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Inflammation influences chronic neurodegeneration but its precise roles are not yet clear. Systemic inflammation caused by infection, trauma or co-morbidity can alter the brain's inflammatory status, produce acute cognitive impairments, such as delirium, and drive new pathology and accelerated decline. Consistent with this, elevated systemic TNF-α is associated with more rapid cognitive decline over 6months in Alzheimer's disease patients. In the current study we challenged normal animals and those with existing progressive neurodegeneration (ME7 prion disease) with TNF-α (i.p.) to test the hypothesis that this cytokine has differential effects on cognitive function, sickness behavior and features of underlying pathology contingent on the animals' baseline condition. TNF-α (50μg/kg) had no impact on performance of normal animals (normal brain homogenate; NBH) on working memory (T-maze) but produced acute impairments in ME7 animals similarly challenged. Plasma TNF-α and CCL2 levels were equivalent in NBH and ME7 TNF-challenged animals but hippocampal and hypothalamic transcription of IL-1β, TNF-α and CCL2 and translation of IL-1β were higher in ME7+TNF-α than NBH+TNF-α animals. TNF-α produced an exaggerated sickness behavior response (hypothermia, weight loss, inactivity) in ME7 animals compared to that in NBH animals. However a single challenge with this dose was not sufficient to produce de novo neuronal death, synaptic loss or tau hyperphosphorylation that was distinguishable from that arising from ME7 alone. The data indicate that acutely elevated TNF-α has robust acute effects on brain function, selectively in the degenerating brain, but more sustained levels may be required to significantly impact on underlying neurodegeneration., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

An infectious illness, attributed to atypically structured cytopathic "stealth" viruses, occurred in 1996 in the Mohave Valley region of the United States. A stealth virus-infected child from this region has developed a severe noninflammatory, vacuolating (spongiform) en cephalopathy. The illness initially presented as a behavioral problem without overt neurological signs. Extensive investigations, including repeated magnetic resonance imaging, two brain biopsies, and stealth virus cultures, have helped define the disease process occurring in this child. Significant clinical benefit with apparent retardation of disease progression occurred during a 6-week course of ganciclovir therapy. The potential contributing role of stealth virus infections in children presenting with behavioral problems needs to be addressed., (Copyright 1999 Academic Press.)