This work was supported by the Joint Project &#8220;The use of plants for the production of an autoimmune diabetes edible vaccine (eDIVA)&#8221; (Project ID: 891854) funded by the University of Verona in the framework of the call 2014.

1. Red beet and spinach cultivation
<ol>
	<li>Grow red beet (B. vulgaris cv Moulin Rouge) and spinach (S. oleracea cv Industria) plants in a growth chamber, using 150 &#181;E of light intensity, 65% relative humidity, 12 h light/dark cycle at 23/21 &#176;C, respectively.</li>
	<li>After seed germination, fertilize the plants twice a week with a 1 g/L solution of a commercially available fertilizer (Table of Materials). For agroinfiltration use five-week-old spinach and six-week-old re...

<ol>
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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Considerations+for+the+recovery+of+recombinant+proteins+from+plants.">Considerations for the recovery of recombinant proteins from plants.</a> Biotechnology Progress. 20 (4), 1001-1014 (2004).</li><li>Avesani, L., Bortesi, L., Santi, L., Falorni, A., Pezzotti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant-made+pharmaceuticals+for+the+prevention+and+treatment+of+autoimmune+diseases:+Where+are+we?.">Plant-made pharmaceuticals for the prevention and treatment of autoimmune diseases: Where are we?.</a> Expert Review of Vaccines. 9 (8), 957 (2010).</li><li>Marillonnet, S., Thoeringer, C., Kandzia, R., Klimyuk, V., Gleba, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systemic+Agrobacterium+tumefaciens-mediated+transfection+of+viral+replicons+for+efficient+transient+expression+in+plants.">Systemic Agrobacterium tumefaciens-mediated transfection of viral replicons for efficient transient expression in plants.</a> Nature Biotechnology. 23, (2005).</li><li>Ludvigsson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Update+on+treatment+of+type+1+diabetes+in+childhood.">Update on treatment of type 1 diabetes in childhood.</a> Current Pediatric Reviews. 1 (2), 118-127 (2013).</li><li>Merlin, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+GAD65+production+in+plants+using+the+MagnICON+transient+expression+system:+Optimization+of+upstream+production+and+downstream+processing.">Enhanced GAD65 production in plants using the MagnICON transient expression system: Optimization of upstream production and downstream processing.</a> Biotechnology Journal. 11 (4), 542-553 (2016).</li><li>Gecchele, E., Merlin, M., Brozzetti, A., Falorni, A., Pezzotti, M., Avesani, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Comparative+Analysis+of+Recombinant+Protein+Expression+in+Different+Biofactories:+Bacteria,+Insect+Cells+and+Plant+Systems.">A Comparative Analysis of Recombinant Protein Expression in Different Biofactories: Bacteria, Insect Cells and Plant Systems.</a> Journal of Visualized Experiments. 23 (97), (2015).</li><li>Dal Santo, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+terroir+concept+interpreted+through+grape+berry+metabolomics+and+transcriptomics.">The terroir concept interpreted through grape berry metabolomics and transcriptomics.</a> Journal of Visualized Experiments. 5 (116), (2016).</li><li>Chen, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agroinfiltration+as+an+effective+and+scalable+strategy+of+gene+delivery+for+production+of+pharmaceutical+proteins.">Agroinfiltration as an effective and scalable strategy of gene delivery for production of pharmaceutical proteins.</a> Advanced Techniques in Biology and Medicine. 1 (1), (2013).</li><li>Bertini, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+of+a+type-1+diabetes+vaccine+candidate+using+edible+plants+expressing+a+major+autoantigen.">Design of a type-1 diabetes vaccine candidate using edible plants expressing a major autoantigen.</a> Frontiers in Plant Science. 9, (2018).</li><li>Avesani, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+in+planta+expression+of+the+human+islet+autoantigen+glutamic+acid+decarboxylase+(GAD65).">Improved in planta expression of the human islet autoantigen glutamic acid decarboxylase (GAD65).</a> Transgenic Research. 12 (2), 203-212 (2003).</li><li>Sep&#250;lveda-Jim&#233;nez, G., Rueda-Ben&#237;tez, P., Porta, H., Rocha-Sosa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+red+beet+(Beta+vulgaris)+UDP-glucosyltransferase+gene+induced+by+wounding,+bacterial+infiltration+and+oxidative+stress.">A red beet (Beta vulgaris) UDP-glucosyltransferase gene induced by wounding, bacterial infiltration and oxidative stress.</a> Journal of Experimental Botany. 56, (2005).</li><li>Renukuntla, J., Vadlapudi, A. D., Patel, A., Boddu, S. H. S., Mitra, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approaches+for+enhancing+oral+bioavailability+of+peptides+and+proteins.">Approaches for enhancing oral bioavailability of peptides and proteins.</a> International Journal of Pharmaceutics. 447, 75-93 (2013).</li><li>. Encapsulation importance in pharmaceutical area, how it is done and issues about herbal extraction Available from: <a target="_blank" href="https://www.researchgate.net/publication/271702091_Encapsulation_importance_in_pharmaceutical_area_how_it_is_done_and_issues_about_herbal_extraction">https://www.researchgate.net/publication/271702091_Encapsulation_importance_in_pharmaceutical_area_how_it_is_done_and_issues_about_herbal_extraction</a> (2015)</li><li>Kamei, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complexation+hydrogels+for+intestinal+delivery+of+interferon+beta+and+calcitonin.">Complexation hydrogels for intestinal delivery of interferon beta and calcitonin.</a> Journal of Controlled Release. 134, 98-102 (2009).</li><li>Tuesca, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complexation+hydrogels+for+oral+insulin+delivery:+effects+of+polymer+dosing+on+in+vivo+efficacy.">Complexation hydrogels for oral insulin delivery: effects of polymer dosing on in vivo efficacy.</a> Journal of Pharmaceutical Sciences. 97, 2607-2618 (2008).</li><li>Twyman, R. M., Schillberg, S., Fischer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimizing+the+yield+of+recombinant+pharmaceutical+proteins+in+plants.">Optimizing the yield of recombinant pharmaceutical proteins in plants.</a> Current Pharmaceutical Design. 19, 5486-5494 (2013).</li><li>Dhama, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant-based+oral+vaccines+for+human+and+animal+pathogens+&#8211;+a+new+era+of+prophylaxis:+current+and+future+perspectives.">Plant-based oral vaccines for human and animal pathogens &#8211; a new era of prophylaxis: current and future perspectives.</a> Journal of Experimental Biology and Agricultural Sciences. 447, 75-93 (2013).</li><li>Hefferon, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconceptualizing+cancer+immunotherapy+based+on+plant+production+systems.">Reconceptualizing cancer immunotherapy based on plant production systems.</a> Future science. O3, (2017).</li></ol>

