Potential of plant biologics to tackle the epidemic like situations - case studies involving viral and bacterial candidates

Background: The art of recombinant protein production in E.coli and mammalian system needs an extensive infrastructure to adopt GMP practice for large-scale production and this makes the final product very expensive and such therapeutics may not be affordable where it is needed the most. The potential of plant biologics over the conventional systems is, it has glycosylation pattern or with a choice of non-glycosylation containment i.e. in chloroplast, established genetic and glycoengineering methods, adaptability, scalability and affordability. Plant molecular farming in simple words ‘the use of plants for the production of protein therapeutics’ became popular due to the Magnifection technology, degenerative vectors and glycoengineered plants. Our studies involved the usage of current technology for expression and purification of Chikungunya vaccine candidates and mAb's in plant system and also manifests the compatibility of plant host system for the expression of S.aureus superantigenic proteins with the proven immunogenic functions. Methods & Materials: The CHIKV vaccine candidates E1 and E2, bacterial superantigenic peptides TSST-1 and fusion gene rTE and anti-CHIKV mAb's (8B10 and 5F10 were retrieved from European patent application EP2374 816 A1) were cloned into the current generation high expression plant constructs like pEAQ-HT-DEST and pTRAK through gateway cloning technology and conventional cloning. Constructs were mobilized into Agrobacterium and vacuum infiltrated in N.benthamiana plants following standard procedures. Following 5th day of post infiltration leaves were harvested and recombinant protein was purified by his-tag and proteinA/G affinity based purification techniques respectively. Results: We have successfully produced CHIKV vaccine candidates E1 and E2 (8-13 mg/kg of fresh leaf weight), antibodies (20-30 mg/kg) and the bacterial recombinant superantigen TSST-1 and hypothetical vaccine candidate rTE fusion proteins (5.4 and 6.7 mg/kg). The in vivo and in vitro immunogenicity and neutralization studies revealed that the plant produced antigens and antibodies elicit good immune responses. Conclusion: The level of expression, glycosylation and immunizing potential are the evidence strongly suggesting the plants are the potential alternate system. So, we propose plant biologics as a promising system during an epidemic like situation as scale-up of this system is infinity at an affordable cost, which will help the people, where it is needed the most.