Infection Of Glial Cells Research Articles

Herpes Simplex Virus type 1 inhibits autophagy in glial cells but requires ATG5 for the success of viral replication.

Herpes Simplex Virus type 1 (HSV-1) 1 is a neurotropic virus that has been associated with neurodegenerative disorders. The dysregulation of autophagy by HSV-1 has been proposed as a potential cause of neurodegeneration. While studies have extensively tackled the interaction between autophagy and HSV-1 in neurons, research in glial cells is currently limited. Our studies demonstrate that HSV-1 inhibits, but not completely blocks, the formation of autophagosomes in human oligodendroglioma- and astrocytoma- derived cell lines. These findings have been confirmed in murine oligodendrocyte precursor cells (OPCs). Finally, this study investigates the impact of autophagy on HSV-1 infection in glial cells. While the lack of basal autophagy in LC3B knockout glial cells does not have a significant effect on viral infection, cells without the autophagy-related protein ATG5 exhibit reduced viral production. The absence of ATG5 leads to a decrease in the transcription and replication of viral genes, as well as a delay in the initial stages of the formation of HSV-1 replication compartments. These findings indicate that while autophagy may not play a significant role in antiviral defense in glial cells, HSV-1 may be inhibiting autophagy to exploit non-canonical functions of certain components of the autophagic machinery, such as ATG5, to benefit its lifecycle.

From bedside to bench: how existing therapies inform the relationship between Epstein-Barr virus and multiplesclerosis.

Therapy for relapsing-remitting multiple sclerosis (MS) has advanced dramatically despite incomplete understanding of the cause of the condition. Current treatment involves inducing broad effects on immune cell populations with consequent off-target side effects, and no treatment can completely prevent disability progression. Further therapeutic advancement will require a better understanding of the pathobiology of MS. Interest in the role of Epstein-Barr virus (EBV) in multiple sclerosis has intensified based on strong epidemiological evidence of an association between EBV seroprevalence and MS. Hypotheses proposed to explain the biological relationship between EBV and MS include molecular mimicry, EBV immortalised autoreactive B cells and infection of glial cells by EBV. Examining the interaction between EBV and immunotherapies that have demonstrated efficacy in MS offers clues to the validity of these hypotheses. The efficacy of B cell depleting therapies could be consistent with a hypothesis that EBV-infected B cells drive MS; however, loss of T cell control of B cells does not exacerbate MS. A number of MS therapies invoke change in EBV-specific T cell populations, but pathogenic EBV-specific T cells with cross-reactivity to CNS antigen have not been identified. Immune reconstitution therapies induce EBV viraemia and expansion of EBV-specific T cell clones, but this does not correlate with relapse. Much remains unknown regarding the role of EBV in MS pathogenesis. We discuss future translational research that could fill important knowledge gaps.

Non-Productive Infection of Glial Cells with SARS-CoV-2 in Hamster Organotypic Cerebellar Slice Cultures.

The numerous neurological syndromes associated with COVID-19 implicate an effect of viral pathogenesis on neuronal function, yet reports of direct SARS-CoV-2 infection in the brain are conflicting. We used a well-established organotypic brain slice culture to determine the permissivity of hamster brain tissues to SARS-CoV-2 infection. We found levels of live virus waned after inoculation and observed no evidence of cell-to-cell spread, indicating that SARS-CoV-2 infection was non-productive. Nonetheless, we identified a small number of infected cells with glial phenotypes; however, no evidence of viral infection or replication was observed in neurons. Our data corroborate several clinical studies that have assessed patients with COVID-19 and their association with neurological involvement.

Activation of the Kynurenine Pathway and Production of Inflammatory Cytokines by Astrocytes and Microglia Infected With Neospora caninum.

