title: CLEC5A-Mediated Enhancement of the Inflammatory Response in Myeloid Cells Contributes to Influenza Virus Pathogenicity In Vivo.
abstract: Human infections with influenza viruses exhibit mild to severe clinical outcomes as a result of complex virus-host interactions. Induction of inflammatory mediators via pattern recognition receptors may dictate subsequent host responses for pathogen clearance and tissue damage. We identified that human C-type lectin domain family 5 member A (CLEC5A) interacts with the hemagglutinin protein of influenza viruses expressed on lentiviral pseudoparticles through lectin screening. Silencing CLEC5A gene expression, blocking influenza-CLEC5A interactions with anti-CLEC5A antibodies, or dampening CLEC5A-mediated signaling using a spleen tyrosine kinase inhibitor consistently reduced the levels of proinflammatory cytokines produced by human macrophages without affecting the replication of influenza A viruses of different subtypes. Infection of bone marrow-derived macrophages from CLEC5A-deficient mice showed reduced levels of tumor necrosis factor alpha (TNF-α) and IP-10 but elevated alpha interferon (IFN-α) compared to those of wild-type mice. The heightened type I IFN response in the macrophages of CLEC5A-deficient mice was associated with upregulated TLR3 mRNA after treatment with double-stranded RNA. Upon lethal challenges with a recombinant H5N1 virus, CLEC5A-deficient mice showed reduced levels of proinflammatory cytokines, decreased immune cell infiltration in the lungs, and improved survival compared to the wild-type mice, despite comparable viral loads noted throughout the course of infection. The survival difference was more prominent at a lower dose of inoculum. Our results suggest that CLEC5A-mediated enhancement of the inflammatory response in myeloid cells contributes to influenza pathogenicity in vivo and may be considered a therapeutic target in combination with effective antivirals. Well-orchestrated host responses together with effective viral clearance are critical for optimal clinical outcome after influenza infections.
  
  
  OBJECTIVE
  Multiple pattern recognition receptors work in synergy to sense viral RNA or proteins synthesized during influenza replication and mediate host responses for viral control. Well-orchestrated host responses may help to maintain the inflammatory response to minimize tissue damage while inducing an effective adaptive immune response for viral clearance. We identified that CLEC5A, a C-type lectin receptor which has previously been reported to mediate flavivirus-induced inflammatory responses, enhanced induction of proinflammatory cytokines and chemokines in myeloid cells after influenza infections. CLEC5A-deficient mice infected with influenza virus showed reduced inflammation in the lungs and improved survival compared to that of the wild-type mice despite comparable viral loads. The survival difference was more prominent at a lower dose of inoculum. Collectively, our results suggest that dampening CLEC5A-mediated inflammatory responses in myeloid cells reduces immunopathogenesis after influenza infections.
authors: HKU-Pasteur Research Pole, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.|Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Ooiean
authors: O
authors: Teng
authors: Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Szu-Ting
authors: ST
authors: Chen
authors: Genomics Research Center, Academia Sinica, Taipei, Taiwan.
authors: Tsui-Ling
authors: TL
authors: Hsu
authors: Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Sin Fun
authors: SF
authors: Sia
authors: Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Suzanne
authors: S
authors: Cole
authors: HKU-Pasteur Research Pole, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.|Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Sophie A
authors: SA
authors: Valkenburg
authors: Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Tzu-Yun
authors: TY
authors: Hsu
authors: Department of Pediatrics and Adolescent Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Jian Teddy
authors: JT
authors: Zheng
authors: Department of Pediatrics and Adolescent Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Wenwei
authors: W
authors: Tu
authors: HKU-Pasteur Research Pole, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.|Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Roberto
authors: R
authors: Bruzzone
authors: HKU-Pasteur Research Pole, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.|Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Joseph Sriyal Malik
authors: JSM
authors: Peiris
authors: Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan slhsieh@gate.sinica.edu.tw hyen@hku.hk.|Genomics Research Center, Academia Sinica, Taipei, Taiwan.|Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan.
authors: Shie-Liang
authors: SL
authors: Hsieh
authors: HKU-Pasteur Research Pole, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China slhsieh@gate.sinica.edu.tw hyen@hku.hk.|Centre of Influenza Research, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors: Hui-Ling
authors: http://orcid.org/0000-0003-2493-3609
authors: HL
authors: Yen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D054357:Chemokine CXCL10 / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000276:immunology*; D054884:Host-Pathogen Interactions; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D053124:Influenza A Virus, H5N1 Subtype / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D016898:Interferon-alpha / Q000235:genetics / Q000276:immunology; D037181:Lectins, C-Type / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D016086:Lentivirus / Q000235:genetics / Q000276:immunology; D008168:Lung / Q000187:drug effects / Q000276:immunology / Q000821:virology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000821:virology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009976:Orthomyxoviridae Infections / Q000235:genetics / Q000276:immunology* / Q000401:mortality / Q000821:virology; D061251:Primary Cell Culture; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D016019:Survival Analysis; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology
chemical_list: D000906:Antibodies; C509771:CLEC5A protein, human; D054357:Chemokine CXCL10; C485433:Cxcl10 protein, mouse; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D016898:Interferon-alpha; D037181:Lectins, C-Type; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D014409:Tumor Necrosis Factor-alpha; C483468:hemagglutinin, human influenza A virus
keywords: C-type lectins; CLEC5A; influenza virus; macrophages; spleen tyrosine kinase (Syk)