Page 251 - PC2019 Program & Proceedings

PLANT CANADA 2019

P75. Plant-made virus-like particles for protection of piglets against porcine epidemic diarrhea
virus
1
2
Zhu, H. ; Z. Khamis ; R. Menassa
3
1 Agriculture and Agri-Food Canada
2 University of Western Ontario
3 Government of Canada
Porcine epidemic diarrhea virus (PEDv) is a coronavirus that causes disease and mortality to piglets
particularly new-born piglets worldwide. Most vaccines used to combat the disease have been ineffective
live attenuated virus vaccines. The goal of this project is to produce a plant-made virus-like particle
(VLP) displaying antigenic epitopes of the PEDv membrane protein, and to administer it orally to
pregnant sows for inducing protective lactogenic immunity. To obtain sufficient protein and subsequent
VLP assembly, we used an elastin-like polypeptide fusion with the membrane protein, and transient
expression in Nicotiana benthamiana. M-ELP accumulated up to 0.8 mg/g of fresh leaf weight . Virus-
like particles were both observed when the membrane protein was overexpressed, and when the
membrane protein was co-expressed with the envelope protein. In the latter case, the VLPs were slightly
larger in size. This represents the first time coronavirus-like particles have been made in plants. We scaled
up production of the VLPs by vacuum infiltration of 15 kg of leaf tissue, and developed a simplified
extraction, concentration and encapsulation process for the VLPs.

Hong Zhu (hong.zhu@canada.ca)

P76. A rationally designed plant-produced IgA has improved yield and exhibits cross serotype
protection against enterohemorrhagic Escherichia coli
*1
Chin-Fatt, A. ; R. Menassa
2
1 Western University
2 Government of Canada

The seven most prevalent strains of Enterohemorrhagic Escherichia coli (EHEC) collectively comprise
more than 95% of the disease burden globally, affecting an estimated 2.8 million people annually.
Although a plant production system is well established as a useful platform for enabling the post-
translational modifications necessary for IgA folding, yield continues to be the most significant hurdle
preventing transitioning of these therapeutics to market. We identified a series of single domain
antibodies that can enable cross-serotype protection against EHEC. Considering the modular nature of the
IgA, we rationalized that we could engineer the Fc component for improved yield of Fc fusions with these
single domain antibodies without impacting the folding of these binders. We have successfully engineered
a more stable Fc, by supercharging and introducing de novo disulfide bonds, that shows higher yield in
planta by three to four fold. Using immunofluorescent labelling, we also have demonstrated that the VHH
is still able to exhibit cross-serotype binding and neutralization across four of the seven strains. Co-
immunoprecipitation experiments indicate that the rationally designed mutations have also not impacted
the Fc’s ability to structurally assemble with other subunits into its secretory form. Overall, this study
provides a proof of concept that stability engineering of plant-produced IgA biologics is a viable strategy
for overcoming the yield hurdle of plant-produced antibodies and related therapeutics.

Adam Chin-Fatt (achinfat@uwo.ca)

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