The authors have nothing to disclose.

In this study we showed preliminary analysis for the design of a candidate oral vaccine for autoimmune diabetes. The target protein for this experiment was a mutated form of the human 65 kDa Glutamate Decarboxylase, which production and functionality are easily detectable and measurable12. Its expression in different edible plant tissues was mediated by the vectors5, which mediate a high level of recombinant protein production in a very short time frame. The selection of th...

Since the plant molecular biology revolution in 1980s, plant-based systems for the production of biopharmaceuticals can be considered as an alternative to traditional systems based on microbial and mammalian cells1. Plants display several advantages over traditional platforms, with scalability, cost-effectiveness and safety being the most relevant2. The recombinant product can be purified from transformed plant tissue and then administered, either parenterally or orally and, moreover, transformed edible plant can be used directly for oral delivery. The oral route simultaneously promotes mucosal and systemic immunity, and it eliminates the need for needles and specialized medical personnel. Furthermore, oral delivery eliminates the complex downstream processing, which normally accounts for 80% of the total manufacturing cost of a recombinant protein3. All those advantages can be translated into savings in production, supplies and labor reducing the costs of each dose, making the drug affordable to most of the global population.
Several strategies, both for stable transformation and transient expression, were developed for the production of recombinant proteins in plants. Among them, a high-yield deconstructed plant virus-based expression system (e.g., magnICON) provides superior performance leading high yields of recombinant proteins over relatively short timescales4. Many examples of transient expression using the plant virus-based expression&#160;system in Nicotiana benthamiana plants are reported, being the gold standard production host. However, this model plant is not regarded as an edible species due to the alkaloids and other toxic metabolites that are accumulated in its leaves.
In this work, we describe the comparison between two edible plant systems, red beet (Beta vulgaris cv Moulin Rouge) and spinach (Spinacea oleracea cv Industria), for the expression of two candidate forms of the 65 kDa isoform of glutamic acid decarboxylase (GAD65), carried out by the plant virus-based vectors5. GAD65 is a major autoantigen associated to Type 1 Diabetes (T1D) and it is currently under investigation in human clinical trials to prevent or delay T1D by inducing tolerance6. The production of GAD65 in plants has been extensively studied in model plant species as Nicotiana tabacum and N. benthamiana4,5,6,7. Here, we describe the use of edible plant species for the production of the molecule in tissues that can be meant for a direct oral delivery. From a technical point of view, we studied and selected the system for plant agroinfiltration and the edible plant platform for GAD65 production by evaluating different parameters: the recombinant protein expression levels, the residual microbial charge in plant tissue meant for oral delivery, the resistance of GAD65 to the gastric digestion, and the bioequivalence of the transformed plants with the wild type.

