Abstracts

Mesial temporal sclerosis (MTS) is one of the most common pathological conditions associated with medically refractory epilepsy, often, requiring brain surgery to control seizures. Children with a history of complex febrile seizures have an increased risk of developing MTS. Complex febrile seizures have a strong association with primary human herpesvirus-6 (HHV-6) infection. HHV-6 is a ubiquitous virus associated with several neurological disorders. It has been suggested that HHV-6 has a higher prevalence in temporal lobe of patients with MTS and epilepsy than in controls. HHV-6 can infect a variety of cells including astrocytes. We studied 12 patients with MTS that underwent temporal lobectomy for control of their epilepsy and tissue from 7 controls that had other brain resections. The brain tissue was immediately brought to the laboratory and used for DNA and RNA analysis and primary cell cultures. Briefly, the tissue was minced, digested with papain, separated using a Percoll gradient and the astrocyte fraction was then cultured. PCR, nested PCR and quantitative real-time PCR were performed on DNA extracted from brain tissue, from PBMCs and from serum from each patient. The astrocytes were characterized using immunofluorescence assay for glial fibrillary acidic protein (GFAP). HHV-6 infection was determined by immunofluorescence assay using an antibody to gp116. DNA was extracted from cultured astrocytes and nested PCR was performed to demonstrate the presence of HHV-6 DNA. Elevated viral loads of HHV-6 were demonstrated in brain tissue from epilepsy patients with MTS in comparison to control tissue. Astrocytes stained positive for gp116 using immunohistochemistry. Adult astrocytes were successfully grown in culture and expression of HHV-6 was confirmed by immunofluorescence staining for gp116. HHV-6 was co-localized to GFAP-positive cells. DNA was extracted from cultured human adult astrocytes and nested-PCR for HHV-6 DNA in these astrocytes was positive. HHV-6 was present in brain specimens from patients with epilepsy and MTS and was localized to astrocytes. HHV-6 infection of human adult astrocytes in culture can be demonstrated by nested-PCR and immunofluoresence. The strength of the relationship between HHV-6 and mesial temporal sclerosis still needs to be determined. Introducing a potential relationship between a specific virus and epilepsy with MTS opens up the avenue for the development of new therapeutic strategies for treatment and possible prevention of a type of epilepsy that frequently can only be controlled by brain surgery. (Supported by NINDS/DIR)