Fig. 1.

Constitutive expression of the recombinant S1 protein in PK-rS1-cFc cells. (A) Immunofluorescence assay for the rS1 protein. PK-15 or PK-rS1-cFc cells grown in a 6-well tissue culture plate were fixed with 4 % formaldehyde at 48 h post-seeding and incubated with anti-chicken IgG antibody (top panels). The cells were then counterstained with DAPI (bottom panels) and examined using a fluorescent microscope at 400× magnification. (B) Purification of the rS1 protein. The recombinant S1 protein was purified from serum-free medium of PK-rS1-cFc cells grown in a 100-mm tissue culture dish. The cell culture supernatant and the purified rS1 protein were resolved on a 4–12 % gradient Bis-Tris gel and stained with SimplyBlue solution (left panel) or electrotransferred onto a PVDF membrane (right panel). The membrane was blotted with a chicken IgG-specific antibody