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Enterovirus D68 (EV-D68) is an emerging pathogen that can cause severe respiratory and neurologic disease [acute flaccid myelitis (AFM)]. Intramuscular (IM) injection of neonatal Swiss Webster (SW) mice with US/IL/14-18952 (IL52), a clinical isolate from the 2014 EV-D68 epidemic, results in many of the pathogenic features of human AFM, including viral infection of the spinal cord, death of motor neurons, and resultant progressive paralysis. In distinction, CA/14-4231 (CA4231), another clinical isolate from the 2014 EV-D68 outbreak, does not cause paralysis in mice, does not grow in the spinal cord, and does not cause motor neuron loss following IM injection. A panel of chimeric viruses containing sequences from IL52 and CA4231 was used to demonstrate that VP1 is the main determinant of EV-D68 neurovirulence following IM injection of neonatal SW mice. VP1 contains four amino acid differences between IL52 and CA4231. Mutations resulting in substituting these four amino acids (CA4231 residues into the IL52 polyprotein) completely abolished neurovirulence. Conversely, mutations resulting in substituting VP1 IL52 amino acid residues into the CA4231 polyprotein created a virus that induced paralysis to the same degree as IL52. Neurovirulence following infection of neonatal SW mice with parental and chimeric viruses was associated with viral growth in the spinal cord., Importance: Emerging viruses allow us to investigate mutations leading to increased disease severity. Enterovirus D68 (EV-D68), once the cause of rare cases of respiratory illness, recently acquired the ability to cause severe respiratory and neurologic disease. Chimeric viruses were used to demonstrate that viral structural protein VP1 determines growth in the spinal cord, motor neuron loss, and paralysis following intramuscular (IM) injection of neonatal Swiss Webster (SW) mice with EV-D68. These results have relevance for predicting the clinical outcome of future EV-D68 epidemics as well as targeting retrograde transport as a potential strategy for treating virus-induced neurologic disease., Competing Interests: The authors declare no conflict of interest.

Although increasing evidence confirms neuropsychiatric manifestations associated mainly with severe COVID-19 infection, long-term neuropsychiatric dysfunction (recently characterized as part of "long COVID-19" syndrome) has been frequently observed after mild infection. We show the spectrum of cerebral impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, ranging from long-term alterations in mildly infected individuals (orbitofrontal cortical atrophy, neurocognitive impairment, excessive fatigue and anxiety symptoms) to severe acute damage confirmed in brain tissue samples extracted from the orbitofrontal region (via endonasal transethmoidal access) from individuals who died of COVID-19. In an independent cohort of 26 individuals who died of COVID-19, we used histopathological signs of brain damage as a guide for possible SARS-CoV-2 brain infection and found that among the 5 individuals who exhibited those signs, all of them had genetic material of the virus in the brain. Brain tissue samples from these five patients also exhibited foci of SARS-CoV-2 infection and replication, particularly in astrocytes. Supporting the hypothesis of astrocyte infection, neural stem cell-derived human astrocytes in vitro are susceptible to SARS-CoV-2 infection through a noncanonical mechanism that involves spike-NRP1 interaction. SARS-CoV-2-infected astrocytes manifested changes in energy metabolism and in key proteins and metabolites used to fuel neurons, as well as in the biogenesis of neurotransmitters. Moreover, human astrocyte infection elicits a secretory phenotype that reduces neuronal viability. Our data support the model in which SARS-CoV-2 reaches the brain, infects astrocytes, and consequently, leads to neuronal death or dysfunction. These deregulated processes could contribute to the structural and functional alterations seen in the brains of COVID-19 patients.

The world faces an exceptional new public health concern caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), subsequently termed the coronavirus disease 2019 (COVID-19) by the World Health Organization (WHO). Although the clinical symptoms mostly have been characterized, the scientific community still doesn´t know how SARS-CoV-2 successfully reaches and spreads throughout the central nervous system (CNS) inducing brain damage. The recent detection of SARS-CoV-2 in the cerebrospinal fluid (CSF) and in frontal lobe sections from postmortem examination has confirmed the presence of the virus in neural tissue. This finding reveals a new direction in the search for a neurotherapeutic strategy in the COVID-19 patients with underlying diseases. Here, we discuss the COVID-19 outbreak in a neuroinvasiveness context and suggest the therapeutic use of high doses of melatonin, which may favorably modulate the immune response and neuroinflammation caused by SARS-CoV-2. However, clinical trials elucidating the efficacy of melatonin in the prevention and clinical management in the COVID-19 patients should be actively encouraged., (© 2020. Springer Science+Business Media, LLC, part of Springer Nature.)

Background: The developmental stages and function of immune cells in the central nervous system during infancy and childhood are poorly understood. We analyzed whether cytokine and chemokine profiles in children and adolescents with viral central nervous system infections were different depending on age., Methods: The acute phase cerebrospinal fluid of 80 children (mean age 98 months, range 1-206 months) were analyzed for protein levels of interleukin-1β (IL-1β), IL-1-RA, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, IL-18, monocyte chemoattractant protein-1 (MCP-1), interferon (IFN) gamma-induced protein 10 (IP-10), IFN-γ, and macrophage migration inhibitory factor (MIF)., Results: We found an age-dependent increased expression of IL-4, IL-6, IL-13, MIF, IP-10, and IFN-γ and a decreased expression of MCP-1 and IL-15 in response to a viral infection of the central nervous system. In contrast, all other cytokines and chemokine were unaffected by the age of the patient., Conclusion: These findings demonstrate that the immunological response to a viral infection matures during childhood and adolescence. This may in turn be of importance for the outcome of a viral infection and the risk for subsequent sequela. It also demonstrates that age is a factor that needs to be considered when using cytokines and chemokines as biomarkers for infections in the central nervous system., Impact: The immunological response to a viral infection matures during childhood and adolescence. This may be of importance for the outcome of a viral infection and the risk for subsequent sequela. It also demonstrates that age is a factor that needs to be considered when using cytokines and chemokines as biomarkers for infections in the central nervous system., (© 2021. The Author(s), under exclusive licence to the International Pediatric Research Foundation, Inc.)

