearly indicates that non-genetic, environmental factors must also contribute to the development of mental disorders, such as major depression, schizophrenia and autism spectrum disorders. Unfortunately, environmental factors are much more difficult to identify than genetic factors. This is in part due to the fact that environmental factors often affect individuals long before the actual disorder develops and therefore are often only identified in retrospect. Genetic factors, on the other hand are in general constant and can be identified at any point in time.

One of the environmental factors that has often been implicated in mental disorders is a viral or bacterial infection during pregnancy. Over the last two decades, multiple epidemiological studies have linked such infections to the development of autism spectrum disorder and schizophrenia. However, recent studies have also provided evidence that such infections can increase the risk of substance abuse disorders and affective disorders such as anxiety disorder, major depression and bipolar disorders).

To investigate the long-term consequences of such infections, we use two different animal models using prenatal injections of either polyI:C or LPS leading to maternal immune activation (MIA). The reasons for using these drugs rather than actual infections, is partly because it is difficult to limit an infection to a single mother. Additionally, by using drugs we have more control regarding the duration of the maternal immune response, allowing us to investigate whether MIA at different points during development leads to different long-term changes.