Trivalent Subunit Vaccine Candidates for COVID-19 and Their Delivery Devices

Abstract

The COVID-19 pandemic highlights the need for platform technologies enabling rapid development of vaccines for emerging viral diseases. The current vaccines target the SARS-CoV-2 spike (S) protein and thus far have shown tremendous efficacy. However, the need for cold-chain distribution, a prime-boost administration schedule, and the emergence of variants of concern (VOCs) call for diligence in novel SARS-CoV-2 vaccine approaches. We studied 13 peptide epitopes from SARS-CoV-2 and identified three neutralizing epitopes that are highly conserved among the VOCs. Monovalent and trivalent COVID-19 vaccine candidates were formulated by chemical conjugation of the peptide epitopes to cowpea mosaic virus (CPMV) nanoparticles and virus-like particles (VLPs) derived from bacteriophage Qβ. Efficacy of this approach was validated first using soluble vaccine candidates as solo or trivalent mixtures and subcutaneous prime-boost injection. The high thermal stability of our vaccine candidates allowed for formulation into single-dose injectable slow-release polymer implants, manufactured by melt extrusion, as well as microneedle (MN) patches, obtained through casting into micromolds, for prime-boost self-administration. Immunization of mice yielded high titers of antibodies against the target epitope and S protein, and data confirms that antibodies block receptor binding and neutralize SARS-CoV and SARS-CoV-2 against infection of human cells. We present a nanotechnology vaccine platform that is stable outside the cold-chain and can be formulated into delivery devices enabling single administration or self-administration. CPMV or Qβ VLPs could be stockpiled, and epitopes exchanged to target new mutants or emergent diseases as the need arises.

Integrating plant molecular farming and materials research for next-generation vaccines

“…The current preclinical development pipeline for VNP-based vaccines includes infectious, cardiovascular and autoimmune diseases as well as substance abuse 95 . Plant VNP vaccine platform technologies also hold promise for pandemic or epidemic vaccines 96 — owing to their high thermal stability they would not be subject to cold chain distribution and/or could be produced in the region for the region through molecular farming.…”

“…Thermostability is especially important in areas in which resources for adequate cold chain distribution of vaccines may be limited. Furthermore, plant viruses, owing to their intrinsic stability, can withstand the processing and manufacturing steps of vaccine packaging into new administration technologies, such as microneedles 96 . VNPs do not only act as carriers, but also as adjuvants, reducing the number of vaccine components.…”

Biological Nanoparticles in Vaccine Development

“…A similar strategy was also used to conjugate Qβ VLPs to CHIKV epitopes ( Basu et al, 2020 ) and Dengue virus (DENV) epitopes ( Warner and Frietze, 2021 ), as well as to conjugate CMV VLPs to recombinant SARS-CoV-2 spike protein ( Zha et al, 2021 ) and ZIKV immunogens ( Cabral-Miranda et al, 2019 ). Other linkers used for conjugation of VLP platforms to pathogenic antigens include SM(PEG) 4 (N-hydroxysuccinimide-poly (ethylene glycol) 4 -maleimide) ( Ortega-Rivera et al, 2021 ) for conjugation of Qβ to SARS-CoV-2 spike protein, and carbodiimide chemistry for conjugation of Yersenia pestis virulence factors ( Arnaboldi et al, 2016 ) to TMV VLPs. Another interesting method that others have used to attach the VLP carrier to the antigen of interest is through the use of sortase-mediated antigen coupling ( Thérien et al, 2017 ; Laliberté-Gagné et al, 2019 ).…”

Compendium on Food Crop Plants as a Platform for Pharmaceutical Protein Production

“…The outbreak of the COVID-19 epidemic has sparked a race among biotech companies to develop an effective vaccine against SARS-CoV-2. Researchers at the University of California San Diego have proposed a cowpea-produced vaccine that is in the preclinical testing phase [ 17 ]. This race was joined by Medicago, which developed CoVLP, a potential vaccine produced in N. benthamiana leaves, which is currently in phase 3 of clinical trials.…”