The brain is the major target of congenital cytomegalovirus (CMV) infection. It is possible that neuron disorder in the developing brain is a critical factor in the development of neuropsychiatric diseases in later life. Previous studies using mouse model of murine CMV (MCMV) infection demonstrated that the viral early antigen (E1 as a product of e1 gene) persists in the postnatal neurons of the hippocampus (HP) and cerebral cortex (CX) after the disappearance of lytic infection from non-neuronal cells in the periventricular (PV) region. Furthermore, neuron-specific activation of the MCMV-e1-promoter (e1-pro) was found in the cerebrum of transgenic mice carrying the e1-pro-lacZ reporter construct. In this study, in order to elucidate the mechanisms of e1-pro activation in cerebral neurons during actual MCMV infection, we have generated the recombinant MCMV (rMCMV) carrying long e1-pro1373- or short e1-pro448-EGFP reporter constructs. The length of the former, 1373 nucleotides (nt), is similar to that of transgenic mice. rMCMVs and wild type MCMV did not significantly differed in terms of viral replication or E1 expression. rMCMV-infected mouse embryonic fibroblasts showed lytic infection and activation of both promoters, while virus-infected cerebral neurons in primary neuronal cultures demonstrated the non-lytic and persistent infection as well as the activation of e1-pro-1373, but not -448. In the rMCMV-infected postnatal cerebrum, lytic infection and the activation of both promoters were found in non-neuronal cells of the PV region until postnatal 8 days (P8), but these disappeared at P12, while the activation of e1-pro-1373, but not -448 appeared in HP and CX neurons at P8 and were prolonged exclusively in these neurons at P12, with preservation of the neuronal morphology. Therefore, e1-pro-448 is sufficient to activate E1 expression in non-neuronal cells, however, the upstream sequence from nt -449 to -1373 in e1-pro-1373 is supposed to work as an enhancer necessary for the neuron-specific activation of e1-pro, particularly around the second postnatal week. This unique activation of e1-pro in developing cerebral neurons may be an important factor in the neurodevelopmental disorders induced by congenital CMV infection.

Tissue-resident memory (T RM ) CD8 T cells provide early frontline defense against regional pathogen reencounter. CD8 T RM are predominantly parked in nonlymphoid tissues and do not circulate. In addition to this anatomic difference, T RM are transcriptionally and phenotypically distinct from central-memory T cells (T CM ) and effector-memory T cells (T EM ). Moreover, T RM differ phenotypically, functionally, and transcriptionally across barrier tissues (e.g., gastrointestinal tract, respiratory tract, urogenital tract, and skin) and in non-barrier organs (e.g., brain, liver, kidney). In the brain, T RM are governed by a contextual milieu that balances T RM activation and preservation of essential post-mitotic neurons. Factors contributing to the development and maintenance of brain T RM , of which T cell receptor (TCR) signal strength and duration is a central determinant, vary depending on the infectious agent and modulation of TCR signaling by inhibitory markers that quell potentially pathogenic inflammation. This review will explore our current understanding of the context-dependent factors that drive the acquisition of brain (b)T RM phenotype and function, and discuss the contribution of T RM to promoting protective immune responses in situ while maintaining tissue homeostasis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Netherby-Winslow, Ayers and Lukacher.)

EV-A120 is a recently identified serotype of the enterovirus A species. Only one full-length genomic sequence is currently available in GenBank, and very few studies have been conducted on EV-A120 globally. Thus, additional information and research on EV-A120 are needed to explore its genetic characteristics, phylogeny, and relationship with enteroviral disease. In this study, we report the phylogenetic characteristics of a EV-A120 strain ( Q0082 /XZ/CHN/2000) from Tibet, China. The amino acid sequence similarity and nucleotide sequence similarity of the full-length genomic sequence of this EV-A120 strain and the EV-A120 prototype strain were 96.3% and 79.9%, respectively, showing an evolutionary trend. Recombination analysis found intraspecies recombination in the 5' -UTR , 2B , 2C , and 3D regions. Serum neutralization testing of the EV-A120 ( Q0082 ) strain was also carried out. Low serum-positive rates and geometric mean titres (GMTs) indicated that the extent of EV-A120 transmission and exposure in the population was very limited compared with that in the outbreaks of EV-A71 and CV-A16 in China since 2008. The EV-A120 strain ( Q0082 ) is non-temperature sensitive, indicating its potential to spread in the population. In summary, this study reports the full-length genomic sequence of EV-A120 and provides important information for its global molecular epidemiology.

Introduction: Contradictory data have been reported on the incidence of stroke in patients with COVID-19 and the risk of SARS-CoV-2 infection among patients with history of stroke., Methods: This study systematically reviews case series reporting stroke as a complication of COVID-19, and analyses the prognosis of patients with COVID-19 and history of stroke. The pathophysiological mechanisms of stroke in patients with COVID-19 are also reviewed., Conclusions: History of stroke increases the risk of death due to COVID-19 by 3 times. Stroke currently seems not to be one of the main complications of COVID-19., (Copyright © 2020 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.)

