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Abstract: TH-PO815

Comparison of IgA1 Hinge-Region O-Glycoforms Between Patients with IgA Nephropathy and Healthy Subjects

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Ohyama, Yukako, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Takahashi, Kazuo, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Yamaguchi, Hisateru, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, Japan
  • Matsushita, Shoko, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Nakajima, Kazuki, Fujita Academy, Fujita Health University, Toyoake, Aichi, Japan
  • Inaguma, Daijo, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Hasegawa, Midori, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Novak, Jan, University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Hiki, Yoshiyuki, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Yuzawa, Yukio, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
Background

IgA1 with galactose (Gal)-deficient hinge-region (HR) O-glycans (Gd-IgA1) plays a key role in the pathogenesis of IgA nephropathy (IgAN). Monoclonal antibody (mAb) specific for Gd-IgA1 developed for detection of Gd-IgA1 was used in ELISA to confirm elevated serum Gd-IgA1 levels in IgAN patients. An earlier study found that IgAN glomerular immunodeposits were enriched for Gd-IgA1, supporting a key role of Gd-IgA1 in IgAN pathogenesis. To identify potentially disease-specific IgA1 HR O-glycoforms, we profiled serum IgA1 HR glycopeptides using specimens from Japanese IgAN patients and healthy controls (HC) of different races.

Methods

IgA1 from sera of 20 Japanese IgAN patients and 50 HC, recruited from Caucasian, Black, Hispanic, Asian, and Japanese populations, was purified by affinity chromatography. After neuraminidase treatment and trypsin digestion, IgA1 HR glycosylation heterogeneity was analyzed by liquid chromatography-high-resolution mass spectrometry (LC-MS). Area under the peaks of extracted ion chromatogram (XIC) of identified IgA1 HR O-glycopeptides was calculated and expressed as relative abundance (RA) for each glycopeptide as percentage of all HR glycopeptides. The amount of each glycopeptide was then calculated by multiplying serum IgA concentration (mg/dL) by RA for the specific glycopeptide.

Results

Approximately 60% of HR O-glycoforms contained one to three Gal-deficient O-glycans in IgA1 from IgAN patients as well as healthy subjects. The amount of Gal-deficient HR variants was increased in IgA1 from IgAN patients compared to that of HC (P =0.043, IgAN vs. all HC; P =0.011, IgAN vs. Japanese HC). IgA1 with single Gal-deficient O-glycan was notably increased in patients with IgAN compared to HC (P =0.043, IgAN vs. all HC; P =0.009, IgAN vs. Japanese HC).

Conclusion

Profiling of IgA1 HR O-glycoforms of IgAN patients and HC indicated that Gd-IgA1 glycoform with single Gal-deficient O-glycan was elevated in Japanese IgAN patients compared to HC. Future analysis of IgA1 HR O-glycoforms in the glomerular immunodeposits will allow comparison with nephritogenic Gd-IgA1 glycoforms in sera of IgAN patients.

Funding

  • Government Support - Non-U.S.