Prevention and Reversal of Lupus in NZB/NZW Mice by Transplantation of Purified Allogeneic Hematopoietic Stem Cells (HSC) with Non-Myeloablative Conditioning (NMT).

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease. Patients’ refractory to therapy may be considered for hematopoietic stem cell transplantation. Using lupus prone female NZB x NZW (NZBW) mice, we tested the ability of highly enriched, allogeneic HSC to prevent and reverse autoimmune symptoms with FACS purified haplo-identical allogeneic HSC. Ablative conditioning: 92 animals were given lethal TBI (14.5 Gy) and divided among 4 groups (Table 1). Urine and serology tested monthly, final time point before death tabulated. Transplantation with either syngeneic HSC or WBM accelerated disease in these mice, resulting in a rate of death exceeding age matched controls. Allogeneic transplanted mice had significantly greater survival above all groups (p= 0.0243). Proteinuria, elevated levels of circulating immune complexes (CIC), and auto-antibodies to dsDNA, nuclear antigens (ANA) and histones were lower in allo-HSC animals compared to the other ablative conditioning groups (p≤ 0.0001). Overall survival (OS) in allo-HSC animals was still unexceptional, possibly due to regimen related toxicity (TRM).

NMT conditioning: To determine if we could attenuate disease in NZBW mice already progressing into lupus-like disease with transplantation of allogeneic, purified HSC and reduce TRM, we developed a non-myeloablative conditioning protocol (2x5 Gy TBI + ATG + a-ASIALO-GM1) achieving an average mixed chimerism of 50%. Animals were treated at ~241 days with established symptoms of lupus (Table 2). While the group receiving conditioning alone, had a slight survival advantage over age matched control mice, the transplanted mice had greatly increased OS with 70% living well beyond 500 days of age (>250 days from transplant). Allo-HSC mice showed reversal or stabilization of their lupus symptoms including proteinuria, CIC, dsDNA and histone.

Conclusions:

1. Ablative and NMT transplant can treat lupus;

2. OS after NMT exceeds ablative conditioning;

3. Induction of mixed chimerism with purified allogeneic HSC using NMT conditioning treats established lupus.

The ability of pure HSC transplant and establishment of durable mixed chimerism to reverse established lupus makes it a reasonable strategy to test in man.