This work was supported by the Key Program of Chongqing Natural Science Foundation (No. cstc2020jcyj-zdxmX0027) and the Chinese National Natural Science Foundation Project (No. 31670936, 82041045).

1. Plasmid construction
<ol>
	<li>Insert DNA encoding SpyCatcher sequence (Supplementary File 1) into an ampicillin-resistant pThioHisA-ClyA plasmid (see Table of Materials) between the BamH I and Sal I sites to construct the plasmid pThioHisA ClyA-SC following a previously published report20.</li>
	<li>Ligate the synthesized SpyTag-RBD-Histag fusion gene (Supplementary File 1) into a pcDNA3.1 plasmid (see Table...

<ol>
	<li>Li, 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=Bacterial+outer+membrane+vesicles+as+a+platform+for+biomedical+applications:+An+update.">Bacterial outer membrane vesicles as a platform for biomedical applications: An update.</a> Journal of Controlled Release. 323, 253-268 (2020).</li><li>Micoli, F., MacLennan, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outer+membrane+vesicle+vaccines.">Outer membrane vesicle vaccines.</a> Seminars in Immunology. 50, 101433 (2020).</li><li>Toyofuku, M., Nomura, N., Eberl, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Types+and+origins+of+bacterial+membrane+vesicles.">Types and origins of bacterial membrane vesicles.</a> Nature Reviews Microbiology. 17 (1), 13-24 (2019).</li><li>Sartorio, M. G., Pardue, E. J., Feldman, M. F., Haurat, M. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploitation+of+Neisseria+meningitidis+group+B+OMV+vaccines+against+N-gonorrhoeae+to+inform+the+development+and+deployment+of+effective+gonorrhea+vaccines.">Exploitation of Neisseria meningitidis group B OMV vaccines against N-gonorrhoeae to inform the development and deployment of effective gonorrhea vaccines.</a> Frontiers in Immunology. 10, 683 (2019).</li><li>Gnopo, Y. M. D., Watkins, H. C., Stevenson, T. C., DeLisa, M. 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T., Liu, Q. <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+outer+membrane+vesicles+as+cancer+vaccines:+A+new+toolkit+for+cancer+therapy.">Design of outer membrane vesicles as cancer vaccines: A new toolkit for cancer therapy.</a> Cancers. 11 (9), 1314 (2019).</li><li>Berleman, J., Auer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+bacterial+outer+membrane+vesicles+for+intra-+and+interspecies+delivery.">The role of bacterial outer membrane vesicles for intra- and interspecies delivery.</a> Environmental Microbiology. 15 (2), 347-354 (2013).</li><li>Huang, W. L., Meng, L. X., Chen, Y., Dong, Z. Q., Peng, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+outer+membrane+vesicles+as+potential+biological+nanomaterials+for+antibacterial+therapy.">Bacterial outer membrane vesicles as potential biological nanomaterials for antibacterial therapy.</a> Acta Biomaterialia. 140, 102-115 (2022).</li><li>Hoffmann, 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=SARS-CoV-2+cell+entry+depends+on+ACE2+and+TMPRSS2+and+is+blocked+by+a+clinically+proven+protease+inhibitor.">SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor.</a> Cell. 181 (2), 271-280 (2020).</li><li>Robbiani, D. F., 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=Convergent+antibody+responses+to+SARS-CoV-2+in+convalescent+individuals.">Convergent antibody responses to SARS-CoV-2 in convalescent individuals.</a> Nature. 584 (7821), 437-442 (2020).</li><li>Wang, M. Y., 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=SARS-CoV-2:+Structure,+Biology,+and+Structure-Based+Therapeutics+Development.">SARS-CoV-2: Structure, Biology, and Structure-Based Therapeutics Development.</a> Frontiers in Cellular and Infection Microbiology. 10, 587269 (2020).