In the central nervous system, astrocytes and microglia contribute to homeostasis, regulating the immune response to infectious agents. Neospora caninum is an obligate intracellular protozoan that infects different animal species and it is encysted in their nervous tissue while triggering an immune response modulated by glia. This study aimed to evaluate the infection of primary cultures of rat glial cells by N. caninum through the catabolites of tryptophan, the expression of inflammatory mediators and the integrity of neural tissue. Infection with this coccidium resulted in morphological and functional changes, particularly astrogliosis and microgliosis, and increased the expression of the inflammatory mediators TNF, IL1β, IL-10, and arginase, as well as mRNA for CCL5 and CCL2, molecules involved in the CNS chemotaxis. The infection with N. caninum in glial cells also triggered the activation of the tryptophan pathway, characterized by increased kynurenine 2,3 monooxygenase (KMO) mRNA expression, and by the production of the excitotoxin quinolinic acid (QUIN). Moreover, glia-neuron co-cultures, when exposed to the secretome derived from N. caninum infected glial cells, presented greater neurons distribution and formation of neurite extensions, associated to morphological changes in astrocytes compatible with neuro-preservation. Considering that the tryptophan catabolism is associated to immune response, these findings suggest that glial activation in N. caninum infection should be responsible for modulating the inflammatory status in an attempt to restore the nervous system homeostasis, since excessive inflammatory response can cause irreversible damage to tissue preservation.

Effect of 17β-Estradiol, Progesterone, and Tamoxifen on Neurons Infected with Toxoplasma gondii In Vitro.

Toxoplasma gondii (T. gondii) is the causal agent of toxoplasmosis, which produces damage in the central nervous system (CNS). Toxoplasma–CNS interaction is critical for the development of disease symptoms. T. gondii can form cysts in the CNS; however, neurons are more resistant to this infection than astrocytes. The probable mechanism for neuron resistance is a permanent state of neurons in the interface, avoiding the replication of intracellular parasites. Steroids regulate the formation of Toxoplasma cysts in mice brains. 17β-estradiol and progesterone also participate in the control of Toxoplasma infection in glial cells in vitro. The aim of this study was to evaluate the effects of 17β-estradiol, progesterone, and their specific agonists–antagonists on Toxoplasma infection in neurons in vitro. Neurons cultured were pretreated for 48 h with 17β-estradiol or progesterone at 10, 20, 40, 80, or 160 nM/mL or tamoxifen 1 μM/mL plus 17β-estradiol at 10, 20, 40, 80, and 160 nM/mL. In other conditions, the neurons were pretreated during 48 h with 4,4′,4″-(4-propyl-[1H] pyrozole-1,3,5-triyl) trisphenol or 23-bis(4-hydroxyphenyl) propionitrile at 1 nM/mL, and mifepristone 1 µM/mL plus progesterone at 10, 20, 40, 80, and 160 nM/mL. Neurons were infected with 5000 tachyzoites of the T. gondii strain RH. The effect of 17β estradiol, progesterone, their agonists, or antagonists on Toxoplasma infection in neurons was evaluated at 24 and 48 h by immunocytochemistry. T. gondii replication was measured with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. 17β-Estradiol alone or plus tamoxifen reduced infected neurons (50%) compared to the control at 48 h. Progesterone plus estradiol decreased the number of intracellular parasites at 48 h of treatment compared to the control (p < 0.001). 4,4′,4″-(4-propyl-[1H] pyrozole-1,3,5-triyl) trisphenol and 23-bis(4-hydroxyphenyl) propionitrile reduced infected neurons at 48 h of treatment significantly compared to the control (p < 0.05 and p < 0.001, respectively). The Toxoplasma infection process was decreased by the effect of 17β-estradiol alone or combined with tamoxifen or progesterone in neurons in vitro. These results suggest the essential participation of progesterone and estradiol and their classical receptors in the regulation of T. gondii neuron infection.

Complications neurologiques de l’infection par le virus JC : revue générale

Although human polyomavirus JC (JCV) seroprevalence in the general population is high, its neurological complications are rare and progressive multifocal leukoencephalopathy (PML), a lethal central nervous system (CNS) demyelinating disease, is the most well-known. After an usually asymptomatic primary infection during late childhood, a latent JCV form persists in different sites, notably the kidneys and lymphocytes. Rearrangement of that archetype into the prototypical neurotropic strain can reactivate JCV, thereby enabling its CNS penetration and infection of glial cells. In a context of defective immune defenses (HIV infection, cancer or immunosuppressant therapies) this infection leads to oligodendrocyte death that contributes, via demyelinization, to PML but also, as more recently described, to other CNS complications, e.g., JCV granule cell neuronopathy, meningitis or encephalitis. Clinical manifestations depend on the localization of the lesions. The increasingly widespread use of new immunomodulatory monoclonal antibodies to treat multiple sclerosis and other inflammatory systemic diseases has increased PML frequency in those previously rarely affected entities. Diagnosis relies on magnetic resonance imaging, JCV detection in cerebrospinal fluid and, when necessary, brain histology. PML is often lethal. No specific, evidence-based treatment with clinically relevant efficacy is available. The therapeutic objective is to restore host immune responses to JCV, while avoiding immune-reconstitution inflammatory syndrome.

