Infectious agents and age-related neurodegenerative disorders

Abstract

chlamdAs with other organ systems, the vulnerability of the nervous system to infectious agents increases with aging. Several different infectious agents can cause neurodegenerative conditions, with prominent examples being human immunodeficiency virus (HIV-1) dementia and prion disorders. Such infections of the central nervous system (CNS) typically have a relatively long incubation period and a chronic progressive course, and are therefore increasing in frequency as more people live longer. Infectious agents may enter the central nervous system in infected migratory macrophages, by transcytosis across blood-brain barrier cells or by intraneuronal transfer from peripheral nerves. Synapses and lipid rafts are important sites at which infectious agents may enter neurons and/or exert their cytotoxic effects. Recent findings suggest the possibility that infectious agents may increase the risk of common age-related neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and stroke. While scenarios can be envisioned whereby viruses such as Chlamydia pneumoniae, herpes simplex and influenza promote damage to neurons during aging, there is no conclusive evidence for a major role of these pathogens in neurodegenerative disorders. In the case of stroke, blood vessels may be adversely affected by bacteria or viruses resulting in atherosclerosis.

Alterations in immunological and neurological gene expression patterns in Alzheimer's disease tissues

“…In 1999, Dobson and Itzhaki reported that herpes simplex type 1 virus (HSV1) is present in the brain of many elderly people and that it may be a risk factor for AD [30]. However, in earlier studies, no evidence of herpes virus RNA was observed in the hippocampus of demented individuals with extensive neuropathological changes of AD [31,32]. Additional studies will be required to discover the possible relevance of this cytokine in AD pathology and in viral infections in neuronal tissues.…”

Периферійна Нейропатія При Хламідійному Реактивному Артриті

“…У больных с другими артритами (ревматоидный, псориатиче-ский, анкилозирующий спондилит) уже достаточно хорошо известно развитие ПНП [6,9,12], тогда как при РХА такое поражение нервной системы пока описывается в виде единичных наблюдений, хотя нейропатия считается прогнознегативным фактором течения этого заболевания [14]. Воспалительно-де-генеративные изменения нервов в виде ПНП спо-собны вызывать Chlamydia psittaci [10] и Chlamydia pneumoniae [2,4,11].…”

Neurodegenerative and Fatiguing Illnesses, Infections and Mitochondrial Dysfunction: Use of Natural Supplements to Improve Mitochondrial Function.

“…Alternatively, they can also gain access by direct penetration of the blood-brain-barrier or entry by intraneuronal transfer from peripheral nerves [32]. Cell wall-deficient bacteria, such as species of Mycoplasma, Chlamydia (Chlamydophila), Borrelia, Brucella, among others and various viruses are candidate brain infectious agents, because they are capable of CNS penetration and have been found routinely in neurodegenerative and neurobehavioral diseases [1-3, 26, 27, 32, 33].…”

“…For example, spirochetes have also been found in the brain Lewy bodies of Lyme-associated PD patients [150]. Other infections, such as viral encephalitis [151], cornavirus [152], Mycoplasma pneumoniae [153], AIDS-associated infections of the basal ganglia [154], HIV [155], among other infections, have been found in PD patients [144,149,155]. Additional research will be necessary to establish whether a causal link exists between PD and chronic infections [143,155,156].…”

“…Cell wall-deficient bacteria, such as species of Mycoplasma, Chlamydia (Chlamydophila), Borrelia, Brucella, among others and various viruses are candidate brain infectious agents, because they are capable of CNS penetration and have been found routinely in neurodegenerative and neurobehavioral diseases [1-3, 26, 27, 32, 33]. Such infections are usually systemic and can affect immune systems and essentially any organ system, resulting in a variety of systemic signs and symptoms that are not limited to the CNS [10,11,26,27,32,33].…”