</li><li>Yang, 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=Safety+and+immunogenicity+of+a+recombinant+tandem-repeat+dimeric+RBD-based+protein+subunit+vaccine+(ZF2001)+against+COVID-19+in+adults:+Two+randomised,+double-blind,+placebo-controlled,+phase+1+and+2+trials.">Safety and immunogenicity of a recombinant tandem-repeat dimeric RBD-based protein subunit vaccine (ZF2001) against COVID-19 in adults: Two randomised, double-blind, placebo-controlled, phase 1 and 2 trials.</a> The Lancet Infectious Disease. 21 (8), 1107-1119 (2021).</li><li>Wang, Z., 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=mRNA+vaccine-elicited+antibodies+to+SARS-CoV-2+and+circulating+variants.">mRNA vaccine-elicited antibodies to SARS-CoV-2 and circulating variants.</a> Nature. 592 (7855), 616-622 (2021).</li><li>Amanat, F., 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=SARS-CoV-2+mRNA+vaccination+induces+functionally+diverse+antibodies+to+NTD,+RBD,+and+S2.">SARS-CoV-2 mRNA vaccination induces functionally diverse antibodies to NTD, RBD, and S2.</a> Cell. 184 (15), 3936-3948 (2021).</li><li>Tan, H. X., 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=Immunogenicity+of+prime-boost+protein+subunit+vaccine+strategies+against+SARS-CoV-2+in+mice+and+macaques.">Immunogenicity of prime-boost protein subunit vaccine strategies against SARS-CoV-2 in mice and macaques.</a> Nature Communication. 12 (1), 1403 (2021).</li><li>Thapa, H. B., Mueller, A. M., Camilli, A., Schild, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+intranasal+vaccine+based+on+outer+membrane+vesicles+against+SARS-CoV-2.">An intranasal vaccine based on outer membrane vesicles against SARS-CoV-2.</a> Frontiers in Microbiology. 12, 752739 (2021).</li><li>Ma, X., 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=Nanoparticle+vaccines+based+on+the+receptor+binding+domain+(RBD)+and+heptad+repeat+(HR)+of+SARS-CoV-2+elicit+robust+protective+immune+responses.">Nanoparticle vaccines based on the receptor binding domain (RBD) and heptad repeat (HR) of SARS-CoV-2 elicit robust protective immune responses.</a> Immunity. 53 (6), 1315-1330 (2020).</li><li>Yang, Z., 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=RBD-modified+bacterial+vesicles+elicited+potential+protective+immunity+against+SARS-CoV-2.">RBD-modified bacterial vesicles elicited potential protective immunity against SARS-CoV-2.</a> Nano Letters. 21 (14), 5920-5930 (2021).</li><li>Rhinesmith, T., Killinger, B. A., Sharma, A., Moszczynska, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multimer-PAGE:+A+method+for+capturing+and+resolving+protein+complexes+in+biological+samples.">Multimer-PAGE: A method for capturing and resolving protein complexes in biological samples.</a> Journal of Visualized Experiments. (123), e55341 (2017).</li><li>Arslan, 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=Determining+total+protein+and+bioactive+protein+concentrations+in+bovine+colostrum.">Determining total protein and bioactive protein concentrations in bovine colostrum.</a> Journal of Visualized Experiments. (178), e63001 (2021).</li><li>Alves, N. J., Turner, K. B., Walper, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+protein+packaging+within+outer+membrane+vesicles+from+Escherichia+coli:+Design,+production+and+purification.">Directed protein packaging within outer membrane vesicles from Escherichia coli: Design, production and purification.</a> Journal of Visualized Experiments. (117), e54458 (2016).</li><li>Kim, 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=Genomic+and+transcriptomic+landscape+of+Escherichia+coli+BL21(DE3).">Genomic and transcriptomic landscape of Escherichia coli BL21(DE3).</a> Nucleic Acids Research. 45 (9), 5285-5293 (2017).</li><li>Daleke-Schermerhorn, M. H., 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=Decoration+of+outer+membrane+vesicles+with+multiple+antigens+by+using+an+autotransporter+approach.">Decoration of outer membrane vesicles with multiple antigens by using an autotransporter approach.