Nonmyeloablative Conditioning Generates Autoantigen-Encoding Bone Marrow That Prevents and Cures an Experimental Autoimmune Disease

Abstract

Autoimmune diseases result from chronic targeted immune responses that lead to tissue pathology and disease. The potential of autologous hematopoietic stem cells transplantation as a treatment for autoimmunity is currently being trialled but disease relapse is an issue. We have previously shown in a mouse model of experimental autoimmune encephalomyelitis (EAE) that the transplantation of bone marrow (BM) transduced to encode the autoantigen myelin oligodendrocyte glycoprotein (MOG) can prevent disease induction. However these studies were performed using lethal irradiation to generate BM chimeras and a critical factor for translation to humans would be the ability to utilize low toxic preconditioning regimes. In this study, treosulfan was used as a nonmyeloablative agent to generate BM chimeras encoding MOG and assessed in models of EAE induction and reversal. We find that treosulfan conditioning can promote a low degree of chimerism that is sufficient to promote antigen specific tolerance and protect mice from EAE. When incorporated into a curative protocol for treating mice with established EAE, nonmyeloablative conditioning and low chimerism was equally efficient in maintaining disease resistance. These studies further underpin the potential and feasibility of utilizing a gene therapy approach to treat autoimmune disease. Keywords: Experimental autoimmune encephalomyelitis, gene therapy, hematopoietic stem cell transfer, multiple sclerosis, nonmyeloablative Abbreviations: BM, bone marrow; BMT, bone marrow transfer; BSA, bovine serum albumin; EAE, experimental autoimmune encephalomyelitis; FCS, fetal calf serum; GFP, green fluorescent protein; HSC, hematopoietic stem cells; HSCT, hematopoietic stem cell transfer; IP, intraperitoneal; IRES, internal ribosomal entry site; MOG, myelin oligodendrocyte glycoprotein; PBS, phosphate buffered saline; ProII, proinsulinII; rmSCF, recombinant mouse stem cell factor; rmIL-6, recombinant mouse interleukin 6; SEM, standard error of the mean; TBI, total body irradiation; Treo, treosulfan.

Tackling autoimmunity with gene therapy

“…13 In our study published in The American Journal of Transplantation, the principle aim was to assess if the protocol of transplanting transduced BM encoding MOG could be employed in the EAE model with non-myeloablative preconditioning to promote long-term remission. 19 The study confirmed that we could utilize non-myeloablative conditioning but also reconfirmed earlier observations that only low levels of chimerism are required to achieve this. Even with chimerism levels of a few percent, tolerance was complete and animals with established EAE remained resistant to relapse in the presence of rechallenge with self-antigen.…”

Gene Therapy Delivery of Myelin Oligodendrocyte Glycoprotein (MOG) via Hematopoietic Stem Cell Transfer Induces MOG-Specific B Cell Deletion

“…Another important aspect of BM transplantations in this setting is the degree of toxicity and mortality associated with the preconditioning regimes (4). Positive inroads are being made on this front, and we have recently shown in our studies that a nonmyeloablative preconditioning regimen can be used to reproduce tolerance to MOG in our EAE model (45). Underpinning this is the observation that only low-level microchimerism is required to promote robust tolerance (45,59).…”

“…Positive inroads are being made on this front, and we have recently shown in our studies that a nonmyeloablative preconditioning regimen can be used to reproduce tolerance to MOG in our EAE model (45). Underpinning this is the observation that only low-level microchimerism is required to promote robust tolerance (45,59). Taken together, the data that are gradually accumulating surrounding this strategy of using a gene therapy approach to tackling autoimmunity will bolster its significance as a feasible and future option for potential clinical translation.…”

“…Although this process can provide benefit to some individuals, the threat of relapse is also present and suggestive that the procedure is not establishing immunological tolerance and long-term protection. Indeed, in EAE, we have shown that in mice with established EAE, treatment with total-body irradiation and syngeneic BM transplantation can promote remission; however, upon rechallenge with Ag, there is rapid relapse (7,45).…”

The hematopoietic system in the context of regenerative medicine

“…This approach has successfully induced tolerance to a diverse range of tissues, including kidney [242, 259, 265, 267–271], heart [245, 268], skin [245, 255], liver [272–275], trachea [251], and vascularized composite tissue allografts (CTA) [255, 257]. It has also successfully reversed autoimmune disorders including SLE [227, 231, 236, 237, 252, 260, 261, 276], Type I diabetes [239, 241, 244, 249, 250, 262], pemphigus vulgaris [276, 277], and experimental allergic encephalomyelitis (a preclinical model for multiple sclerosis) [235, 238, 247, 248, 260, 278]. However, results of clinical trials using HSC transplantation to treat “true” multiple sclerosis have been more mixed; some trials have reported very positive impact on clinical scores and disease progression [278–281], while others have found either no improvement at all, or perhaps even a worsening of neuroinflammation and demyelination following HSC transplant [282, 283].…”