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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

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

Abstract

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-derivedĀ OMVs were utilized as a carrier and SARS-CoV-2 receptor-binding domain (RBD) as an antigen to construct a "Plug-and-Display" 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.

Introduction

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 en....

Protocol

1. Plasmid construction

  1. 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.
  2. Ligate the synthesized SpyTag-RBD-Histag fusion gene (Supplementary File 1) into a pcDNA3.1 plasmid (see Table.......

Representative Results

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 2Ā 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' terminal of the RBD gene with a His-tag gene for purif.......

Discussion

To create a "Plug-and-Display" 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.......

Acknowledgements

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).

....

Materials

NameCompanyCatalog NumberComments
Ampicillin sodiumSangon BiotechA610028
Automated cell counterCountstarBioTech
BCA protein quantification Kitcwbiocw0014s
ChemiDoc Touching Imaging SystemBio-rad
Danamic Light ScatteringMalvernZetasizer Nano S90
Electrophoresis apparatusCavoyPower BV
EZ-Buffers H 10X TBST BufferSangon BiotechC520009
Goat pAb to mouse IgG1Abcamab97240
High speed freezing centrifugeBioridgeH2500R
His-Tag mouse mAbCell signaling technology2366s
ImidazoleSangon BiotechA600277
Isopropyl beta-D-thiogalactopyranosideSangon BiotechA600118
Ni-NTA His-Bind SuperflowQiagen70691
Non-fat powdered milkSangon BiotechA600669
OPM-293 cell culture mediumOpm biosciences81075-001
pcDNA3.1 RBD-ST plasmidWuhan genecreat biological techenology
Phosphate buffer salineZSGB-bioZLI-9061
Polyethylenimine LinearPolysciences23966-1
Prestained protein ladderThermo26616
pThioHisA ClyA-SC plasmidWuhan genecreat biological techenology
PVDF Western Blotting MembranesRoche03010040001
Quixstand benchtop systems (100 kD hollow fiber column)GE healthcare
SDS-PAGE loading buffer (5x)BeyotimeP0015
Sodium chlorideSangon BiotechA100241
Supersignal west pico PLUS (enhanced chemiluminescence solution)Thermo34577
Suspension instrumentLife TechnologyHula Mixer
Transmission Electron MicroscopeHitachiHT7800
TryptoneOxoidLP0042B
UltracentrifugeBeckman coulterXPN-100
Ultraviolet spectrophotometerHitachiU-3900
Yeast extractSangon BiotechA610961

References

  1. Li, M., et al. Bacterial outer membrane vesicles as a platform for biomedical applications: An update. Journal of Controlled Release. 323, 253-268 (2020).
  2. Micoli, F., MacLennan, C. A. Outer membrane vesicle vaccines.

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