In situ hybridization analysis for herpes simplex virus nucleic acids in Alzheimer disease.

Histological sections of brain from patients showing evidence of advanced pathology of Alzheimer disease (AD) were examined for the presence of herpes simplex type-1 (HSV-1) nucleic acids by a sensitive in-situ hybridization technique. Samples from neurologically normal patients were examined in parallel. Sensitivity of the assay was verified by the detection of HSV-1 nucleic acids in neurons of trigeminal ganglia taken from cases of AD and normal controls. This indicated that the hybridization reaction was sufficiently sensitive to detect latent HSV-1 infections. Positive hybridization in the brain was only detected in a confirmed case of herpes simplex virus encephalitis. These results appear to confirm previous reports that HSV-1 infection is not directly involved in the pathology associated with AD.