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Order Picornavirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
The structures of the first two caliciviruses were determined by electron cryomicroscopy and image reconstruction, i.e. baculovirus-expressed NoV VLPs (Prasad et al. 1994b) and primate calicivirus (Prasad et al. 1994a). The VLP structures revealed a diameter of 38 nm and exhibited a T = 3 icosahedral lattice composed of 90 arch-like capsomers formed by dimers of the capsid protein at 22 Å resolution. These structures showed distinct similarity to the single-stranded RNA plant viruses such as tomato bushy stunt virus (TBSV) and turnip crinkle virus (TCV) from the Tolivirales order, which is described in Chapter 24. The smaller form of the NoV VLPs found in insect cells, 23 nm in diameter, appeared to be a T = 1 symmetry variant of capsid self-assembly, consisting of 60 polypeptide molecules (White LJ et al. 1997).
Modern vaccine strategies for emerging zoonotic viruses
Published in Expert Review of Vaccines, 2022
Atif Ahmed, Muhammad Safdar, Samran Sardar, Sahar Yousaf, Fiza Farooq, Ali Raza, Muhammad Shahid, Kausar Malik, Samia Afzal
The major strategies used to produce plant-based vaccines are nuclear, transplastomic, and viral vector transformation. Nuclear transformation is a very simple and widely used method because the foreign antigen is inserted into the nuclear genome. Agrobacterium tumefaciens or gene gun-mediated transformation is used for gene transfer. The nuclear transformation results in the continuous production of recombinant proteins. Additionally, nuclear transformation also results in the post-translational modification that takes place in eukaryotic systems [93,94]. But it is also coupled with some disadvantages including, lower expression level, gene silencing, position effect, and a chance of contamination. The chloroplast transformation overcomes some of the drawbacks of nuclear transformation, which has hampered commercialization as a plant-based recombinant vaccine. The desired gene (for an antigen) is directly introduced into the genome of the plant chloroplast by using a particle cannon. Most of the currently reported edible vaccines were produced by this method because of the high stability in gene expression. In chloroplasts, many viral antigens like rotavirus and canine parvovirus were expressed. Through overcoat and epic at technologies, several viruses such as cowpea mosaic virus (CPMV), alfalfa mosaic virus, tobacco mosaic virus (TMV), cauliflower mosaic virus (CaMV), tomato bushy stunt virus, and potato virus are designed to express the part of antigenic protein on their surface as reviewed in [95].