title: Broadly Neutralizing Hemagglutinin Stalk-Specific Antibodies Induce Potent Phagocytosis of Immune Complexes by Neutrophils in an Fc-Dependent Manner.
abstract: Broadly neutralizing antibodies that recognize the conserved hemagglutinin (HA) stalk have emerged as exciting new biotherapeutic tools to combat seasonal and pandemic influenza viruses. Our general understanding of the mechanisms by which stalk-specific antibodies achieve protection is rapidly evolving. It has recently been demonstrated that broadly neutralizing HA stalk-specific IgG antibodies require Fc-Fcγ receptor (FcγR) interactions for optimal protection in vivo Here we examine the neutrophil effector functions induced by stalk-specific antibodies. As the most abundant subset of blood leukocytes, neutrophils represent a critical innate effector cell population and serve an instrumental role in orchestrating downstream adaptive responses to influenza virus infection. Yet, the interplay of HA stalk-specific IgG, Fc-FcγR engagement, and neutrophils has remained largely uncharacterized. Using an in vitro assay to detect the production of reactive oxygen species (ROS), we show that human and mouse monoclonal HA stalk-specific IgG antibodies are able to induce the production of ROS by neutrophils, while HA head-specific antibodies do not. Furthermore, our results indicate that the production of ROS is dependent on Fc receptor (FcR) engagement and phagocytosis. We went on to assess the ability of monoclonal HA stalk-specific IgA antibodies to induce ROS. Consistent with our findings for monoclonal IgGs, only HA stalk-specific IgA antibodies elicited ROS production by neutrophils. This induction is dependent on the engagement of FcαR1. Taken together, our findings describe a novel FcR-dependent effector function induced by HA stalk-specific IgG and IgA antibodies, and importantly, our studies shed light on the mechanisms by which HA stalk-specific antibodies achieve protection.
  
  
  
  The present study provides evidence that broadly neutralizing HA stalk-specific antibodies induce downstream Fc-mediated neutrophil effector functions. In addition to their ability to neutralize, this class of antibodies has been shown to rely on Fc-Fc receptor interactions for optimal protection in vivo Curiously, neutralizing antibodies that bind the HA head domain do not require such interactions. Our findings build on these previous observations and provide a more complete picture of the relationship between stalk-specific antibodies and cells of the innate immune compartment. Furthermore, our data suggest that the ability of HA stalk-specific antibodies to mediate Fc-Fc receptor engagement is epitope dependent. Overall, this work will inform the rational design of improved influenza virus vaccines and therapeutics.
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Caitlin E
authors.initials: CE
authors.lastname: Mullarkey
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Bailey
authors.affiliation: Department of Pathology and Molecular Medicine, Institute for Infectious Disease Research, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Diana A
authors.initials: DA
authors.lastname: Golubeva
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Gene S
authors.initials: GS
authors.lastname: Tan
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Raffael
authors.initials: R
authors.lastname: Nachbagauer
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Wenqian
authors.initials: W
authors.lastname: He
authors.affiliation: Department of Pathology and Molecular Medicine, Institute for Infectious Disease Research, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Kyle E
authors.initials: KE
authors.lastname: Novakowski
authors.affiliation: Department of Pathology and Molecular Medicine, Institute for Infectious Disease Research, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Bowdish
authors.affiliation: Department of Biochemistry and Biomedical Sciences, Institute for Infectious Disease Research, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Miller
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA peter.palese@mssm.edu.
authors.forename: Peter
authors.initials: P
authors.lastname: Palese
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D000936:Antigen-Antibody Complex / Q000378:metabolism*; D002478:Cells, Cultured; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D009504:Neutrophils / Q000276:immunology*; D009975:Orthomyxoviridae / Q000276:immunology; D010587:Phagocytosis; D017382:Reactive Oxygen Species / Q000378:metabolism; D011961:Receptors, Fc / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000936:Antigen-Antibody Complex; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D017382:Reactive Oxygen Species; D011961:Receptors, Fc