One of the first signs of viral infection is body-wide aches and pain. Although this type of pain usually subsides, at the extreme, viral infections can induce painful neuropathies that can last for decades. Neither of these types of pain sensitization is well understood. A key part of the response to viral infection is production of interferons (IFNs), which then activate their specific receptors (IFNRs) resulting in downstream activation of cellular signaling and a variety of physiological responses. We sought to understand how type I IFNs (IFN-α and IFN-β) might act directly on nociceptors in the dorsal root ganglion (DRG) to cause pain sensitization. We demonstrate that type I IFNRs are expressed in small/medium DRG neurons and that their activation produces neuronal hyper-excitability and mechanical pain in mice. Type I IFNs stimulate JAK/STAT signaling in DRG neurons but this does not apparently result in PKR-eIF2α activation that normally induces an anti-viral response by limiting mRNA translation. Rather, type I IFNs stimulate MNK-mediated eIF4E phosphorylation in DRG neurons to promote pain hypersensitivity. Endogenous release of type I IFNs with the double-stranded RNA mimetic poly(I:C) likewise produces pain hypersensitivity that is blunted in mice lacking MNK-eIF4E signaling. Our findings reveal mechanisms through which type I IFNs cause nociceptor sensitization with implications for understanding how viral infections promote pain and can lead to neuropathies. SIGNIFICANCE STATEMENT It is increasingly understood that pathogens interact with nociceptors to alert organisms to infection as well as to mount early host defenses. Although specific mechanisms have been discovered for diverse bacterial and fungal pathogens, mechanisms engaged by viruses have remained elusive. Here we show that type I interferons, one of the first mediators produced by viral infection, act directly on nociceptors to produce pain sensitization. Type I interferons act via a specific signaling pathway (MNK-eIF4E signaling), which is known to produce nociceptor sensitization in inflammatory and neuropathic pain conditions. Our work reveals a mechanism through which viral infections cause heightened pain sensitivity., (Copyright © 2020 the authors.)

Infiltration of infected leukocytes culminates in establishment of a brain niche for Human Immunodeficiency Virus (HIV) during acute phase of infection, initiating an ongoing cascade of persistent viral replication and inflammation, that causes irreversible neuronal injury and HIV associated neurocognitive disease (HAND). In this study, humanized mice were treated with Smoothened Agonist (SAG), a Sonic Hedgehog (Shh) mimetic in order to fortify blood brain barrier (BBB) and dampen leukocyte extravasation into CNS during AHI. Results indicate that SAG treatment reduced viral burden in the CNS immediately after HIV transmission, but also conferred extended neuroprotection via increased BBB integrity (elevated levels of tight-junction protein, Claudin 5, and reduced S100B levels in periphery). These mice also showed healthier neurons with thick, uniform dendrites and reduced numbers of activated astrocytes. Additional in vitro experiments suggested SAG treatment was not associated with the establishment or reversal of latency in the target cells. Altogether, these findings validate neuroprotective role of Shh signaling and highlight the therapeutic potential of Shh mimetics against CNS complications associated with HIV infection. Further our results strongly demonstrate that pharmacological interventions to reduce leukocyte mobilization during early HIV infection, can provide prolonged neuroprotection, which might significantly delay the onset of HAND.

History is replete with emergent pandemic infections that have decimated the human population. Given the shear mass of humans that now crowd the earth, there is every reason to suspect history will repeat itself. We describe three RNA viruses that have recently emerged in the human population to mediate severe neurological disease. These new diseases are results of new mutations in the infectious agents or new exposure pathways to the agents or both. To appreciate their pathogenesis, we summarize the essential virology and immune response to each agent. Infection is described in the context of known host defenses. Once the viruses evade immune defenses and enter central nervous system (CNS) cells, they rapidly co-opt host RNA processing to a cataclysmic extent. It is not clear why the brain is particularly susceptible to RNA viruses; but perhaps because of its tremendous dependence on RNA processing for physiological functioning, classical mechanisms of host defense (eg, interferon disruption of viral replication) are diminished or not available. Effectiveness of immunity, immunization and pharmacological therapies is reviewed to contextualize the scope of the public health challenge. Unfortunately, vaccines that confer protection from systemic disease do not necessarily confer protection for the brain after exposure through unconventional routes., (© 2015 International Society of Neuropathology.)

Exosomes are small membrane-bound vesicles that carry biological macromolecules from the site of production to target sites either in the microenvironment or at distant sites away from the origin. Exosomal content of cells varies with the cell type that produces them as well as environmental factors that alter the normal state of the cell such as viral infection. Human DNA and RNA viruses alter the composition of host proteins as well as incorporate their own viral proteins and other cargo into the secreted exosomes. While numerous viruses can infect various cell types of the CNS and elicit damaging neuropathologies, few have been studied for their exosomal composition, content, and function on recipient cells. Therefore, there is a pressing need to understand how DNA and RNA viral infections in CNS control exosomal release. Some of the more recent studies including HIV-1, HTLV-1, and EBV-infected B cells indicate that exosomes from these infections contain viral miRNAs, viral transactivators, and a host of cytokines that can control the course of infection. Finally, because exosomes can serve as vehicles for the cellular delivery of proteins and RNA and given that the blood-brain barrier is a formidable challenge in delivering therapeutics to the brain, exosomes may be able to serve as ideal vehicles to deliver protein or RNA-based therapeutics to the brain.

Four uncommon cases of canine distemper (CD) were diagnosed in vaccinated adult dogs. All dogs had acute onset of neurologic signs, including seizures, abnormal mentation, ataxia, and proprioceptive deficits. Polymerase chain reaction for CD virus was positive on cerebrospinal fluid in 2 cases. Due to rapid deterioration the dogs were euthanized and CD was confirmed by postmortem examination.

