Construction and expression of nanoparticle vaccines. (A) Schematic of vaccine components which were RBD-Fe, S1-Fe and ECD-Fe. Fe: Ferritin, RBD: receptor-binding domain, ECD: ectodomain. (B) Schematic of nanoparticle of the three vaccines. PyMOL software was used for visualization14. (C) Western Blot analysis of the products prepared in silkworm by using an anti-RBD antibody. (D) ELISA of the S proteins to evaluate the expression levels. ECD-Fe with 287 ug/mL larval haemolymph, S1-Fe with 468 ug/mL larval haemolymph, RBD-Fe with 187 ug/mL larval haemolymph. (E) TEM image and two-dimensional (2D) reconstruction confirmed the successful assembly of each nanoparticle, IEM confirmed the S protein on the surface of the nanoparticle.
