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Abstract

Protein replacement therapy for patients with hemophilia or other inherited protein deficiencies is often complicated by pathogenic antibody responses, including antibodies that neutralize the therapeutic protein or that predispose to potentially life-threatening anaphylactic reactions by formation of IgE. Using murine hemophilia B as a model, we have developed a prophylactic protocol against such responses that is non-invasive and does not include immune suppression or genetic manipulation of the patient's cells. Oral delivery of coagulation factor IX (F. IX) expressed in chloroplasts, bioencapsulated in plant cells, effectively blocked formation of inhibitory antibodies in protein replacement therapy. Inhibitor titers were mostly undetectable and up to 100-fold lower in treated mice when compared to controls. Moreover, this treatment eliminated fatal anaphylactic reactions that occurred after 4 to 6 exposures to intravenous F. IX protein. While only 20-25% of control animals survived after 6-8 F. IX doses, 90-95% of tolerized mice survived 12 injections without signs of allergy or anaphylaxis. This high-responder strain of hemophilia B mice represents the first hemophilic animal model to study anaphylactic reactions. The plant material was effective over a range of oral antigen doses (equivalent to 5-80 μg recombinant F.IX/kg), and controlled inhibitor formation and anaphylaxis long-term, up to 7 months. Oral antigen administration caused a deviant immune response that suppressed formation of IgE and inhibitory antibodies. This cost-effective and efficient approach to oral delivery of protein antigens to the gut should be applicable to several genetic diseases that are prone to pathogenic antibody responses during treatment.

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