CLEC5A-Mediated Enhancement of the Inflammatory Response in Myeloid Cells Contributes to Influenza Virus Pathogenicity In Vivo

J Virol. 2016 Dec 16;91(1):e01813-16. doi: 10.1128/JVI.01813-16. Print 2017 Jan 1.

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.

Importance: 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.

Keywords: C-type lectins; CLEC5A; influenza virus; macrophages; spleen tyrosine kinase (Syk).

MeSH terms

  • Animals
  • Antibodies / pharmacology
  • Chemokine CXCL10 / genetics
  • Chemokine CXCL10 / immunology
  • Gene Expression Regulation
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • Hemagglutinin Glycoproteins, Influenza Virus / immunology*
  • Host-Pathogen Interactions
  • Humans
  • Influenza A Virus, H1N1 Subtype / growth & development
  • Influenza A Virus, H1N1 Subtype / immunology
  • Influenza A Virus, H1N1 Subtype / pathogenicity*
  • Influenza A Virus, H5N1 Subtype / growth & development
  • Influenza A Virus, H5N1 Subtype / immunology
  • Influenza A Virus, H5N1 Subtype / pathogenicity*
  • Interferon-alpha / genetics
  • Interferon-alpha / immunology
  • Lectins, C-Type / antagonists & inhibitors
  • Lectins, C-Type / genetics
  • Lectins, C-Type / immunology*
  • Lentivirus / genetics
  • Lentivirus / immunology
  • Lung / drug effects
  • Lung / immunology
  • Lung / virology
  • Macrophages / drug effects
  • Macrophages / immunology
  • Macrophages / virology
  • Macrophages, Alveolar / drug effects
  • Macrophages, Alveolar / immunology
  • Macrophages, Alveolar / virology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Orthomyxoviridae Infections / genetics
  • Orthomyxoviridae Infections / immunology*
  • Orthomyxoviridae Infections / mortality
  • Orthomyxoviridae Infections / virology
  • Primary Cell Culture
  • Protein Binding
  • Protein Isoforms / genetics
  • Protein Isoforms / immunology
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Receptors, Cell Surface / antagonists & inhibitors
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / immunology*
  • Survival Analysis
  • Toll-Like Receptor 3 / genetics
  • Toll-Like Receptor 3 / immunology
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / immunology

Substances

  • Antibodies
  • CLEC5A protein, human
  • Chemokine CXCL10
  • Cxcl10 protein, mouse
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Interferon-alpha
  • Lectins, C-Type
  • Protein Isoforms
  • RNA, Small Interfering
  • Receptors, Cell Surface
  • TLR3 protein, mouse
  • Toll-Like Receptor 3
  • Tumor Necrosis Factor-alpha
  • hemagglutinin, human influenza A virus