<table>
	<tbody>
		<tr>
			<td>0.2-&#956;m Minisart RC4 membrane filters</td>
			<td>Sartorius-Stedim</td>
			<td>17764</td>
			<td></td>
		</tr>
		<tr>
			<td>2&#8211;mercaptoethanol</td>
			<td>Sigma</td>
			<td>M3148</td>
			<td>Toxic; 4 % to make loading buffer with glycerol, SDS and Tris-HCl</td>
		</tr>
		<tr>
			<td>4-Morpholineethanesulfonic acid (MES)</td>
			<td>Sigma</td>
			<td>M8250</td>
			<td>pH 5.5</td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>Sarstedt</td>
			<td>833924</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma</td>
			<td>27221</td>
			<td>Corrosive</td>
		</tr>
		<tr>
			<td>Acetonitrile LC-MS grade</td>
			<td>Sigma</td>
			<td>34967</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetosyringone</td>
			<td>Sigma</td>
			<td>D134406</td>
			<td>Toxic &#8211; 0.1 M stock in DMSO</td>
		</tr>
		<tr>
			<td>Agar Bacteriological Grade</td>
			<td>Applichem</td>
			<td>A0949</td>
			<td>15 g/L to make LB medium (pH 7.5 with NaOH) with Yeast extract, NaCl and Tryptone</td>
		</tr>
		<tr>
			<td>Ammonium formate</td>
			<td>Sigma</td>
			<td>70221</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-eGFP antibody</td>
			<td>ABCam</td>
			<td>ab290</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-GAD 65/67 antibody</td>
			<td>Sigma</td>
			<td>G5163</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-LHCB2 antibody</td>
			<td>Agrisera</td>
			<td>AS01 003</td>
			<td></td>
		</tr>
		<tr>
			<td>Brilliant Blue R-250</td>
			<td>Sigma</td>
			<td>B7920</td>
			<td></td>
		</tr>
		<tr>
			<td>C18 Column</td>
			<td>Grace</td>
			<td>&#160;&#160; -</td>
			<td>Alltima HP C18 (150 mm x 2.1 mm; 3 &#956;m) Column</td>
		</tr>
		<tr>
			<td>C18 Guard Column</td>
			<td>Grace</td>
			<td>&#160;&#160; -</td>
			<td>Alltima HP C18 (7.5 mm x 2.1 mm; 5 &#956;m) Guard&#160; Column</td>
		</tr>
		<tr>
			<td>CalMag Grower</td>
			<td>Peter Excel</td>
			<td>15-5-15</td>
			<td>Fertilizer</td>
		</tr>
		<tr>
			<td>Carbenicillin disodium</td>
			<td>Duchefa Biochemie</td>
			<td>C0109</td>
			<td>Toxic</td>
		</tr>
		<tr>
			<td>Chemiluminescence imaging system</td>
			<td>BioRad</td>
			<td>1708370</td>
			<td>ChemiDoc Touch Imaging System</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Sigma</td>
			<td>C2432</td>
			<td></td>
		</tr>
		<tr>
			<td>Detergent</td>
			<td>Sigma</td>
			<td>P5927</td>
			<td>Polysorbate 20</td>
		</tr>
		<tr>
			<td>Fluorescence reader</td>
			<td>Perkin-Elmer</td>
			<td>&#160;1420-011</td>
			<td>VICTOR Multilabel Counter</td>
		</tr>
		<tr>
			<td>Formic acid LC-MS grade</td>
			<td>Sigma</td>
			<td>94318</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td>15 % to make loading buffer with Tris-HCl, SDS and 2&#8211;mercaptoethanol</td>
		</tr>
		<tr>
			<td>GoTaq G2 polymerase</td>
			<td>Promega</td>
			<td>M7841</td>
			<td></td>
		</tr>
		<tr>
			<td>HCl</td>
			<td>Sigma</td>
			<td>H1758</td>
			<td>Corrosive</td>
		</tr>
		<tr>
			<td>HILIC Column</td>
			<td>Grace</td>
			<td>&#160;&#160; -</td>
			<td>Ascentis Express HILIC (150 mm x 2.1 mm; particles size 2.7 &#956;m) Column</td>
		</tr>
		<tr>
			<td>HILIC Guard Column</td>
			<td>Grace</td>
			<td>&#160;&#160; -</td>
			<td>Vision HT HILIC (7.5 mm x 2.1 mm; 3 &#956;m) Guard&#160; Column</td>
		</tr>
		<tr>
			<td>Horseradish peroxidase (HRP)-conjugate anti-rabbit antibody</td>
			<td>Sigma</td>
			<td>A6154</td>
			<td>Do not freeze/thaw too many times</td>
		</tr>
		<tr>
			<td>HPLC Autosampler</td>
			<td>Beckman Coulter</td>
			<td>&#160;&#160; -</td>
			<td>System Gold 508 Autosampler</td>
		</tr>
		<tr>
			<td>HPLC System</td>
			<td>Beckman Coulter</td>
			<td>&#160;&#160; -</td>
			<td>System Gold 128 Solvent Module HPLC</td>
		</tr>
		<tr>
			<td>Isopropanol</td>
			<td>Sigma</td>
			<td>24137</td>
			<td>Flamable</td>
		</tr>
		<tr>
			<td>Kanamycin sulfate</td>
			<td>Sigma</td>
			<td>K4000</td>
			<td>Toxic</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P9541</td>
			<td>2 g/L with NaCl , Na2HPO4 and KH2PO4 to make PBS</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma</td>