Temporal In Vitro Raman Spectroscopy for Monitoring Replication Kinetics of Epstein-Barr Virus Infection in Glial Cells.

Raman spectroscopy can be used as a tool to study virus entry and pathogen-driven manipulation of the host efficiently. To date, Epstein–Barr virus (EBV) entry and altered biochemistry of the glial cell upon infection are elusive. In this study, we detected biomolecular changes in human glial cells, namely, HMC-3 (microglia) and U-87 MG (astrocytes), at two variable cellular locations (nucleus and periphery) by Raman spectroscopy post-EBV infection at different time points. Two possible phenomena, one attributed to the response of the cell to viral attachment and invasion and the other involved in duplication of the virus followed by egress from the host cell, are investigated. These changes corresponded to unique Raman spectra associated with specific biomolecules in the infected and the uninfected cells. The Raman signals from the nucleus and periphery of the cell also varied, indicating differential biochemistry and signaling processes involved in infection progression at these locations. Molecules such as cholesterol, glucose, hyaluronan, phenylalanine, phosphoinositide, etc. are associated with the alterations in the cellular biochemical homeostasis. These molecules are mainly responsible for cellular processes such as lipid transport, cell proliferation, differentiation, and apoptosis in the cells. Raman signatures of these molecules at distinct time points of infection indicated their periodic involvement, depending on the stage of virus infection. Therefore, it is possible to discern the details of variability in EBV infection progression in glial cells at the biomolecular level using time-dependent in vitro Raman scattering.

Zika Virus Infects Primary Human Glial Cells and Results in Neuroinflammation and Cell Death

Abstract Zika virus (ZIKV) infection in humans has been linked to serious birth defects, including abnormalities of the brain and eyes. Here, we used two lines of primary human glial cells from the brain and found both are susceptible to ZIKV infection. Viral RNA abundance increased from 6 to 36 h post-infection (hpi). Both cells showed cytopathic effects with cell shedding, suspension and death at 48 hpi. We found increased mRNA levels of IL-6, IL-1b, CXCL10 (IP-10), IL-8 and CCL2 in ZIKV-infected microglial cells, as well as those of TNF-a in astrocytes. Elevated levels of CXCL10 protein were also observed in microglial cells at 48 hpi. These results suggested that glial cells may directly contribute to neuroinflammation by releasing pro-inflammatory cytokines. ZIKV infection can also activate ISGs, as evidenced by increased mRNA levels of IFN-b, OAS1, Mx1 and IFITM1 in infected microglia at 48 hpi. In addition, ZIKV can induce levels of caspase-1 and caspase-3 expression in microglia and astrocytes, respectively. These findings suggest that activation of glial cells contributes to neuroinflammation and induces distinct cell death pathways in different glial cells. Finally, we examined the antiviral effect of azithromycin in infected glial cells and found a dose-dependent effect (0, 10 and 20 uM) on viral reduction. Azithromycin treatment significantly decreased gene expression of TNF-a. Moreover, the antiviral effect of azithromycin was confirmed in mouse models of ZIKV infection. Collectively, our study demonstrated that ZIKV can infect primary human glial cells, leading to inflammatory responses and cell death. Azithromycin treatment inhibits viral load in glial cells and alleviate neuroinflammation during ZIKV infection.

Burkholderia pseudomallei invades the olfactory nerve and bulb after epithelial injury in mice and causes the formation of multinucleated giant glial cells in vitro.

