Synaptic Plasticity and Neurological Disorders in Neurotropic Viral Infections

Neural Plasticity, Nov 2015

Based on the type of cells or tissues they tend to harbor or attack, many of the viruses are characterized. But, in case of neurotropic viruses, it is not possible to classify them based on their tropism because many of them are not primarily neurotropic. While rabies and poliovirus are considered as strictly neurotropic, other neurotropic viruses involve nervous tissue only secondarily. Since the AIDS pandemic, the interest in neurotropic viral infections has become essential for all clinical neurologists. Although these neurotropic viruses are able to be harbored in or infect the nervous system, not all the neurotropic viruses have been reported to cause disrupted synaptic plasticity and impaired cognitive functions. In this review, we have discussed the neurotropic viruses, which play a major role in altered synaptic plasticity and neurological disorders.

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Synaptic Plasticity and Neurological Disorders in Neurotropic Viral Infections

Synaptic Plasticity and Neurological Disorders in Neurotropic Viral Infections Venkata Subba Rao Atluri, Melissa Hidalgo, Thangavel Samikkannu, Kesava Rao Venkata Kurapati, and Madhavan Nair Department of Immunology, Institute of NeuroImmune Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA Received 30 January 2015; Revised 16 June 2015; Accepted 18 June 2015 Academic Editor: Alexandre H. Kihara Copyright © 2015 Venkata Subba Rao Atluri et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Based on the type of cells or tissues they tend to harbor or attack, many of the viruses are characterized. But, in case of neurotropic viruses, it is not possible to classify them based on their tropism because many of them are not primarily neurotropic. While rabies and poliovirus are considered as strictly neurotropic, other neurotropic viruses involve nervous tissue only secondarily. Since the AIDS pandemic, the interest in neurotropic viral infections has become essential for all clinical neurologists. Although these neurotropic viruses are able to be harbored in or infect the nervous system, not all the neurotropic viruses have been reported to cause disrupted synaptic plasticity and impaired cognitive functions. In this review, we have discussed the neurotropic viruses, which play a major role in altered synaptic plasticity and neurological disorders. 1. Introduction Over the years, Central Nervous System (CNS) has been shown to be the major target site for viral infections. Different viruses have different routes of entry and some viruses have been shown to penetrate the CNS (neuroinvasion) and can infect neurons and glial cells (neurotropism). Neurotropic viruses are categorized into neuroinvasive and neurovirulent groups and both of them are known to cause neuronal dysfunction. Interestingly, neuroinvasive virus is capable of accessing or entering the nervous system whereas neurovirulent virus is capable of causing disease within the nervous system. These neurotropic viruses such as coxsackie, Japanese, Venezuelan equine, and California encephalitis viruses, polio, mumps, echo, influenza, measles, and rabies cause acute infection. Other viruses that come under this category are members of the family Herpesviridae, such as Cytomegalo, Varicella-zoster, Herpes simplex, and Epstein-Barr viruses. The ones that cause a latent infection are Varicella-zoster and Herpes simplex viruses, whereas other viruses like measles, rubella, John Cunningham, and retroviruses such as human T-lymphotropic virus 1 and human immunodeficiency virus are also reported to be neuropathogenic [1]. All of these pathogens have different modes of entry into the human brain, causing the neuropathogenesis that leads to the neurocognitive disorders. However, the neuropathogenic mechanisms that are involved in these disorders neither are clear nor are elucidated yet and require further studies to identify the therapeutic targets. Neuropathogenic mechanisms that lead to these disorders need to be better understood to identify therapeutic targets. Viral infections of the CNS that injure or destroy specific populations of brain cells are frequently associated with behavioral disturbances. These events occur either directly due to virus replication or indirectly as a result of the host immune response against the infectious agent. Neurotropic viruses can also persist in the CNS and, in the absence of cell destruction or inflammation, cause defects in goal-oriented behavior. Therefore, viruses may contribute to human CNS disorders whose etiology remains elusive. The finding of virally mediated impairment in neuronal function in the absence of cell destruction raises the possibility that noncytolytic viruses that persistently infect neurons may contribute to many human CNS disorders whose etiology is unknown. Since neurons are not destroyed by the viral infection, antiviral therapies resulting in viral clearance from these cells may restore normal brain function. Studies to test this hypothesis are currently underway. Borna disease virus (BDV) is an enveloped virus with a nonsegmented, negative-strand RNA genome belonging to the Bornaviridae family within the Mononegavirales order. This neurotropic virus infects a wide variety of mammals, and serological evidence suggests that BDV, or a BDV-like virus, also infects humans. Infected hosts develop a wide spectrum of neurological disorders, ranging from immune-mediated diseases to behavioral alterations without inflammation, reminiscent of symptoms observed in human psychiatric diseases such as schizophrenia, mood disorders, and autism [2, 3]. BDV has a noncytolytic strategy of replication and primarily infects neurons of the limbic system, notably the cortex and hip (...truncated)


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Venkata Subba Rao Atluri, Melissa Hidalgo, Thangavel Samikkannu, Kesava Rao Venkata Kurapati, Madhavan Nair. Synaptic Plasticity and Neurological Disorders in Neurotropic Viral Infections, Neural Plasticity, 2015, 2015, DOI: 10.1155/2015/138979