Infectious and immune factors in the pathogenesis of neurodevelopmental disorders: epidemiology, hypotheses, and animal models.

Both genetic and environmental factors contribute to the pathogenesis of a wide variety of neurodevelopmental disorders, including autism, mental retardation, and schizophrenia. Some heritable disorders approach 100% penetrance; nonetheless, even in these disorders, subtle aspects of clinical disease expression may be influenced by the environment. In other disorders with genetic influences, exogenous factors, and the timepoint(s) during nervous system development at which they are introduced, modulate expression of disease. Elucidation of the mechanisms guiding this intricate interplay between host response genes, environmental agents, and the neurodevelopmental context within which these interactions occur, is necessary to understand the continuum of clinical outcomes. This chapter will review the evidence that infectious and immune factors may contribute to the pathogenesis of neurodevelopmental disorders, describe an animal model of neurodevelopmental disorders based upon viral infection, identify processes by which neural circuitry may be compromised, and outline areas for future research.