Special Issue Editorial: "Infections, Inflammation and Neurodegeneration in Alzheimer Disease" Infections, Neuronal Senescence, and Dementia.

Alzheimer's disease (AD) is a complex chronic disease of the brain characterized by several neurodegenerative mechanisms and is responsible for most dementia cases in the elderly. Declining immunity during ageing is often associated with peripheral chronic inflammation, and chronic neuroinflammation is a constant component of AD brain pathology. In the Special Issue published in 2021 eight papers were collected regarding different aspects of neurodegeneration associated with AD. Five papers presented and discussed infectious agents involved in brain AD pathology and three discussed data regarding receptors regulation and possible treatment of the disease. Below I will discuss and further elaborate on topics related to infections, inflammation, and neurodegenerative pathways in AD and brain senescence. The topic presented here may contribute to early intervention protocols for preventing or slowing the progression of cognitive deterioration in the elderly.

Activation of Endogenous Retrovirus, Brain Infections and Environmental Insults in Neurodegeneration and Alzheimer's Disease.

Chronic neurodegenerative diseases are complex, and their pathogenesis is uncertain. Alzheimer's disease (AD) is a neurodegenerative brain alteration that is responsible for most dementia cases in the elderly. AD etiology is still uncertain; however, chronic neuroinflammation is a constant component of brain pathology. Infections have been associated with several neurological diseases and viruses of the Herpes family appear to be a probable cause of AD neurodegenerative alterations. Several different factors may contribute to the AD clinical progression. Exogeneous viruses or other microbes and environmental pollutants may directly induce neurodegeneration by activating brain inflammation. In this paper, we suggest that exogeneous brain insults may also activate retrotransposons and silent human endogenous retroviruses (HERVs). The initial inflammation of small brain areas induced by virus infections or other brain insults may activate HERV dis-regulation that contributes to neurodegenerative mechanisms. Chronic HERV activation in turn may cause progressive neurodegeneration that thereafter merges in cognitive impairment and dementia in genetically susceptible people. Specific treatment for exogenous end endogenous pathogens and decreasing pollutant exposure may show beneficial effect in early intervention protocol to prevent the progression of cognitive deterioration in the elderly.