Immunological methods for quantifying free and total serum IgE levels in allergy patients receiving Omalizumab (Xolair) therapy

• Published in: Journal of immunological methods Vol. 303; no. 1; pp. 81 - 91
• Main Authors: Hamilton, Robert G., Marcotte, Gregory V., Saini, Sarbjit S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-08-2005; Elsevier
• Subjects: Adult; Aged; Animals; Antibodies, Anti-Idiotypic; Antibodies, Monoclonal - therapeutic use; Antibodies, Monoclonal, Humanized; Asthma - immunology; Asthma - therapy; Basophils - immunology; Biological and medical sciences; FcεR1α; Female; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Human IgE; Humans; IgE antibody; Immunoenzyme Techniques - methods; Immunoenzymetric assay; Immunoglobulin E - blood; Linear Models; Male; Mast Cells - immunology; Mice; Middle Aged; Molecular immunology; Omalizumab; Recombinant humanized IgG1 anti-human IgE Fc; Regression Analysis; Techniques; Xolair; PBS; Immunoenzymetric assay; FcεR1; Omalizumab (Xolair); Human IgE; Omalizumab; FcεR1α; IU; Xolair; Recombinant humanized IgG1 anti-human IgE Fc; BSA; IgE antibody; IEMA; CV; Human; Allergy; Antibody; IgE; Immunological method; Recombinant humanized IgGI anti-human IgE Fc; Treatment; Serum
• ISSN: 0022-1759; 1872-7905
• DOI: 10.1016/j.jim.2005.06.008

Omalizumab (humanized-IgG1 anti-human IgE Fc, Xolair®) complexes circulating IgE, blocking IgE binding to high affinity epsilon Fc receptors (FcεR1) on mast cells and basophils. Free (non-Omalizumab bound) IgE levels in serum are a measure of effective Omalizumab dosing. The goal of this study was to quantify free (non-Omalizumab-complexed) and total serum IgE levels in asthma patients on Xolair®. The concentration of (non-Omalizumab bound) free IgE in human serum was measured using a solid phase immunoenzymetric assay (IEMA) in which IgE was captured from serum with monoclonal anti-human IgE (clone HP6061) and detected with labeled-FcεR1α. In a companion total human serum IEMA, IgE was captured from serum with the same anti-human IgE (clone HP6061) and all bound IgE was detected with labeled monoclonal anti-human IgE Fc (clone HP6029). Free and total IgE levels were quantified in pre- and 1 and 3 months post Omalizumab therapy sera from 12 allergic asthma patients. In the absence of Omalizumab, working ranges of the free and total IgE IEMAs were comparable (10–1000 kIU/l), with excellent precision, reproducibility and parallelism. Pre-Omalizumab total and free IgE levels by IEMA were highly correlated (
r
2
=
0.99,
Y
=
0.9
X
+
0.32,
p
<
0.001), as were total serum IgE levels by IEMA and ImmunoCAP-250 (
r
2
=
0.98,
Y
=
1.1
X
−
0.05,
p
<
0.001, n
=
33). In vitro reduction of free IgE (>
90%) occurred at [Omalizumab:IgE] molar ratios of 2–20. Total IgE levels in 12 asthmatics increased from pre-therapy levels (52–658 kIU/l) by 1.5–5.5-fold at 1 month and 1.7–8.6 fold at 3 months of uninterrupted Omalizumab treatment. Free IgE levels fell by 49%–97% at 1 month and 45%–98% by 3 months of Omalizumab treatment. Free and total IgE levels by IEMA aid in monitoring patients receiving Omalizumab therapy.