title: Mechanism of a decrease in potency for the recombinant influenza A virus hemagglutinin H3 antigen during storage.
abstract: The recombinant hemagglutinin (rHA)-based influenza vaccine Flublok® has recently been approved in the United States as an alternative to the traditional egg-derived flu vaccines. Flublok is a purified vaccine with a hemagglutinin content that is threefold higher than standard inactivated influenza vaccines. When rHA derived from an H3N2 influenza virus was expressed, purified, and stored for 1 month, a rapid loss of in vitro potency (∼50%) was observed as measured by the single radial immunodiffusion (SRID) assay. A comprehensive characterization of the rHA protein antigen was pursued to identify the potential causes and mechanisms of this potency loss. In addition, the biophysical and chemical stability of the rHA in different formulations and storage conditions was evaluated over time. Results demonstrate that the potency loss over time did not correlate with trends in changes to the higher order structure or hydrodynamic size of the rHA. The most likely mechanism for the early loss of potency was disulfide-mediated cross-linking of rHA, as the formation of non-native disulfide-linked multimers over time correlated well with the observed potency loss. Furthermore, a loss of free thiol content, particularly in specific cysteine residues in the antigen's C-terminus, was correlated with potency loss measured by SRID.
authors.affiliation: Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047.
authors.forename: John M
authors.initials: JM
authors.lastname: Hickey
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Holtz
authors.forename: Prakash
authors.initials: P
authors.lastname: Manikwar
authors.forename: Sangeeta B
authors.initials: SB
authors.lastname: Joshi
authors.forename: Clifton E
authors.initials: CE
authors.lastname: McPherson
authors.forename: Barry
authors.initials: B
authors.lastname: Buckland
authors.forename: Indresh K
authors.initials: IK
authors.lastname: Srivastava
authors.forename: C Russell
authors.initials: CR
authors.lastname: Middaugh
authors.forename: David B
authors.initials: DB
authors.lastname: Volkin
mesh_terms: D055598:Chemical Phenomena; D003545:Cysteine / Q000032:analysis / Q000737:chemistry; D003553:Cystine / Q000032:analysis / Q000737:chemistry; D004355:Drug Stability; D004356:Drug Storage; D005079:Excipients / Q000737:chemistry; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D057446:Hydrodynamics; D005779:Immunodiffusion; D053122:Influenza A Virus, H3N2 Subtype / Q000187:drug effects / Q000254:growth & development / Q000276:immunology / Q000378:metabolism*; D007252:Influenza Vaccines / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017830:Octoxynol / Q000737:chemistry; D010084:Oxidation-Reduction; D010449:Peptide Mapping; D055550:Protein Stability; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013864:Thioglycolates / Q000737:chemistry
chemical_list: D005079:Excipients; C528512:FluBlok; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D011994:Recombinant Proteins; D013864:Thioglycolates; D003553:Cystine; C017487:2-mercaptoacetate; D017830:Octoxynol; D003545:Cysteine
keywords: Flublok®; influenza; mass spectrometry; physicochemical; potency; protein formulation; recombinant hemagglutinin; single-radial immunodiffusion assay; stability; vaccines