The causes of most cases of Alzheimer’s are currently unknown, but there is growing evidence to suggest microbial organisms are involved, in particular, herpes simplex virus type 1 (HSV-1), the so-called cold sore virus. This virus has long been known to reside lifelong, after infection in the peripheral nervous system, usually in a dormant form, from which it can be reactivated by events such as stress and immune-mediated mechanisms.
Professor Ruth Itzhaki has been researching the potential role of HSV-1 in AD for more than 30 years, beginning at the University of Manchester, where her team discovered HSV-1 DNA is present in the human brain in a high proportion of older people - the first microbe to be detected definitively in normal human brains. The researchers later indicated that the virus, when in the brain, in combination with a specific genetic factor, confers a high risk of developing AD.
Subsequent studies revealed major links between the effects of the virus and the characteristic features of AD, and showed also that treating laboratory-grown HSV1-infected cells with antivirals protected against AD.