Fig. 1.

Construction and expression of nanoparticle vaccines. (A) Schematic diagram of the vaccine components RBD-Fe, S1-Fe and ECD-Fe. Fe: Ferritin, RBD: receptor-binding domain, ECD: ectodomain. (B) Schematic diagram of the nanoparticles of the three vaccines. PyMOL software was used for visualization[23]. (C) Western blot analysis of the products prepared in silkworm using an anti-RBD antibody. (D) ELISA of the S proteins was performed to evaluate the expression levels. ECD-Fe with 287 µg/mL of larval hemolymph, S1-Fe with 468 µg/mL of larval hemolymph, and RBD-Fe with 187 µg/mL of larval hemolymph; n = 3; error bar, SEM. (E) TEM image and two-dimensional (2D) reconstruction confirmed the successful assembly of each nanoparticle, and IEM confirmed the S protein on the surface of the nanoparticle. Arrows, gold nanoparticles labeled with secondary antibody.