			<td>P9791</td>
			<td>2.4 g/L with NaCl , Na2HPO4 and KCl to make PBS</td>
		</tr>
		<tr>
			<td>Loading Buffer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Luminol solution</td>
			<td>Ge Healthcare</td>
			<td>RPN2232</td>
			<td>Prepare the solution using the ECL Prime Western Blotting System commercial kit</td>
		</tr>
		<tr>
			<td>Lyophilizator</td>
			<td>5Pascal</td>
			<td>LIO5P0000DGT</td>
			<td></td>
		</tr>
		<tr>
			<td>Mass Spectometer</td>
			<td>Bruker Daltonics</td>
			<td>&#160; -</td>
			<td>Bruker Esquire 6000; the mass spectrometer was equipped with an ESI source and the analyzer was an ion trap</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma</td>
			<td>32213</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma</td>
			<td>M7506</td>
			<td></td>
		</tr>
		<tr>
			<td>Milk-blocking solution</td>
			<td>Ristora</td>
			<td>&#160;&#160; -</td>
			<td>3 % in PBS</td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td>Sigma</td>
			<td>S7907</td>
			<td>Use with NaH2PO4 to make Sodium Phospate buffer</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S3014</td>
			<td>80 g/L with KCl, Na2HPO4 and KH2PO4 to make PBS; 10 g/L to make LB medium (pH 7.5 with NaOH) with Yeast extract, Tryptone and Agar Bacteriological Grade</td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma</td>
			<td>S8282</td>
			<td>&#160;Use with Na2HPO4 to make Sodium Phospate buffer; 14.4 g/L to make PBS</td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Sigma</td>
			<td>S8045</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrocellulase membrane</td>
			<td>Ge Healthcare</td>
			<td>10600002</td>
			<td></td>
		</tr>
		<tr>
			<td>Pepsin from porcine gastric mucosa</td>
			<td>Sigma</td>
			<td>P7000</td>
			<td></td>
		</tr>
		<tr>
			<td>Peroxidase substrate ECL</td>
			<td>GE Healthcare</td>
			<td>RPN2235</td>
			<td>Light sensitive material</td>
		</tr>
		<tr>
			<td>Pump Vacuum Press</td>
			<td>VWR</td>
			<td>111400000098</td>
			<td></td>
		</tr>
		<tr>
			<td>Reagent A</td>
			<td>Sigma</td>
			<td>B9643</td>
			<td>Use 50 parts of this reagent with 1 part of reagent B to prepare BCA working solution</td>
		</tr>
		<tr>
			<td>Reagent B</td>
			<td>Sigma</td>
			<td>B9643</td>
			<td>Use 1 part of this reagent with 50 parts of reagent A to prepare BCA working solution</td>
		</tr>
		<tr>
			<td>Rifampicin</td>
			<td>Duchefa Biochemie</td>
			<td>R0146</td>
			<td>Toxic &#8211; 25 mg/mL stock in DMSO</td>
		</tr>
		<tr>
			<td>SDS (Sodium dodecyl sulphate)</td>
			<td>Sigma</td>
			<td>L3771</td>
			<td>Flamable, toxic, corrosive-10 % stock; 3 % to make loading buffer with Tris-HCl, Glycerol and 2&#8211;mercaptoethanol</td>
		</tr>
		<tr>
			<td>Sodium metabisulphite</td>
			<td>Sigma</td>
			<td>7681-57-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator system</td>
			<td>Soltec</td>
			<td>090.003.0003</td>
			<td>Sonica&#174; 2200 MH; frequency 40 khz</td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>Terumo</td>
			<td>&#160;&#160; -</td>
			<td></td>
		</tr>
		<tr>
			<td>Transparent fixed 300-&#181;L insert glass tubes</td>
			<td>Thermo Scientific</td>
			<td>11573680</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma Base</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td>Adjust pH with 1N HCl to make Tris-HCl buffer, use 1,5M Tris-HCl (pH 6.8) to make loading buffer with SDS, Glycerol and 2&#8211;mercaptoethanol</td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Formedium</td>
			<td>TRP03</td>
			<td>10 g/L to make LB medium (pH 7.5 with NaOH) with Yeast extract, NaCl and Agar Bacteriological Grade</td>
		</tr>
		<tr>
			<td>Vacuum concentrator</td>
			<td>Heto</td>
			<td>3878 F1-3</td>
			<td>Speed-vac System</td>
		</tr>
		<tr>
			<td>Water LC-MS grade</td>
			<td>Sigma</td>
			<td>39253</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract</td>
			<td>Sigma</td>
			<td>Y1333</td>
			<td>5 g/L to make LB medium (pH 7.5 with NaOH) with Tryptone, NaCl and Agar Bacteriological Grade</td>
		</tr>
	</tbody>
</table>

