Background: The application of B cell/plasma cell-targeted CAR-T therapy in Refractory Systemic Lupus Erythematosus (rSLE) represents a paradigm shift from chronic immunosuppression towards a potential single-intervention, curative-intent strategy. While the majority of the patients demonstrated deep and drug-free remissions, some rSLE patients experienced autoantibody rebounding and relapse at late time. Thus, it is urgent to investigate how B cells are reset and the underlying mechanisms in CAR-T-treated rSLE patients.

Objectives: To explore B cell reconstitution processes and immune microenvironment in the bone marrow of the rSLE patients who received CD19/BCMA CAR-T therapy.

Methods: Bone marrow and peripheral blood were collected at baseline, month 1 and month 6 from ten rSLE patients who received autologous CD19/BCMA CAR-T therapy. Mononuclear cells (MNCs) were subjected to scRNA-seq and scBCR-seq using the 10x Genomics Chromium platform, and multi-parameter flow cytometry for immune phenotyping. Plasma was subjected to cytokine/chemokine detection by Luminex.

Results: All rSLE patients achieved B cell and plasma cell deep depletion both in the blood and bone marrow one month after CD19/BCMA CAR-T infusion. Serum anti-dsDNA antibody from all early positive patients became negative within 2 months and other autoantibodies were also decreased with different kinetics. B cells began to reappear in the blood at month 3 and were detected in bone marrow from all patients at month 6. There is no BCR repertoire overlap between month 6 and baseline for the bone marrow B cells, suggesting a complete resetting for the newly developed B cells. Interestingly, we observed that 3 patients regained anti-dsDNA antibody positivity in the blood between month 6 and 12. Bone marrow single B cell analysis at month 6 revealed that BCR repertoire abnormality was corrected in anti-dsDNA negative patients, but still persistent in anti-dsDNA re-positive patients. Furthermore, the latter patients were associated with a proinflammatory status in bone marrow and peripheral blood.

Conclusions: Our study reveals that while the majority of rSLE patients can benefit from the CD19/BCMA CAR-T therapy with B cell resetting, there is a small proportion of rSLE patients failing to do so. Future studies will be dedicated to identifying the underlying mechanisms and biomarkers in order to select the most appropriate patients for CAR-T therapy.

REFERENCES: NIL.

Acknowledgments: NIL.

Disclosure of Interests: None declared.