Age-related changes in susceptibility of rat brain slice cultures including hippocampus to encephalomyocarditis virus

Experimental encephalomyocarditis virus infection in small laboratory rodents

Encephalomyocarditis virus (EMCV) is a cardiovirus that belongs to the family Picornaviridae. EMCV is an important cause of acute myocarditis in piglets and of fetal death or abortion in pregnant sows. Small rodents, especially rats, have been suspected to be reservoir hosts or carriers. This virus also induces type 1 diabetes mellitus, encephalomyelitis, myocarditis, orchitis and/or sialodacryoadenitis in small laboratory rodents. This paper reviews the pathology and pathogenesis of experimental infection with EMCV in small laboratory rodents.

Alzheimer's disease and infection: do infectious agents contribute to progression of Alzheimer's disease?

Infection with several important pathogens could constitute risk factors for cognitive impairment, dementia, and Alzheimer's disease (AD) in particular. This review summarizes the data related to infectious agents that appear to have a relationship with AD. Infections with herpes simplex virus type 1, picornavirus, Borna disease virus, Chlamydia pneumoniae, Helicobacter pylori, and spirochete were reported to contribute to the pathophysiology of AD or to cognitive changes. Based on these reports, it may be hypothesized that central nervous system or systemic infections may contribute to the pathogenesis or pathophysiology of AD, and chronic infection with several pathogens should be considered a risk factor for sporadic AD. If this hypothesis holds true, early intervention against infection may delay or even prevent the future development of AD.

Disrupted spatial memory is a consequence of picornavirus infection

Picornaviruses are a socioeconomically important family of viruses that includes the rhinoviruses and enteroviruses. Many of these viruses, including the "common cold" Coxsackie virus A21, maintain neurovirulent potential and may induce hippocampal injury. The behavioral implications of this injury have not been adequately explored. Using C57BL/6J mice infected with Theiler's murine encephalomyelitis virus, we examined the formation of spatial memories using the Morris water maze test. Virus-infected mice had greater search error compared to sham-infected animals during the location of a hidden platform and were unable to discriminate the location of the training quadrant during the final probe trial. Furthermore, sham-infected mice were place responders whereas virus-infected mice were cue responders, indicating a lack of spatial memory formation in infected animals. Importantly, the degree of memory impairment was correlated to the extent of hippocampal injury. This suggests that picornavirus infection of the human CNS may also result in at least some degree of neurologic deficit. An important implication of such subclinical virus-induced neurologic deficit is that the injury may accumulate over the lifetime of the individual, eventually leading to the manifestation of clinical cognitive or memory deficits.

Susceptibility of primary culture neurons from rats of different ages to encephalomyocarditis (EMC) virus infection

The changes in susceptibility of neurons to the D variant of EMC virus (EMC-D) (10(6) PFU/well) were investigated in developing hippocampal primary cultures from postnatal days of 1, 7, and 56 Fischer 344 rats (P1, P7, and P56) for up to 12 h after infection (12 HAI). The virus titer of primary culture neurons increased at 1 HAI, decreased at 2 HAI, increased at 3 HAI, peaked at 8 HAI, and decreased at 12 HAI in all age groups. The titers at 1 and 8 HAI were lowest in P56 cultures. The virus titer of neurons was always higher than that of culture media, especially at 1 HAI, in P1 cultures, whereas the former was lower than the latter from 2 to 3 HAI in P7 cultures and from 2 to 4 HAI in P56 cultures, respectively. Signals of viral RNA detected by in situ hybridization were first observed in the peripheral cytoplasm of neurons at 1 HAI in P1 and P7 cultures and at 4 HAI in P56 cultures, respectively. The signals spread to a large or whole area of cytoplasm and also to processes thereafter. The number of viral RNA-positive neurons and the amount of signals decreased with age. The present results indicated that the susceptibility of primary culture neurons to EMC-D decreased with age but viral replication still occurred in P56 cultures.