transient expression in red beet of a biopharmaceutical candidate vaccine for type-1 diabetes

Plant molecular farming is the use of plants to produce molecules of interest. In this perspective, plants may be used both as bioreactors for the production and subsequent purification of the final product and for the direct oral delivery of heterologous proteins when using edible plant species. In this work, we present the development of a candidate oral vaccine against Type 1 Diabetes (T1D) in edible plant systems using deconstructed plant virus-based recombinant DNA technology, delivered with vacuum infiltration. Our results show that a red beet is a suitable host for the transient expression of a human derived autoantigen associated to T1D, considered to be a promising candidate as a T1D vaccine. Leaves producing the autoantigen were thoroughly characterized for their resistance to gastric digestion, for the presence of residual bacterial charge and for their secondary metabolic profile, giving an overview of the process production for the potential use of plants for direct oral delivery of a heterologous protein. Our analysis showed almost complete degradation of the freeze-dried candidate oral vaccine following a simulated gastric digestion, suggesting that an encapsulation strategy in the manufacture of the plant-derived GAD vaccine is required.

In this work, the workflow for the development of an oral vaccine in edible plant tissues is presented. The focus of this work is the expression of a target protein in an edible host plant species and the characterization of the potential oral vaccine.
The first step involved the evaluation of the suitability of the plant virus-based expression technology to produce recombinant proteins in edible plant systems. For this aim, we ...

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Transient Expression in Red Beet of a Biopharmaceutical Candidate Vaccine for Type-1 Diabetes

Here, we present a protocol to produce an oral vaccine candidate against Type 1 diabetes in an edible plant.

Plant molecular farming is the use of plants to produce molecules of interest. In this perspective, plants may be used both as bioreactors for the ...

