Fig. 2. Structure and engineering design space of plant virus nanotechnologies and virus-like particle vaccines.

a | Display of epitopes or peptides on cowpea mosaic virus (CPMV) through genetic fusion or bioconjugation. b | Encapsidation of molecular payloads within the cowpea chlorotic mosaic virus (CCMV) through dis-assembly and re-assembly of coat proteins following changes in the solvent conditions. c | Delivery of molecular payloads with tobacco mosaic virus (TMV) using internal glutamate (Glu) or external tyrosine (Tyr) residues. Therapeutic payloads can be loaded into the interior of the TMV or conjugated to the exterior surface of TMV. d | Epitope delivery using plant viral nanoparticles (VNPs). Vaccination with VNPs leads to intracellular processing of the antigen or genomic material encoding the antigen. The antigen is then displayed on the cell surface, leading to the activation of CD4⁺ and CD8⁺ T cells. CD4⁺ T cells go on to activate memory B cells, leading to immune memory against future infections. APC, antigen-presenting cell; BCR, B cell receptor; MHC, major histocompatibility complex; VLP, virus-like particle. The plant VNPs were drawn using UCSF Chimera (CPMV PDB ID: 1NY7; CCMV PDB ID: 1CWP; TMV PDB ID: 2TMV), and parts of Fig. 3d were made using https://smart.servier.com/.