Screening of the suitable silkworm strain for PEDV S protein expression. A The Western blotting analysis of 25 silkworm strains infected with recombinant baculovirus encoding PEDV/S(1–1320) + CMP + Tags. The sera of 0.5 μL were subjected to 8% SDS-PAGE, and the specific band was detected using HisProbe-HRP. Three individual samples were prepared from each strain, and f38 sera were used as a control. B Comparison of relative band intensities among silkworm strains by Western blotting detecting PEDV/S(1–1320) + CMP + Tags protein. The intensities of each band were measured, and the relative intensities were calculated using the average band intensity of f38 strain as 1. Bars represent mean relative intensities ± SE (N = 3). C Expression analysis of the hybrid silkworm of n22 strain and xa50 strain. Three individual serum samples of each n22 (lane1-3), xa50 (lane4-6), and n22 × xa50 (lane7-9), and xa50 × n22 (lane10-12) were resolved in an 8% SDS-PAGE with CBB stain (upper panel) and Western blotting using HisProbe-HRP (lower panel). Orange arrows indicate the PEDV S protein.