Among the different strategies for production of recombinant protein in plants, the deconstructed plant-based VERS expression provides superior performance, leading to high yields over a relative short time frame. Replication of this technology for the production of an oral vaccine holds a great potential to become an alternative to conventional vaccines in the near future. Lyophilized red beet leaves transiently transformed accumulates an amount of photo antigens suitable for oral tolerance induction in type one diabetes prevention.This experimental protocol could be extended to many different edible species after a case-by-case evaluation of recombinant protein accumulation. Demonstrating the procedure will be Edoardo Bertini, Mattia Santoni, Anna Cuccurullo, and Roberta Zampieri. To begin this procedure, grow red beet and spinach plants in a growth chamber as outlined in the text protocol.After seed germination, fertilize the plants twice a week with a solution of commercially available fertilizer at a concentration of one gram per liter. For agroinfiltration, use five week old spinach and six week old red beet plants. After constructing the plant expression vectors, inoculate the three A.tumefaciens transformants in 50 milliliters of LB medium containing rifampicin at a concentration of 50 micrograms per milliliter and vector-specific antibiotics as outlined in the text protocol.Grow by shaking overnight at 28 degrees Celsius. The next day, pellet the bacterial cultures by centrifuging at 4500 times G for 20 minutes. Resuspend the pellet in 100 milliliters of infiltration buffer containing 10 millimolar MES and 10 millimolar magnesium sulfate.Incubate the suspensions at room temperature for three hours. Mix an equal volume of a bacterial suspension containing one of the modules shown here, with the five prime module and the integrase module. Using a syringe without a needle, take out five milliliters of the suspension mix.Press the tip of the syringe against the underside of the plant leaf while applying gently counter pressure to the other side of the leaf. Infiltrate the first three completely expanded leaves, starting from the apex, for each plant. Label the agroinfiltrated leaves with the paper tag on the leaf stem.Then return the plants to the growth chamber under standard conditions. On days four to 14 post-infection, collect the agroinfiltrated leaves and freeze them in liquid nitrogen. Store this plant tissue at minus 80 degrees Celsius.First, separately grow the three A.tumefaciens transformants in 50 milliliters of LB medium containing rifampicin at a concentration of 50 microliters per milliliter, and appropriate vector-specific antibiotics by shaking overnight at 28 degrees Celsius. The next day, pellet the bacterial cultures by centrifuging at 4500 times G for 20 minutes. Resuspend the pellet in 1 liter of infiltration buffer to an OD600 of 0.35, and incubate the suspensions at room temperature for three hours.Then add 0.01%of the detergent to each suspension. Mix an equal volume of a bacterial suspension containing one of the modules shown here with the five prime module and the integrase module. Insert one six week old red beet plant into the holder.Invert the holder and place it on top of a beaker containing two liters of an infiltration bath to submerge the leaves in the infiltration suspension. After this, transfer the infiltration bath with the submerged plant to the infiltration chamber and close it. Turn on the vacuum pump and open the vacuum intake valve on the infiltration chamber.Once the pressure in the chamber has fallen to 90 millibar, maintain the vacuum for three minutes. Then release the vacuum for 45 seconds. When the chamber has returned to atmospheric pressure, open the chamber and remove the infiltrated plant from the bacterial bath.Return the plant to the growth chamber. On the day of maximum expression, harvest the infiltrated leaves and freeze them in liquid nitrogen as previously described. First, harvest the vacuum agroinfiltrated delta 87 GAD65mut expressing red beet leaves at the expression peak, and freeze them in liquid nitrogen.Lyophilize the frozen leaves at minus 50 degrees Celsius and at 0.04 millibar for 72 hours. Then store them at minus 80 degrees Celsius. When ready to proceed, grind the leaves to a fine powder and store at room temperature in a sealed container with silica gel to exclude the moisture.For the gastric digestion simulation, weigh 100 milligrams of the finely