title: Adjuvanted pandemic influenza vaccine: variation of emulsion components affects stability, antigen structure, and vaccine efficacy.
abstract: BACKGROUND
  Adjuvant formulations are critical components of modern vaccines based on recombinant proteins, which are often poorly immunogenic without additional immune stimulants. Oil-in-water emulsions comprise an advanced class of vaccine adjuvants that are components of approved seasonal and pandemic influenza vaccines. However, few reports have been published that systematically evaluate the in vitro stability and in vivo adjuvant effects of different emulsion components.
  
  
  OBJECTIVE
  To evaluate distinct classes of surfactants, oils, and excipients, for their effects on emulsion particle size stability, antigen structural interactions, and in vivo activity when formulated with a recombinant H5N1 antigen.
  
  
  METHODS
  Emulsions were manufactured by high pressure homogenization and characterized alone or in the presence of vaccine antigen by dynamic light scattering, zeta potential, viscosity, pH, hemolytic activity, electron microscopy, fluorescence spectroscopy, and SDS-PAGE. In vivo vaccine activity in the murine model was characterized by measuring antibody titers, antibody-secreting plasma cells, hemagglutination inhibition titers, and cytokine production.
  
  
  RESULTS
  We demonstrate that surfactant class and presence of additional excipients are not critical for biological activity, whereas oil structure is crucial. Moreover, we report that simplified two-component emulsions appear more stable by particle size than more complex formulations.Finally, differences in antigen structural interactions with the various emulsions do not appear to correlate with in vivo activity.
  
  
  CONCLUSIONS
  Oil-in-water emulsions can significantly enhance antibody and cellular immune responses to a pandemic influenza antigen. The dramatic differences in adjuvant activity between squalene-based emulsion and medium chain triglyceride-based emulsion are due principally to the biological activity of the oil composition rather than physical interactions of the antigen with the emulsion.
authors.affiliation: Infectious Disease Research Institute, Seattle, WA 98104, USA.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Fox
authors.forename: Lucien
authors.initials: L
authors.lastname: Barnes V
authors.forename: Tara
authors.initials: T
authors.lastname: Evers
authors.forename: James D
authors.initials: JD
authors.lastname: Chesko
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Vedvick
authors.forename: Rhea N
authors.initials: RN
authors.lastname: Coler
authors.forename: Steven G
authors.initials: SG
authors.lastname: Reed
authors.forename: Susan L
authors.initials: SL
authors.lastname: Baldwin
mesh_terms: D000276:Adjuvants, Immunologic / Q000737:chemistry*; D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000737:chemistry* / Q000276:immunology*; D002626:Chemistry, Pharmaceutical; D016207:Cytokines / Q000276:immunology; D004655:Emulsions / Q000737:chemistry; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000737:chemistry* / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D058873:Pandemics; D014783:Viscosity
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D000956:Antigens, Viral; D016207:Cytokines; D004655:Emulsions; D007252:Influenza Vaccines
keywords: Oil-in-water emulsion; pandemic influenza; vaccine adjuvant