Background/Purpose: Human plasmacytoid dendritic cells (pDCs) have been implicated in the pathogenesis of Systemic Sclerosis (SSc) through their ability to infiltrate the skin and secrete interferons (IFN), interleukin-6 (IL-6) and other proinflammatory chemokines directly, or through type-I IFN response of resident cells. Blood dendritic cell antigen 2 (BDCA-2) is a human-specific pDC-type II C-type lectin that potently inhibits IFN secretion. Here we determined the effects of CBS004, a novel monoclonal antibody against BDCA-2, on Toll-like receptor (TLR)-induced transcriptome

and IFN secretion in pDCs from healthy volunteers (HV) or patients with SSc in vitro, and tested its effect on two different  xeno-transplant mouse models of human pDC dependent tissue inflammation and fibrosis

Methods: Peripheral blood mononuclear cells (PBMCs) were collected from 26 SSc patients and 16 HV. IFN secretion were evaluated by ELISA. TLR7-9 stimulation was induced by Imiquimod or ODN. pDCs were isolated by magnetic cell sorting. Full transcriptome was analysed by RNA-sequencing. For the xenotransplant models,  NOD/SCID mice were injected in the tail vein with 25×10⁴human pDCs, 12 h after topical application of Imiquimod for the inflammation model, and along bleomycin skin injections in the fibrotic model. CBS004 was delivered by intraperitoneal injection at 5 mg/kg. Harvested skin was analysed by FACS for human pDC infiltration, by real-time PCR using a mouse type-I IFN response array (Qiagen) and by histology for dermal thickness.

Results: PBMCs from SSc patients spontaneously produced higher levels of IFN-I compared to HV ex vivo (206.7±23.4 vs. 43.4±6.8 pg/ml, P< 0.0001). CBS004 significantly inhibited basal levels of IFN-I in 83% of SSc samples. TLR9 stimulation of SSc PBMCs induced >30-fold increase in IFN-I secretion (7167±4377 pg/ml), which was completely abrogated by treatment with CBS004 (209±40.5 pg/ml, P< 0.001). RNA-seq analysis of human pDCs stimulated with TLR-9 agonist revealed 168 Differentially Expressed Genes (DEGs, FDR < 1%) mapping to IFN, JAK/STAT, IL-6, NF-kB and angiogenesis pathways. Pretreatment with CBS004 prevented upregulation of most DEGs, which drove an expression profile similar to non-stimulated pDCs. In the xenotransplant model, tail vein injection of pDC resulted in detection of human pDCs in the skin (0.3%) with at least 2-fold upregulation of 35/74 mouse type-I IFN response genes including Ccl2, 4, 5 and Cxcl10, Ifit1, 2 and 3, Mx1 and 2, Oas1, Tlr7, 8 and 9 compared to imiquimod treatment alone (P< 0.005). Mice receiving IP injection of CBS004 had a 3-fold reduction in infiltrating pDCs (0.1%) and suppression of 85% of the type-I IFN response genes upregulated by pDC injection (Anova P< 0.01). In the bleomycin model, pDC injection significantly increased dermal thickness (30%, P< 0.01), which was completely prevented by CBS004 treatment.

Conclusion: Our study demonstrates that BDCA-2 targeting with CBS004 mAb may block both the spontaneous and TLR dependent pDC driven IFN activation in Scleroderma. Further, we show that BDCA2 targeting with CBS004 can revert human pDC driven tissue inflammation and fibrosis in two distinct human pDC xenotransplant mouse models.

« Back to 2019 ACR/ARP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/bdca2-targeting-of-human-plasmacytoid-dendritic-cells-via-cbs004-reverts-dependent-ifn-activation-and-tissue-fibrosis-in-vitro-and-in-vivo/