Multichannel immunofluorescent detection of FMDV capsid protein (VP1) in porcine paraepiglottic tonsils at 6 hpi (A) and 12 hpi (B–C).

A) At 6 hpi FMDV VP1 is localized to individual cells within reticular crypt epithelium of the paraepiglottic tonsil. Virus antigen (red) is detected within few cytokeratin-positive epithelial cells (green) and CD172a-expressing non-lymphoid leukocytes (turquoise). 40× magnification, scale-bar 25 µm. B and C) At 12 hpi, foci of multiple FMDV VP1-positive cells are detected within similar regions of reticular crypt epithelium of the paraepiglottic tonsil. Detection of virus antigen (red) is restricted to cytokeratin-positive epithelial cells (green) in close proximity of CD172a-expressing leukocytes (turquoise). B: 20× magnification, scale bar 50 µm. C: 40× magnification, scale bar 25 µm.