Virological and immunological aspects of seizure disorders

The brain is a symptom-producing organ, and one of the symptoms due to a basic brain dysfunction is epilepsy. The pathophysiologic background is in most epilepsies multifactorial, as different pre-, peri-, and postnatal triggers or environmental conditions influence one or several genetic factors, where also gender is of importance. One of the genetic factors is immunodysfunction, and the trigger mechanism may be a virus infection. Viruses are the most common agents to which the human being is exposed throughout life. The herpes virus group is of special interest with respect to complications of the central nervous system. Herpes viruses, especially herpes simplex virus type 1 (HSV-1), human herpes virus type 6 (HHV-6), cytomegalovirus (CMV) and Epstein-Barr virus (EBV), are capable of establishing latent infection and reactivating under a variety of stimuli. In this review especially HHV-6 will be emphasized, as well as CMV in relation to Rasmussen's syndrome. The immunological aspects will focus on immunoglobulins, antibodies, especially the glutamate receptors, human leukocyte antigens, T- and B-lymphocytes, and their respective interaction with the antigen presenting cell. This course of events concerns the 'immunological synapse'. Finally, reports on herpes virus genomes in the human brain are discussed. A study on herpes viral DNA in brain tissue from patients operated for focal epilepsy is briefly mentioned.