ground freeze dried red beet leaves, and resuspend it in six milliliters of PBS. Use six molar hydrochloric acid to adjust the sample pH to two. Add four milligrams per milliliters pepsin from porcine gastric mucosa, and 10 millimolar hydrochloric acid, to obtain a final pepsin concentration of one milligram per milliliter.Shake the sample at 37 degrees Celsius for 120 minutes. Next, use sodium hydroxide to adjust the sample pH to eight and inactivate the pepsin. Transfer 750 microliter aliquots of each sample to microcentrifuge tubes, and centrifuge the aliquots at 20, 000 times G and at four degrees Celsius for 20 minutes.Collect each supernatant separately, and resuspend each pellet in one supernatant volume of loading buffer. Then analyze both the supernatant and the resuspended pellet by Western blot analysis. For the cell integrity analysis, prepare two samples of 100 milligrams of the finely ground freeze-dried red beet leaves, and resuspend both in six milliliters of PBS.Use six molar hydrochloric acid to adjust the pH of one sample to two. Shake both samples at 37 degrees Celsius for 120 minutes. Then aliquot 750 microliters of each sample to microcentrifuge tubes.Centrifuge at 20, 000 times G and at 4 degrees Celsius for 20 minutes. Collect each supernatant separately, and resuspend each pellet in one supernatant volume of loading buffer. Then analyze both the supernatant and the resuspended pellet by Western blot analysis.First, weigh 100 milligrams of the finely ground freeze-dried red beet leaves, and resuspend it in eight milliliters of sterile PBS. Vortex for one minute. Plate one milliliter of each freeze-dried leaf homogenate in one of the five prepared selective LB media.Incubate the plates at 28 degrees Celsius for three days. After this, count the agrobacterium colonies grown on each plate, and calculate the residual bacterial charge as the number of colony forming units per milliliter of the freeze-dried leaf homogenate. In this work, an oral vaccine is developed in edible plant tissue.Red beet and spinach plants are manually agroinfiltrated with suspensions of A.tumefaciens carrying EGFP recombinant expression vectors, and the fluorescent protein expression is visualized by Western blot analysis and quantified under UV light. The red beet system is characterized by a higher EGFP expression, reaching approximately 544 micrograms per gram of fresh leaf weight at nine days post-infection, while the spinach only reached a maximum level of approximately 113.4 micrograms per gram of fresh leaf weight on 11 days post-infection. Because of this, the red beet is selected as the expression host for all subsequent experiments.Plants are then vacuum infiltrated with an A.tumefaciens suspension. After the TSP extraction from agroinfiltration leaves, the samples are analyzed by Western blot, and the recombinant protein is relatively quantified by a densitometry analysis. Finally, the parameters for the development of a potential oral vaccine are evaluated.As seen here, the target protein is seen to be stable after the lyophilization process. Gastric digestion is simulated by adding the porcine gastric enzyme pepsin to freeze-dried material, either to a final concentration of one milligram per milliliter, or a ratio of one to 20, to TSP. Both digestive treatment conditions result in degradation of the recombinant protein.The absence of a specific signal in the pellet samples after pepsin digestion suggest that after freeze-drying, the plant cells lost their integrity, and this led to the target protein degradation. The procedure should be carefully adapted to the plant species in respect to vacuum infiltration and to the target recombinant protein in respect to time course analysis. The demonstrating procedure might also be used for the production of biopharmaceutical intended for oral delivery, like vaccine and antibodies.

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Research

JoVE Journal

Bioengineering

7.8K vues.  University of Verona. Parmi les différentes stratégies de production de protéines recombinantes dans les plantes, l’expression vers déconstruite à base de plantes offre des performances supérieures, conduisant à des rendements élevés sur une période relativement courte. La réplication de cette technologie pour la production d’un vaccin oral présente un grand potentiel pour devenir une alternative aux vaccins conventionnels dans un proche avenir. Les feuilles de betterave rouge lyophilisées transfo...