_:b16714644 _:b16714650 . _:b16714644 _:b16714651 . _:b16714573 . _:b16714672 "Oligodendroglia are indeed highly responsive to IFN\u03B3 as indicated by upregulation of Class I MHC molecules and associated antigen processing components during peak IFN\u03B3, but not IFN\u03B1/\u03B2 induction during JHMV infection (Malone et al.,>>2008<<). Moreover, specific blockade of IFN\u03B3 receptor signaling on oligodendroglia prolongs JHMV infection in this cell type (Gonzalez et al." . . _:b16714663 "Optimal IFN\u03B1/\u03B2 induction requires amplification through IFNAR to elevate PRRs and IRF7 (Honda and Taniguchi,2006; Honda et al.,2005; Malmgaard et al.,>>2002<<). However, in contrast to Ifn\u03B1/\u03B2 induction, IFNAR signaling was intact in oligodendroglia." . _:b16714575 "Furthermore, due to the potency of IFN\u03B1/\u03B2 in inhibiting viral replication, many viruses have evolved mechanisms to antagonize the IFN\u03B1/\u03B2 pathway, either at the induction or signaling level (Levy and Garcia\u2010Sastre,2001; Sen,>>2001<<). Microglia and astrocytes are primary sentinels within the CNS parenchyma responding to stimuli triggered by either microbial infection or degenerative events (Dong and Benveniste,2001; Hanisch,2002; Paul et al.,2007). This function is" . . _:b16714654 "astrocytes, and neurons, the ability of plasmacytoid dendritic cells, macrophages/microglia, and an oligodendroglia cell line to induce IFN\u03B1/\u03B2 via TLR7, MDA5 and MDA5/RIG\u2010I dependent pathways (Cervantes\u2010Barragan et al.,2007; Li et al.,>>2010<<; Roth\u2010Cross et al.,2008; Zhou and Perlman,2007) suggests sufficient PRR activation by viral RNA structures to mediate protective responses in select cell types." . . _:b16714636 "While IRF3 is constitutively expressed, IRF7 is induced by IFN\u03B1/\u03B2 and amplifies IFN\u03B1/\u03B2 production (Honda and Taniguchi,>>2006<<; Honda et al." . _:b16714643 . _:b496485733 . _:b16714655 "the ability of plasmacytoid dendritic cells, macrophages/microglia, and an oligodendroglia cell line to induce IFN\u03B1/\u03B2 via TLR7, MDA5 and MDA5/RIG\u2010I dependent pathways (Cervantes\u2010Barragan et al.,2007; Li et al.,2010; Roth\u2010Cross et al.,>>2008<<; Zhou and Perlman,2007) suggests sufficient PRR activation by viral RNA structures to mediate protective responses in select cell types." . _:b16714581 ",2002; Carty and Bowie,2011; Hanke and Kielian,>>2011<<; Okun et al.,2009; van Noort and Bsibsi,2009)." . . _:b496485693 . _:b16714599 "Importantly, a protective effect of IFN\u03B1/\u03B2 in vivo was highlighted by uncontrolled MHV replication in mice deficient in IFN\u03B1/\u03B2 signaling (Cervantes\u2010Barragan et al.,>>2007<<; Ireland et al.,2008)." . _:b16714579 "to stimuli triggered by either microbial infection or degenerative events (Dong and Benveniste,2001; Hanisch,2002; Paul et al.,2007). This function is partially attributed to basal expression of a vast array of PRRs (Bsibsi et al.,>>2002<<; Carty and Bowie,2011; Hanke and Kielian,2011; Okun et al.,2009; van Noort and Bsibsi,2009)." . _:b496485750 . _:b16714569 . _:b496485737 . . . _:b16714633 "Furthermore, IFN\u03B1/\u03B2 induction in response to coronavirus infection has been demonstrated in microglia in vitro and in vivo (Roth\u2010Cross et al.,2008) as well as in an oligodendroglial cell line (Li et al.,>>2010<<). Given the distinct basal and inducible levels of Mda5 transcripts in mature CNS derived glial populations, the contribution of infected oligodendroglia and microglia to IFN\u03B1/\u03B2 induction was assessed in vivo by comparing Ifn\u03B2 and Ifn\u03B14" . . _:b496485727 . _:b496485700 . . . _:b16714675 "IFN\u03B3, but not IFN\u03B1/\u03B2 induction during JHMV infection (Malone et al.,2008). Moreover, specific blockade of IFN\u03B3 receptor signaling on oligodendroglia prolongs JHMV infection in this cell type (Gonzalez et al.,2005, 2006; Parra et al.,>>2010<<). Whether early events favoring robust infection of oligodendroglia prior to emergence of T cells, contribute to ultimate persistence of JHMV in oligodendroglia, remains to be elucidated." . . _:b496485698 . . _:b16714605 "C57BL/6 wild type (Wt) mice were purchased from the National Cancer Institute (Frederick, MD). Mice expressing green fluorescent protein (GFP) under the control of the proteolipid protein (PLP) promoter (PLP\u2010GFP) (Fuss et al.,>>2000<<) were backcrossed six times with C57BL/6 mice prior to use (Malone et al.,2008)." . . _:b16714601 "Furthermore, protection following peripheral MHV infection is associated with TLR7 dependent IFN\u03B1/\u03B2 production by plasmacytoid dendritic cells (Cervantes\u2010Barragan et al.,>>2007<<). The na\u00EFve CNS is devoid of plasmacytoid dendritic cells (Serafini et al." . . _:b16714665 "In addition to mediating PRR signaling, IKK\u03B5 influences ISG induction through participation in JAK/STAT mediated IFN\u03B1/\u03B2 signaling (Pham and Tenoever,>>2010<<; Tenoever et al." . _:b496485712 . . _:b16714636 . _:b16714565 "immune responses. In addition to inducing an antiviral state, IFN\u03B1/\u03B2 exert numerous other functions including induction of apoptosis, mobilizing innate cells, and regulating adaptive immune responses (Barton,2008; Borden et al.,>>2007<<; Stetson and Medzhitov,2006; Vilcek,2006). As these pleiotropic effects can be detrimental if left unregulated, the innate antiviral response has to be controlled to minimize cell injury and maintain cellular homeostatic functions." . _:b16714633 . . _:b496485697 . . . _:b16714612 . _:b16714625 ",2005; Sharma and Maheshwari,>>2009<<). However, the relative contribution of infiltrating leukocytes versus resident CNS cells was not directly assessed." . . _:b16714564 "In addition to inducing an antiviral state, IFN\u03B1/\u03B2 exert numerous other functions including induction of apoptosis, mobilizing innate cells, and regulating adaptive immune responses (Barton,>>2008<<; Borden et al." . . _:b16714628 "Confirming previous results (Malone et al.,>>2008<<) Ifn\u03B14 and Ifn\u03B2 mRNA were increased at Day 3 and peaked at Day 5 p.i." . _:b16714567 ",2007; Stetson and Medzhitov,2006; Vilcek,>>2006<<). As these pleiotropic effects can be detrimental if left