Platform for practical delivery of oral autoantigens as co-therapies for neurological disease

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ABSTRACT The difficulties for creating an efficacious oral autoantigen therapy are basically twofold: practicality and efficacy. Practically, most protein autoantigens will be expensive to manufacture, to administer, and may not remain intact following passage through the gastrointestinal tract. Therapeutically, even if some of the protein autoantigens survive to interact with immune cells in the Gut Associated Lymphoid Tissue (GALT), their ability to significantly reduce autoimmune T and B cells responses in patients has not been effectively demonstrated. Developing a routine, practical strategy for oral autoantigen therapy is certainly a difficult and risky proposition. Demonstrating the feasibility of a technology for routine and practical oral autoantigen therapy would be unique. As a proof of principle, we have expressed an autoantigen (the alpha 1 subunit of the human nicotinic acetylcholine receptor) as a fusion with the reovirus sigma1 protein in transgenic soybean seeds. The logic behind such an approach lies in the ability of the reovirus sigma1 protein (sigma1) to bind microfold cells covering mucosal lymphoid tissues. Autoantigens fused to sigma1 target the immunogen to these cells, and deliver the autoantigen in a “tolerizing context” to limit an ongoing autoimmune response. Further, while such autoantigens and fusion proteins are difficult to manufacture, the ability to express large quantities of a sizeable protein, and administer it as a consumable soymilk formulation is unique to this platform expression system. The autoantigen that we will focus on for these studies is one that most patients with myasthenia gravis mount an immune response against: i.e. the extracelluar portion of the nicotinic acetylcholine receptor alpha 1 chain (AChR). In this proposal, we will manufacture quantities of an AChR-sigma1 concentrate made from transgenic soybean seeds expressing this fusion protein. Studies to define manufacturing and encapsulation of this powdered material will be conducted. We will also use a rat model to begin to define safety, in vivo distribution, and therapeutic efficacy using a model of experimental autoimmune myasthenia gravis. Completion of these studies will address some of the most important regulatory hurdles for approval of oral soy-based concentrates containing this novel fusion protein. If successful, the therapeutic efficacy studies will suggest that we have developed a candidate oral tolerance therapy for the autoimmune disease, myasthenia gravis (MG). The practical advantages of soybean-derived therapeutics, combined with the efficacy of delivering an autoantigen in a tolerizing context to the gut immune system, represent a novel solution for therapeutic intervention for myasthenia gravis, and potentially many other autoimmune diseases.