title: Broadly neutralizing anti-influenza virus antibodies: enhancement of neutralizing potency in polyclonal mixtures and IgA backbones.
abstract: Current influenza virus vaccines rely upon the accurate prediction of circulating virus strains months in advance of the actual influenza season in order to allow time for vaccine manufacture. Unfortunately, mismatches occur frequently, and even when perfect matches are achieved, suboptimal vaccine efficacy leaves several high-risk populations vulnerable to infection. However, the recent discovery of broadly neutralizing antibodies that target the hemagglutinin (HA) stalk domain has renewed hope that the development of "universal" influenza virus vaccines may be within reach. Here, we examine the functions of influenza A virus hemagglutinin stalk-binding antibodies in an endogenous setting, i.e., as polyclonal preparations isolated from human sera. Relative to monoclonal antibodies that bind to the HA head domain, the neutralization potency of monoclonal stalk-binding antibodies was vastly inferior in vitro but was enhanced by several orders of magnitude in the polyclonal context. Furthermore, we demonstrated a surprising enhancement in IgA-mediated HA stalk neutralization relative to that achieved by antibodies of IgG isotypes. Mechanistically, this could be explained in two ways. Identical variable regions consistently neutralized virus more potently when in an IgA backbone compared to an IgG backbone. In addition, HA-specific memory B cells isolated from human peripheral blood were more likely to be stalk specific when secreting antibodies of IgA isotypes compared to those secreting IgG. Taken together, our data provide strong evidence that HA stalk-binding antibodies perform optimally when in a polyclonal context and that the targeted elicitation of HA stalk-specific IgA should be an important consideration during "universal" influenza virus vaccine design.
  
  
  OBJECTIVE
  Influenza viruses remain one of the most worrisome global public health threats due to their capacity to cause pandemics. While seasonal vaccines fail to protect against the emergence of pandemic strains, a new class of broadly neutralizing antibodies has been recently discovered and may be the key to developing a "universal" influenza virus vaccine. While much has been learned about the biology of these antibodies, most studies have focused only on monoclonal antibodies of IgG subtypes. However, the study of monoclonal antibodies often fails to capture the complexity of antibody functions that occur during natural polyclonal responses. Here, we provide the first detailed analyses of the biological activity of these antibodies in polyclonal contexts, comparing both IgG and IgA isotypes isolated from human donors. The striking differences observed in the functional properties of broadly neutralizing antibodies in polyclonal contexts will be essential for guiding design of "universal" influenza virus vaccines and therapeutics.
authors.affiliation: Department of Microbiology, Division of Infectious Diseases, 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 Microbiology, Division of Infectious Diseases, 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, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Duty
authors.affiliation: Department of Microbiology, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Moran
authors.affiliation: Department of Microbiology, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Palese
authors.affiliation: Department of Microbiology, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA Department of Biochemistry and Biomedical Sciences, Institute of Infectious Diseases Research, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada mmiller@mcmaster.ca.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Miller
mesh_terms: D000328:Adult; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007070:Immunoglobulin A; D007252:Influenza Vaccines