Safety and immunogenicity of bacterial and tobacco plant cell line derived recombinant native and mutant Escherichia coli heat-labile toxin in chickens

Dendritic Cell-Mediated Mechanisms Triggered by LT-IIa-B5, a Mucosal Adjuvant Derived from a Type II Heat-Labile Enterotoxin of Escherichia coli

Mucosal tissues are the initial site through which most pathogens invade. As such, vaccines and adjuvants that modulate mucosal immune functions have emerged as important agents for disease prevention. Herein, we investigated the immunomodulatory mechanisms of the B subunit of Escherichia coli heat-labile enterotoxin type IIa (LT-IIa-B₅), a potent non-toxic mucosal adjuvant. Alternations in gene expression in response to LT-IIa-B₅ were identified using a genome-wide transcriptional microarray that focused on dendritic cells (DC), a type of cell that broadly orchestrates adaptive and innate immune responses. We found that LT-IIa-B₅ enhanced the homing capacity of DC into the lymph nodes and selectively regulated transcription of pro-inflammatory cytokines, chemokines, and cytokine receptors. These data are consistent with a model in which directional activation and differentiation of immune cells by LT-IIa-B₅ serve as a critical mechanism whereby this potent adjuvant amplifies mucosal immunity to co-administered antigens.

LTB-Syn: a recombinant immunogen for the development of plant-made vaccines against synucleinopathies

A recombinant antigen targeting α-synuclein was produced in the plant cell rendering an immunogenic protein capable to induce humoral responses in mice upon oral administration. Synucleinopathies are neurodegenerative diseases characterized by the abnormal accumulation of α-synuclein (α-Syn, a 140 amino acid protein that normally plays various neurophysiologic roles) aggregates. Parkinson's disease (PD) is the synucleinopathy with the highest epidemiologic impact and although its etiology remains unknown, α-Syn aggregation during disease progression pointed out α-Syn as target in the development of immunotherapies. Herein a chimeric protein, comprising the B subunit of the enterotoxin from enterotoxigenic Escherichia coli and α-Syn epitopes, was expressed in the plant cell having the potential to induce humoral responses following oral immunization. This approach will serve as the basis for the development of oral plant-based vaccines against PD with several potential advantages such as low cost, easy scale-up during production, and easy administration.

Plant-Based Vaccines: Production and Challenges

Plant-based vaccine technologies involve the integration of the desired genes encoding the antigen protein for specific disease into the genome of plant tissues by various methods. Agrobacterium-mediated gene transfer and transformation via genetically modified plant virus are the common methods that have been used to produce effective vaccines. Nevertheless, with the advancement of science and technology, new approaches have been developed to increase the efficiency of former methods such as biolistic, electroporation, agroinfiltration, sonication, and polyethylene glycol treatment. Even though plant-based vaccines provide many benefits to the vaccine industry, there are still challenges that limit the rate of successful production of these third-generation vaccines. Even with all the limitations, continuous efforts are still ongoing in order to produce efficient vaccine for many human and animals related diseases owing to its great potentials. This paper reviews the existing conventional methods as well as the development efforts by researchers in order to improve the production of plant-based vaccines. Several challenges encountered during and after the production process were also discussed.

The case for plant-made veterinary immunotherapeutics

The excessive use of antibiotics in food animal production has contributed to resistance in pathogenic bacteria, thereby triggering regulations and consumer demands to limit their use. Alternatives for disease control are therefore required that are cost-effective and compatible with intensive production. While vaccines are widely used and effective, they are available against a minority of animal diseases, and development of novel vaccines and other immunotherapeutics is therefore needed. Production of such proteins recombinantly in plants can provide products that are effective and safe, can be orally administered with minimal processing, and are easily scalable with a relatively low capital investment. The present report thus advocates the use of plants for producing vaccines and antibodies to protect farm animals from diseases that have thus far been managed with antibiotics; and highlights recent advances in product efficacy, competitiveness, and regulatory approval.

Mucosal Vaccines from Plant Biotechnology

The use of plants for production of recombinant proteins has evolved over the past 25 years. The first plant-based vaccines were expressed in stably transgenic plants, with the idea to conveniently deliver “edible vaccines” by ingestion of the antigen-containing plant material. These systems provided a proof of concept that oral delivery of vaccines in crude plant material could stimulate antigen-specific serum and mucosal antibodies. Transgenic grains like rice in particular provide a stable and robust vehicle for antigen delivery. However, some issues exist with stably transgenic plants, including relatively low expression levels and regulatory issues. Thus, many recent studies use transient expression with plant viral vectors to achieve rapid high expression in Nicotiana benthamiana, followed by purification of antigen and intranasal delivery for effective stimulation of mucosal immune responses.