An agonistic anti-CD137 antibody promotes inflammatory signatures in immune cells that disrupt germinal center formation and T cell-dependent antibody responses II

CD137 is a costimulatory receptor expressed on natural killer cells, T cells, and subsets of dendritic cells. An agonistic monoclonal antibody (mAb) against CD137 has been used to reduce tumor burden or reverse autoimmunity in animal models and clinical trials. When testing the ability of agonistic anti-CD137 mAb to promote clearance of persistent virus infection, we recently reported reduced numbers of germinal center B (GC B) cells and follicular dendritic cells (FDC) in lymphoid tissues. Here, we show that agonistic anti-CD137 agonistic mAb treatment impairs antibody responses with multiple T cell-dependent antigens including virus infection, recombinant viral antigens, and conjugated haptens but not with a T cell-independent antigen or at homeostasis. These effects were not due to enhanced apoptosis or impaired proliferation of B cells but instead correlated with disorganization of the stromal cell compartment of the GC, and were mediated by CD137 signaling in CD4+ and CD8+ T cells. Anti-CD137 treatment in the context of acute infection also resulted in reduced numbers of marginal zone B cells, greater numbers of antibody-secreting plasmablasts, and pro-inflammatory signatures in several myeloid and lymphoid cell populations of the spleen. Our experiments in mice suggest that agonistic anti-CD137 mAbs used in cancer and autoimmunity therapy may alter stromal cell populations to causes GC collapse and impaired long-term antibody and B cell memory responses. Overall design: Droplet-based 5' end massively parallel single-cell RNA sequencing was performed by isolating single cells from mouse spleen after collagenase digestion, and libraries were prepared using Chromium Single Cell 5' Reagent Kits in a BSL-3 level laboratory according to manufacturer's protocol (10x Genomics). For B Cell repertoire libraries, amplified cDNA underwent two rounds of Target Enrichment using nested primer pairs specific for mouse B cell Ig constant regions. The generated scRNAseq libraries were sequenced a NovaSeq S4 flow cell. Splenocytes from 3 biologically independent mice were pooled per sample.