Infectious Agents and Neurodegeneration

Abstract

A growing body of epidemiologic and experimental data point to chronic bacterial and viral infections as possible risk factors for neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Infections of the central nervous system, especially those characterized by a chronic progressive course, may produce multiple damage in infected and neighbouring cells. The activation of inflammatory processes and host immune responses cause chronic damage resulting in alterations of neuronal function and viability, but different pathogens can also directly trigger neurotoxic pathways. Indeed, viral and microbial agents have been reported to produce molecular hallmarks of neurodegeneration, such as the production and deposit of misfolded protein aggregates, oxidative stress, deficient autophagic processes, synaptopathies and neuronal death. These effects may act in synergy with other recognized risk factors, such as aging, concomitant metabolic diseases and the host’s specific genetic signature. This review will focus on the contribution given to neurodegeneration by herpes simplex type-1, human immunodeficiency and influenza viruses, and by Chlamydia pneumoniae.

Radical scavenging, prolyl endopeptidase inhibitory, and antimicrobial potential of a cultured Himalayan lichenCetrelia olivetorum

“…A pneumococcal exotoxin (ExoY) has been reported for its potential to cause endothelial Tau hyperphosphorylation (Ochoa et al, 2012). While reports related to direct role of ExoY in the onset of AD are lacking, there are reports regarding bacterial and viral involvement in the pathogenesis of neurodegeneration (Braun et al, 2007;Chiara et al, 2012;Nicolson & Haier, 2009). Pseudomonas aeruginosa is known to be an opportunistic human pathogen that causes microbial infection in immunocompromised condition, especially in old age (Gellatly & Hancock, 2013).…”

“…The study indicates therapeutic potential of Himalayan lichen C. olivetorum against neurodegenerative diseases, encourages its commercial exploitation through mass culture and suggests further research on purification of bioactive components responsible for the observed biological activities. Furthermore, it has also been reported that herpes simplex virus (HSV-1) has considerable involvement in neuronal damage (Braun et al, 2007;Chiara et al, 2012), hence antiviral potential of bioactive components should also be analyzed.…”

“…Involvement of microbial infections as well as the role of their byproducts in the pathogenesis of neurodegeneration has already been reported (Chiara et al, 2012;Nicolson, 2008). Neurodegenerative disease accompanied by the immunocompromised condition of the host in old age is likely to attract opportunistic infections that could be involved in the progression of disease (Nicolson, 2008).…”

NK Cells in Central Nervous System Disorders

“…Overall, in CNS infections, NK cells can be beneficial or detrimental according to the experimental model used. An emerging concept states that neuroinflammation following infection may play an important role in the etiology of neurodegenerative diseases (41).…”

Investigation of Herpes simplex-1 latency in vivo and in vitro

“…Recurrent lesions develop during the life of an infected individual, generally at epithelial sites such as lips (herpes labialis), oral cavity (herpetic stomatitis), the eye (herpetic keratitis), orofacial complex (herpes facialis) and skin. Additionally, epidemiological data suggest that HSV-1 is one of the environmental risk factors for Alzheimer's disease which disease characterized by progressive neuron loss, brain atrophy, and cognitive impairment [66,67].…”