</a> Applied and Environmental Microbiology. 80 (18), 5854-5865 (2014).</li><li>Kuipers, 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=Salmonella+outer+membrane+vesicles+displaying+high+densities+of+pneumococcal+antigen+at+the+surface+offer+protection+against+colonization.">Salmonella outer membrane vesicles displaying high densities of pneumococcal antigen at the surface offer protection against colonization.</a> Vaccine. 33 (17), 2022-2029 (2015).</li><li>Veggiani, G., 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=Programmable+polyproteams+built+using+twin+peptide+superglues.">Programmable polyproteams built using twin peptide superglues.</a> Proceedings of the National Academy of Sciences of the United States of America. 113 (5), 1202-1207 (2016).</li><li>Saunders, K. O., 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=Neutralizing+antibody+vaccine+for+pandemic+and+pre-emergent+coronaviruses.">Neutralizing antibody vaccine for pandemic and pre-emergent coronaviruses.</a> Nature. 594, 553-559 (2021).</li><li>van Saparoea, H. B. V., Houben, D., Kuijl, C., Luirink, J., Jong, W. S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combining+protein+ligation+systems+to+expand+the+functionality+of+semi-synthetic+outer+membrane+vesicle+nanoparticles.">Combining protein ligation systems to expand the functionality of semi-synthetic outer membrane vesicle nanoparticles.</a> Frontiers in Microbiology. 11, 890 (2020).</li><li>Needham, B. D., 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=Modulating+the+innate+immune+response+by+combinatorial+engineering+of+endotoxin.">Modulating the innate immune response by combinatorial engineering of endotoxin.</a> Proceedings of the National Academy of Sciences of the United States of America. 110 (4), 1464-1469 (2013).</li><li>Zanella, I., 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=Proteome-minimized+outer+membrane+vesicles+from+Escherichia+coli+as+a+generalized+vaccine+platform.">Proteome-minimized outer membrane vesicles from Escherichia coli as a generalized vaccine platform.</a> Journal of Extracellular Vesicles. 10 (4), 12066 (2021).</li><li>Wang, J. 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=Truncating+the+structure+of+lipopolysaccharide+in+Escherichia+coli+can+effectively+improve+poly-3-hydroxybutyrate+production.">Truncating the structure of lipopolysaccharide in Escherichia coli can effectively improve poly-3-hydroxybutyrate production.</a> ACS Synthetic Biology. 9 (5), 1201-1215 (2020).</li><li>Liu, 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=Outer+membrane+vesicles+from+flagellin-deficient+Salmonella+enterica+serovar+Typhimurium+induce+cross-reactive+immunity+and+provide+cross-protection+against+heterologous+Salmonella+challenge.">Outer membrane vesicles from flagellin-deficient Salmonella enterica serovar Typhimurium induce cross-reactive immunity and provide cross-protection against heterologous Salmonella challenge.</a> Scientific Reports. 6, 34776 (2016).</li><li>Balhuizen, M. D., Veldhuizen, E. J. A., Haagsman, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outer+membrane+vesicle+induction+and+isolation+for+vaccine+development.">Outer membrane vesicle induction and isolation for vaccine development.</a> Frontiers in Microbiology. 12, 629090 (2021).</li><li>Hua, 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=A+novel+immunomodulator+delivery+platform+based+on+bacterial+biomimetic+vesicles+for+enhanced+antitumor+immunity.">A novel immunomodulator delivery platform based on bacterial biomimetic vesicles for enhanced antitumor immunity.</a> Advanced Materials. 33 (43), 2103923 (2021).</li></ol>

