The IgG Galactosylation Ratio is Higher in Spondyloarthritis Patients and Associated with the MRI and the Response of TNF Blocker

Abstract

Objectives: MRI is an important tool for evaluating inflammation levels and assessing treatment response in patients with ankylosing spondylitis (AS). However, it is expensive, and requires experienced physicians. The goal of this study was to identify a biomarker correlated with MRI score in assessing treatment response of AS. Methods: A total of 558 spondyloarthritis (SpA) patients including 527 AS patients, 10 Psoriasis (PsA) and 21 non-radigographic SpA (nrSpA,) and 725 controls were enrolled for the studies. Plasma IgG galactosylation (IgG-Gal) level was measured by mass spectrometry. Clinical indexes such as Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and C-reactive protein (CRP) were measured in all AS patients. MRIs and X-rays were obtained from 65 AS patients who were treated with a TNF blocker and longitudinally followed up for 6 months. Results: The IgG-Gal ratio was twice as high in the AS patients compared to the controls. It correlated with sacroiliac joint (SIJ) and spine inflammation indices (Pearson coefficient/p value was 0.52/2E10-4 and 0.29/1E-3, respectively). In addition, AS patients with a higher IgG-Gal ratio at baseline tended to show greater improvement in SIJ inflammation scores by MRI, and the IgG-Gal ratio of AS patients was able to predict the response of TNF blocker measured by Assessment of SpondyloArthritis international Society (ASAS40) (AUC = 0.85). Conclusion: IgG-Gal ratio was significantly increased in AS patients. In clinical care, it may be used as a potential biomarker for diagnosis and prediction of drug response of AS patients in the future. Funding Statement: The study was supported by research grants from the National Basic Research Program (2014CB541801), National key research and development program (2016YFA0501303), National Natural Science Foundation of China (31521003, 31630088), Shanghai Municipal Science and Technology Major Project (2017SHZDZX01), International S&T Cooperation Program of China (2013DFA30870), 111 Project (B13016) and US NIH NIAID U01 (1U01AI090909), and China Medical Foundation (CMF). Computational support was provided by the High-End Computing Center located at Fudan University. Declaration of Interests: All authors declare no conflicts of interest. Ethics Approval Statement: This study was approved by the Ethical Committees of the School of Life Sciences of Fudan University and all participants provided written informed consent.