The infectious disease melioidosis is caused by the bacterium Burkholderia pseudomallei. Melioidosis is characterised by high mortality and morbidity and can involve the central nervous system (CNS). We have previously discovered that B. pseudomallei can infect the CNS via the olfactory and trigeminal nerves in mice. We have shown that the nerve path is dependent on mouse strain, with outbred mice showing resistance to olfactory nerve infection. Damage to the nasal epithelium by environmental factors is common, and we hypothesised that injury to the olfactory epithelium may increase the vulnerability of the olfactory nerve to microbial insult. We therefore investigated this, using outbred mice that were intranasally inoculated with B. pseudomallei, with or without methimazole-induced injury to the olfactory neuroepithelium. Methimazole-mediated injury resulted in increased B. pseudomallei invasion of the olfactory epithelium, and only in pre-injured animals were bacteria found in the olfactory nerve and bulb. In vitro assays demonstrated that B. pseudomallei readily infected glial cells isolated from the olfactory and trigeminal nerves (olfactory ensheathing cells and trigeminal Schwann cells, respectively). Bacteria were degraded by some cells but persisted in other cells, which led to the formation of multinucleated giant cells (MNGCs), with olfactory ensheathing cells less likely to form MNGCs than Schwann cells. Double Cap mutant bacteria, lacking the protein BimA, did not form MNGCs. These data suggest that injuries to the olfactory epithelium expose the primary olfactory nervous system to bacterial invasion, which can then result in CNS infection with potential pathogenic consequences for the glial cells.

Zika virus infection of glia leads to secondary injury to axons and dendrites

Zika virus infection was recently linked to microcephaly and peripheral neuropathy (GBS) in Zika virus epidemic areas. Building on our previous work (Cumberworth et al, 2017) we investigated, in a time-course study, how the viral infection and the injury of cell processes of oligodendrocytes and neurons are related to each other in the same in vitro model. We generated CNS myelinating cultures from a reporter mouse (Thy1-YFP) on the Ifnar1 -/-background. A proportion of neurons and their processes are positive for YFP in those cultures, which enabled us to visualise single neurons. Cultures were infected with the Brazilian Zika virus strain (PE243) at an MOI of 0.3 and cultured for up to 6 days post infection. We observed that the neuronal cell processes were affected as early as the appearance of the first clusters of infected glial cells. To analyse the interrelation of neurons and myelin further, cultures were labeled with an antibody recognising proteolipid protein. We found that the myelin got injured as early as neuronal processes. These results suggest that the injury to neuronal processes might be a consequence of the infection of the primary target of Zika virus: oligodendroglia. These data help us to understand disease pathogenesis of Zika virus infection of the CNS, and whether there is a time-window to intervene therapeutically. Furthermore, this gives an insight as to how viral infection of glial cells can affect neuronal processes such as axons.

Human induced pluripotent stem cell-derived glial cells and neural progenitors display divergent responses to Zika and dengue infections

Maternal Zika virus (ZIKV) infection during pregnancy is recognized as the cause of an epidemic of microcephaly and other neurological anomalies in human fetuses. It remains unclear how ZIKV accesses the highly vulnerable population of neural progenitors of the fetal central nervous system (CNS), and which cell types of the CNS may be viral reservoirs. In contrast, the related dengue virus (DENV) does not elicit teratogenicity. To model viral interaction with cells of the fetal CNS in vitro, we investigated the tropism of ZIKV and DENV for different induced pluripotent stem cell-derived human cells, with a particular focus on microglia-like cells. We show that ZIKV infected isogenic neural progenitors, astrocytes, and microglia-like cells (pMGLs), but was only cytotoxic to neural progenitors. Infected glial cells propagated ZIKV and maintained ZIKV load over time, leading to viral spread to susceptible cells. DENV triggered stronger immune responses and could be cleared by neural and glial cells more efficiently. pMGLs, when cocultured with neural spheroids, invaded the tissue and, when infected with ZIKV, initiated neural infection. Since microglia derive from primitive macrophages originating in proximity to the maternal vasculature, they may act as a viral reservoir for ZIKV and establish infection of the fetal brain. Infection of immature neural stem cells by invading microglia may occur in the early stages of pregnancy, before angiogenesis in the brain rudiments. Our data are also consistent with ZIKV and DENV affecting the integrity of the blood-brain barrier, thus allowing infection of the brain later in life.

