Background: Lupus nephritis (LN) represents a severe manifestation of systemic lupus erythematosus (SLE) that is characterised by unpredictable short- and long-term outcomes due to the absence of reliable biomarkers. Distinct roles for immunoglobulin G (IgG), complement component 3 (C3), and alpha-1-acid glycoprotein (AGP; acute phase glycoprotein) in inflammation are recognised, and the importance of their N-glycosylation has been postulated in studies where biomarker potentiality has been documented within several autoimmune diseases.

Objectives: To investigate whether changes in the N-glycosylation of IgG, C3, and AGP over one year of treatment for LN are associated with short-term outcomes, including histological and clinical parameters, and long-term kidney outcomes, including renal flares and impairment of renal function.

Methods: Serum samples from 19 treatment-naïve patients with incident LN were collected before and one year after commencement of treatment. From those, we isolated IgG (Fc, Fab, total), C3, AGP, and total serum glycoproteins, which were analyses either as released N-glycans or N-glycopeptides using high-throughput glycoanalytical approaches. All patients underwent per-protocol repeat kidney biopsy. Paired t-test was used to identify significantly altered levels of N-glycosylation traits following treatment. Spearman’s rank correlation was applied to assess the relationship between changes in N-glycosylation trait levels (delta, Δ) and changes in short-term outcomes (delta, Δ), including renal pathology National Institutes of Health (NIH) activity and chronicity index scores, urinary protein-to-creatinine ratio (UPCR), serum creatinine (sCr), and estimated glomerular filtration rate (eGFR). Logistic regression was applied to examine whether changes in N-glycosylation trait levels are associated with treatment responses at one year, as well as with long-term outcomes, including renal flares and renal impairment (eGFR <60 mL/min/1.73m², sustained for at least two measurements, at least three months apart).

Results: In total, we identified 44/243 increased N-glycosylation traits(7 total IgG, 8 IgG Fc, 8 IgG Fab, 11 serum glycoproteins, 9 AGP, and 1 C3) and 41/243 decreased N-glycosylation traits (10 total IgG, 4 IgG Fc, 3 IgG Fab, 7 serum proteins, 11 AGP, and 2 C3) following treatment. We observed a significant negative correlation between changes of NIH activity index scores and the changes of the increased total IgG A2[6]G1 N-glycan (GP16; r=-0.64; p=0.005), total IgG asialylated N-glycans (S0; r=-0.53; p=0.03), serum high-mannose N-glycans (HM; r=-0.56; p=0.02), and a significant positive correlation between changes of NIH activity index scores and changes of the decreased C3 N2H5 N-glycopeptide (CIIIKTVLT1N2H5; r=0.51; p=0.04) and total IgG A2G2[6]S1 N-glycan (GP9; r=0.51; p=0.04). However, Nglycosylation changes were not associated with changes in NIH chronicity index score changes. Of the increased N-glycosylation traits, changes of serum M6 and FA2[3]BG1 N-glycans (GP7; r=-0.65; p=0.002), serum A2G2 N-glycan (GP8, r=-0.56; p=0.01), serum M9 N-glycan (GP19; r=-0.49; p=0.03), and serum high-mannose N-glycans (HM; r=-0.57; p=0.01) negatively correlated with ΔsCr, while changes of the decreased C3 N2H5 N-glycopeptide (CIIIKTVLT1N2H5; r=0.56; p=0.01) positively correlated with ΔsCr. As expected, the same correlations were seen with the ΔeGFR, yet in the opposite direction. Changes in UPCR levels positively correlated with the changes of the increased IgG Fab A2BG2S2 N-glycan (GP2; r=0.53; p=0.02) and serum A3F1G3S2 and A3G3S3 N-glycans (GP27; r=0.59; p=0.007), and the decreased AGP N6H7S3 N-glycopeptide (IIORM1N6H7S3; r=0.47; p=0.04) and AGP N5H6S3F1 N-glycopeptide (VORMI1N5H6S3F1; r=0.56; p=0.01). Eleven increased N-glycosylation traits positively correlated with changes in serum albumin and eleven decreased glycans negatively correlated with changes in levels of serum albumin. The change in the decreased total IgG GP4 (OR=27.1; 95% CI=1.1–678.5; p=0.04) was significantly associated with clinical and histological response at month 12, while changes in glycan levels were not associated with renal impairment or subsequent renal flares during follow-up.

Conclusion: This study provides a comprehensive characterisation of the glycosylation profile of proteins involved in the inflammatory response in a unique cohort of incident cases of LN, with available data from per-protocol repeat kidney biopsies and long-term follow-up. Our findings suggest that glycosylation changes over one year of treatment are associated with certain features of clinical and histological renal outcome, warranting further exploration of the potential role of glycans as biomarkers in LN.

REFERENCES: [1] Parodis, I., Adamichou, C., Aydin, S., Gomez, A., Demoulin, N., Weinmann-Menke, J., Houssiau, F. A., & Tamirou, F. (2020). Per-protocol repeat kidney biopsy portends relapse and long-term outcome in incident cases of proliferative lupus nephritis. Rheumatology (Oxford, England ), 59 (11), 3424–3434. https://doi.org/10.1093/rheumatology/keaa129

[2] Shkunnikova, S., Mijakovac, A., Sironic, L., Hanic, M., Lauc, G., & Kavur, M. M. (2023). IgG glycans in health and disease: Prediction, intervention, prognosis, and therapy. Biotechnology advances , 67 , 108169. https://doi.org/10.1016/j.biotechadv.2023.108169 .

Acknowledgements: NIL.

Disclosure of Interests: Dionysis Nikolopoulos: None declared, Maja Pučić-Baković Genos Glycoscience Research Laboratory, Jelena Šimunović Genos Glycoscience Research Laboratory, Anne-Marie Patenaude Genos Glycoscience Research Laboratory, Frano Vučković Genos Glycoscience Research Laboratory, Tea Pribić Genos Glycoscience Research Laboratory, Farah Tamirou: None declared, Gordan Lauc Genos Glycoscience Research Laboratory, Frederic Houssiau: None declared, Ioannis Parodis: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.