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Itzhaki RF, Wozniak MA. J Alzheimers Dis 2008; 13: 393–405

This fascinating review explores the putative role of herpes simplex virus type 1 (HSV1) in Alzheimer's disease (AD). HSV1 is present in the 'temporal and frontal cortices but absent from the occipital cortex' of a high proportion of brains of older people, some of whom have AD, but not the majority of the young. 'A known susceptibility factor' for AD is a gene variation known as APOE. 'Intriguingly (APOE)...is a risk factor for cold sores' but also other infectious conditions. It has been suggested that HSV1 might act as a 'seed' for amyloid plaques and neurofibrillary tangles that are characteristics of AD brains. 'Interestingly, HSV1 infection leads to a marked accumulation of cholesterol' in brain cells. This observation may link with reports that show that statins reduce the risk of AD. The authors argue that there is a strong rationale for treating AD using antiviral therapy and, perhaps in early life, vaccination against HSV1.