unregulated, the innate antiviral response has to be controlled to minimize cell injury and maintain cellular homeostatic functions." . . . _:b16714578 . . _:b16714650 "of oligodendroglia to induce Ifn\u03B1/\u03B2 mRNA, despite their high load of viral RNA, contrasted with in vitro studies demonstrating MDA5 and RIG\u2010I dependent IFN\u03B1/\u03B2 induction in the infected N20.1 oligodendroglia cell line (Li et al.,>>2010<<). This discrepancy likely reflects differences in expression and/or induction of IFN\u03B1/\u03B2 pathway components, rather than distinct viral loads, as even poly I:" . . _:b16714650 . _:b16714590 . _:b16714642 . _:b16714664 . _:b496485693 "5"^^ . _:b16714594 ",2008, >>2009<<). Coronaviruses are poor inducers of IFN\u03B1/\u03B2 in numerous cell types due to their 5\u2032RNA structures mimicking self RNA (Daffis et al." . _:b16714641 . _:b16714651 . _:b496485692 "6"^^ . _:b16714604 "materials and methods" . _:b16714654 . _:b496485753 . _:b496485695 "5"^^ . _:b16714646 "are critical for the induction of IFN\u03B1/\u03B2, as well proinflammatory cytokines and chemokines. While PRR expression and activation in microglia and astrocytes has been extensively explored in vitro (Butchi et al.,2010; Carpentier et al.,>>2008<<; Jin et al.,2011; So and Kim,2009), expression of PRR and associated signaling components in glia in vivo are poorly defined, especially in oligodendroglia." . _:b16714681 "abundance of PRR at basal levels rather provide a mechanism underlying the apparent paucity of oligodendroglia to express cytokines during multiple sclerosis or other CNS inflammatory conditions (Cannella and Raine,2004; Zeis et al.,>>2008<<). Our data thus support the notion that oligodendroglia are defensive players under inflammatory conditions." . _:b496485694 "5"^^ . . . _:b16714585 . _:b16714577 "Microglia and astrocytes are primary sentinels within the CNS parenchyma responding to stimuli triggered by either microbial infection or degenerative events (Dong and Benveniste,2001; Hanisch,>>2002<<; Paul et al." . . . _:b496485703 . . _:b496485701 "3"^^ . _:b16714602 "following peripheral MHV infection is associated with TLR7 dependent IFN\u03B1/\u03B2 production by plasmacytoid dendritic cells (Cervantes\u2010Barragan et al.,2007). The na\u00EFve CNS is devoid of plasmacytoid dendritic cells (Serafini et al.,>>2000<<), implicating infected glia as primary candidates contributing to protective IFN\u03B1/\u03B2 production following CNS infection." . . _:b496485734 . _:b496485700 "3"^^ . . _:b16714581 . _:b496485703 "3"^^ . _:b496485702 "3"^^ . _:b496485749 . _:b496485697 "4"^^ . . _:b496485696 "5"^^ . _:b496485699 "3"^^ . _:b16714677 . _:b496485698 "3"^^ . _:b496485709 "2"^^ . . . _:b16714588 . _:b496485708 "2"^^ . . . _:b496485711 "2"^^ . _:b16714676 "demonstrate a limited role of oligodendroglia as both inducers of, and responders to, IFN\u03B1/\u03B2 compared with microglia. Limited innate antiviral activity may predispose oligodendroglia to be potent responders to IFN\u03B3 (Gonzalez et al.,>>2005<<; Popko and Baerwald,1999). While there is no evidence supporting toxicity of IFN\u03B1/\u03B2 (Akwa et al." . _:b496485710 "2"^^ . _:b496485705 "2"^^ . _:b496485704 "3"^^ . _:b496485715 . . _:b496485707 "2"^^ . _:b496485752 . _:b496485706 "2"^^ . _:b16714564 . _:b496485717 "2"^^ . . _:b496485693 . _:b496485716 "2"^^ . _:b496485692 . _:b496485719 "2"^^ . _:b496485695 . _:b16714624 . _:b496485718 "2"^^ . _:b16714566 ",2007; Stetson and Medzhitov,>>2006<<; Vilcek,2006). As these pleiotropic effects can be detrimental if left unregulated, the innate antiviral response has to be controlled to minimize cell injury and maintain cellular homeostatic functions." . _:b496485694 . . _:b496485704 . _:b16714667 "Although not as severe as the complete abrogation of ISG induction in STAT1\u2212/\u2212 mice, IKK\u03B5\u2212/\u2212 mice lack induction of \u223C30% of ISGs, including Adar1 (Durbin et al.,>>1996<<; Tenoever et al.,2007)." . _:b496485713 "2"^^ . _:b16714586 . _:b16714587 "of infected neurons with detectable IFN\u03B1/\u03B2 expression in mice infected with lymphocytic choriomeningitis virus (Delhaye et al.,2006). Furthermore, IFN\u03B1/\u03B2 inducible Irf7 transcripts mapped closely to sites of viral RNA (Ousman et al.,>>2005<<), supporting highly focal IFN\u03B1/\u03B2 responses. Overall however, little is known about responsiveness of distinct CNS cell types to viral infections in vivo." . _:b496485712 "2"^^ . _:b16714608 . _:b496485715 "2"^^ . _:b16714617 "results" . . _:b496485714 "2"^^ . _:b16714610 "Mononuclear cells were isolated from spinal cords as described previously (Malone et al.,2008; Phares et al.,>>2009<<). Briefly, spinal cords from six to seven mice were finely minced, digested in PBS containing 0.25% trypsin for 30 min at 37\u00B0C, and trypsin quenched by addition of 20% new born calf serum." . _:b496485725 "2"^^ . _:b16714620 . _:b496485701 . _:b496485724 "2"^^ . _:b16714641 "Transcripts encoding adenosine deaminase specific for mRNA (Adar1), which limits viral replication via introduction of mRNA mutations (Bass,>>1997<<), were also more abundant in microglia (Fig." . _:b496485700 . _:b496485727 "2"^^ . _:b16714658 . _:b496485703 . _:b16714680 "The low abundance of PRR at basal levels rather provide a mechanism underlying the apparent paucity of oligodendroglia to express cytokines during multiple sclerosis or other CNS inflammatory conditions (Cannella and Raine,>>2004<<; Zeis et al." . _:b496485696 . _:b496485726 "2"^^ . _:b496485702 . _:b496485721 "2"^^ . _:b496485697 . _:b16714608 "described (Ireland et al.,2008). Mice at 6\u20137 weeks of age were infected via intracerebral injection with 250 Plaque Forming Units of the neutralizing monoclonal antibody (mAb)\u2010derived JHMV variant, designated V2.2v\u20101 (Fleming et al.,>>1986<<) in 30 \u03BCL of endotoxin\u2010free Dulbecco's modified phosphate\u2010buffered saline (PBS)." . _:b496485720 "2"^^ . _:b496485696 . _:b496485723 "2"^^ . . _:b496485699 . _:b16714679 . _:b496485722 "2"^^ . _:b16714616 . _:b496485698 . _:b496485733 "2"^^ . . _:b16714664 "those reached in microglia, as exemplified by Stat1 and Irf7 mRNA. Furthermore, peak expression