MicroRNA-219 Reduces Viral Load and Pathologic Changes in Theiler's Virus-Induced Demyelinating Disease.

Analysis of microRNA (miR) expression in the central nervous system white matter of SJL mice infected with the BeAn strain of Theiler's murine encephalomyelitis virus (TMEV) revealed a significant reduction of miR-219, a critical regulator of myelin assembly and repair. Restoration of miR-219 expression by intranasal administration of a synthetic miR-219 mimic before disease onset ameliorates clinical disease, reduces neurogliosis, and partially recovers motor and sensorimotor function by negatively regulating proinflammatory cytokines and virus RNA replication. Moreover, RNA sequencing of host lesions showed that miR-219 significantly downregulated two genes essential for the biosynthetic cholesterol pathway, Cyp51 (lanosterol 14-α-demethylase) and Srebf1 (sterol regulatory element-binding protein-1), and reduced cholesterol biosynthesis in infected mice and rat CG-4 glial precursor cells in culture. The change in cholesterol biosynthesis had both anti-inflammatoryand anti-viral effects. Because RNA viruses hijack endoplasmic reticulum double-layered membranes to provide a platform for RNA virus replication and are dependent on endogenous pools of cholesterol, miR-219 interference with cholesterol biosynthesis interfered virus RNA replication. These findings demonstrate that miR-219 inhibits TMEV-induced demyelinating disease through its anti-inflammatory and anti-viral properties.

MiR-16-1 expression, heat shock protein 70 and inflammatory reactions in astrocytes of mice with epilepsy induced by encephalitis B virus infection.

The upregulation of miR-16-1 expression and heat shock protein 70 (HSP70) and inflammatory reaction mechanism in astrocytes of mice with epilepsy induced by encephalitis B virus infection were studied. Six-to-eight-week-old healthy male C57BL/6 mice received intraperitoneal injection of pilocarpine (320–340 mg/kg, 40 mg/ml) to induce status epilepsy. After 7 days, mice were inoculated with 100 µl Dulbecco's modified Eagle's medium (DMEM) in the neck, including 6.25×23 PFU Japanese encephalitis virus P3 wild strain. The experiment was divided into 4 groups, including, the healthy control group, the epilepsy model group, the model group + negative inoculation group and the virus infection group with 10 mice in each group. The healthy control group received intraperitoneal injection of the same amount of normal saline; the model group + negative inoculation group was injected with the same amount of DMEM without P3. One and three days after infection, 5 mice from each group were sacrificed, hippocampus tissues were obtained and astrocytes were isolated. After purification, glial fibrillary acidic protein was identified by immunohistochemical staining. Infected glial cells were detected by P3 antigen of immunofluorescence staining. RT-PCR method was used to detect the expression of miR-16-1 mRNA in astrocytes. Western blot analysis was used to detect the expression of HSP70. ELISA method was used to detect the levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α and nuclear factor-κB (NF-κB) inflammatory factors in tail vein blood. Level of expression of miR-16-1 mRNA, HSP70 as well as IL-6, TNF-α and NF-κB inflammatory factor levels of virus infected mice of 1 and 3 days were significantly higher (P<0.05) than those of model group and negative inoculation group and lowest in control group. In conclusion, the level of expression of miR-16-1 and HSP70 can be increased by the infection of Japanese encephalitis virus on the astrocytes of mice with epilepsy, to promote the expression of IL-6, TNF-α and NF-κB of inflammatory factors.

Axl Mediates ZIKA Virus Entry in Human Glial Cells and Modulates Innate Immune Responses

ZIKA virus (ZIKV) is an emerging pathogen responsible for neurological disorders and congenital microcephaly. However, the molecular basis for ZIKV neurotropism remains poorly understood. Here, we show that Axl is expressed in human microglia and astrocytes in the developing brain and thatitmediates ZIKV infection of glial cells. Axl-mediated ZIKV entry requires the Axl ligand Gas6, which bridges ZIKV particles to glial cells. Following binding, ZIKV is internalized through clathrin-mediated endocytosis and traffics to Rab5+ endosomes to establish productive infection. During entry, the ZIKV/Gas6 complex activates Axl kinase activity, which downmodulates interferon signaling and facilitates infection. ZIKV infection of human glial cells is inhibited by MYD1, an engineered Axl decoy receptor, and by the Axl kinase inhibitor R428. Our results highlight the dual role of Axl during ZIKV infection ofglial cells: promoting viral entry and modulating innate immune responses. Therefore, inhibiting Axl function may represent a potential target for future antiviral therapies.

