title: The C-type Lectin Langerin Functions as a Receptor for Attachment and Infectious Entry of Influenza A Virus.
abstract: It is well established that influenza A virus (IAV) attachment to and infection of epithelial cells is dependent on sialic acid (SIA) at the cell surface, although the specific receptors that mediate IAV entry have not been defined and multiple receptors may exist. Lec2 Chinese hamster ovary (CHO) cells are SIA deficient and resistant to IAV infection. Here we demonstrate that the expression of the C-type lectin receptor langerin in Lec2 cells (Lec2-Lg) rendered them permissive to IAV infection, as measured by replication of the viral genome, transcription of viral mRNA, and synthesis of viral proteins. Unlike SIA-dependent infection of parental CHO cells, IAV attachment and infection of Lec2-Lg cells was mediated via lectin-mediated recognition of mannose-rich glycans expressed by the viral hemagglutinin glycoprotein. Lec2 cells expressing endocytosis-defective langerin bound IAV efficiently but remained resistant to IAV infection, confirming that internalization via langerin was essential for infectious entry. Langerin-mediated infection of Lec2-Lg cells was pH and dynamin dependent, occurred via clathrin- and caveolin-mediated endocytic pathways, and utilized early (Rab5(+)) but not late (Rab7(+)) endosomes. This study is the first to demonstrate that langerin represents an authentic receptor that binds and internalizes IAV to facilitate infection. Moreover, it describes a unique experimental system to probe specific pathways and compartments involved in infectious entry following recognition of IAV by a single cell surface receptor.
  
  
  OBJECTIVE
  On the surface of host cells, sialic acid (SIA) functions as the major attachment factor for influenza A viruses (IAV). However, few studies have identified specific transmembrane receptors that bind and internalize IAV to facilitate infection. Here we identify human langerin as a transmembrane glycoprotein that can act as an attachment factor and a bone fide endocytic receptor for IAV infection. Expression of langerin by an SIA-deficient cell line resistant to IAV rendered cells permissive to infection. As langerin represented the sole receptor for IAV infection in this system, we have defined the pathways and compartments involved in infectious entry of IAV into cells following recognition by langerin.
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Wy Ching
authors.initials: WC
authors.lastname: Ng
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Londrigan
authors.affiliation: Westmead Millennium Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Najla
authors.initials: N
authors.lastname: Nasr
authors.affiliation: Westmead Millennium Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Cunningham
authors.affiliation: The Kirby Institute, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Stuart
authors.initials: S
authors.lastname: Turville
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Brooks
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia WHO Collaborating Centre for Reference and Research on Influenza, Victorian Infectious Diseases Reference Laboratory, at the 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; D015703:Antigens, CD / Q000378:metabolism*; D016466:CHO Cells; D003412:Cricetulus; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009980:Influenza A virus / Q000502:physiology*; D037181:Lectins, C-Type / Q000378:metabolism*; D037241:Mannose-Binding Lectins / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D011991:Receptors, Virus / Q000378:metabolism*; D053585:Virus Attachment; D053586:Virus Internalization
chemical_list: D015703:Antigens, CD; C121916:CD207 protein, human; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D037181:Lectins, C-Type; D037241:Mannose-Binding Lectins; D011134:Polysaccharides; D011991:Receptors, Virus; D034281:Dynamins