title: Replication-dependent potent IFN-alpha induction in human plasmacytoid dendritic cells by a single-stranded RNA virus.
abstract: Plasmacytoid dendritic cells sense viral ssRNA or its degradation products via TLR7/8 and CpG motifs within viral DNA via TLR9. Although these two endosomal pathways operate independently of viral replication, little is known about the detection of actively replicating viruses in plasmacytoid dendritic cell (PDC). Replication and transcription of the viral genome of ssRNA viruses as well as many DNA viruses lead to the formation of cytosolic dsRNA absent in noninfected cells. In this study, we used human respiratory syncytial virus (HRSV) encoding a fusion (F) protein for direct cytosolic entry. Both HRSV infection and cytosolic delivery of a 65-nt dsRNA led to potent IFN-alpha induction in PDC, but not in myeloid dendritic cells. Inactivation of HRSV by UV irradiation abrogated IFN-alpha induction in PDC. The comparison of two respiratory syncytial virus (RSV) constructs carrying either the HRSV or the bovine RSV F protein revealed that F-mediated cytosolic entry of RSV was absolutely required for IFN-alpha induction in PDC. HRSV-induced IFN-alpha production was independent of endosomal acidification and of protein kinase R (PKR) kinase activity, as demonstrated with chloroquine and the PKR inhibitor 2-aminopurine, respectively. In contrast, the induction of IFN-alpha by the TLR7/8 ligand R848, by the TLR9 ligand CpG-A ODN 2216, and by inactivated influenza virus (TLR7/8 dependent) was completely blocked by 2-aminopurine. IFN-alpha induction by mouse pathogenic Sendai virus was not affected in PKR- and MyD88-deficient mice, confirming that a ssRNA virus, which is able to directly enter host cells via fusion at the plasma membrane, can be detected by PDC independently of PKR, TLR7/8, and TLR9.
authors.affiliation: Department of Internal Medicine, Division of Clinical Pharmacology, Ludwig-Maximillians-University, Ziemssenstrasse 1, 80336 Munich, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Hornung
authors.forename: Jörg
authors.initials: J
authors.lastname: Schlender
authors.forename: Margit
authors.initials: M
authors.lastname: Guenthner-Biller
authors.forename: Simon
authors.initials: S
authors.lastname: Rothenfusser
authors.forename: Stefan
authors.initials: S
authors.lastname: Endres
authors.forename: Karl-Klaus
authors.initials: KK
authors.lastname: Conzelmann
authors.forename: Gunther
authors.initials: G
authors.lastname: Hartmann
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000502:physiology; D016175:B-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism / Q000821:virology*; D011992:Endosomes / Q000276:immunology / Q000378:metabolism; D006801:Humans; D016898:Interferon-alpha / Q000096:biosynthesis* / Q000528:radiation effects; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000276:immunology / Q000378:metabolism / Q000821:virology; D022423:Myeloid Cells / Q000276:immunology / Q000378:metabolism / Q000821:virology; D053594:Myeloid Differentiation Factor 88; D012330:RNA, Double-Stranded / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000096:biosynthesis; D011971:Receptors, Immunologic / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D018113:Respiratory Syncytial Virus, Human / Q000276:immunology* / Q000502:physiology / Q000528:radiation effects; D029082:Sendai virus / Q000276:immunology; D051199:Toll-Like Receptor 7; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; D014466:Ultraviolet Rays; D014760:Viral Fusion Proteins / Q000502:physiology; D014764:Viral Proteins / Q000502:physiology; D014779:Virus Replication / Q000276:immunology* / Q000528:radiation effects; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; D016898:Interferon-alpha; C507779:MYD88 protein, human; D008562:Membrane Glycoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D012330:RNA, Double-Stranded; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C495348:TLR7 protein, human; C495371:TLR9 protein, human; D051199:Toll-Like Receptor 7; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; D014760:Viral Fusion Proteins; D014764:Viral Proteins; D015075:2-Aminopurine; D019892:eIF-2 Kinase