The authors have nothing to disclose.

To create a &#34;Plug-and-Display&#34; nanoparticle vaccine platform, SC-fused ClyA was expressed in BL21(DE3) strains, which is one of the most widely used models for recombinant protein production because of its advantages in protein expression24, so that there would be enough SC fragment displaying on the surface of the OMVs during the process of bacteria proliferation. At the same time, an ST-fused target antigen was prepared for the chemical coupling between the antigens and OMVs. This experi...

As a potential vaccine platform, outer membrane vesicles (OMVs) have attracted more and more attention in recent years1,2. OMVs, mainly secreted naturally by gram-negative bacteria3, are spherical nanoscale particles composed of a lipid bilayer, usually in the size of 20-300 nm4. OMVs contain various parental bacterial components, including bacterial antigens and pathogen-associated molecular patterns (PAMPs), which serve as solid immune potentiators5. Benefiting from their unique components, natural vesicle structure, and great genetic engineering modification sites, OMVs have been developed for use in many biomedical fields, including bacterial vaccines6, adjuvants7, cancer immunotherapy drugs8, drug delivery vectors9, and anti-bacterial adhesives10.
The SARS-CoV-2 pandemic, which has spread worldwide since 2020, has taken a heavy toll on global society. The receptor-binding domain (RBD) in spike protein (S protein) can bind with human angiotensin-converting enzyme 2 (ACE2), which then mediates the entry of the virus into the cell11,12,13. Thus, RBD seems to be a prime target for vaccine discovery14,15,16. However, monomeric RBD is poorly immunogenic, and its small molecular weight makes it difficult for the immune system to recognize, so adjuvants are often required17.
In order to increase the immunogenicity of RBD, OMVs displaying polyvalent RBDs were constructed. Existing studies using OMV to display RBD usually fuse RBD with OMV to be expressed in bacteria18. However, RBD is a virus-derived protein, and prokaryotic expression is likely to affect its activity. To solve this problem, the SpyTag (ST)/SpyCatcher (SC) system, derived from Streptococcus pyogenes, was used to form a covalent isopeptide with OMV and RBD in a conventional buffer system19. The SC domain was expressed with Cytolysin A (ClyA) as a fusion protein by bioengineered Escherichia coli, and ST was expressed with RBD via the HEK293F cellular expression system. OMV-SC and RBD-ST were mixed and incubated overnight. After purification by ultracentrifugation or size-exclusion chromatography (SEC), OMV-RBD was obtained.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Ampicillin sodium</td>
			<td>Sangon Biotech</td>
			<td>A610028</td>
			<td></td>
		</tr>
		<tr>
			<td>Automated cell counter</td>
			<td>Countstar</td>
			<td>BioTech</td>
			<td></td>
		</tr>
		<tr>
			<td>BCA protein quantification Kit</td>
			<td>cwbio</td>
			<td>cw0014s</td>
			<td></td>
		</tr>
		<tr>
			<td>ChemiDoc Touching Imaging System</td>
			<td>Bio-rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Danamic Light Scattering</td>
			<td>Malvern</td>
			<td>Zetasizer Nano S90</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrophoresis apparatus</td>
			<td>Cavoy</td>
			<td>Power BV</td>
			<td></td>
		</tr>
		<tr>
			<td>EZ-Buffers H 10X TBST Buffer</td>
			<td>Sangon Biotech</td>
			<td>C520009</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat pAb to mouse IgG1</td>
			<td>Abcam</td>
			<td>ab97240</td>
			<td></td>
		</tr>
		<tr>
			<td>High speed freezing centrifuge</td>
			<td>Bioridge</td>
			<td>H2500R</td>
			<td></td>
		</tr>
		<tr>
			<td>His-Tag mouse mAb</td>
			<td>Cell signaling technology</td>
			<td>2366s</td>
			<td></td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Sangon Biotech</td>
			<td>A600277</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl beta-D-thiogalactopyranoside</td>
			<td>Sangon Biotech</td>
			<td>A600118</td>
			<td></td>
		</tr>
		<tr>
			<td>Ni-NTA His-Bind Superflow</td>
			<td>Qiagen</td>
			<td>70691</td>
			<td></td>
		</tr>
		<tr>
			<td>Non-fat powdered milk</td>
			<td>Sangon Biotech</td>
			<td>A600669</td>
			<td></td>
		</tr>
		<tr>
			<td>OPM-293 cell culture medium</td>
			<td>Opm biosciences</td>
			<td>81075-001</td>
			<td></td>
		</tr>
		<tr>
			<td>pcDNA3.1 RBD-ST plasmid</td>
			<td>Wuhan genecreat biological techenology</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffer saline</td>
			<td>ZSGB-bio</td>
			<td>ZLI-9061</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylenimine Linear</td>
			<td>Polysciences</td>
			<td>23966-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Prestained protein ladder</td>
			<td>Thermo</td>
			<td>26616</td>
			<td></td>
		</tr>
		<tr>
			<td>pThioHisA ClyA-SC plasmid</td>
			<td>Wuhan genecreat biological techenology</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PVDF Western Blotting Membranes</td>
			<td>Roche</td>
			<td>03010040001</td>
			<td></td>
		</tr>
		<tr>
			<td>Quixstand benchtop systems (100 kD hollow fiber column)</td>
			<td>GE healthcare</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SDS-PAGE loading buffer (5x)</td>
			<td>Beyotime</td>
			<td>P0015</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sangon Biotech</td>
			<td>A100241</td>
			<td></td>
		</tr>
		<tr>
			<td>Supersignal west pico PLUS (enhanced chemiluminescence solution)</td>
			<td>Thermo</td>
			<td>34577</td>
			<td></td>
		</tr>
		<tr>
			<td>Suspension instrument</td>
			<td>Life Technology</td>
			<td>Hula Mixer</td>
			<td></td>
		</tr>
		<tr>
			<td>Transmission Electron Microscope</td>
			<td>Hitachi</td>
			<td>HT7800</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Oxoid</td>
			<td>LP0042B</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultracentrifuge</td>
			<td>Beckman coulter</td>
			<td>XPN-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultraviolet spectrophotometer</td>
			<td>Hitachi</td>
			<td>U-3900</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract</td>
			<td>Sangon Biotech</td>
			<td>A610961</td>
			<td></td>
		</tr>
	</tbody>
</table>

