The varicella-zoster virus (VZV) has been implicated in Alzheimer’s disease (AD), and vaccination against shingles, caused by VZV, has been shown to decrease the risk of dementia and Alzheimer’s.
The virus might reside latently in the brain, and reactivation might cause direct damage leading to AD, as proposed for herpes simplex virus type 1 (HSV-1), a virus strongly implicated in AD.
Recently, researchers at Tufts University and the University of Oxford, using a three-dimensional human tissue culture model that mimicked the brain, have found that the varicella-zoster virus may activate herpes simplex to set in motion the early stages of Alzheimer’s disease.
The importance of vaccination
According to the study, the virus that lies dormant within the neurons of the brain is activated, which leads to the accumulation of tau and amyloid beta proteins, and loss of neuronal function.
Cells infected with VZV did not show the main AD characteristics, Aβ and P-tau accumulation, which HSV-1 does cause, but did show gliosis and increased levels of pro-inflammatory cytokines, suggesting that VZV’s action relating to AD/dementia is indirect.
Their results suggest that shingles cause reactivation of HSV-1 in the brain, causing the accumulation of Aβ and P-tau, having an indirect role in the development of dementia.
The team also noticed that patients that had COVID-19, especially the elderly, can have a reactivation of VZV and HSV-1.
The study results showed us one more time the importance of vaccines. The use of the VZV vaccine can reduce considerably the risk of dementia and Alzheimer’s disease.
Tufts University. “Common viruses may be triggering the onset of Alzheimer’s disease: Shingles infection may activate dormant neurological herpes viruses, causing inflammation and accumulation of Alzheimer’s associated proteins in the brain.” ScienceDaily. ScienceDaily, 2 August 2022.
Dana M. Cairns, Ruth F. Itzhaki, David L. Kaplan. Potential Involvement of Varicella Zoster Virus in Alzheimer’s Disease via Reactivation of Quiescent Herpes Simplex Virus Type 1. Journal of Alzheimer’s Disease, 2022; 1 DOI: 10.3233/JAD-220287