ICAM-5 modulates cytokine/chemokine production in the CNS during the course of herpes simplex virus type 1 infection

Contemporary Circulating Enterovirus D68 Strains Infect and Undergo Retrograde Axonal Transport in Spinal Motor Neurons Independent of Sialic Acid

Enterovirus D68 (EV-D68) is an emerging virus that has been identified as a cause of recent outbreaks of acute flaccid myelitis (AFM), a poliomyelitis-like spinal cord syndrome that can result in permanent paralysis and disability. In experimental mouse models, EV-D68 spreads to, infects, and kills spinal motor neurons following infection by various routes of inoculation. The topography of virus-induced motor neuron loss correlates with the pattern of paralysis. The mechanism(s) by which EV-D68 spreads to target motor neurons remains unclear. We sought to determine the capacity of EV-D68 to spread by the neuronal route and to determine the role of known EV-D68 receptors, sialic acid and intracellular adhesion molecule 5 (ICAM-5), in neuronal infection. To do this, we utilized a microfluidic chamber culture system in which human induced pluripotent stem cell (iPSC) motor neuron cell bodies and axons can be compartmentalized for independent experimental manipulation. We found that EV-D68 can infect motor neurons via their distal axons and spread by retrograde axonal transport to the neuronal cell bodies. Virus was not released from the axons via anterograde axonal transport after infection of the cell bodies. Prototypic strains of EV-D68 depended on sialic acid for axonal infection and transport, while contemporary circulating strains isolated during the 2014 EV-D68 outbreak did not. The pattern of infection did not correspond with the ICAM-5 distribution and expression in either human tissue, the mouse model, or the iPSC motor neurons.IMPORTANCE Enterovirus D68 (EV-D68) infections are on the rise worldwide. Since 2014, the United States has experienced biennial spikes in EV-D68-associated acute flaccid myelitis (AFM) that have left hundreds of children paralyzed. Much remains to be learned about the pathogenesis of EV-D68 in the central nervous system (CNS). Herein we investigated the mechanisms of EV-D68 CNS invasion through neuronal pathways. A better understanding of EV-D68 infection in experimental models may allow for better prevention and treatment strategies of EV-D68 CNS disease.

Enterovirus D68 - The New Polio?

Enterovirus D68 (EV-D68) has emerged over the recent years, with large outbreaks worldwide. Increased occurrence has coincided with improved clinical awareness and surveillance of non-polio enteroviruses. Studies showing its neurotropic nature and the change in pathogenicity have established EV-D68 as a probable cause of Acute Flaccid Myelitis (AFM). The EV-D68 storyline shows many similarities with poliovirus a century ago, stimulating discussion whether EV-D68 could be ascertaining itself as the "new polio." Increasing awareness amongst clinicians, incorporating proper diagnostics and integrating EV-D68 into accessible surveillance systems in a way that promotes data sharing, will be essential to reveal the burden of disease. This will be a necessary step in preventing EV-D68 from becoming a threat to public health.

Intercellular Adhesion Molecular-5 as Marker in HIV Associated Neurocognitive Disorder

Despite the use of antiretroviral drugs HIV associated neurocognitive disorders (HAND) are still common in HIV-seropositive patients. Identification of HIV patients with cognitive impairment in early-stage might benefit a great deal from disease progression monitoring and treatment adjustment. Intercellular adhesion molecule-5 (ICAM5), characteristically expressed on neuron, may suppress immune functions by inhibition of T cell activation in central nervous system. Previous studies have shown that ICAM5 could be detected in patients with brain injury. To investigate the relationship between cognitive impairment and ICAM5 in HIV patients, we compared soluble ICAM5 levels in paired CSF and plasma specimens from HIV-infected individuals with or without neurocognitive impairment. sICAM5 concentrations were measured by ICAM5 ELISA kit. A total of 41 Patients were classified into HIV infected with normal cognition (HIV-NC) and impaired cognition groups (HIV-CI) based on Memorial Sloan-Kettering Scale. CSF and plasma levels of sICAM5 in HIV-CI patients were significantly higher than HIV-NC group (p<0.0001, p=0.0054 respectively). sICAM5 concentrations in plasma strongly correlated with sICAM5 in CSF (r=0.7250, p<0.0001) and S100B in CSF (r=0.3812, p<0.0139). Among 6 follow-up patients we found that sICAM5 levels in CSF and plasma might change consistently with HAND progression. In summary, we have shown that the expressions of sICAM5 in CSF and plasma may correlate with neurocognitive impairment in HIV infected patients. The elevation of sICAM5 in plasma were correspond with that in CSF as a consequence of blood-brain barrier permeability changes. ICAM5 can serve as a potential and readily accessible biomarker to predict HIV associated neurocognitive disorder.

