Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Prolonged but Variable Effects of B Cell Depletion Therapy in Murine Lupus Nephritis
Bekar1, Kai, Owen1, Teresa, Dunn2, Robert, Ichikawa1, Travis, Hossler1, Jennifer Barnard, Nevarez1, Sarah, Brady1, Sean
The pathogenic significance of B cells in systemic lupus (SLE) has been highlighted by the abrogation of disease in B cell deficient mice. However, the benefit of B cell depletion therapy (BCDT) in human SLE has recently been questioned by lack of clinical efficacy observed in the Explorer and Lunar studies. Development of a murine lupus model of BCD would be helpful to better understand the mechanisms and effects on disease outcomes.
Young NZB/NZWF1 female (812 weeks), early disease (18 weeks), and established nephritis (2430 weeks with durable proteinuria > 2+ or 100 mg/dl) animals were dosed with anti-CD20 antibody (IgG2a), BR3-Fc, or control antibody (10 mg/kg) i.v. Additionally, normal BALB/c were dosed with anti-CD20, CpG1826, and/or anti-CD40. Peripheral blood (PB), lymph node (LN), bone marrow (BM), spleen and peritoneal cells were harvested and analyzed by flow cytometry. Nephritis was monitored by proteinuria (Uristix) and kidney IHC. Serum IgG anti-dsDNA levels were measured by ELISA.
A single injection of anti-CD20 in normal mice caused rapid depletion of B cell subsets although with a gradation of sensitivity (%depletion): PB>spleen>LN>peritoneum>BM. Germinal center (GC) B cells in immunized mice were relatively resistant to depletion, an effect potentiated by anti-CD40 and a B cell stimulatory TLR9 CpG agonist. B cell reconstitution began ~6 weeks after initial treatment. Administration of a CpG agonist resulted in significantly earlier B cell reconstitution. In young NZB/NZWF1 mice BCD was incomplete with early reconstitution at 3 weeks. A sequential weekly dosing × 4 was subsequently utilized and improved depletion of more resistant subsets, including splenic marginal zone (30% depletion at 1 week to 97% depletion at 4 weeks). Treatment of older mice with established nephritis (2+) resulted in a significant decrease in the %B220+ cells compared to control antibody treated animals (12.19±3.69 vs. 44.40±3.69, p<0.001). However, there was significant variability among animals ranging from 7% to 91% depletion in the spleen, with relative resistance of the MZ and GC B cells. Depletion was improved by combination with BAFF blockade (BR3-Fc). BCDT prevented the progression of nephritis, with a significant difference in protein free survival that was maintained 20 weeks beyond completion of treatment (p<0.01). Serum anti-dsDNA antibodies were not different between the two groups, but activated and memory T cells were decreased with BCD (p<0.05). In a prevention study, treatment of 18 wk mice with 4 wks of anti-CD20 significantly delayed the onset of disease by over 20 wks (p=0.0007), a prolonged benefit that extended well after B cell reconstitution.
The lasting benefit of a short course of BCDT in NZB/NZWF1 mice supports a critical role of B cells in this disease model. Resistance of B cell populations to depletion may explain some heterogeneity in clinical response but could be overcome by combination therapeutic approaches. Supported by a Lupus Research Institute grant
To cite this abstract, please use the following information:
Bekar, Kai, Owen, Teresa, Dunn, Robert, Ichikawa, Travis, Hossler, Jennifer Barnard, Nevarez, Sarah, et al; Prolonged but Variable Effects of B Cell Depletion Therapy in Murine Lupus Nephritis [abstract]. Arthritis Rheum 2009;60 Suppl 10 :677