Glial Cell-Elicited Activation of Brain Microvasculature in Response to Brucella abortus Infection Requires ASC Inflammasome-Dependent IL-1β Production.

Blood-brain barrier activation and/or dysfunction are a common feature of human neurobrucellosis, but the underlying pathogenic mechanisms are largely unknown. In this article, we describe an immune mechanism for inflammatory activation of human brain microvascular endothelial cells (HBMEC) in response to infection with Brucella abortus Infection of HBMEC with B. abortus induced the secretion of IL-6, IL-8, and MCP-1, and the upregulation of CD54 (ICAM-1), consistent with a state of activation. Culture supernatants (CS) from glial cells (astrocytes and microglia) infected with B. abortus also induced activation of HBMEC, but to a greater extent. Although B. abortus-infected glial cells secreted IL-1β and TNF-α, activation of HBMEC was dependent on IL-1β because CS from B. abortus-infected astrocytes and microglia deficient in caspase-1 and apoptosis-associated speck-like protein containing a CARD failed to induce HBMEC activation. Consistently, treatment of CS with neutralizing anti-IL-1β inhibited HBMEC activation. Both absent in melanoma 2 and Nod-like receptor containing a pyrin domain 3 are partially required for caspase-1 activation and IL-1β secretion, suggesting that multiple apoptosis-associated speck-like protein containing CARD-dependent inflammasomes contribute to IL-1β-induced activation of the brain microvasculature. Inflammasome-mediated IL-1β secretion in glial cells depends on TLR2 and MyD88 adapter-like/TIRAP. Finally, neutrophil and monocyte migration across HBMEC monolayers was increased by CS from Brucella-infected glial cells in an IL-1β-dependent fashion, and the infiltration of neutrophils into the brain parenchyma upon intracranial injection of B. abortus was diminished in the absence of Nod-like receptor containing a pyrin domain 3 and absent in melanoma 2. Our results indicate that innate immunity of the CNS set in motion by B. abortus contributes to the activation of the blood-brain barrier in neurobrucellosis and IL-1β mediates this phenomenon.

Neuropathogenicity of Two Saffold Virus Type 3 Isolates in Mouse Models.

ObjectiveSaffold virus (SAFV), a picornavirus, is occasionally detected in children with acute flaccid paralysis, meningitis, and cerebellitis; however, the neuropathogenicity of SAFV remains undetermined.MethodsThe virulence of two clinical isolates of SAFV type 3 (SAFV-3) obtained from a patient with aseptic meningitis (AM strain) and acute upper respiratory inflammation (UR strain) was analyzed in neonatal and young mice utilizing virological, pathological, and immunological methods.ResultsThe polyproteins of the strains differed in eight amino acids. Both clinical isolates were infective, exhibited neurotropism, and were mildly neurovirulent in neonatal ddY mice. Both strains pathologically infected neural progenitor cells and glial cells, but not large neurons, with the UR strain also infecting epithelial cells. UR infection resulted in longer inflammation in the brain and spinal cord because of demyelination, while the AM strain showed more infectivity in the cerebellum in neonatal ddY mice. Additionally, young BALB/c mice seroconverted following mucosal inoculation with the UR, but not the AM, strain.ConclusionsBoth SAFV-3 isolates had neurotropism and mild neurovirulence but showed different cell tropisms in both neonatal and young mouse models. This animal model has the potential to recapitulate the potential neuropathogenicity of SAFV-3.

Evaluating the Role of Viral Proteins in HIV-Mediated Neurotoxicity Using Primary Human Neuronal Cultures.