Background: Highly active antiretroviral therapy (HAART) restores inflammatory immune responses in AIDS patients which may unmask previous subclinical infections or paradoxically exacerbate symptoms of opportunistic infections. In resource-poor settings, 25% of patients receiving HAART may develop CNS-related immune reconstitution inflammatory syndrome (IRIS). Here we describe a reliable mouse model to study underlying immunopathological mechanisms of CNS-IRIS., Methods: Utilizing our HSV brain infection model and mice with MAIDS, we investigated the effect of immune reconstitution on MAIDS mice harboring opportunistic viral brain infection. Using multi-color flow cytometry, we quantitatively measured the cellular infiltrate and microglial activation., Results: Infection with the LP-BM5 retroviral mixture was found to confer susceptibility to herpes simplex virus (HSV)-1 brain infection to normally-resistant C57BL/6 mice. Increased susceptibility to brain infection was due to severe immunodeficiency at 8 wks p.i. and a marked increase in programmed death-1 (PD-1) expression on CD4+ and CD8+ T-cells. Both T-cell loss and opportunistic brain infection were associated with high level PD-1 expression because PD-1-knockout mice infected with LP-BM5 did not exhibit lymphopenia and retained resistance to HSV-1. In addition, HSV-infection of MAIDS mice stimulated peripheral immune cell infiltration into the brain and its ensuing microglial activation. Interestingly, while opportunistic herpes virus brain infection of C57BL/6 MAIDS mice was not itself lethal, when T-cell immunity was reconstituted through adoptive transfer of virus-specific CD3+ T-cells, it resulted in significant mortality among recipients. This immune reconstitution-induced mortality was associated with exacerbated neuroinflammation, as determined by MHC class II expression on resident microglia and elevated levels of Th1 cytokines in the brain., Conclusions: Taken together, these results indicate development of an immune reconstitution disease within the central nervous system (CNS-IRD). Experimental immune reconstitution disease of the CNS using T-cell repopulation of lymphopenic murine hosts harboring opportunistic brain infections may help elucidate neuroimmunoregulatory networks that produce CNS-IRIS in patients initiating HAART.

Neuro-tropism is a major feature in many viral infections. Chandipura virus produces neurological symptoms in naturally infected young children and experimentally infected suckling mice. This study was undertaken to find out the neuro-invasive behaviour of Chandipura virus in suckling mice. The suckling mice were infected with the virus via footpad injection. Different tissues were collected at 24-h intervals up to 96-h post infection and processed for virus quantification and histological study. Further confirming the virus predilection to nerves tissues, the adult mice were inoculated with the virus via different routes. The suckling mice experimental results revealed a progressive replication of virus in spinal cord and brain. The progressive-virus replication was not observed in the other tissues like kidney, spleen, liver etc. Histo-pathological lesions noticed in the spinal cord and brain tissues suggested the extensive damages in these tissues. In adult mice experiment, the virus replication observed only in the brain of the mice infected via intra-cerebral route. From this study, we conclude that nervous tissues are predilection sites for Chandipura virus replication in suckling and adult mice. In suckling mice, virus might transmit through nervous tissues for dissemination. In contrast, the adult mice the nervous terminal might not pick up the virus through footpad infection. The pathogenesis in mice might be due to the virus replication mediated damage in the central nervous system.

The A/VN/1203/04 strain of the H5N1 influenza virus is capable of infecting the CNS of mice and inducing a number of neurodegenerative pathologies. Here, we examined the effects of H5N1 on several pathological aspects affected in parkinsonism, including loss of the phenotype of dopaminergic neurons located in the substantia nigra pars compacta (SNpc), expression of monoamines and indolamines in brain, alterations in SNpc microglia number and morphology, and expression of cytokines, chemokines, and growth factors. We find that H5N1 induces a transient loss of the dopaminergic phenotype in SNpc and now report that this loss recovers by 90 d after infection. A similar pattern of loss and recovery was seen in monoamine levels of the basal ganglia. The inflammatory response in lung and different regions of the brain known to be targets of the H5N1 virus (brainstem, substantia nigra, striatum, and cortex) were examined at 3, 10, 21, 60, and 90 d after infection. In each of these brain regions, we found a significant increase in the number of activated microglia that lasted at least 90 d. We also quantified expression of IL-1α, IL-1β, IL-2, IL-6, IL-9, IL-10, IL-12(p70), IL-13, TNF-α, IFN-γ, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, eotaxin, interferon-inducible protein 10, cytokine-induced neutrophil chemoattractant, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP) 1α, MIP-1β, and VEGF, and found that the pattern and levels of expression are dependent on both brain region and time after infection. We conclude that H5N1 infection in mice induces a long-lasting inflammatory response in brain and may play a contributing factor in the development of pathologies in neurodegenerative disorders.

The synchrony of neural firing is believed to underlie the integration of information between and within neural networks in the brain. Abnormal synchronization of neural activity between distal brain regions has been proposed to underlie the core symptomatology in schizophrenia. This study investigated whether abnormal synchronization occurs between the medial prefrontal cortex (mPFC) and the hippocampus (HPC), two brain regions implicated in schizophrenia pathophysiology, using the maternal immune activation (MIA) animal model in rats. This neurodevelopmental model of schizophrenia is induced through a single injection of the synthetic immune system activator polyriboinosinic-polyribocytidylic acid, a synthetic analog of double-stranded RNA, a molecular pattern associated with viral infection, in pregnant rat dams. It is based on epidemiological evidence of increased risk of schizophrenia in adulthood after prenatal exposure to infection. In the present study, EEG coherence and neuronal phase-locking to underlying EEG were measured in freely moving MIA and control offspring. The MIA intervention produced significant reductions in mPFC-HPC EEG coherence that correlated with decreased prepulse inhibition of startle, a measure of sensory gating and a hallmark schizotypal behavioral measure. Furthermore, changes in the synchronization of neuronal firing to the underlying EEG were evident in the theta and low-gamma frequencies. Firing within a putative population of theta-modulated, gamma-entrained mPFC neurons was also reduced in MIA animals. Thus, MIA in rats produces a fundamental disruption in long-range neuronal synchrony in the brains of the adult offspring that models the disruption of synchrony observed in schizophrenia.

