title: Evaluation of Epic® label-free technology to quantify functional recombinant hemagglutinin.
abstract: BACKGROUND
  Alternative methods are being sought to measure the potency of influenza vaccines. Label-free technologies that do not require the use of hemagglutinin (HA)-specific antisera are particularly attractive as the preparation of antiserum delays availability of potency reagents. The objective of these experiments was to evaluate the use of a Corning Epic® label-free method to quantify functional influenza hemagglutinin in rHA preparations. The method was optimized to quantify recombinant HA (rHA) of B/Brisbane/60/2008 (B/BR/08). Fetuin was immobilized onto plates and the change in wavelength of refracted light measured using an Enspire (Perkin Elmer) instrument.
  
  
  RESULTS
  The change in wavelength measured in response to addition of rHA of B/BR/08 was proportional to its concentration and was optimal in the presence of native rHA conformations. However, the assay was strain-dependent and did not correlate with HAU measured using turkey red blood cells.
  
  
  CONCLUSIONS
  The Corning Epic® label-free method is suitable for quantifying the native forms of rHA for B/BR/08 and A/Brisbane/59/2007 (H1N1) and A/Hangxhou/3/2013 (H7N9). This method is a useful tool for research purposes but further investigation is needed to identify suitable glycoproteins to use as ligands that allow quantification of HAs from a broader range of virus strains.
authors.affiliation: Division of Viral Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993 USA.
authors.forename: Lianlian
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Division of Viral Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993 USA.
authors.forename: Maryna C
authors.initials: MC
authors.lastname: Eichelberger
keywords: Corning; Enspire; Epic; Fetuin; Hemagglutinin; Influenza; Label-free technology; Potency; Recombinant