title: Infection of Mouse Macrophages by Seasonal Influenza Viruses Can Be Restricted at the Level of Virus Entry and at a Late Stage in the Virus Life Cycle.
abstract: Airway epithelial cells are susceptible to infection with seasonal influenza A viruses (IAV), resulting in productive virus replication and release. Macrophages (MΦ) are also permissive to IAV infection; however, virus replication is abortive. Currently, it is unclear how productive infection of MΦ is impaired or the extent to which seasonal IAV replicate in MΦ. Herein, we compared mouse MΦ and epithelial cells for their ability to support genomic replication and transcription, synthesis of viral proteins, assembly of virions, and release of infectious progeny following exposure to genetically defined IAV. We confirm that seasonal IAV differ in their ability to utilize cell surface receptors for infectious entry and that this represents one level of virus restriction. Following virus entry, we demonstrate synthesis of all eight segments of genomic viral RNA (vRNA) and mRNA, as well as seven distinct IAV proteins, in IAV-infected mouse MΦ. Although newly synthesized hemagglutinin (HA) and neuraminidase (NA) glycoproteins are incorporated into the plasma membrane and expressed at the cell surface, electron microscopy confirmed that virus assembly was defective in IAV-infected MΦ, defining a second level of restriction late in the virus life cycle.
  
  
  OBJECTIVE
  Seasonal influenza A viruses (IAV) and highly pathogenic avian influenza viruses (HPAI) infect macrophages, but only HPAI replicate productively in these cells. Herein, we demonstrate that impaired virus uptake into macrophages represents one level of restriction limiting infection by seasonal IAV. Following uptake, seasonal IAV do not complete productive replication in macrophages, representing a second level of restriction. Using murine macrophages, we demonstrate that productive infection is blocked late in the virus life cycle, such that virus assembly is defective and newly synthesized virions are not released. These studies represent an important step toward identifying host-encoded factors that block replication of seasonal IAV, but not HPAI, in macrophages.
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Londrigan
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia.
authors.forename: Kirsty R
authors.initials: KR
authors.lastname: Short
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia.
authors.forename: Joel
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia.
authors.forename: Leah
authors.initials: L
authors.lastname: Gillespie
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Victorian Infectious Diseases Reference Laboratory, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Rockman
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Brooks
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia bioCSL Limited, Parkville, Victoria, Australia WHO Collaborating Centre for Reference and Research on Influenza, Victorian Infectious Diseases Reference Laboratory, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia preading@unimelb.edu.au.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Reading
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism / Q000821:virology; D004285:Dogs; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism* / Q000821:virology; D061985:Madin Darby Canine Kidney Cells; D051379:Mice; D009439:Neuraminidase / Q000235:genetics / Q000378:metabolism; D009976:Orthomyxoviridae Infections / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000096:biosynthesis / Q000235:genetics; D013045:Species Specificity; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly / Q000502:physiology*; D053586:Virus Internalization; D014779:Virus Replication / Q000502:physiology*
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D014764:Viral Proteins; C483468:hemagglutinin, human influenza A virus; C487630:NA protein, influenza A virus; D009439:Neuraminidase