ICAM-5/Telencephalin Is a Functional Entry Receptor for Enterovirus D68

Enterovirus D68 (EV-D68) is a member of the Picornaviridae family. Although EV-D68-associated infection was once considered rare, it has been increasing in recent years. EV-D68 infection is most frequently associated with respiratory illness. However, it has also been implicated in a polio-like neurological disorder, acute flaccid myelitis. Although sialic acid has been implicated in EV-D68 entry, the existence of a protein receptor has yet to be clarified. Here we identify neuron-specific intercellular adhesion molecule 5 (ICAM-5/telencephalin) as a cellular receptor for sialic acid-dependent and -independent EV-D68 viruses. EV-D68 bound specifically and efficiently to ICAM-5, and replication of EV-D68 in diverse cell types was inhibited by soluble ICAM-5 fragments. ICAM-5 silencing attenuated EV-D68 replication in permissive cells, and ICAM-5 expression in non-permissive cells allowed EV-D68 replication. The discovery of a neuron-specific adhesion molecule as an EV-D68 receptor has important implications for EV-D68 pathogenesis and may facilitate the development of novel intervention strategies.

Varicella zoster virus infection of human fetal lung cells alters mitochondrial morphology

Varicella zoster virus (VZV) is a ubiquitous alphaherpesvirus that establishes latency in ganglionic neurons throughout the neuraxis after primary infection. Here, we show that VZV infection induces a time-dependent significant change in mitochondrial morphology, an important indicator of cellular health, since mitochondria are involved in essential cellular functions. VZV immediate-early protein 63 (IE63) was detected in mitochondria-rich cellular fractions extracted from infected human fetal lung fibroblasts (HFL) by Western blotting. IE63 interacted with cytochrome c oxidase in bacterial 2-hybrid analyses. Confocal microscopy of VZV-infected HFL cells at multiple times after infection revealed the presence of IE63 in the nucleus, mitochondria, and cytoplasm. Our data provide the first evidence that VZV infection induces alterations in mitochondrial morphology, including fragmentation, which may be involved in cellular damage and/or death during virus infection.

The Interleukin-1 Balance During Encephalitis Is Associated With Clinical Severity, Blood-Brain Barrier Permeability, Neuroimaging Changes, and Disease Outcome

BACKGROUND

Encephalitis is parenchymal brain inflammation, commonly due to herpes simplex virus (HSV). Key host inflammatory mediators and their relationship to blood-brain barrier (BBB) permeability, neuroimaging changes, and disease outcome are poorly understood.

METHODS

We measured levels of 38 mediators in serum (n = 78) and cerebrospinal fluid (n = 37) specimens from patients with encephalitis, including 17 with disease due to HSV infection. Outcome measures were Glasgow coma and outcome scores; CSF to serum albumin ratio, reflecting BBB permeability; and, in patients with HSV infection, magnetic resonance imaging-based temporal lobe volume.

RESULTS

Serum interleukin 1 receptor antagonist (IL-1RA) levels were elevated in patients with a good outcome (P= .004). Among patients infected with HSV, the ratio of CSF IL-1β to IL-1RA was associated with a worse outcome (P= .009); a ratio of ≥0.55 pg/mL had high specificity and sensitivity for a poor outcome (100% and 83%;P= .015). Temporal lobe volume had a negative correlation with serum IL-1RA level (P= .012) and a positive correlation with serum IL-1α level (P= .0003) and CSF IL-1β level (P= .007). A normal coma score was associated with an elevated interleukin 10 (IL-10) level in serum specimens from HSV-infected patients (P= .007) and CSF specimens from all patients (P= .016); the IL-10 level correlated inversely with BBB permeability (P= .005).

CONCLUSIONS

A proinflammatory cytokine response is associated with greater clinical severity, BBB permeability, and neuroimaging damage during encephalitis. IL-1 antagonists should be investigated as adjunctive treatment in encephalitis.

ICAM-5: a neuronal dendritic adhesion molecule involved in immune and neuronal functions

The neuron-specific intercellular adhesion molecule-5 (ICAM-5, telencephalin) is a member of the ICAM family of adhesion proteins. It has a complex structure with nine external immunoglobulin domains followed by a transmembrane and a cytoplasmic domain. The external part binds to beta1- and beta2-integrins and the matrix protein vitronectin, whereas its transmembrane domain binds to presenilins and the cytoplasmic domain to alpha-actinin and the ERM family of cytoplasmic proteins. In neurons it is confined to the soma and dendrites and it is enriched in dendritic filopodia with less expression in more mature dendritic spines. ICAM-5 strongly stimulates neurite outgrowth. ICAM-5 is cleaved by matrix metalloproteases upon activation of glutamate receptors or degraded through endocytosis resulting in increased spine maturation. Ablation of ICAM-5 expression increases functional synapse formation. The cleaved soluble fragment of ICAM-5 is immunosuppressive, which may be important in neuronal inflammatory diseases.

Intercellular adhesion molecules (ICAMs) and spermatogenesis

BACKGROUND

During the seminiferous epithelial cycle, restructuring takes places at the Sertoli-Sertoli and Sertoli-germ cell interface to accommodate spermatogonia/spermatogonial stem cell renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation since developing germ cells, in particular spermatids, move 'up and down' the seminiferous epithelium. Furthermore, preleptotene spermatocytes differentiated from type B spermatogonia residing at the basal compartment must traverse the blood-testis barrier (BTB) to enter the adluminal compartment to prepare for meiosis at Stage VIII of the epithelial cycle, a process also accompanied by the release of sperm at spermiation. These cellular events that take place at the opposite ends of the epithelium are co-ordinated by a functional axis designated the apical ectoplasmic specialization (ES)-BTB-basement membrane. However, the regulatory molecules that co-ordinate cellular events in this axis are not known.