a "plug-and-display" nanoparticle vaccine platform based on outer membrane vesicles displaying sars-cov-2 receptor-binding domain

Biomimetic nanoparticles obtained from bacteria or viruses have attracted substantial interest in vaccine research and development. Outer membrane vesicles (OMVs) are mainly secreted by gram-negative bacteria during average growth, with a nano-sized diameter and self-adjuvant activity, which may be ideal for vaccine delivery. OMVs have functioned as a multifaceted delivery system for proteins, nucleic acids, and small molecules. To take full advantage of the biological characteristics of OMVs, bioengineered Escherichia coli-derived&#160;OMVs were utilized as a carrier and SARS-CoV-2 receptor-binding domain (RBD) as an antigen to construct a &#34;Plug-and-Display&#34; vaccine platform. The SpyCatcher (SC) and SpyTag (ST) domains in Streptococcus pyogenes were applied to conjugate OMVs and RBD. The Cytolysin A (ClyA) gene was translated with the SC gene as a fusion protein after plasmid transfection, leaving a reactive site on the surface of the OMVs. After mixing RBD-ST in a conventional buffer system overnight, covalent binding was formed between the OMVs and RBD. Thus, a multivalent-displaying OMV vaccine was achieved. By replacing with diverse antigens, the OMVs vaccine platform can efficiently display a variety of heterogeneous antigens, thereby potentially rapidly preventing infectious disease epidemics. This protocol describes a precise method for constructing the OMV vaccine platform, including production, purification, bioconjugation, and characterization.

The flowchart for this protocol is shown in Figure 1. This protocol could be a general approach to utilizing OMVs as a vaccine platform; one only needs to choose the appropriate expression systems based on the type of antigens.
Figure 2&#160;provides a feasible plasmid design scheme. The SC gene is connected with the ClyA gene via a flexible linker, while ST connects to the 5&#39; terminal of the RBD gene with a His-tag gene for purif...

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A &quot;Plug-And-Display&quot; Nanoparticle Vaccine Platform Based on Outer Membrane Vesicles Displaying SARS-CoV-2 Receptor-Binding Domain

The present protocol describes the bioengineering of outer membrane vesicles to be a "Plug-and-Display" vaccine platform, including production, purification, bioconjugation, and characterization.

A "Plug-And-Display" Nanoparticle Vaccine Platform Based on Outer Membrane Vesicles Displaying SARS-CoV-2 Receptor-Binding Domain

Biomimetic nanoparticles obtained from bacteria or viruses have attracted substantial interest in vaccine research and development. Outer membrane ...