for many genes did not correlate with maximal Ifn\u03B1/\u03B2 mRNA levels, but rather with peak IFN\u03B3 mRNA and protein at Day 7 p.i. (Phares et al.,>>2011<<). The distinct pattern of ISG expression in oligodendroglia compared with microglia may further reside in low IKK\u03B5." . _:b496485709 . _:b16714666 "compared with microglia may further reside in low IKK\u03B5. In addition to mediating PRR signaling, IKK\u03B5 influences ISG induction through participation in JAK/STAT mediated IFN\u03B1/\u03B2 signaling (Pham and Tenoever,2010; Tenoever et al.,>>2007<<). Although not as severe as the complete abrogation of ISG induction in STAT1\u2212/\u2212 mice, IKK\u03B5\u2212/\u2212 mice lack induction of \u223C30% of ISGs, including Adar1 (Durbin et al." . _:b496485730 . _:b496485732 "2"^^ . _:b496485708 . . _:b496485735 "2"^^ . _:b16714644 "discussion" . _:b496485711 . _:b496485734 "2"^^ . . _:b496485710 . _:b496485729 "2"^^ . _:b496485729 . _:b496485705 . _:b496485728 "2"^^ . _:b16714665 . _:b496485736 . _:b496485745 . _:b496485704 . _:b16714673 . _:b496485731 "2"^^ . _:b496485713 . . _:b496485707 . _:b496485730 "2"^^ . . _:b496485706 . _:b496485741 "2"^^ . . _:b496485717 . . _:b496485740 "2"^^ . _:b16714610 . _:b496485716 . _:b496485743 "2"^^ . _:b16714587 . _:b496485719 . _:b16714676 . _:b496485742 "2"^^ . _:b16714584 . _:b496485742 . _:b496485718 . _:b496485737 "2"^^ . _:b496485713 . _:b16714604 _:b16714612 . _:b16714604 _:b16714613 . _:b496485736 "2"^^ . _:b16714604 _:b16714614 . _:b16714604 _:b16714615 . _:b16714681 . _:b496485712 . _:b16714604 _:b16714608 . _:b16714604 _:b16714609 . _:b496485739 "2"^^ . _:b16714604 _:b16714610 . _:b16714659 "and supported the superior initiation of Ifn\u03B1/\u03B2 responses by microglia. This concept is consistent with the inability of primary cultured neurons and astrocytes to induce IFN\u03B1/\u03B2 expression following MHV infection (Roth\u2010Cross et al.,>>2008<<). It remains to be confirmed whether other CNS infections involving oligodendroglia reveal a similarly muted pattern of IFN\u03B1/\u03B2 induction and responsiveness." . _:b16714592 "strand RNA coronavirus family, was used to better characterize the ability of oligodendroglia to mount innate antiviral immune responses in vivo based on its prominent infection and persistence in oligodendroglia (Bergmann et al.,>>2006<<). In adult mice, JHMV infection causes an acute encephalomyelitis, which resolves into a persistent infection of the spinal cord associated with demyelination." . _:b16714604 _:b16714611 . _:b496485715 . . . _:b496485738 "2"^^ . _:b16714643 "JHMV infection, we assessed IFN\u03B1/\u03B2 and ISG induction following intracerebral injection of the PRR ligand poly I:C. Poly I:C is a strong agonist of both TLR3 and the RIG\u2010like receptors RIG\u2010I/MDA5 (Alexopoulou et al.,2001; Kato et al.,>>2006<<). Ifn\u03B1/\u03B2 upregulation was initially tested in total tissue to characterize the time course of poly I:" . _:b16714645 . _:b496485714 . _:b16714604 _:b16714616 . _:b496485749 "2"^^ . _:b496485725 . _:b16714567 . _:b496485748 "2"^^ . _:b16714568 . _:b496485716 . _:b496485724 . _:b496485751 "2"^^ . _:b16714566 . _:b496485727 . _:b16714604 _:b16714605 . _:b496485750 "2"^^ . _:b16714604 _:b16714606 . _:b16714604 _:b16714607 . _:b496485726 . _:b496485745 "2"^^ . _:b496485721 . _:b16714598 "types due to their 5\u2032RNA structures mimicking self RNA (Daffis et al.,2010; Zust et al.,2011). However, IFN\u03B1/\u03B2 is induced in microglia, macrophages, and plasmacytoid dendritic cells (Cervantes\u2010Barragan et al.,2007; Roth\u2010Cross et al.,>>2008<<). Importantly, a protective effect of IFN\u03B1/\u03B2 in vivo was highlighted by uncontrolled MHV replication in mice deficient in IFN\u03B1/\u03B2 signaling (Cervantes\u2010Barragan et al." . _:b496485744 "2"^^ . _:b496485720 . _:b496485701 . _:b496485747 "2"^^ . . _:b496485723 . _:b496485746 "2"^^ . . _:b496485722 . _:b16714656 ",2008; Zhou and Perlman,>>2007<<) suggests sufficient PRR activation by viral RNA structures to mediate protective responses in select cell types." . _:b496485733 . _:b16714644 . "PMC0" . _:b496485732 . _:b16714652 ",2010; Zust et al.,>>2011<<). However, in contrast to cultured fibroblasts, bone marrow\u2010derived dendritic cells, astrocytes, and neurons, the ability of plasmacytoid dendritic cells, macrophages/microglia, and an oligodendroglia cell line to induce IFN\u03B1/\u03B2 via TLR7," . _:b496485735 . . _:b496485722 . _:b496485731 . _:b496485734 . _:b16714591 "They also do not appear to contribute to extensive proinflammatory cytokine secretion (Cannella and Raine,>>2004<<)." . _:b496485753 "2"^^ . _:b496485729 . _:b16714591 . _:b16714632 "Furthermore, IFN\u03B1/\u03B2 induction in response to coronavirus infection has been demonstrated in microglia in vitro and in vivo (Roth\u2010Cross et al.,>>2008<<) as well as in an oligodendroglial cell line (Li et al.,2010)." . _:b496485752 "2"^^ . _:b16714583 . _:b496485728 . . _:b496485731 . _:b16714635 . _:b496485754 "2"^^ . _:b496485730 . _:b496485694 . _:b496485741 . _:b496485706 . _:b496485740 . . _:b496485743 . _:b16714617 _:b16714618 . _:b16714660 . _:b16714617 _:b16714619 . _:b496485742 . _:b16714617 _:b16714620 . _:b16714617 _:b16714621 . _:b16714617 _:b16714622 . _:b16714617 _:b16714623 . . _:b496485737 . _:b16714617 _:b16714624 . _:b16714563 _:b16714600 . _:b16714617 _:b16714625 . _:b16714563 _:b16714601 . _:b16714563 _:b16714602 . _:b16714617 _:b16714626 . _:b16714563 _:b16714603 . _:b16714617 _:b16714627 . _:b496485736 . _:b16714617 _:b16714628 . _:b16714617 _:b16714629 . _:b16714617 _:b16714630 . _:b496485711 . . _:b16714617 _:b16714631 . _:b496485739 . _:b16714563 _:b16714592 . _:b16714617 _:b16714632 . _:b16714617 _:b16714633 . _:b16714563 _:b16714593 . _:b16714617 _:b16714634 . _:b16714647 . _:b16714563 _:b16714594 . _:b16714563 _:b16714595 . _:b16714629 . _:b16714617 _:b16714635 . _:b496485738 . _:b16714617 _:b16714636 . _:b16714563 _:b16714596 . _:b16714617 _:b16714637 . _:b16714563 _:b16714597 . _:b16714617 _:b16714638 . _:b16714563 _:b16714598 . _:b16714617 _:b16714639 . _:b16714563 _:b16714599 . _:b496485749 . _:b16714617 _:b16714640 . _:b16714617 _:b16714641 . _:b16714617 _:b16714642 . _:b16714588 "Specifically oligodendroglia appear to express a limited TLR repertoire at basal levels compared with microglia (Hanke and Kielian,>>2011<<; Okun et al." . _:b16714617 _:b16714643 . _:b496485748 . _:b16714653 . _:b496485751 . _:b16714571 . _:b16714619 "Induction of IFN\u03B1/\u03B2 by murine coronaviruses is mediated via TLR7 in pDC and via MDA5 in microglia/monocytes (Cervantes\u2010Barragan et al.,2007; Roth\u2010Cross et al.,>>2008<<). Furthermore, both MDA5 and RIG\u20101 act as PRR in an oligodendroglia cell line (Li et al." . . _:b496485750 . . _:b496485707 . _:b496485745 . _:b16714563 _:b16714568 . _:b16714563 _:b16714569 . _:b16714647 "the induction of IFN\u03B1/\u03B2, as well proinflammatory cytokines and chemokines. While PRR expression and activation in microglia and astrocytes has been extensively explored in vitro (Butchi et al.,2010; Carpentier et al.,2008; Jin et al.,>>2011<<; So and Kim,2009), expression of PRR and associated signaling components in glia in vivo are poorly defined, especially in oligodendroglia." . _:b16714563 _:b16714570 . _:b16714563 _:b16714571 . _:b496485744 . _:b16714563 _:b16714572 . _:b16714563 _:b16714573 . _:b16714646 . _:b16714563 _:b16714574 . _:b16714563 _:b16714575 . _:b496485747 . _:b496485746 . _:b16714563 _:b16714564 . _:b16714563 _:b16714565 . _:b16714563 _:b16714566 . _:b16714563 _:b16714567 . _:b16714563 _:b16714584 . _:b496485726 . _:b16714563 _:b16714585 . _:b16714563 _:b16714586 . _:b16714563 _:b16714587 . _:b16714563 _:b16714588 . _:b16714563 _:b16714589 . _:b16714563 _:b16714590 . _:b16714563 _:b16714591 . _:b16714620 "by murine coronaviruses is mediated via TLR7 in pDC and via MDA5 in microglia/monocytes (Cervantes\u2010Barragan et al.,2007; Roth\u2010Cross et al.,2008). Furthermore, both MDA5 and RIG\u20101 act as PRR in an oligodendroglia cell line (Li et al.,>>2010<<). However, the expression of these viral sensors in oligodendroglia in the adult CNS is unknown." . _:b16714563 _:b16714576 . _:b16714563 _:b16714577 . _:b16714563 _:b16714578 . _:b16714563 _:b16714579 . _:b16714563 _:b16714580 . _:b16714621 "analyze their capacity to initiate innate responses, oligodendroglia and microglia were isolated from spinal cords of uninfected PLP\u2010GFP mice by FACS based on their respective CD45\u2212 GFP+ and CD45lo/int F4/80+ phenotypes (Malone et al.,>>2008<<). Spinal cords were used as donor tissue based on higher oligodendroglia yields compared with brains." . _:b16714563 _:b16714581 . _:b16714563 _:b16714582 . _:b16714648 . . . _:b16714602 . _:b16714563 _:b16714583 . _:b16714630 "IFNAR\u2212/\u2212 relative to Wt mice, they were only slightly reduced in oligodendroglia (Fig. 3). These results are reminiscent of previous observations that PRR expression in neurons is controlled by basal IFN\u03B1/\u03B2 signaling (Shrestha et al.,>>2003<<). Importantly, the absence of IFN\u03B1/\u03B2 signaling abrogated upregulation of Mda5 and Rig\u2010I transcripts in both microglia and oligodendroglia following JHMV infection (Fig." . _:b16714582 "events (Dong and Benveniste,2001; Hanisch,2002; Paul et al.,2007). This function is partially attributed to basal expression of a vast array of PRRs (Bsibsi et al.,2002; Carty and Bowie,2011; Hanke and Kielian,2011; Okun et al.,>>2009<<; van Noort and Bsibsi,2009). Irf3 mRNA, and to a lesser extent Irf7 mRNA, are constitutively expressed in the CNS." . _:b496485753 . . _:b16714631 "IFN\u03B1/\u03B2 signaling is crucial to prevent dissemination of gliatropic coronavirus within the CNS parenchyma (Ireland et al.,>>2008<<). Furthermore, IFN\u03B1/\u03B2 induction in response to coronavirus infection has been demonstrated in microglia in vitro and in vivo (Roth\u2010Cross et al." . . _:b496485752 . _:b16714570 . . _:b496485754 . _:b16714645 "While PRR expression and activation in microglia and astrocytes has been extensively explored in vitro (Butchi et al.,>>2010<<; Carpentier et al.,2008; Jin et al." . _:b16714570 "a signaling cascade leading to transcription of a variety of interferon stimulated genes (ISG). ISG encode both direct antiviral factors as well as PRR and signal transduction components, such as IRF7 and STAT1 (Borden et al.,>>2007<<). This amplification loop thus elevates the ability of cells to induce and respond to IFN\u03B1/\u03B2." . _:b16714666 . _:b16714564 . _:b16714669 . _:b16714574 . _:b16714604 . _:b16714565 . _:b16714668 . _:b496485746 . _:b16714592 . _:b16714566 . _:b16714567 . _:b16714578 "Sen,2001). Microglia and astrocytes are primary sentinels within the CNS parenchyma responding to stimuli triggered by either microbial infection or degenerative events (Dong and Benveniste,2001; Hanisch,2002; Paul et al.,>>2007<<). This function is partially attributed to basal expression of a vast array of PRRs (Bsibsi et al." . _:b16714671 "logs between Days 3 and 5 p.i., coincident with no Ifn\u03B1/\u03B2 and tentative induction of antiviral ISGs. These data indicate that oligodendroglia rely largely on T cell effector function, prominently IFN\u03B3, for viral control (Parra et al.,>>2010<<). Oligodendroglia are indeed highly responsive to IFN\u03B3 as indicated by upregulation of Class I MHC molecules and associated antigen processing components during peak IFN\u03B3, but not IFN\u03B1/\u03B2 induction during JHMV infection (Malone et al." . _:b16714617 . _:b16714678 "with microglia. Limited innate antiviral activity may predispose oligodendroglia to be potent responders to IFN\u03B3 (Gonzalez et al.,2005; Popko and Baerwald,1999). While there is no evidence supporting toxicity of IFN\u03B1/\u03B2 (Akwa et al.,>>1998<<), more restricted induction of antiviral mediators, especially those also affecting host cell translation, may circumvent apoptosis and guarantee maintenance of critical myelin housekeeping functions and survival." . _:b16714563 . . _:b16714572 . _:b496485728 . _:b16714589 . _:b16714573 . . _:b16714565 . _:b16714574 . . _:b16714568 "PRRs comprise members of the Toll\u2010like receptor (TLR) family and the cytosolic helicase sensors, retinoic acid\u2010inducible gene 1 (RIG\u2010I), and melanoma differentiation\u2010associated antigen 5 (MDA5) (Kawai and