Publication / Source: Neurology Central
Authors: Ruth F Itzhaki (Universities of Manchester & Oxford, UK)
Dementia afflicts over 20 million people worldwide, and the numbers affected will rise as more people survive to old age. The emotional costs to the sufferer and the carer are huge, as are the economic costs – estimated worldwide as US $818 billion, and the cost too will increase with increasing longevity. It is imperative, therefore, that effective treatments are found so that the social and economic consequences are reduced.
The main cause of dementia is Alzheimer’s disease (AD), accounting for approximately 60% of cases. Aβ and P‐tau are implicated in disease progression but the causes of their formation are unknown despite the vast number of studies devoted to elucidating their role. Tau is a microtubule‐associated protein with a role in axonal transport, which is disrupted when tau is abnormally phosphorylated. The function of Aβ is unclear but it exerts toxic effects on cells, especially when in oligomeric form. As for treatment, one possible strategy would be to use antiviral agents to slow disease progression, a proposal based on research implicating a common virus – herpes simplex virus type 1 (HSV1) – in the development of AD: the first cause to be proposed.
HSV1 is well known as the main cause of cold sores (herpes labialis). In the past, it infected most humans in infancy but with rising socio-economic levels resulting in better hygiene, it now infects most people later in life; however, by the age of approximately 60 years, 80% of the population harbor the virus. Once it enters the body it remains in the peripheral nervous system in latent form for life, but during events such as stress or immunosuppression, the virus reactivates and in approximately 20–40% of those infected, it then causes visible damage in the form of cold sores.