Development of a SARS-CoV-2 Vaccine Candidate Using Plant-Based Manufacturing and a Tobacco Mosaic Virus-like Nano-Particle

Abstract

Stable, effective, easy-to-manufacture vaccines are critical to stopping the COVID-19 pandemic resulting from the coronavirus SARS-CoV-2. We constructed a vaccine candidate CoV-RBD121-NP, which is comprised of the SARS-CoV-2 receptor-binding domain (RBD) of the spike glycoprotein (S) fused to a human IgG1 Fc domain (CoV-RBD121) and conjugated to a modified tobacco mosaic virus (TMV) nanoparticle. In vitro, CoV-RBD121 bound to the host virus receptor ACE2 and to the monoclonal antibody CR3022, a neutralizing antibody that blocks S binding to ACE2. The CoV-RBD121-NP vaccine candidate retained key SARS-CoV-2 spike protein epitopes, had consistent manufacturing release properties of safety, identity, and strength, and displayed stable potency when stored for 12 months at 2–8 °C or 22–28 °C. Immunogenicity studies revealed strong antibody responses in C57BL/6 mice with non-adjuvanted or adjuvanted (7909 CpG) formulations. The non-adjuvanted vaccine induced a balanced Th1/Th2 response and antibodies that recognized both the S1 domain and full S protein from SARS2-CoV-2, whereas the adjuvanted vaccine induced a Th1-biased response. Both adjuvanted and non-adjuvanted vaccines induced virus neutralizing titers as measured by three different assays. Collectively, these data showed the production of a stable candidate vaccine for COVID-19 through the association of the SARS-CoV-2 RBD with the TMV-like nanoparticle.

Biological Nanoparticles in Vaccine Development

“…As VLPs directly mimic native viruses, these nanoparticle systems can induce strong, T-independent stimulation of B cells through BCR crosslinking ( Bachmann et al, 1993 ; Fries et al, 2021 ). VLPs also contain viral PAMPs, such as nucleic acids, that help activate, in many cases, and an adjuvant-free protective immune response ( Venter et al, 2011 ; Li M. et al, 2021 ; Ortega-Rivera et al, 2021 ; Royal et al, 2021 ; Warner and Frietze, 2021 ). Additionally, if they are made in bacteria, VLPs may contain some bacterial components that further promote a protective response without use of classical alum adjuvants ( Mohsen et al, 2021 , 2022 ).…”

“…Chimeric viruses contain genetic material from two different viruses, which results in fusion proteins that incorporate epitopes from both viruses. Recombinant chimeric VLP vaccines have been developed for Chikungunya virus (CHIKV), based on the insect-specific alphavirus, Eilat virus (EILV) ( Erasmus et al, 2017 ); Bacillus anthracis , based on cowpea mosaic virus (CPMV) ( Phelps et al, 2007 ) and Flock house virus ( Venter et al, 2011 ); SARS-CoV-2 and MERS, based on cucumber mosaic virus (CMV) ( Mohsen et al, 2021 , 2022 ); and SARS-CoV-2 and Yersinia pestis , based on tobacco mosaic virus (TMV) ( Arnaboldi et al, 2016 ; Royal et al, 2021 ).…”

Polymerized porin as a novel delivery platform for coronavirus vaccine

“…In the existing biopolymeric nanoparticles, researchers use self-assembled proteins such as I53-50 [ 19 ], ferritin [ 12 , 65 ], mi3 [ 65 ], E2p [ 66 ], I3-01v9 [ 66 ], and modified tobacco mosaic virus [ 67 ] are used as nanoparticle carriers and gene fusion [ 19 , 66 ], chemical coupling [ 67 ] and the SpyTag-SpyCatcher system [ 12 , 65 , 66 ] are used to display the RBDs expressed by the eukaryotic system on the surface of nanoparticles. These RBD-displaying nanoparticles significantly improve the immune effect compared with that elicited by RBD monomers.…”

Plant-Derived Human Vaccines: Recent Developments

“…Kentucky Bioprocessing Inc, the US biotech subsidiary of BAT, together with several others have also developed a SARS-CoV-2 vaccine candidate (CoV-RBD121-NP) by using a previously developed virus-like particle-type nano-particle (VLP-type NP) vaccine platform [ 47 ] to produce a TMV-like NP displaying a chemically conjugated SARS-CoV-2 antigen [ 128 ]. The antigen—CoV-RBD121—comprised amino acids 331–632 of the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) fused to a human IgG1 Fc domain to enhance stability of the RBD as well as facilitate ease of purification.…”

“…Most importantly, characterisation of the NPs and stability assays showed that this vaccine candidate was stable for up to 12 months at 2–8 °C as well as 22–28 °C, fulfilling an important criterion for worldwide distribution requirements for vaccines. In addition, the pilot batch of CoV-RBD121-NP was manufactured within 28 days of receiving the SARS-Cov-2 RBD sequence showing that the platform can adapt rapidly to vaccine target demands in the event of a pandemic [ 128 ]. BAT/KBP has recently been given approval to commence with a phase I clinical trial to test its safety and immunogenicity (NCT04473690).…”