Akira,>>2009<<; Mogensen,2009)." . _:b16714575 . . _:b16714568 . _:b16714563 . . _:b16714622 "The potential of mature oligodendroglia to recognize viral RNA in comparison to microglia was assessed by comparing basal transcript levels of genes encoding the viral RNA sensors MDA5, RIG\u2010I, TLR3, and TLR7 (Kawai and Akira,>>2007<<). Whereas transcription of all four PRR was readily detected in microglia, Mda5, Rig\u2010I, and Tlr3 transcripts were significantly reduced and Tlr7 was below detection in oligodendroglia (Fig. 1A). Basal levels of PRR mRNAs are low in the" . _:b16714569 . _:b496485741 . _:b16714634 "Viral loads were monitored by measuring viral mRNA encoding the N protein, the most abundant viral RNA in infected cells (Skinner and Siddell,>>1983<<). Viral\u2010N transcripts prevailed in microglia at Day 3 p.i., but decreased by Days 5 and 7 p.i. (Fig. 4). By contrast, although viral mRNA was near detection levels at Day 3 p.i. in oligodendroglia, the levels increased \u223C20 fold relative" . _:b16714570 . _:b16714658 "consistent with higher basal Irf3 than Irf7 levels observed in whole na\u00EFve brains (Ousman et al.,2005). Reduced basal PRR levels in oligodendroglia were reminiscent of sparsely expressed PRRs in primary neurons (Carpentier et al.,>>2008<<), and supported the superior initiation of Ifn\u03B1/\u03B2 responses by microglia. This concept is consistent with the inability of primary cultured neurons and astrocytes to induce IFN\u03B1/\u03B2 expression following MHV infection (Roth\u2010Cross et al." . _:b16714625 . _:b16714618 "Induction of IFN\u03B1/\u03B2 by murine coronaviruses is mediated via TLR7 in pDC and via MDA5 in microglia/monocytes (Cervantes\u2010Barragan et al.,>>2007<<; Roth\u2010Cross et al.,2008). Furthermore, both MDA5 and RIG\u20101 act as PRR in an oligodendroglia cell line (Li et al." . _:b16714571 . _:b16714580 . _:b16714623 . _:b16714580 . _:b496485725 . _:b16714612 "from IFNAR\u2212/\u2212 and Wt control mice were identified by consecutive staining with unconjugated O4 mAb and anti\u2010mouse IgM (PE) mAb (R6\u201060.2) (BD Pharmingen) and purified based on their CD45\u2212 O4+ phenotype as described (Gonzalez et al.,>>2005<<; Phares et al.,2011). Cells were purified on a BD FACSAria (BD Biosciences), resuspended in TRIzol (Invitrogen, Carlsbad, CA) and stored at \u221280\u00B0C." . _:b16714581 . _:b16714582 . . _:b16714583 . _:b16714669 "biological consequences are demonstrated by impaired clearance of influenza virus infection by IKK\u03B5\u2212/\u2212 mice, despite similar expression of IL2, IL6, IL12, IFN\u03B3, and RANTES as well as induction of antiviral antibody (Tenoever et al.,>>2007<<). The paucity of Ikk\u03B5 mRNA and modest, if any, increase of Irf7 mRNA in oligodendroglia, despite abundant viral and Mda5 mRNA upregulation, may partially explain the absence of Ifn\u03B1/\u03B2 expression and more selective and delayed ISG" . _:b16714582 . _:b16714576 . _:b16714577 . . _:b16714578 . . . _:b16714590 "of distinct CNS cell types to viral infections in vivo. Specifically oligodendroglia appear to express a limited TLR repertoire at basal levels compared with microglia (Hanke and Kielian,2011; Okun et al.,2009; Paul et al.,>>2007<<). They also do not appear to contribute to extensive proinflammatory cytokine secretion (Cannella and Raine,2004)." . _:b16714579 . _:b16714588 . . _:b16714589 . . _:b16714590 . _:b16714634 . _:b16714607 "protein (PLP) promoter (PLP\u2010GFP) (Fuss et al.,2000) were backcrossed six times with C57BL/6 mice prior to use (Malone et al.,2008). Congenic mice defective in IFN\u03B1/\u03B2 signaling (IFNAR\u2212/\u2212) were previously described (Ireland et al.,>>2008<<). Mice at 6\u20137 weeks of age were infected via intracerebral injection with 250 Plaque Forming Units of the neutralizing monoclonal antibody (mAb)\u2010derived JHMV variant, designated V2.2v\u20101 (Fleming et al." . _:b496485744 . _:b16714630 . _:b16714591 . _:b16714584 . _:b16714639 "IFN\u03B1/\u03B2 binds a common receptor complex consisting of two transmembrane proteins, IFNAR1 and IFNAR2. As IFNAR2 exists as a soluble (IFNAR2a) and transmembrane (IFNAR2c) and isoform generated by alternative splicing (Domanski et al.,>>1995<<), we examined basal expression patterns of IFNAR1, and both IFNAR2 isoforms in microglia and oligodendroglia." . _:b16714670 . _:b16714585 . _:b16714586 . _:b16714595 . _:b16714576 . _:b16714600 "et al.,2007; Roth\u2010Cross et al.,2008). Importantly, a protective effect of IFN\u03B1/\u03B2 in vivo was highlighted by uncontrolled MHV replication in mice deficient in IFN\u03B1/\u03B2 signaling (Cervantes\u2010Barragan et al.,2007; Ireland et al.,>>2008<<). Furthermore, protection following peripheral MHV infection is associated with TLR7 dependent IFN\u03B1/\u03B2 production by plasmacytoid dendritic cells (Cervantes\u2010Barragan et al." . _:b16714587 . _:b16714596 . _:b16714678 . _:b16714597 . . _:b16714598 . _:b496485721 . _:b16714594 . _:b16714577 . _:b16714599 . _:b16714579 . _:b16714592 . _:b16714626 . _:b16714624 "tissue, with the exception of Tlr3 (McKimmie et al.,2005). Nevertheless, PRR are rapidly upregulated during viral encephalitis initiated by Semliki Forest virus, Rabies virus, and Venezuelan Equine Encephalitis virus (McKimmie et al.,>>2005<<; Sharma and Maheshwari,2009). However, the relative contribution of infiltrating leukocytes versus resident CNS cells was not directly assessed." . _:b16714615 "dehydrogenase (GAPDH) using the following formula: 2[CT(GAPDH) \u2013 CT(Target Gene)] \u00D7 1,000, where CT represents the threshold cycle at which the fluorescent signal becomes higher than the background (Kapil et al.,>>2009<<; Phares et al.,2009)." . _:b16714593 . _:b16714572 . _:b16714627 "to microglia. Induction of Mda5 and Rig\u2010I in oligodendroglia, as well as all RNA sensing PRR in microglia, correlated with induction of Ifn\u03B14 and Ifn\u03B2 mRNA in the CNS following JHMV infection (Ireland et al.,2008; Malone et al.,>>2008<<). To evaluate additional contributions of Type II (IFN\u03B3) and Type III (IFN\u03BB) IFN, which also induce ISG, the RNA expression kinetics of all three IFN families were assessed in spinal cords (Fig." . . _:b16714594 . . _:b16714595 . _:b496485735 . _:b16714659 . _:b16714584 "al.,2009; van Noort and Bsibsi,2009). Irf3 mRNA, and to a lesser extent Irf7 mRNA, are constitutively expressed in the CNS. While Irf7 expression is highly inducible, Irf3 transcripts remain constant following infection (Ousman et al.,>>2005<<). However, their relative expression in different cell types has not been extensively explored." . _:b16714604 . . _:b16714631 . _:b16714605 . . _:b16714606 . _:b16714607 . _:b16714600 . . _:b16714601 . _:b16714606 . _:b16714602 . _:b16714611 "PLP\u2010GFP transgenic mice facilitated identification of oligodendroglia via their CD45\u2212 GFP+ phenotype (Malone et al.,>>2008<<). Oligodendroglia from IFNAR\u2212/\u2212 and Wt control mice were identified by consecutive staining with unconjugated O4 mAb and anti\u2010mouse IgM (PE) mAb (R6\u201060.2) (BD Pharmingen) and purified based on their CD45\u2212 O4+ phenotype as described" . _:b16714575 . _:b16714603 . _:b16714612 . . _:b16714637 "inducible kinase IKK\u03B5 (also known as Ikbke or Ikki) and the transcription factors IRF3 and IRF7. While IRF3 is constitutively expressed, IRF7 is induced by IFN\u03B1/\u03B2 and amplifies IFN\u03B1/\u03B2 production (Honda and Taniguchi,2006; Honda et al.,>>2005<<). Therefore to investigate the potential for PRR signaling, oligodendroglia were examined for expression of mRNAs encoding IKK\u03B5, IRF3, and IRF7." . . _:b16714611 . _:b16714649 "Microglia were prominent inducers of Ifn\u03B1/\u03B2 mRNA following infection, consistent with IFN\u03B1/\u03B2 induction in primary microglia as well as bone marrow derived macrophages infected with a heterologous MHV (Roth\u2010Cross et al., >>2008<<). However, the inability of oligodendroglia to induce Ifn\u03B1/\u03B2 mRNA, despite their high load of viral RNA, contrasted with in vitro studies demonstrating MDA5 and RIG\u2010I dependent IFN\u03B1/\u03B2 induction in the infected N20.1 oligodendroglia cell" . _:b16714613 . . . _:b16714614 . . _:b16714609 . _:b16714615 . . _:b16714608 . . _:b16714609 . . _:b16714610 . . _:b16714611 . _:b16714615 . _:b16714596 . _:b16714620 . _:b496485705 . _:b16714629 "IFN\u03BB was minimally induced, yet with similar kinetics as IFN\u03B1/\u03B2, confirming very low expression and function in the CNS following heterologous infections, including a closely related MHV strain (Sommereyns et al.,>>2008<<). IFN\u03B3 mRNA was not upregulated until Day 5 p." . _:b16714638 "tended to decline following infection (Fig. 5). Lastly, Irf7 transcripts were sparse in both microglia and oligodendroglia derived from naive mice (Fig. 5), consistent with lower basal CNS expression relative to Irf3 (Ousman et al.,>>2005<<). However, in contrast to the increase of Irf7 mRNA detected in microglia by Day 3 p." . _:b16714621 . _:b16714622 . _:b496485724 . _:b16714585 "following infection (Ousman et al.,2005). However, their relative expression in different cell types has not been extensively explored. Consistent with PRR activation, microglia, astrocytes, and neurons all induce IFN\u03B1/\u03B2 (Paul et al.,>>2007<<). However, the vast majority of information on CNS innate responsiveness is derived from primary glia and neuronal cultures established from neonates and may not reflect responsiveness of fully differentiated cells." . . _:b16714623 . _:b16714595 "Coronaviruses are poor inducers of IFN\u03B1/\u03B2 in numerous cell types due to their 5\u2032RNA structures mimicking self RNA (Daffis et al.,>>2010<<; Zust et al.,2011)." . _:b16714651 "The restricted ability of coronaviruses to induce IFN\u03B1/\u03B2 was recently attributed to the O\u2010methylated cap structure of the viral RNA, making it difficult for the host to distinguish viral from self mRNA (Daffis et al.,>>2010<<; Zust et al.,2011)." . . _:b16714613 "Wt control mice were identified by consecutive staining with unconjugated O4 mAb and anti\u2010mouse IgM (PE) mAb (R6\u201060.2) (BD Pharmingen) and purified based on their CD45\u2212 O4+ phenotype as described (Gonzalez et al.,2005; Phares et al.,>>2011<<). Cells were purified on a BD FACSAria (BD Biosciences), resuspended in TRIzol (Invitrogen, Carlsbad, CA) and stored at \u221280\u00B0C." . . _:b16714616 . _:b496485718 . . . _:b16714662 "Optimal IFN\u03B1/\u03B2 induction requires amplification through IFNAR to elevate PRRs and IRF7 (Honda and Taniguchi,2006; Honda et al.,>>2005<<; Malmgaard et al.,2002). However, in contrast to Ifn\u03B1/\u03B2 induction, IFNAR signaling was intact in oligodendroglia." . _:b16714617 . . _:b496485710 . _:b16714622 . _:b16714618 . _:b16714632 . _:b16714621 . _:b16714619 . _:b16714652 . _:b16714628 . . _:b16714629 . _:b16714653 "cells, astrocytes, and neurons, the ability of plasmacytoid dendritic cells, macrophages/microglia, and an oligodendroglia cell line to induce IFN\u03B1/\u03B2 via TLR7, MDA5 and MDA5/RIG\u2010I dependent pathways (Cervantes\u2010Barragan et al.,>>2007<<; Li et al.,2010; Roth\u2010Cross et al.,2008; Zhou and Perlman,2007) suggests sufficient PRR activation by viral RNA structures to mediate protective responses in select cell types." . _:b16714596 "however, neuronal and astrocyte infection is sparse (Ireland et al.,2008, 2009). Coronaviruses are poor inducers of IFN\u03B1/\u03B2 in numerous cell types due to their 5\u2032RNA structures mimicking self RNA (Daffis et al.,2010; Zust et al.,>>2011<<). However, IFN\u03B1/\u03B2 is induced in microglia, macrophages, and plasmacytoid dendritic cells (Cervantes\u2010Barragan et al." . _:b16714660 "responsiveness. However, most RNA viruses are neuronotropic, with only some variants of Theilers murine encephalomyelitis virus displaying tropism for oligodendroglia in mouse strains susceptible to persistent infection (Brahic et al.,>>2005<<). However, during the acute CNS infection, this virus primarily infects neurons and oligodendroglia and is only infected during the persistent stage, making direct comparisons difficult." . _:b16714630 . _:b16714631 . _:b496485738 . _:b496485739 . _:b16714603 "This is supported by MDA5 mediated IFN\u03B1/\u03B2 production in infected microglia (Roth\u2010Cross et al.,>>2008<<)." . . _:b16714624 . . _:b496485695 . _:b16714625 . _:b16714626 . _:b16714627 . _:b496485714 . _:b496485752 . _:b496485753 . _:b496485754 . _:b16714636 . _:b496485748 . _:b496485749 . _:b496485750 . _:b16714637 . _:b496485751 . _:b496485744 . _:b496485745 . _:b496485746 . _:b16714638 . _:b496485747 . _:b496485740 . _:b496485741 . _:b496485742 . _:b16714639 . _:b496485743 . _:b496485736 . _:b496485737 . _:b16714655 . _:b496485738 . _:b16714632 . _:b496485739 . _:b496485732 . _:b496485733 . _:b496485734 . _:b16714633 . _:b496485735 . _:b496485728 . _:b496485729 . _:b16714649 . _:b496485730 . _:b16714656 . _:b16714634 . . _:b496485731 . _:b496485724 . _:b496485725 . _:b496485726 . _:b16714635 . _:b496485727 . _:b496485720 . _:b496485721 . _:b496485722 . _:b496485723 . _:b16714644 . _:b496485716 . _:b496485717 . _:b16714674 . _:b496485718 . _:b16714645 . _:b496485719 . _:b496485712 . _:b496485713 . _:b496485714 . _:b16714646 . _:b16714571 "In general IRF7 is considered the master switch in IFN\u03B1/\u03B2 induction following various viral infections due to its role in amplifying IFN\u03B1/\u03B2 production (Honda and Taniguchi,>>2006<<). Because the pattern as well as levels of PRR, IRF, and IFN\u03B1/\u03B2 receptor expression and activation varies with each cell type, initial IFN\u03B1/\u03B2 induction and amplification can be very distinct depending on the cell types infected" . . _:b496485715 . _:b496485708 . . _:b496485709 . _:b496485710 . _:b16714647 . _:b496485711 . _:b496485704 . _:b496485705 . _:b496485706 . _:b16714640 . _:b496485707 . _:b496485700 . _:b16714657 "Ikk\u03B5. However, basal Irf3 transcripts were only reduced by \u223C50%, and Irf7 transcripts were barely detectable in either cell population, consistent with higher basal Irf3 than Irf7 levels observed in whole na\u00EFve brains (Ousman et al.,>>2005<<). Reduced basal PRR levels in oligodendroglia were reminiscent of sparsely expressed PRRs in primary neurons (Carpentier et al." . _:b496485701 . _:b16714580 ",2002; Carty and Bowie,>>2011<<; Hanke and Kielian,2011; Okun et al.,2009; van Noort and Bsibsi,2009)." . _:b16714641 . _:b16714640 . _:b496485702 . . _:b496485703 . _:b496485696 . _:b496485697 . _:b496485698 . _:b16714642 . _:b496485699 . . _:b496485692 . _:b496485693 . _:b496485694 . _:b16714643 . _:b496485695 . _:b16714635 "The contribution of infiltrating infected monocyte\u2010derived macrophages (Ireland et al.,>>2009<<) to Ifn\u03B1/\u03B2 induction was also assessed." . _:b16714652 . _:b496485708 . _:b16714653 . _:b16714657 . _:b16714654 . _:b16714670 "This concept is consistent with data indicating that microglia are a dominant source of IFN\u03B1/\u03B2 within the CNS during JHMV induced encephalomyelitis (Roth\u2010Cross et al., >>2008<<). The biological relevance of suboptimal IFN\u03B1/\u03B2 responses is clearly evident from differential viral control in both cell types. A direct response to infection by microglia is supported by the correlation between peak viral and Ifn\u03B1/\u03B2" . _:b496485743 . _:b16714639 . _:b16714655 . . _:b16714648 . _:b16714674 "Moreover, specific blockade of IFN\u03B3 receptor signaling on oligodendroglia prolongs JHMV infection in this cell type (Gonzalez et al.,2005, >>2006<<; Parra et al.,2010)." . _:b16714637 . _:b16714649 . _:b16714650 . _:b16714589 "Specifically oligodendroglia appear to express a limited TLR repertoire at basal levels compared with microglia (Hanke and Kielian,2011; Okun et al.,>>2009<<; Paul et al.,2007)." . _:b16714651 . . _:b16714603 . _:b16714609 "Mononuclear cells were isolated from spinal cords as described previously (Malone et al.,>>2008<<; Phares et al.,2009). Briefly, spinal cords from six to seven mice were finely minced, digested in PBS containing 0.25% trypsin for 30 min at 37\u00B0C, and trypsin quenched by addition of 20% new born calf serum." . _:b16714660 . _:b16714661 . _:b16714662 . . _:b16714663 . _:b16714656 . _:b16714598 . . _:b16714657 . _:b16714640 "Irf9 levels were also elevated in microglia compared with oligodendroglia derived from na\u00EFve mice (Fig. 6B). STAT1 is inducible by both IFN\u03B1/\u03B2 and IFN\u03B3, while IRF9 is constitutively expressed in most non CNS cell types (Borden et al.,>>2007<<). Consistent with a response to IFN\u03B1/\u03B2, Stat1 mRNA indeed increased \u223C10 fold by Day 3 p." . _:b16714658 . _:b16714659 . . . . _:b16714668 . _:b16714613 . _:b496485732 . _:b16714669 . . . . _:b16714668 "(Pham and Tenoever,2010; Tenoever et al.,2007). Although not as severe as the complete abrogation of ISG induction in STAT1\u2212/\u2212 mice, IKK\u03B5\u2212/\u2212 mice lack induction of \u223C30% of ISGs, including Adar1 (Durbin et al.,1996; Tenoever et al.,>>2007<<). The biological consequences are demonstrated by impaired clearance of influenza virus infection by IKK\u03B5\u2212/\u2212 mice, despite similar expression of IL2, IL6, IL12, IFN\u03B3, and RANTES as well as induction of antiviral antibody (Tenoever et al." . _:b16714670 . . _:b16714680 . _:b16714626 "Induction of Mda5 and Rig\u2010I in oligodendroglia, as well as all RNA sensing PRR in microglia, correlated with induction of Ifn\u03B14 and Ifn\u03B2 mRNA in the CNS following JHMV infection (Ireland et al.,>>2008<<; Malone et al.,2008)." . _:b16714671 . _:b16714614 . _:b16714675 . _:b16714623 "and Tlr3 transcripts were significantly reduced and Tlr7 was below detection in oligodendroglia (Fig. 1A). Basal levels of PRR mRNAs are low in the resting CNS relative to lymphoid tissue, with the exception of Tlr3 (McKimmie et al.,>>2005<<). Nevertheless, PRR are rapidly upregulated during viral encephalitis initiated by Semliki Forest virus, Rabies virus, and Venezuelan Equine Encephalitis virus (McKimmie et al." . _:b16714664 . . _:b16714665 . _:b16714573 "well as levels of PRR, IRF, and IFN\u03B1/\u03B2 receptor expression and activation varies with each cell type, initial IFN\u03B1/\u03B2 induction and amplification can be very distinct depending on the cell types infected (Colonna,2007; Stewart et al.,>>2005<<). Furthermore, due to the potency of IFN\u03B1/\u03B2 in inhibiting viral replication, many viruses have evolved mechanisms to antagonize the IFN\u03B1/\u03B2 pathway, either at the induction or signaling level (Levy and Garcia\u2010Sastre,2001; Sen,2001)." . _:b16714666 . _:b16714563 "introduction" . _:b496485747 . _:b16714667 . _:b16714569 "PRRs comprise members of the Toll\u2010like receptor (TLR) family and the cytosolic helicase sensors, retinoic acid\u2010inducible gene 1 (RIG\u2010I), and melanoma differentiation\u2010associated antigen 5 (MDA5) (Kawai and Akira,2009; Mogensen,>>2009<<). PRR recognition of viral RNA triggers the activation and nuclear localization of interferon regulatory factors (IRF) IRF3 and IRF7 leading to IFN\u03B1/\u03B2 induction." . . _:b16714619 . _:b16714676 . . _:b16714677 . . _:b16714678 . _:b16714593 "of the spinal cord associated with demyelination. In addition to oligodendroglia, JHMV also infects microglia and infiltrating macrophages during acute infection; however, neuronal and astrocyte infection is sparse (Ireland et al.,>>2008<<, 2009). Coronaviruses are poor inducers of IFN\u03B1/\u03B2 in numerous cell types due to their 5\u2032RNA structures mimicking self RNA (Daffis et al." . _:b496485699 . _:b496485717 . _:b16714679 . _:b16714576 "Microglia and astrocytes are primary sentinels within the CNS parenchyma responding to stimuli triggered by either microbial infection or degenerative events (Dong and Benveniste,>>2001<<; Hanisch,2002; Paul et al." . . _:b16714662 . _:b16714672 . _:b16714672 . _:b16714673 . _:b16714677 ",2005; Popko and Baerwald,>>1999<<). While there is no evidence supporting toxicity of IFN\u03B1/\u03B2 (Akwa et al." . _:b496485709 . . _:b16714674 . _:b16714673 "Moreover, specific blockade of IFN\u03B3 receptor signaling on oligodendroglia prolongs JHMV infection in this cell type (Gonzalez et al.,>>2005<<, 2006; Parra et al.,2010)." . _:b16714675 . _:b16714618 . _:b16714671 . _:b16714661 "Optimal IFN\u03B1/\u03B2 induction requires amplification through IFNAR to elevate PRRs and IRF7 (Honda and Taniguchi,>>2006<<; Honda et al.,2005; Malmgaard et al.,2002). However, in contrast to Ifn\u03B1/\u03B2 induction, IFNAR signaling was intact in oligodendroglia." . _:b16714614 "RNA was extracted by dissociation in TRIzol reagent (Invitrogen) according to the manufacturer's instructions and subjected to real\u2010time PCR analysis as described (Phares et al.,>>2011<<). In brief, snap\u2010frozen spinal cords or FACS\u2010purified cells were homogenized with TRIzol in a Tissuelyser II (Qiagen, Valencia, CA) or by pipetting, respectively, and treated with chloroform." . _:b16714605 . . _:b16714667 . _:b496485719 . _:b16714638 . . _:b16714586 "in vitro studies, IFN\u03B1/\u03B2 production in vivo is highly restricted as indicated by the small proportion (<5%) of infected neurons with detectable IFN\u03B1/\u03B2 expression in mice infected with lymphocytic choriomeningitis virus (Delhaye et al.,>>2006<<). Furthermore, IFN\u03B1/\u03B2 inducible Irf7 transcripts mapped closely to sites of viral RNA (Ousman et al." . . _:b16714680 . _:b16714597 "However, IFN\u03B1/\u03B2 is induced in microglia, macrophages, and plasmacytoid dendritic cells (Cervantes\u2010Barragan et al.,>>2007<<; Roth\u2010Cross et al.,2008)." . _:b16714599 . _:b16714681 . _:b496485751 . _:b16714600 . _:b16714606 "(Frederick, MD). Mice expressing green fluorescent protein (GFP) under the control of the proteolipid protein (PLP) promoter (PLP\u2010GFP) (Fuss et al.,2000) were backcrossed six times with C57BL/6 mice prior to use (Malone et al.,>>2008<<). Congenic mice defective in IFN\u03B1/\u03B2 signaling (IFNAR\u2212/\u2212) were previously described (Ireland et al." . _:b16714663 . _:b496485720 . _:b16714597 . _:b16714583 ",2009; van Noort and Bsibsi,>>2009<<). Irf3 mRNA, and to a lesser extent Irf7 mRNA, are constitutively expressed in the CNS." . _:b16714616 ",2009; Phares et al.,>>2009<<)." . _:b16714627 . _:b16714642 "Poly I:C is a strong agonist of both TLR3 and the RIG\u2010like receptors RIG\u2010I/MDA5 (Alexopoulou et al.,>>2001<<; Kato et al.,2006)." . _:b16714607 . _:b16714679 "Our findings also contradict the hypothesis suggesting that virus initiated IFN\u03B1/\u03B2 production by oligodendroglia drives inflammatory responses during viral\u2010induced demyelinating disease (Lipton et al.,>>2007<<). The low abundance of PRR at basal levels rather provide a mechanism underlying the apparent paucity of oligodendroglia to express cytokines during multiple sclerosis or other CNS inflammatory conditions (Cannella and Raine,2004; Zeis et" . . . _:b16714572 "Because the pattern as well as levels of PRR, IRF, and IFN\u03B1/\u03B2 receptor expression and activation varies with each cell type, initial IFN\u03B1/\u03B2 induction and amplification can be very distinct depending on the cell types infected (Colonna,>>2007<<; Stewart et al.,2005)." . . . . _:b16714648 ",2011; So and Kim,>>2009<<), expression of PRR and associated signaling components in glia in vivo are poorly defined, especially in oligodendroglia." . _:b16714661 . _:b16714593 . _:b16714628 . _:b496485723 . _:b16714574 "Furthermore, due to the potency of IFN\u03B1/\u03B2 in inhibiting viral replication, many viruses have evolved mechanisms to antagonize the IFN\u03B1/\u03B2 pathway, either at the induction or signaling level (Levy and Garcia\u2010Sastre,>>2001<<; Sen,2001)." . _:b16714644 _:b16714676 . _:b16714601 . _:b16714644 _:b16714677 . _:b16714644 _:b16714678 . . _:b16714644 _:b16714679 . _:b16714644 _:b16714672 . _:b16714644 _:b16714673 . _:b16714644 _:b16714674 . _:b16714644 _:b16714675 . . _:b16714644 _:b16714680 . _:b16714644 _:b16714681 . . _:b16714644 _:b16714660 . . _:b16714644 _:b16714661 . "10.1002%2Fglia.22375" . _:b16714644 _:b16714662 . _:b16714644 _:b16714663 . _:b496485702 . _:b16714644 _:b16714656 . _:b16714644 _:b16714657 . _:b496485740 . _:b16714644 _:b16714658 . _:b16714644 _:b16714659 . _:b16714644 _:b16714668 . _:b496485748 . _:b16714644 _:b16714669 . _:b16714644 _:b16714670 . _:b16714644 _:b16714671 . _:b16714644 _:b16714664 . _:b496485754 . _:b16714644 _:b16714665 . _:b16714644 _:b16714666 . _:b16714644 _:b16714667 . _:b16714644 _:b16714645 . _:b16714644 _:b16714646 . _:b496485692 . _:b16714644 _:b16714647 . . _:b16714644 _:b16714652 . _:b16714644 _:b16714653 . _:b16714644 _:b16714654 . . _:b16714644 _:b16714655 . _:b16714644 _:b16714648 . . _:b16714644 _:b16714649 .