title: Induction of broadly reactive anti-hemagglutinin stalk antibodies by an H5N1 vaccine in humans.
abstract: Influenza virus infections are a major public health concern and cause significant morbidity and mortality worldwide. Current vaccines are effective but strain specific due to their focus on the immunodominant globular head domain of the hemagglutinin (HA). It has been hypothesized that sequential exposure of humans to hemagglutinins with divergent globular head domains but conserved stalk domains could refocus the immune response to broadly neutralizing epitopes in the stalk. Humans have preexisting immunity against H1 (group 1 hemagglutinin), and vaccination with H5 HA (also group 1)--which has a divergent globular head domain but a similar stalk domain--represents one such sequential-exposure scenario. To test this hypothesis, we used novel reagents based on chimeric hemagglutinins to screen sera from an H5N1 clinical trial for induction of stalk-specific antibodies by quantitative enzyme-linked immunosorbent assay (ELISA) and neutralization assays. Importantly, we also investigated the biological activity of these antibodies in a passive transfer in a mouse challenge model. We found that the H5N1 vaccine induced high titers of stalk-reactive antibodies which were biologically active and protective in the passive-transfer experiment. The induced response showed exceptional breadth toward divergent group 1 hemagglutinins but did not extend to group 2 hemagglutinins. These data provide evidence for the hypothesis that sequential exposure to hemagglutinins with divergent globular head domains but conserved stalk domains can refocus the immune response toward the conserved stalk domain. Furthermore, the results support the concept of a chimeric hemagglutinin universal influenza virus vaccine strategy that is based on the same principle.
  
  
  OBJECTIVE
  Influenza virus vaccines have to be reformulated and readministered on an annual basis. The development of a universal influenza virus vaccine could abolish the need for this cumbersome and costly process and would also enhance our pandemic preparedness. This study addressed the following questions, which are essential for the development of a hemagglutinin stalk-based universal influenza virus vaccine. (i) Can stalk-reactive antibodies be boosted by vaccination with divergent HAs that share conserved epitopes? (ii) How long-lived are these vaccine-induced stalk-reactive antibody responses? (iii) What is the breadth of this reactivity? (iv) Are these antibodies functional and protective? Our results further strengthen the concept of induction of stalk-reactive antibodies by sequential exposure to hemagglutinin immunogens with conserved stalk and divergent head domains. A universal influenza virus vaccine based on the same principles seems possible and might have a significant impact on global human health.
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA Faculty of Life Sciences, University of Vienna, Vienna, Austria.
authors.forename: Raffael
authors.initials: R
authors.lastname: Nachbagauer
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA Graduate School of Biological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Teddy John
authors.initials: TJ
authors.lastname: Wohlbold
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Ariana
authors.initials: A
authors.lastname: Hirsh
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Hai
authors.affiliation: The Influenza Centre, Department of Clinical Science, University of Bergen, Bergen, Norway Section for Infectious Diseases, Medical Department, Haukeland University Hospital, Bergen, Norway.
authors.forename: Haakon
authors.initials: H
authors.lastname: Sjursen
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Palese
authors.affiliation: The Influenza Centre, Department of Clinical Science, University of Bergen, Bergen, Norway Jebsen Centre for Influenza Vaccine Research, Department of Clinical Science, University of Bergen, Bergen, Norway Department of Research and Development, Haukeland University Hospital, Bergen, Norway florian.krammer@mssm.edu rebecca.cox@gades.uib.no.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Cox
authors.affiliation: Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA florian.krammer@mssm.edu rebecca.cox@gades.uib.no.
authors.forename: Florian
authors.initials: F
authors.lastname: Krammer
mesh_terms: D000328:Adult; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood*; D003429:Cross Reactions; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology*; D006801:Humans; D007116:Immunization, Passive; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D008297:Male; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D009500:Neutralization Tests; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control; D055815:Young Adult
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; C109963:hemagglutinin, avian influenza A virus