Background: Systemic lupus erythematosus (SLE) is a complex autoimmune disorder driven by autoreactive B cells and characterised by the production of pathogenic autoantibodies [1]. Belimumab, an anti-BAFF monoclonal antibody, has demonstrated efficacy in reducing disease activity and corticosteroid use in SLE patients, although responses remain variable. B-cell activating factor (BAFF) is essential for B cell survival and autoantibody production, positioning it as a key target in SLE pathogenesis [2]. MicroRNAs (miRNAs), critical regulators of gene expression and immune homeostasis, have an emerging role in SLE pathophysiology [3]. However, their regulation in response to anti-BAFF therapies, such as belimumab, remains unexplored. This study investigates miRNA-mRNA interactions in T cells, B cells, and myeloid cells from SLE patients before and after belimumab treatment.

Objectives: To explore the mechanisms underlying anti-BLyS therapy in SLE, this study investigated miRNA-mRNA interaction networks and biological pathways in immune cellular subsets associated with clinical improvement.

Methods: Ten consecutive SLE patients treated with belimumab, classified as LLDA responders at 6 months with available PBMC samples, were included in the study. Peripheral blood immunophenotyping was performed on PBMCs using using a 17-color flow cytometry panel, followed by cell sorting for subsequent miRNA analyses. To perfom Mrna and miRNA transcriptomic analysis, Clariom S assay and GeneChip miRNA 4.0 arrays were used. Integrative analysis of mRNA and miRNA data was performed using the DIABLO method from the mixOmics R package. Validation was performed in a new cohort of 18 responders patient using Qpcr-rt experiments.

Results: After 6 months of belimumab therapy, there was a significant improvement in disease activity, with the mean SLEDAI-2K score decreasing to 2.4 ± 1.1 and a PGA score to 0.3 ± 0.2 at week 24 (both p < 0.001). In our study, we observed a general reduction in total B-cell counts but no significant changes in the proportions of different B-cell subsets after six months. Notably, we observed a significant increase in effector memory T-helper cells and a reduction in effector memory cytotoxic T cells. A total of 79 miRNAs associated with treatment response and 525 miRNA-gene interactions were identified. Validation in 18 SLE responders revealed significant changes in miRNA expression in T and myeloid cells, but not in B cells. Belimumab was found to modulate B cell development by regulating genes such as BLNK, BANK1, and MEF2C, as well as the CD40/CD40L axis. In T cells, miRNAs influenced interferon signalling and inflammatory cytokines via NF-κB activation. Changes in myeloid cells, characterised by the downregulation of KLF13, CCL5, and IL4, appear to be secondary to T cell modulation.

Conclusion: These findings provide novel insights into the miRNA-mediated regulatory networks underlying belimumab’s immunomodulatory effects in SLE. Further research is required to validate these findings and through in vitro experiments to better understand the role of miRNAs in guiding treatment responses.

REFERENCES: [1] Pan L, Lu M-P, Wang J-H, Xu M, Yang S-R. Immunological pathogenesis and treatment of systemic lupus erythematosus. World J Pediatr. (2020) 16(1):19–30. doi: 10.1007/s12519-019-00229-3.

[2] Davidson A. The rationale for BAFF inhibition in systemic lupus erythematosus. Curr Rheumatol Rep. (2012) 14(4):295–302. doi: 10.1007/s11926-012-0258-2.

[3] Choi D, Kim J, Yang JW, Kim JH, Park S, Shin JI. Dysregulated microRNAs in the pathogenesis of systemic lupus erythematosus: a comprehensive review. Int J Biol Sci. (2023) 19(8):2495–514. doi: 10.7150/ijbs.74315.

Acknowledgements: This work was kindly supported by the lupus patient association AILES (Associació per la Investigació en LES, Spain). The authors sincerely thank all patients and healthy donors for their participation in this study.

Disclosure of Interests: 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.