Evidence for the relation of herpes simplex virus type 1 to Down syndrome and Alzheimer's disease

Abstract

The peripheral and central nervous system are harbouring herpes simplex virus type 1 (HSV‐1) and this virus has been proposed to be implicated in the aetiology of Alzheimer's disease (AD). We tested whether the HSV‐1 genome is found indeed in the brain of controls, patients with AD and Down syndrome (DS) and whether HSV‐1 infectious proteins in brain were induced. Moreover, we tested whether interleukin (IL)‐6, a marker for neuroinflammation, is found in brains of AD and DS. HSV‐1 glycoprotein D gene, as well as viral phosphoprotein and glycoprotein were detected in all brain samples. IL‐6 was detectable in seven out of the eight AD and all of the eight DS patients, but only three out of ten controls in the frontal cortex. IL‐6 in cerebellum was detectable in all AD and DS patients, but only three out of nine controls. In conclusion, we propose that the detection of HSV‐1 genome and HSV‐1 inducible protein IL‐6 not only shows the presence in human brain, but may indicate a role for HSV‐1 in the process of neuroinflammation and apoptosis, known to occur in both neurodegenerative disorders, AD and DS.