Serum proteomic profiling in granumomatosis with polyangiitis using two-dimensional gel electrophoresis along with matrix assisted laser desorption ionization time of flight mass spectrometry.

Aim: The present study is a proteomic approach to find differentially expressed proteins in sera of limited and systemic subsets of active disease versus their remitting state in patients with granulomatosis with polyangiitis (GPA) and their correlation with disease activity.

Methods: Eighteen patients with GPA in active as well as in remitting state and four healthy controls (HC) were included in the study. For proteomics analysis, two-dimensional gel electrophoresis along with matrix-assisted laser desorption ionization time-of-flight mass spectrometry were performed. A total of 14 gels were run from pooled patients' sera from active GPA and remission as well as pooled HC serum.

Results: There was significant differential expression of proteins in limited versus systemic GPA and between active systemic versus remitting patients of systemic disease. We identified nine maximally differentially expressed and five proteins which were not detected in HC. Among nine proteins, one (Prolow density lipoprotein receptor-related protein 1) was downregulated and four proteins (haptoglobin Hp, Hp2, vitamin D binding protein, killer cell lectin-like receptor subfamily F member 2), were up-regulated in both limited and systemic active disease, two proteins like Ig gamma-4 chain C region protein and serum albumin were up-regulated in limited active GPA and two proteins, that is, cysteine rich secretory protein LCCL domain-containing 2 precursor and serine-threonine-protein kinase A-Raf were up-regulated in systemic active disease. Levels of interleukin-17 and vitamin-D binding protein (VDBP) by enzyme-linked immunosorbent assay could distinctly demarcate active disease versus remission.

Conclusion: Our study provides potential protein markers of active disease versus remission in GPA.