Figure 5

PB1-F2 does not alter the systemic viral tissue spread. By means of IHC for IAV M1, ΔF2 and wild type infection yielded high virus antigen scores in the brain, respiratory tract, skin and immune organs. Both viruses exhibited strong endotheliotropism. IHC, blind scoring, dots represent individual scores, bar represents median group score. Scores given as no antigen = 0, rare/focal = 1, multifocal = 2, coalescing = 3, diffuse = 4. Asterisks indicate cumulative scores for the brain (for neurons, glial cells, ependymal cells), respiratory tract (respiratory and glandular epithelium of conchae and lung), skin (epidermal and mesenchymal cells), immune organs (immune and mesenchymal cells of thymus, spleen and bursa), and endothelium (all organs tested) (A). Representative images for IHC-based detection of M protein in target cell indicating neurons (asterisk) and glial cells (arrow) in the brain (B), air capillaries in the lung (arrow) (C), endothelium (arrow) exemplarily shown in the nasal conchae (D), sinusoid lining cells (arrow) of the liver (E), epidermal epithelium (arrow) and dermal mesenchymal cells (asterisk) in the skin (F) and glands (arrow) in the nasal conchae (G). B–G IHC, using avidin and biotinylated enzyme method, 3-Amino-9-Ethylcarbazole chromogen (red), and haematoxylin (blue) counterstain. Bar 50 µm (B–F), 100 µm (G).