24 nov. 2025
Liu, J. et al (BioRxiv)
Keywords
Autoimmunity
Immunotherapy
CAR-T
Main Findings
Despite advances in therapeutic options for systemic lupus erythematosus (SLE), immunosuppressive drugs still present significant risks, including serious infections. Autologous CD19-targeted chimeric antigen receptor (CAR) T cells are a promising treatment avenue, but they can result in dangerous cytokine-related toxicities. A recent preprint (not peer reviewed) by Liu et al. reports the design of precision cellular therapies targeting 9G4 idiotope (9G4id) B cells, which offer a more specific approach to depleting autoreactive B cells in SLE and other autoimmune diseases while reducing cytokine-related toxicities.
9G4id B cells, which use the VH4-34 heavy chain gene, are inherently autoreactive and are the source of multiple autoantibodies in SLE, making them a viable depletion target. The authors designed multiple 9G4-targeted CAR and chimeric T cell receptor (cTCR) constructs and demonstrated successful editing, construct expression and binding to 9G4id monoclonal antibodies.
To test B cell targeting, the authors edited the IGH locus of Ramos B cells to express three separate 9G4id monoclonal antibodies derived from patients with SLE and one control, non-9G4id monoclonal antibody. The 9G4-targeted CAR T cells and cTCR T cells selectively killed the 9G4id-expressing B cells while sparing non-9G4 B cells. Importantly, compared with control T cells, co-culture with the engineered T cells resulted in decreased production of both 9G4id and anti-dsDNA antibodies. Also, the 9G4-targeted cTCR T cells secreted lower levels of IFNg, granzyme A and B, and other pro-inflammatory cytokines in co-culture, suggesting that cTCRs might reduce the risk of cytokine toxicity.
Incubation of primary human B cells isolated from patients with SLE together with autologous 9G4-targeted CAR T cells and cTCR T cells resulted in almost complete depletion of IgG+ 9G4id antibody-secreting cells (ASCs) without reducing total IgG+ ASCs, as confirmed by fluorescence-linked immunospot assays and bulk B cell receptor repertoire sequencing. By contrast, incubation with autologous CD19-targeted CAR T cells depleted all IgG+ ASCs. Lastly, compared with autologous CD19-targeted CAR T cells, the 9G4-targeted CAR T cells and cTCR T cells produced less IFNg, IL-2Ra, granzyme A and granzyme B.
In addition to SLE, 9G4id B cells contribute to other disease states, including in cold agglutinin disease (CAD) and B cell cancers. The authors generated Ramos B cell lines that expressed patient-derived cold agglutinin positive 9G4id BCRs and showed elimination of these CAD 9G4id B cells when co-cultured with 9G4 CAR-T and 9G4 cTCR1-Tcells, while non-9G4 B cells were not decreased in co-culture. Additionally, as B cell cancers have been reported to have an overrepresentation of the 9G4 idiotope and Ramos RA1 B cells naturally use VH4-34, the authors also showed the ability of the 9G4 CAR-T and 9G4 cTCR1-T cells to eliminate these endogenous 9G4id B cell clones, suggesting their possible usefulness in B cell cancer contexts. These experiments reveal a broader applicability for these anti-9G4 CAR-T and cTCR-T cells in eliminating 9G4id B cells across relevant disease states.
This study offers a novel approach for targeting autoreactive B cells in SLE while potentially reducing safety concerns regarding cytokine-related toxicities. Ultimately, this preprint offers a novel and promising direction for treating autoreactive B cells in SLE.
Limitations
Although the 9G4 idiotope B cell compartment contributes significantly to autoimmunity in SLE, it does not comprise the entire autoreactive B cell population. More work should be done to understand how only depleting the 9G4id B cells does or does not abrogate broader autoimmunity in patients with SLE.
This paper offers a promising start for designing these anti-9G4 CAR-T and cTCR constructs; however, more work must be done to assess safety and efficacy in patients.
Significance/Novelty
This preprint offers a novel approach to targeting autoimmune 9G4id B cells, particularly in diseases in which a single autoantigen is not dominant, and it provides solid evidence for possible improved safety and efficacy over current SLE treatments. Additionally, 9G4id B cells are not only found in SLE, but also in other autoimmune diseases and B cell cancers, making this approach more broadly impactful for treating individuals with various diseases.
Credit
Reviewed by Meredith Ramba as part of a cross-institutional journal club between the Icahn School of Medicine at Mount Sinai, the University of Oxford, the Karolinska Institute and the University of Toronto.
The author declares no conflict of interests in relation to their involvement in the review.