Concentrated protein body product derived from rice endosperm as an oral tolerogen for allergen-specific immunotherapy--a new mucosal vaccine formulation against Japanese cedar pollen allergy

Plant Platforms for Efficient Heterologous Protein Production

Production of recombinant proteins is primarily established in cultures of mammalian, insect and bacterial cells. Concurrently, concept of using plants to produce high-value pharmaceuticals such as vaccines, antibodies, and dietary proteins have received worldwide attention. Newer technologies for plant transformation such as plastid engineering, agroinfiltration, magnifection, and deconstructed viral vectors have been used to enhance the protein production in plants along with the inherent advantage of speed, scale, and cost of production in plant systems. Production of therapeutic proteins in plants has now a more pragmatic approach when several plant-produced vaccines and antibodies successfully completed Phase I clinical trials in humans and were further scheduled for regulatory approvals to manufacture clinical grade products on a large scale which are safe, efficacious, and meet the quality standards. The main thrust of this review is to summarize the data accumulated over the last two decades and recent development and achievements of the plant derived therapeutics. It also attempts to discuss different strategies employed to increase the production so as to make plants more competitive with the established production systems in this industry.

Solid-in-Oil Nanodispersions for Transcutaneous Immunotherapy of Japanese Cedar Pollinosis

Japanese cedar pollinosis (JCP) is a common affliction caused by an allergic reaction to cedar pollen and is considered a disease of national importance in Japan. Antigen-specific immunotherapy (AIT) is the only available curative treatment for JCP. However, low compliance and persistence have been reported among patients subcutaneously or sublingually administered AIT comprising a conventional antigen derived from a pollen extract. To address these issues, many research studies have focused on developing a safer, simpler, and more effective AIT for JCP. Here, we review the novel antigens that have been developed for JCP AIT, discuss their different administration routes, and present the effects of anti-allergy treatment. Then, we describe a new form of AIT called transcutaneous immunotherapy (TCIT) and its solid-in-oil (S/O) nanodispersion formulation, which is a promising antigen delivery system. Finally, we discuss the applications of S/O nanodispersions for JCP TCIT. In this context, we predict that TCIT delivery by using a S/O nanodispersion loaded with novel antigens may offer an easier, safer, and more effective treatment option for JCP patients.

Development of Rice-Seed-Based Oral Allergy Vaccines Containing Hypoallergenic Japanese Cedar Pollen Allergen Derivatives for Immunotherapy

Allergen-specific immunotherapy is the only available curative treatment for IgE-mediated allergen diseases. A safe hypoallergenic allergen derivative with high efficiency is required as a tolerogen to induce immune tolerance to the causitive allergens. In this study, to generate a rice-based oral allergy vaccine for Japanese cedar (JC) pollinosis, the tertiary structures of major JC pollen allergens, Cry j 1 and Cry j 2, were more completely destructed by shuffling than the previous ones without losing immunogenicity and then were specifically expressed in the endosperm of transgenic rice seed. They accumulated at high levels and were deposited in endoplasmic reticulum (ER) and ER-derived protein bodies. The low allergenicity of these deconstructed Cry j 1 and Cry j 2 allergens was evaluated by examining their binding activities to the specific IgE antibody and by the basophil degranulation test.

T-cell activation by transgenic rice seeds expressing the genetically modified Japanese cedar pollen allergens

Transgenic rice seeds that contain genetically modified Cry j 1 and Cry j 2, the two major allergens of Cryptomeria japonica (Japanese cedar; JC), have been developed as immunotherapeutic candidates for JC pollinosis. Because the transgenic rice (TG-rice) seeds express allergens containing whole amino acid sequences of Cry j 1 and Cry j 2 in the endosperm tissue (edible part of rice grain), they can potentially target all Cry j 1- and Cry j 2-specific T-cells. However, it was unknown whether antigenicity of Cry j 1 and Cry j 2 could be completely preserved in TG-rice seeds. We verified the antigenicity of TG-rice seeds to T-cells through the analysis of the proliferative responses of T-cells in Cry j 1- or Cry j 2-immunized mice or T-cell lines to TG-rice seed extract. First, four mouse strains were immunized with Cry j 1 or Cry j 2. T-cells in the immunized mice proliferated on treatment with TG-rice seed extract, but not non-transgenic wild-type rice (WT-rice) seed extract. Furthermore, T-cell lines were established from the spleen cells of the immunized mice. Each T-cell line resulted in a proliferative response to TG-rice seed extract, but not to WT-rice seed extract, suggesting that TG-rice seeds certainly express T-cell epitopes corresponding to T-cell lines. Considering the modified amino acid sequences of Cry j 1 and Cry j 2 in TG-rice seeds, the expression of specific T-cell epitopes suggested that TG-rice seeds express all possible T-cell epitope repertoires of Cry j 1 and Cry j 2.

Evaluation of basophil activation caused by transgenic rice seeds expressing whole T cell epitopes of the major Japanese cedar pollen allergens

Background

Japanese cedar (JC) pollinosis is a serious type I allergic disease in Japan. Although subcutaneous immunotherapy and sublingual immunotherapy have been applied to treat JC pollinosis, high doses of allergens may cause IgE-mediated allergic reactions. The transgenic rice seeds that contain genetically modified Cry j 1 and Cry j 2, the two major allergens of JC pollen, have been developed as candidates for oral immunotherapy. Although the antigens in the transgenic rice seeds (Tg-rice seeds) were engineered such that they decrease binding ability with IgE and they are of insufficient length to cross-link IgE on the surface of mast cells or basophils, the safety of Tg-rice seeds for patients with JC pollinosis was unclear.

