title: Development of assay for determining free IgE levels in serum from patients treated with omalizumab.
abstract: BACKGROUND
  Omalizumab, a monoclonal anti-IgE antibody, is currently indicated for the treatment of moderate-to-severe allergic asthma. To measure active IgE levels in sera from patients treated with omalizumab, the IgE subfraction in complex with omalizumab should be eliminated from total IgE, and free IgE levels can then be determined. With the aim of therapeutic monitoring for anti-IgE therapy, we developed a new ELISA for free IgE.
  
  
  METHODS
  We used recombinant human soluble FcεRIα as a capture antigen and a biotinylated polyclonal anti-IgE antibody for detection. Using the newly developed ELISA, we measured the serum free IgE levels weekly in four asthmatic patients after their first omalizumab injection. We also measured the serum free IgE levels in 54 patients treated with omalizumab for over 4 weeks.
  
  
  RESULTS
  This assay was technically robust, the mean recovery rate in serum was 93.16% ± 5.34%. For all patients, omalizumab treatment significantly reduced serum free IgE levels prior to the second omalizumab injection. To maintain the benefit of omalizumab, serum free IgE concentrations should be <50 ng/ml. However, in 14 of 54 patients treated with omalizumab for over 4 weeks, serum free IgE concentrations measured by our ELISA were >50 ng/ml.
  
  
  CONCLUSIONS
  Our data suggest that the measurement of free IgE levels using our newly developed ELISA would be useful for monitoring serum free IgE levels during omalizumab therapy.
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Reiko
authors.initials: R
authors.lastname: Ito
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Gon
authors.affiliation: Allergy and Immunology Group, Research Institute of Medical Science, Medical Education Plan and Promotion Room, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nunomura
authors.affiliation: Department of Respiratory Medicine, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Atsuta
authors.affiliation: Department of Respiratory Medicine, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Harada
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hattori
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Maruoka
authors.affiliation: Allergy and Immunology Group, Research Institute of Medical Science, Medical Education Plan and Promotion Room, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Okayama
authors.affiliation: Allergy and Immunology Group, Research Institute of Medical Science, Medical Education Plan and Promotion Room, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Chisei
authors.initials: C
authors.lastname: Ra
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D000888:Antibodies, Anti-Idiotypic / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D000069444:Omalizumab; D012015:Reference Standards; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D018927:Anti-Asthmatic Agents; D000888:Antibodies, Anti-Idiotypic; D061067:Antibodies, Monoclonal, Humanized; D000069444:Omalizumab; D007073:Immunoglobulin E