Human herpes virus infections and Alzheimer's disease

Herpes viruses cause acute and chronic diseases of the peripheral and central nervous systems and have been implicated in the aetiology of Alzheimer's disease (AD). In this investigation the relevance of human herpes virus infection to AD was assessed by in situ hybridization. The abundant latency associated transcript(s) of herpes simplex virus type 1 (HSV-1) were detected at a significantly higher incidence in the trigeminal ganglia of individuals with AD than in controls. But we could find no evidence of viral RNA in the central nervous system (CNS), looking specifically in the hippocampal cortex of demented individuals with extensive neuropathological changes of AD. These studies solve one problem in testing the viral hypothesis of causation, i.e. the sensitivity of the methods used in the search for latent infection. But the central issue remains unresolved because of necessity, only the end stage of a prolonged pathophysiological process has been examined. Our conclusions are qualified accordingly.