Viral pathogenesis depends on a suitable milieu in target host cells permitting viral gene expression, propagation, and spread. In many instances, viral genomes can be manipulated to select for propagation in certain tissues or cell types. This has been achieved for the neurotropic poliovirus (PV) by exchange of the internal ribosomal entry site (IRES), which is responsible for translation of the uncapped plus-strand RNA genome. The IRES of human rhinovirus type 2 (HRV2) confers neuron-specific replication deficits to PV but has no effect on viral propagation in malignant glioma cells. We report here that placing the critical gamma(1)34.5 virulence genes of herpes simplex virus type 1 (HSV) under translation control of the HRV2 IRES results in neuroattenuation in mice. In contrast, IRES insertion permits HSV propagation in malignant glioma cell lines that do not support replication of HSV recombinants carrying gamma(1)34.5 deletions. Our observations indicate that the conditions for alternative translation initiation at the HRV2 IRES in malignant glioma cells differ from those in normal central nervous system (CNS) cells. Picornavirus regulatory sequences mediating cell type-specific gene expression in the CNS can be utilized to target cancerous cells at the level of translation regulation outside their natural context.

Lion lentivirus (LLV; also known as feline immunodeficiency virus of lion, Panthera leo [FIVPle]) is present in free-ranging and captive lion populations at a seroprevalence of up to 100%; however, clinical signs are rarely reported. LLV displays up to 25% interclade sequence diversity, suggesting that it has been in the lion population for some time and may be significantly host adapted. Three captive lions diagnosed with LLV infection displayed lymphocyte subset alterations and progressive behavioral, locomotor, and neuroanatomic abnormalities. No evidence of infection with other potential neuropathogens was found. Antemortem electrodiagnostics and radiologic imaging indicated a diagnosis consistent with lentiviral neuropathy. PCR was used to determine a partial lentiviral genomic sequence and to quantify the proviral burden in eight postmortem tissue specimens. Phylogenetic analysis demonstrated that the virus was consistent with the LLV detected in other captive and free-ranging lions. Despite progressive neurologic signs, the proviral load in tissues, including several regions of the brain, was low; furthermore, gross and histopathologic changes in the brain were minimal. These findings suggest that the symptoms in these animals resulted from nonspecific encephalopathy, similar to human immunodeficiency virus, FIV, and simian immunodeficiency virus (SIV) neuropathies, rather than a direct effect of active viral replication. The association of neuropathy and lymphocyte subset alterations with chronic LLV infection suggests that long-term LLV infection can have detrimental effects for the host, including death. This is similar to reports of aged sootey mangabeys dying from diseases typically associated with end-stage SIV infection and indicates areas for further research of lentiviral infections of seemingly adapted natural hosts, including mechanisms of host control and viral adaptation.

Proinflammatory cytokines and chemokines are often detected in brain tissue of patients with neurological diseases such as multiple sclerosis (MS), HIV-associated dementia (HAD) and Alzheimer's disease (AD). We have utilized a mouse model of retrovirus-induced neurological disease to examine how these proinflammatory responses contribute to neuropathogenesis. In previous studies with this model, a correlation was found between neurovirulence and cytokine and chemokine expression. However, it was unclear whether the induction of these cytokines and chemokines was in response to specific virus envelope determinants or was regulated by the level of virus infection in the brain. In the current study, we demonstrated that multiple polytropic retroviruses induced cytokine and chemokine mRNA expression following increased virus levels in the brain. Increased virus levels of polytropic viruses also correlated with increased neuropathogenesis. In contrast, the ecotropic retrovirus, FB29, did not induce cytokine or chemokine mRNA expression or neurological disease, despite virus levels either similar to or higher than the polytropic retroviruses. As polytropic and ecotropic viruses utilize different receptors for entry, these receptors may play a critical role in the induction of these innate immune responses in the brain.

Measles virus (MV) infection causes an acute childhood disease, associated in certain cases with infection of the central nervous system and development of a severe neurological disease. We have generated transgenic mice ubiquitously expressing the human protein SLAM (signaling lymphocytic activation molecule), or CD150, recently identified as an MV receptor. In contrast to all other MV receptor transgenic models described so far, in these mice infection with wild-type MV strains is highly pathogenic. Intranasal infection of SLAM transgenic suckling mice leads to MV spread to different organs and the development of an acute neurological syndrome, characterized by lethargy, seizures, ataxia, weight loss, and death within 3 weeks. In addition, in this model, vaccine and wild-type MV strains can be distinguished by virulence. Furthermore, intracranial MV infection of adult transgenic mice generates a subclinical infection associated with a high titer of MV-specific antibodies in the serum. Finally, to analyze new antimeasles therapeutic approaches, we created a recombinant soluble form of SLAM and demonstrated its important antiviral activity both in vitro and in vivo. Taken together, our results show the high susceptibility of SLAM transgenic mice to MV-induced neurological disease and open new perspectives for the analysis of the implication of SLAM in the neuropathogenicity of other morbilliviruses, which also use this molecule as a receptor. Moreover, this transgenic model, in allowing a simple readout of the efficacy of an antiviral treatment, provides unique experimental means to test novel anti-MV preventive and therapeutic strategies.

Infection of the central nervous system (CNS) by the neurotropic JHM strain of mouse hepatitis virus (JHMV) induces an acute encephalomyelitis associated with demyelination. To examine the anti-viral and/or regulatory role of interferon-gamma (IFN-gamma) signaling in the cell that synthesizes and maintains the myelin sheath, we analyzed JHMV pathogenesis in transgenic mice expressing a dominant-negative IFN-gamma receptor on oligodendroglia. Defective IFN-gamma signaling was associated with enhanced oligodendroglial tropism and delayed virus clearance. However, the CNS inflammatory cell composition and CD8(+) T-cell effector functions were similar between transgenic and wild-type mice, supporting unimpaired peripheral and CNS immune responses in transgenic mice. Surprisingly, increased viral load in oligodendroglia did not affect the extent of myelin loss, the frequency of oligodendroglial apoptosis, or CNS recruitment of macrophages. These data demonstrate that IFN-gamma receptor signaling is critical for the control of JHMV replication in oligodendroglia. In addition, the absence of a correlation between increased oligodendroglial infection and the extent of demyelination suggests a complex pathobiology of myelin loss in which infection of oligodendroglia is required but not sufficient.