Methods

To verify the safety of Tg-rice seeds in terms of allergies, we investigated the percentage of activated basophils induced by Tg-rice seed extract in the basophil activation test. Blood samples from 29 patients with JC pollinosis were collected. Tg-rice seed extract, non-transgenic wild-type rice seed extract, and Cry j 1 and Cry j 2 were mixed with the blood with reagents. The percentage of activated basophils was assessed by CD203c expression, a basophil activation marker.

Results

The percentage of activated basophils after the stimulation with Tg-rice seed extract was 4.5 ± 1.6% (mean ± SD) compared with 62.9 ± 20.2% after Cry j 1- and Cry j 2-stimulation (difference 58.4%, P < 0.001, 95% confidence interval 51.0–65.9%).

Conclusions

The results will contribute to the safety of Tg-rice seeds in terms of allergies.

Next generation immunotherapy for tree pollen allergies

Tree pollen induced allergies are one of the major medical and public health burdens in the industrialized world. Allergen-Specific Immunotherapy (AIT) through subcutaneous injection or sublingual delivery is the only approved therapy with curative potential to pollen induced allergies. AIT often is associated with severe side effects and requires long-term treatment. Safer, more effective and convenient allergen specific immunotherapies remain an unmet need. In this review article, we discuss the current progress in applying protein and peptide-based approaches and DNA vaccines to the clinical challenges posed by tree pollen allergies through the lens of preclinical animal models and clinical trials, with an emphasis on the birch and Japanese red cedar pollen induced allergies.

An overview on the strategies to exploit rice endosperm as production platform for biopharmaceuticals

Cereal seed has been utilized as production platform for high-value biopharmaceutical proteins. Especially, protein bodies (PBs) in seeds are not only natural specialized storage organs of seed storage proteins (SSPs), but also suitable intracellular deposition compartment for recombinant proteins. When various recombinant proteins were produced as secretory proteins by attaching N terminal ER signal peptide and C terminal KDEL endoplasmic reticulum (ER) retention signal or as fusion proteins with SSPs, high amounts of recombinant proteins can be predominantly accumulated in the PBs. Recombinant proteins bioencapsulated in PBs exhibit high resistance to digestive enzymes in gastrointestinal tract than other intracellular compartments and are highly stable at ambient temperature, thus allowing oral administration of PBs containing recombinant proteins as oral drugs or functional nutrients in cost-effective minimum processed formulation. In this review, we would like to address key factors determining accumulation levels of recombinant proteins in PBs. Understanding of bottle neck parts and improvement of specific deposition to PBs result in much higher levels of production of high quality recombinant proteins.

Analysis of Recombinant Proteins in Transgenic Rice Seeds: Identity, Localization, Tolerance to Digestion, and Plant Stress Response

Rice seeds are an ideal production platform for high-value recombinant proteins in terms of economy, scalability, safety, and stability. Strategies for the expression of large amounts of recombinant proteins in rice seeds have been established in the past decade and transgenic rice seeds that accumulate recombinant products such as bioactive peptides and proteins, which promote the health and quality of life of humans, have been generated in many laboratories worldwide. One of the most important advantages is the potential for direct oral delivery of transgenic rice seeds without the need for recombinant protein purification (downstream processing), which has been attributed to the high expression levels of recombinant products. Transgenic rice will be beneficial as a delivery system for pharmaceuticals and nutraceuticals in the future. This chapter introduces the strategy for producing recombinant protein in the edible part (endosperm) of the rice grain and describes methods for the analysis of transgenic rice seeds in detail.

Edible plants for oral delivery of biopharmaceuticals

Molecular farming is the use of plants for the production of high value recombinant proteins. Over the last 25 years, molecular farming has achieved the inexpensive, scalable and safe production of pharmaceutical proteins using a range of strategies. One of the most promising approaches is the use of edible plant organs expressing biopharmaceuticals for direct oral delivery. This approach has proven to be efficacious in several clinical vaccination and tolerance induction trials as well as multiple preclinical studies for disease prevention. The production of oral biopharmaceuticals in edible plant tissues could revolutionize the pharmaceutical industry by reducing the cost of production systems based on fermentation, and also eliminating expensive downstream purification, cold storage and transportation costs. This review considers the unique features that make plants ideal as platforms for the oral delivery of protein-based therapeutics and describes recent developments in the production of plant derived biopharmaceuticals for oral administration.

Rice seed for delivery of vaccines to gut mucosal immune tissues

Gut-associated lymphoid tissue (GALT) is the biggest lymphoid organ in the body. It plays a role in robust immune responses against invading pathogens while maintaining immune tolerance against nonpathogenic antigens such as foods. Oral vaccination can induce mucosal and systemic antigen-specific immune reactions and has several advantages including ease of administration, no requirement for purification and ease of scale-up of antigen. Thus far, taking advantage of these properties, various plant-based oral vaccines have been developed. Seeds provide a superior production platform over other plant tissues for oral vaccines; they offer a suitable delivery vehicle to GALT due to their high stability at room temperature, ample and stable deposition space, high expression level, and protection from digestive enzymes in gut. A rice seed production system for oral vaccines was established by combining stable deposition in protein bodies or protein storage vacuoles and enhanced endosperm-specific expression. Various types of rice-based oral vaccines for infectious and allergic diseases were generated. Efficacy of these rice-based vaccines was evaluated in animal models.