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.