Despite the inability of HIV-1 to infect neurons, over half of the HIV-1-infected population in the USA suffers from neurocognitive dysfunction. HIV-infected immune cells in the periphery enter the central nervous system by causing a breach in the blood-brain barrier. The damage to the neurons is mediated by viral and host toxic products released by activated and infected immune and glial cells. To evaluate the toxicity of any viral isolate, viral protein, or host inflammatory protein, we describe a protocol to assess the neuronal apoptosis and synaptic compromise in primary cultures of human neurons and astrocytes.

Lack of Major Histocompatibility Complex Class I Upregulation and Restrictive Infection by JC Virus Hamper Detection of Neurons by T Lymphocytes in the Central Nervous System.

The human polyomavirus JC (JCV) infects glial cells in immunosuppressed individuals, leading to progressive multifocal leukoencephalopathy. Polyomavirus JC can also infect neurons in patients with JCV granule cell neuronopathy and JCV encephalopathy. CD8-positive T cells play a crucial role in viral containment and outcome in progressive multifocal leukoencephalopathy, but whether CD8-positive T cells can also recognize JCV-infected neurons is unclear. We used immunohistochemistry to determine the prevalence of T cells in neuron-rich areas of archival brain samples from 77 patients with JCV CNS infections and 94 control subjects. Neurons predominantly sustained a restrictive infection with expression of JCV regulatory protein T antigen (T Ag), whereas glial cells were productively infected and expressed both T Ag and the capsid protein VP1. T cells were more prevalent near JCV-infected cells with intact nuclei expressing both T Ag and VP1 compared with those expressing either protein alone. CD8-positive T cells also colocalized more with JCV-infected glial cells than with JCV-infected neurons. Major histocompatibility complex class I expression was upregulated in JCV-infected areas but could only be detected in rare neurons interspersed with infected glial cells. These results suggest that isolated neurons harboring restrictive JCV infection do not upregulate major histocompatibility complex class I and thus may escape recognition by CD8-positive T cells.

JC virus granule cell neuronopathy: A cause of infectious cerebellar degeneration

JC virus (JCV) infection of glial cells can lead to progressive multifocal leukoencephalopathy (PML) in immunocompromised patients. A newly described phenotype of the infection is infection of neurons. This distinct clinical and radiological syndrome is named JCV granule cell neuronopathy, characterized by exclusive or predominant cerebellar atrophy. We report the clinical and radiological longitudinal findings of 5 HIV-infected patients referred to us between September 2004 and November 2011 who exhibited JCV granule cell neuronopathy (4 probable cases and 1 possible). The association of immunocompromised status, progressive cerebellar syndrome, MRI abnormalities with cortical cerebellar atrophy and cerebrospinal fluid positive for JCV on PCR allowed for a highly probable diagnosis. The reversal of the immunocompromised status is the only way to stop the disease evolution. Motor functioning can remain impaired, but the illness itself, unlike progressive multifocal leukoencephalopathy, does not seem to threaten life.

HIV, opiates, and enteric neuron dysfunction.

Human immune deficient virus (HIV) is an immunosuppressive virus that targets CD4(+) T-lymphocytes. HIV infections cause increased susceptibility to opportunistic infections and cancer. HIV infection can also alter central nervous system (CNS) function causing cognitive impairment. HIV does not infect neurons but it does infect astrocytes and microglia in the CNS. HIV can also infect enteric glia initiating an intestinal inflammatory response which causes enteric neural injury and gut dysfunction. Part of the inflammatory response is HIV induced production of proteins including, Transactivator of transcription (Tat) which contribute to neuronal injury after release from HIV infected glial cells. A risk factor for HIV infection is intravenous drug use with contaminated needles and chronic opiate use can exacerbate neural injury in the nervous system. While most research focuses on the actions of Tat and other HIV related proteins and opiates on the brain, recent data indicate that Tat can cause intestinal inflammation and disruption of enteric neuron function, including alteration of Na(+) channel activity and action potential generation. A paper published in this issue of Neurogastroenterology and Motility extends these findings by identifying an interaction between Tat and morphine on enteric neuron Na(+) channels and on intestinal motility in vivo using a Tat expressing transgenic mouse model. These new data show that Tat protein can enhance the inhibitory actions of morphine on action potential generation and propulsive motility. These findings are important to our understanding of how HIV causes diarrhea in infected patients and for the use of opioid drugs to treat HIV-induced diarrhea.