Pseudorabies virus (PRV) is a herpesvirus of swine, a member of the Alphaherpesvirinae subfamily, and the etiological agent of Aujeszky's disease. This review describes the contributions of PRV research to herpesvirus biology, neurobiology, and viral pathogenesis by focusing on (i) the molecular biology of PRV, (ii) model systems to study PRV pathogenesis and neurovirulence, (iii) PRV transsynaptic tracing of neuronal circuits, and (iv) veterinary aspects of pseudorabies disease. The structure of the enveloped infectious particle, the content of the viral DNA genome, and a step-by-step overview of the viral replication cycle are presented. PRV infection is initiated by binding to cellular receptors to allow penetration into the cell. After reaching the nucleus, the viral genome directs a regulated gene expression cascade that culminates with viral DNA replication and production of new virion constituents. Finally, progeny virions self-assemble and exit the host cells. Animal models and neuronal culture systems developed for the study of PRV pathogenesis and neurovirulence are discussed. PRV serves asa self-perpetuating transsynaptic tracer of neuronal circuitry, and we detail the original studies of PRV circuitry mapping, the biology underlying this application, and the development of the next generation of tracer viruses. The basic veterinary aspects of pseudorabies management and disease in swine are discussed. PRV infection progresses from acute infection of the respiratory epithelium to latent infection in the peripheral nervous system. Sporadic reactivation from latency can transmit PRV to new hosts. The successful management of PRV disease has relied on vaccination, prevention, and testing.

Background and Purpose: West Nile virus (WNV) infection is an ongoing seasonal epidemic. We correlated the MR imaging findings with the clinical presentations and outcomes of WNV infection., Methods: We reviewed 14 brain and three spinal MR images: nonenhanced and contrast-enhanced T1-weighted images (T1WIs) and T2-weighted images (T2WIs), nonenhanced fluid-attenuated inversion recovery (FLAIR) images (11 patients) and enhanced FLAIR images (three patients), with diffusion-weighted (DW) images and apparent diffusion coefficient maps. WNV infection was diagnosed by means of enzyme-linked immunosorbent assay with a plaque reduction neutralization test. We also correlated the MR findings with the clinical presentation, course, and outcome to determine their prognostic importance., Results: MR imaging findings included: 1) normal (five patients); 2) DW imaging-only abnormalities in the white matter, corona radiata, and internal capsule (four patients); 3) hyperintensity on FLAIR images and T2WIs in the lobar gray and white matter, cerebellum, basal ganglia, thalamus and internal capsule, pons and midbrain (three patients); 4) meningeal involvement (two patients); and 5) spinal cord, cauda equina, and nerve root involvement (three patients). All patients with finding 1 and all but one with finding 2 recovered completely. Two patients with finding 3 died. Those with finding 4 or 5 had residual neurologic deficits that were severe or moderate to severe, respectively., Conclusion: Patients with normal MR images or abnormalities on only DW images had the best prognosis, while those with abnormal signal intensity on T2WI and FLAIR images had the worst outcomes. No definite predilection for any specific area of the brain parenchyma was noted.

Mumps virus is highly neurotropic and, prior to widespread vaccination programs, was the major cause of viral meningitis in the United States. Nonetheless, the genetic basis of mumps virus neurotropism and neurovirulence was until recently not understood, largely due to the lack of an animal model. Here, nonneurovirulent (Jeryl Lynn vaccine) and highly neurovirulent (88-1961 wild type) mumps virus strains were passaged in human neural cells or in chicken fibroblast cells with the goal of neuroadapting or neuroattenuating the viruses, respectively. When tested in our rat neurovirulence assay against the respective parental strains, a Jeryl Lynn virus variant with an enhanced propensity for replication (neurotropism) and damage (neurovirulence) in the brain and an 88-1961 wild-type virus variant with decreased neurotropic and neurovirulent properties were recovered. To determine the molecular basis for the observed differences in neurovirulence and neuroattenuation, the complete genomes of the parental strains and their variants were fully sequenced. A comparison at the nucleotide level associated three amino acid changes with enhanced neurovirulence of the neuroadapted vaccine strain: one each in the nucleoprotein, matrix protein, and polymerase and three amino acid changes with reduced neurovirulence of the neuroattenuated wild-type strain: one each in the fusion protein, hemagglutinin-neuraminidase protein, and polymerase. The potential role of these amino acid changes in neurotropism, neurovirulence, and neuroattenuation is discussed.

Transcription of vesicular stomatitis virus is controlled by the position of a gene relative to the single 3' genomic promoter: promoter-proximal genes are transcribed at higher levels than those in more 5' distal positions. In previous work, we generated viruses having rearranged gene orders. These viruses had the promoter-proximal gene that encodes the nucleocapsid protein, N, moved to the second or fourth position in the genome in combination with the glycoprotein gene, G, moved from its usual promoter-distal fourth position to the first or third position. This resulted in three new viruses identified by the positions of the N and G genes in the gene order: G3N4, G1N4, and G1N2. The viruses G3N4 and G1N4 were attenuated for lethality in mice. In the present study, we addressed the basis of this attenuation by measuring the ability of each of the rearranged viruses to travel to and replicate in the olfactory bulb and brain following intranasal inoculation. In addition, the neuropathogenicity, serum cytokine levels, and immunoglobulin G isotype profiles in infected mice were determined. All the viruses reached the olfactory bulb and brain, but the outcomes of these infections were dramatically different. Viruses N1G4(wt) and G1N2 caused lethal encephalitis in 100% of animals within 7 days postinoculation; however, viruses G3N4 and G1N4 were cleared from the brain by 7 days postinoculation and all animals survived without apparent distress. The viruses differed in the distribution and intensity of lesions produced and the type and levels of cytokines induced. Animals inoculated with N1G4(wt) or G1N2 displayed extensive encephalitis and meningitis and had elevated levels of serum gamma interferon compared to what was seen with G3N4- or G1N4-infected mice. In contrast to what occurred with intranasal inoculation, all four viruses caused lethal encephalitis when administered by direct inoculation to the brain, a route that circumvents the majority of the host immune response, demonstrating that G3N4 and G1N4 were not deficient in their abilities to cause disease in the brain. These findings indicate that gene rearrangement and its consequent alteration of gene expression can, without any other changes, alter the viral spread and cytokine response following intranasal infection.

