Oral delivery of human biopharmaceuticals, autoantigens and vaccine antigens bioencapsulated in plant cells

Abstract

Among 12 billion injections administered annually, unsafe delivery leads to >20 million infections and >100 million reactions. In an emerging new concept, freeze-dried plant cells (lettuce) expressing vaccine antigens/biopharmaceuticals are protected in the stomach from acids/enzymes but are released to the immune or blood circulatory system when plant cell walls are digested by microbes that colonize the gut. Vaccine antigens bioencapsulated in plant cells upon oral delivery after priming, conferred both mucosal and systemic immunity and protection against bacterial, viral or protozoan pathogens or toxin challenge. Oral delivery of autoantigens was effective against complications of type 1diabetes and hemophilia, by developing tolerance. Oral delivery of proinsulin or exendin-4 expressed in plant cells regulated blood glucose levels similar to injections. Therefore, this new platform offers a low cost alternative to deliver different therapeutic proteins to combat infectious or inherited diseases by eliminating inactivated pathogens, expensive purification, cold storage/transportation and sterile injections.

Plant-based oral tolerance to hemophilia therapy employs a complex immune regulatory response including LAP+CD4+ T cells

“…43 Upon migration from LPs to MLNs, CD103 Bioencapsulated antigens are protected from stomach acids and enzymes, but are released to the immune system in the gut. [6][7][8]14,35 Although the presence of microbes capable of lysing plant cells in the small intestine has been debated, it appears unlikely that the widespread delivery of FIX antigen that we observed could have been possible without a contribution of such commensal bacteria that digest plant cell walls. GM1 receptors are widely distributed over the intestinal mucosa with a rapid turnover rate.…”

“…4,38,39 Edible crop plants are potentially ideal for oral tolerance because they can be costeffectively grown and provide natural encapsulation for the antigen through the plant cell wall without a need for protein purification, cold chain, or sterile injections. 6 However, an oral tolerance protocol that could prevent antibody responses in protein replacement therapies for genetic disease had been elusive until recently. We developed chloroplast transgenic plants expressing high levels of coagulation factor antigens in green leaves and obtained substantial suppression of inhibitor formation in hemophilia A and B mice.…”

“…Taking advantage of the high number of chloroplast genomes per cell, we overcame these hurdles with our optimized technology for chloroplast transformation and gene expression. 6 Oral administration of factor VIII or FIX antigens expressed in transplastomic tobacco plants suppressed inhibitor formation and anaphylaxis in hemophilic mice. 7,8 Here, we demonstrate that plant cell-based oral tolerance for hemophilia is the result of a complex immune regulatory mechanism in response to the combination of orally and systemically administered antigen, ultimately inducing 2 types of Treg that suppress antibody formation.…”

Suppression of inhibitor formation against FVIII in a murine model of hemophilia A by oral delivery of antigens bioencapsulated in plant cells

“…12,14,16,20 Therefore, oral delivery of FVIII antigen may be an acceptable form of prophylactic tolerance induction in pediatric patients. Our current study demonstrates that multiple domains of FVIII can be expressed in plant chloroplasts.…”

“…14 To address this issue, we have developed a cost-effective system for production of high levels of protein in chloroplasts of transplastomic plant cells, which provide bioencapsulation of the antigen through the cellulose containing cell walls. 15,16 Because of the high number of chloroplast genomes per cell and our optimized expression system, transgenic proteins can accumulate in green leaves at much higher levels than is the case for more traditional transgenic plant technologies. 17,18 Oral delivery of transplastomic plant cells has been effective in prevention of insulitis in nonobese diabetic mice and of inhibitor formation in mice with hemophilia B.…”