Nanoscience can effectively enhance the antigen-specific immune response after displaying antigens on the surface of The main advantage in this vaccine platform can achieve the go off plaque and display. In other words, the platform is able to display the variety of antigens in This method can also be applied to other biological nanoparticles to display engine to nano-sized carriers. To perform cytolysin A spy catheter transformation, start with adding five microliters of plasma solution to 50 microliters of BL 21 competent strain.Gently blow and let cool on ice for 30 minutes. Place the solution for 90 seconds in the water bath at 42 degrees Celsius, and then immediately put the mixed solution on ice for three minutes. Add 500 microliters of luria bertani medium to the bacterial suspension and after mixing culture at 220 rotations per minute at 37 degrees Celsius for one hour.Next, plate all the transformation luria bertani agar plate containing ampicillin and culture overnight at 37 degrees Celsius. For OMV spycatcher production, start by isolating a single colony from the plate to 20 milliliters of luria bertani medium and culture overnight at 220 rotations per minute at 37 degrees Celsius. Incubate the bacterial solution into a two liter medium and culture at 220 rotations per minute at 37 degree Celsius for five hours until the logarithmic growth stage is reached.Add isopropyl beta D-IPTG to make the final concentration of the bacterial solution to be 0.5 millimolar and then culture overnight at 220 rotations per minute at 25 degree Celsius. Next, perform OMV spycatcher purification. Start with centri fusing the bacterial solution.Filter the supernatant with a 0.22 micrometer membrane filter, then concentrate it using a hollow fiber column. Filter the concentrate through a 0.22 micrometer membrane filter, then centri fuse it at 150, 000 times G at four degree Celsius for two hours using an ultra centri fuse, and discard the supernatant with a pipette. Re-suspend the precipitation with PBS, and store it at minus 80 degrees Celsius.To perform RBD spytag transfection, begin with selecting an appropriate eukaryotic expression system and culture the cells overnight at 130 rotations per minute at 37 degrees Celsius after recovery. Add 20 microliters HEK 293F of cell solution into the automated cell counter. Record the number of cells, adjust the concentration to one times 10 to the six cells per milliliter.And then culture the cells at 130 rotations per minute at 37 degrees Celsius for four hours. Filter RBD spy tag plasmid through a 0.22 micrometer membrane filter and add 300 micrograms of plasmids into the cell culture medium until the final volume is 10 milliliters. Shake for 10 seconds.Heat PEI to 65 degrees Celsius in the water bath. Mix 0.7 milliliters of PEI with 9.3 milliliters of cell culture medium, and shake intermittently for 10 seconds. Add plasmid solution to the PEI solution.Shake the mixture intermittently for 10 seconds, and incubate it at 37 degrees Celsius for 15 minutes. Add the mixture to 280 milliliters of cell culture medium, and culture at 130 rotations per minute at 37 degrees Celsius for five days. Next, perform RBD spytag purification.Start with centri fusing the cells at 6, 000 times G at 25 degrees Celsius for 20 minutes, and use a pipette to collect the supernatant. Fill the column with two milliliters of nickel NTA agarose and wash it three times with PBS. Add imidazole into the cell supernatant to make the final concentration of 20 millimolar, and load the cell supernatant.Add three column volumes of PBS containing 20 millimolar of imidazole for washing, and collect the washing fraction. Gradient elute with three column volumes of PBS containing low to high concentrations of imidazole elute twice for each concentration. To determine the protein concentration by the BCA method, serially dilute the standard BSA protein solution from two to 0.0625 milligrams per milliliter, dilute the purified OMV spycatcher and RBD spy tag 10 times.Then mix BCA working solutions A and B at a ratio of 50 to one. Add diluted protein solution, and mix with BCA working solution. Incubate at 37 degrees for 30 minutes.Measure the absorbance at 562 nanometers of each well, and calculate the protein concentration from the standard curve. To perform bioconjugation of OMV spycatcher and RBD spy tag, mix OMV spycatcher and RBD spytag and PBS at a 40 to one ratio. Vertically rotate to blend the mixture overnight at 15 rotations per minute at four degrees Celsius.Perform purification of OMV RBD using PBS solution using a procedure similar to OMV spycatcher purification. The plasma design scheme shows that the spycatcher gene is connected with the cly A gene via flexible linker while the spytag connects to the five prime terminal of the RBD gene with a hys tag gene for purification and verification. After ultracentrifugation, almost all the un-reacted RBD spytag remained in the supernatant.The second ultracentrifugation did not provide a further significant advantage over the first time. The z average hydrodynamic diameter of OMV spycatcher was 133 nanometers while it was 152.6 nanometers for OMV-RBD. These differences may be because RBD increases OMV particle size after intensive displaying.The results of TEM are consistent with the particle size distribution obtained from the DLS results. Rotation for blending the mixture is very important. The efficiency of reaction can be much lower without rotation.

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2.3K 조회수.  Third Military Medical University. 나노 과학은 표면에 항원을 표시 한 후 항원 특이 적 면역 반응을 효과적으로 향상시킬 수 있습니다.이 백신 플랫폼의 주요 장점은 플라크 및 디스플레이를 제거 할 수 있습니다. 즉, 플랫폼에서 다양한 항원을 표시할 수 있게 되어 이 방법은 나노크기의 담체에 다른 생체 나노입자를 디스플레이엔진으로 적용할 수도 있다. cytolysin A 스파이 카테터 변형을 수행하려면 50 마이?...