We studied the pathogenicity of five different genotypes (A to E) of highly pathogenic avian H5N1 viruses, which contained HA genes similar to those of the H5N1 virus A/goose/Guangdong/1/96 and five different combinations of "internal" genes, in a mouse model. Highly pathogenic, neurotropic variants of genotypes A, C, D, and E were isolated from the brain after a single intranasal passage in mice. Genotype B virus was isolated from lungs only. The mouse brain variants had amino acid changes in all gene products except PB1, NP, and NS1 proteins but no common sets of mutations. We conclude that the original H5N1/01 isolates of genotypes A, C, D, and E were heterogeneous and that highly pathogenic neurotropic variants can be rapidly selected in mice.

Borna disease virus (BDV) causes central nervous system (CNS) disease that is frequently manifested by behavioral abnormalities. BDV is a nonsegmented, negative, single-stranded RNA virus. On the basis of its unique genetic and biologic features, BDV is the prototypic member of a new virus family, Bornaviridae, within the order Mononegavirales. Therefore, the investigation of the molecular and cell biology of BDV may provide new insights about virus-cell interactions in the CNS. BDV is an important model system for the investigation of viral persistence in the CNS. Serologic and molecular epidemiologic studies suggest that BDV can infect humans. Despite controversy about potential association with human neuropsychiatric illnesses, BDV affords an intriguing model for the study of these illnesses. Neonatal BDV-infected rats display neurodevelopmental, physiologic, and neurobehavioral abnormalities that closely parallel some of the main features associated with several human mental disorders.

In 1998, an outbreak of acute encephalitis with high mortality rates among pig handlers in Malaysia led to the discovery of a novel paramyxovirus named Nipah virus. A multidisciplinary investigation that included epidemiology, microbiology, molecular biology, and pathology was pivotal in the discovery of this new human infection. Clinical and autopsy findings were derived from a series of 32 fatal human cases of Nipah virus infection. Diagnosis was established in all cases by a combination of immunohistochemistry (IHC) and serology. Routine histological stains, IHC, and electron microscopy were used to examine autopsy tissues. The main histopathological findings included a systemic vasculitis with extensive thrombosis and parenchymal necrosis, particularly in the central nervous system. Endothelial cell damage, necrosis, and syncytial giant cell formation were seen in affected vessels. Characteristic viral inclusions were seen by light and electron microscopy. IHC analysis showed widespread presence of Nipah virus antigens in endothelial and smooth muscle cells of blood vessels. Abundant viral antigens were also seen in various parenchymal cells, particularly in neurons. Infection of endothelial cells and neurons as well as vasculitis and thrombosis seem to be critical to the pathogenesis of this new human disease.

To facilitate identification of rhesus cytomegalovirus (RhCMV)-infected cells, a recombinant virus expressing enhanced green fluorescent protein (EGFP), designated RhCMV-EGFP, was constructed. An expression cassette for EGFP under the control of the simian virus 40 (SV40) early promoter was inserted into the intergenic region between unique short 1 (US1) and US2 of the RhCMV genome by homologous recombination. RhCMV-EGFP exhibited comparable growth kinetics to that of wild-type virus in rhesus fibroblast cultures and retained its pathogenicity in monkey fetuses. Typical neurologic syndromes caused by CMV infection were observed in all fetuses experimentally inoculated with RhCMV-EGFP, as evidenced by sonographic and gross examinations. Systemic RhCMV infections were established in all fetuses, as viral antigen was detected in multiple organs and virus was isolated from fetal blood samples. The engineered viral genome was stable following rapid serial passages in vitro and multiple rounds of replication in vivo. Infected cells could be readily distinguished by green fluorescence both in tissue cultures and in the fetuses. In addition, EGFP expression was detected in various cell types that were permissive to RhCMV infection, consistent with a broad tissue tropism of the SV40 promoter. These results demonstrate that RhCMV can be successfully engineered without loss of wild-type replication and pathogenic potential. Further, the spectrum of cortical anomalies and the distribution of infected cells in the brain tissues indicated that RhCMV may have preferentially targeted immature neuronal cells. The pattern of RhCMV infection in the central nervous system may offer an explanation for the severe developmental outcomes associated with congenital human CMV infection early in gestation.

The release of neurotoxins by activated brain macrophages or microglia is one mechanism proposed to contribute to the development of neurological disease following infection by lentiviruses, including feline immunodeficiency virus (FIV). Since molecular diversity in the lentiviral envelope gene influences the expression of host molecules implicated in neuronal injury, the role of the envelope sequence in FIV neuropathogenesis was investigated by using the neurovirulent FIV strain V1CSF, the nonneurovirulent strain Petaluma, and a chimera (FIVCh) containing the V1CSF envelope gene in a Petaluma background. All three viruses replicated in primary feline macrophages with equal efficiency, but conditioned medium from V1CSF- or FIVCh-infected cells was significantly more neurotoxic than medium from Petaluma-infected cultures (P < 0.001) and could be attenuated in a dose-dependent manner by treatment with either the matrix metalloproteinase (MMP) inhibitor prinomastat (PMT) or function-blocking antibodies to MMP-2. Although FIV sequences were detectable by PCR in brain tissue from neonatal cats infected with each of the viral strains, immunohistochemistry revealed increased astrogliosis and macrophage activation in the brains of V1CSF- and FIVCh-infected cats relative to the other groups, together with elevated markers of neuronal stress that included morphological changes and increased c-fos immunoreactivity. Similarly, MMP-2, but not MMP-9, mRNA and protein expression was increased in brain tissues of V1CSF- and FIVCh-infected cats relative to Petaluma-infected animals (P < 0.01). Infection with V1CSF or FIVCh was also associated with greater CD4(+) cell depletion (P < 0.001) and neurodevelopmental delays (P < 0.005), than in Petaluma-infected animals; these deficits improved following PMT therapy. These findings indicated that diversity in the envelope gene sequence influenced the neurovirulence exhibited by FIV both in vitro and in vivo, possibly through a mechanism involving the differential induction of MMP-2.

