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Abstract: PO1801

Developing Molecular-Specific Biomarker Assays for IgA Nephropathy and IgA Vasculitis with Nephritis

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Hansen, Alyssa L., The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Craine, Ellenore P., The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Hargett, Audra A., The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Hall, Stacy D., The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Rizk, Dana, The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Julian, Bruce A., The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Novak, Jan, The University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Renfrow, Matthew B., The University of Alabama at Birmingham, Birmingham, Alabama, United States
Background

Patients with IgA nephropathy (IgAN) develop characteristic glomerular immunodeposits containing IgA that is enriched for IgA1 glycoforms with galactose-deficient hinge-region O-glycans (Gd-IgA1). Blood levels of Gd-IgA1 are elevated in patients with IgAN and those with IgA vasculitis with nephritis (IgAV-N), suggesting a key role of Gd-IgA1 in pathogenesis of these diseases. In contrast, patients with IgA vasculitis (IgAV) without renal involvement do not have elevated blood levels of Gd-IgA1. These observations suggest a potential prognostic role for a minimally invasive biomarker based on profiling serum/plasma IgA1 O-glycoforms. Here, we describe a novel workflow to qualitatively and quantitatively assess molecular IgA1 phenotype(s) in IgAN by profiling serum IgA1. This validated approach can be extended to IgAV-N patients.

Methods

Isolation of IgA1 from sera is based on lectin-affinity chromatography followed by size-exclusion chromatography to separate IgA1 monomeric and polymeric forms and IgA1 bound in immune complexes. IgA1 O-glycosylation was analyzed by liquid chromatography-high-resolution mass spectrometry (LC-MS). In a pilot study, we used monomeric IgA1 from sera of 10 healthy controls and 10 IgAN patients. LC-MS runs were standardized using internal and external calibration methods.

Results

Quantitative LC-MS analysis revealed variations in the abundance of individual IgA1 O-glycoforms in the tested samples. We used quantitative data for 10-15 IgA1 glycoforms, expressed as relative ratios, to distinguish IgA1 from patients with IgAN vs. healthy controls. Furthermore, the LC-MS assay was standardized with internal and external calibration methods, an approach that will enable sample normalization, longitudinal studies, as well as evaluation of IgA1 from patients with IgAV-N.

Conclusion

Quantitative profiling of IgA1 clustered O-glycosylation can determine molecular IgA1 phenotype(s) and identify IgA1 glycoforms as biomarkers related to disease pathogenesis. These approaches are applicable to differential profiling of IgA1 from patients with IgAV-N vs. IgAV vs. healthy controls to identify pathogenic IgA1 glycoforms involved in the formation of nephritogenic immune complexes in IgAV-N.

Funding

  • Other NIH Support