METHODS

Literature was searched at http://www.pubmed.org and http://scholar.google.com to identify published findings regarding intercellular adhesion molecules (ICAMs) and the regulation of this axis.

RESULTS

Members of the ICAM family, namely ICAM-1 and ICAM-2, and the biologically active soluble ICAM-1 (sICAM-1) are the likely regulatory molecules that co-ordinate these events. sICAM-1 and ICAM-1 have antagonistic effects on the Sertoli cell tight junction-permeability barrier, involved in Sertoli cell BTB restructuring, whereas ICAM-2 is restricted to the apical ES, regulating spermatid adhesion during the epithelial cycle. Studies in other epithelia/endothelia on the role of the ICAM family in regulating cell movement are discussed and this information has been evaluated and integrated into studies of these proteins in the testis to create a hypothetical model, depicting how ICAMs regulate junction restructuring events during spermatogenesis.

CONCLUSIONS

ICAMs are crucial regulatory molecules of spermatogenesis. The proposed hypothetical model serves as a framework in designing functional experiments for future studies.

Enhancement of chemokine function as an immunomodulatory strategy employed by human herpesviruses

Herpes simplex virus (HSV) types 1 and 2 are highly prevalent human neurotropic pathogens that cause a variety of diseases, including lethal encephalitis. The relationship between HSV and the host immune system is one of the main determinants of the infection outcome. Chemokines play relevant roles in antiviral response and immunopathology, but the modulation of chemokine function by HSV is not well understood. We have addressed the modulation of chemokine function mediated by HSV. By using surface plasmon resonance and crosslinking assays we show that secreted glycoprotein G (SgG) from both HSV-1 and HSV-2 binds chemokines with high affinity. Chemokine binding activity was also observed in the supernatant of HSV-2 infected cells and in the plasma membrane of cells infected with HSV-1 wild type but not with a gG deficient HSV-1 mutant. Cell-binding and competition experiments indicate that the interaction takes place through the glycosaminoglycan-binding domain of the chemokine. The functional relevance of the interaction was determined both in vitro, by performing transwell assays, time-lapse microscopy, and signal transduction experiments; and in vivo, using the air pouch model of inflammation. Interestingly, and in contrast to what has been observed for previously described viral chemokine binding proteins, HSV SgGs do not inhibit chemokine function. On the contrary, HSV SgGs enhance chemotaxis both in vitro and in vivo through increasing directionality, potency and receptor signaling. This is the first report, to our knowledge, of a viral chemokine binding protein from a human pathogen that increases chemokine function and points towards a previously undescribed strategy of immune modulation mediated by viruses.

Chemokines are chemotactic cytokines that direct the flux of leukocytes to the site of injury and infection, playing a relevant role in the antiviral response. An uncontrolled, unorganized chemokine response is beneath the onset and maintenance of several immunopathologies. During millions of years of evolution, viruses have developed strategies to modulate the host immune system. One of such strategies consists on the secretion of viral proteins that bind to and inhibit the function of chemokines. However, the modulation of the chemokine network mediated by the highly prevalent human pathogen herpes simplex virus (HSV) is unknown. We have addressed this issue and show that HSV-1, causing cold sores and encephalitis and HSV-2, causing urogenital tract infections, interact with chemokines. We determined that the viral protein responsible for such activity is glycoprotein G (gG). gG binds chemokines with high affinity and, in contrast to all viral chemokine binding proteins described to date that inhibit chemokine function, we found that HSV gG potentiates chemokine function in vitro and in vivo. The implications of such potentiation in HSV viral cycle, pathogenesis and chemokine function are discussed.

Structure, Expression, and Function of ICAM-5

Cell adhesion is of utmost importance in normal development and cellular functions. ICAM-5 (intercellular adhesion molecule-5, telencephalin, TLN) is a member of the ICAM family of adhesion proteins. As a novel cell adhesion molecule, ICAM-5 shares many structural similarities with the other members of IgSF, especially the ICAM subgroup; however, ICAM-5 has several unique properties compared to the other ICAMs. With its nine extracellular Ig domains, ICAM-5 is the largest member of ICAM subgroup identified so far. Therefore, it is much more complex than the other ICAMs. The expression of ICAM-5 is confined to the telencephalic neurons of the central nervous system whereas all the other ICAM members are expressed mostly by cells in the immune and blood systems. The developmental appearance of ICAM-5 parallels the time of dendritic elongation and branching, and synapse formation in the telencephalon. As a somatodendrite-specific adhesion molecule, ICAM-5 not only participates in immune-nervous system interactions, it could also participate in neuronal activity, Dendrites' targeting signals, and cognition. It would not be surprising if future investigations reveal more binding partners and other related functions of ICAM-5.