In recent years, advances in the diagnosis and treatment of herpes simplex encephalitis (HSE) have been achieved due to the prevalence of antiviral drugs and the introduction of the polymerase chain reaction (PCR) to test the cerebrospinal fluid. The several clinical forms of herpes simplex virus type 1 (HSV-1) infections of the central nervous system (CNS), including acute disseminated encephalomyelitis and brainstem encephalitis, have been clarified. However, fatal, prolonged, or relapsed cases are still observed, and early detection and appropriate treatment is necessary to lead to a good prognosis for these intractable HSE cases. In adult HSV-2 infections, meningitis and myelitis associated with genital herpes are common. In the past, HSV-2 myelitis has been reported as a form of fatal necrotizing myelopathy; however, using PCR and magnetic resonance imaging studies, mild surviving cases are increasingly likely to be identified. Meanwhile, various CNS syndromes resulting from the herpes group viruses, including varicella-zoster virus and Epstein-Barr virus have also been reported. These herpesviruses have several characteristics in common, e.g., they exist in the latent state and they occur in both mucocutaneous and CNS infections. Adult HSV-1 and -2 infections of the CNS are discussed together with other herpes group virus infections of the CNS.

We provide a comprehensive clinical, radiological and virological analysis of four patients with Epstein-Barr virus (EBV) infection of the nervous system. One patient developed acute myeloradiculitis, one had acute encephalomyeloradiculitis, one had acute meningoencephalomyeloradiculitis and one had a subacute meningomyeloradiculitis. The ability of EBV to affect multiple parts of the entire neuraxis from meninges and brain to the spinal cord and peripheral nerves was evidenced by combinations of stiff neck and mental status changes, as well as patterns of weakness and sensory loss due to transverse myelitis or peripheral nerve disease. The CSF of all four patients contained a pleocytosis, predominantly mononuclear with elevated levels of protein, but a normal glucose level. In the two patients with acute myeloradiculitis and subacute meningomyeloradiculitis, the MRI revealed an increased signal in the spinal cord and lumbosacral roots, but in the two patients with acute encephalomyeloradiculitis and acute meningoencephalomyeloradiculitis, the brain and spinal cord MRIs were normal. In all four patients, EBV DNA, but not cytomegalovirus (CMV), herpes simplex virus (HSV) or varicella-zoster virus (VZV) DNA, was found in the CSF. The antibody pattern in serum was consistent with recent infection, and both EBV immunoglobulin (Ig) M and IgG antibodies, but not antibodies to HSV, VZV or CMV, were found in the CSF. Finally, there were reduced serum/CSF ratios of antibody to EBV, but not to total IgG or albumin, consistent with intrathecal antibody synthesis. None of the four patients died and none had brain swelling or focal changes according to brain MRI. Residual neurological deficits were evident. The two patients with acute myeloradiculitis and acute meningomyeloradiculitis had residual lower extremity weakness, and one of these patients later developed optic neuritis. The patient with acute encephalomyeloradiculitis had a moderate flaccid paraparesis, and the patient with subacute meningomyeloradiculitis was left with sensory loss in the feet. Compared with neurological disease caused by other herpes viruses, the clinical features of acute EBV myeloradiculitis, encephalomyeloradiculitis, encephalomyeloradiculitis and subacute meningomyeloradiculitis are distinctive. Of the eight human herpesviruses, EBV and VZV produce the most protean neurological syndromes. The mechanism by which EBV produces neurological disease is unknown. More correlative pathological, virological and immunological studies are needed in EBV-associated neurological disease.

The neurovirulent WSN strain of influenza A virus, introduced into the olfactory bulb of C57BL/6 mice, selectively attacks several brain nuclei which are highly implicated in the pathogenesis of neuropsychiatric disturbances. The virus-infected neurons are eradicated through apoptotic neurodegeneration. On the other hand, activated microglia serve the neuroprotection against virus infection.

Neurodegeneration in the brain induced by the WSN strain of influenza A virus was investigated after stereotaxic introduction into the olfactory bulb of C57BL/6 mice. Immunohistochemistry detected WSN virus-infected neurons in the anterior olfactory nucleus as early as day 3 postinfection. Thereafter, they became shrunken and showed loss of neurite-immunolabeling and chromatin condensation. Infected neurons died by day 12, degenerating into multiple small granular bodies. The terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling method demonstrated DNA fragmentation in infected neurons at day 7 and also in such granular bodies at day 12. In perforin-deficient mice, the appearance of virally induced apoptotic neurodegeneration was delayed and virus infection continued for a longer period of 35 days postinfection. These findings indicate that perforin-mediated neuroapoptosis appears significant in exterminating the intracellular pathogen at an early stage of infection.

Borna disease virus (BDV) infection of newborn rats leads to a persistent infection of the brain, which is associated with behavioral and neuroanatonomical abnormalities. These disorders occur in the absence of lymphoid cell infiltrates, and BDV-induced cell damage is restricted to defined brain areas. To investigate if damage to synaptic structures anteceded neuronal loss in BDV neonatally infected rats, we analyzed at different times postinfection the expression levels of growth-associated protein 43 and synaptophysin, two molecules involved in neuroplasticity processes. We found that BDV induced a progressive and marked decrease in the expression of these synaptic markers, which was followed by a significant loss of cortical neurons. Our findings suggest that BDV persistent infection interferes with neuroplasticity processes in specific cell populations. This, in turn, could affect the proper supply of growth factors and other molecules required for survival of selective neuronal populations within the cortex and limbic system structures.