CK1 and AH1 replication profile in mouse lung.

<p>A. Representative images of immunohistochemically stained influenza nucleoprotein (NP) in formalin fixed mouse lung tissue infected with CK1 or AH1 at day 2 p.i. Viral NP protein was labeled brown by 3,3′-diaminobenzidine (DAB). Uninfected mouse lung as negative control (<i>a)</i>, amplified image (b); Representative images of CK1(c) and AH1 (d) infected mouse lung stained NP positive at 40x magnification. Trachea epithelial cells (e and f), bronchiole epithelial and alveolar epithelial cells (g and h) were stained positive for viral NP protein. (Original magnification ×200). B. Viral load in infected mouse lung homogenates. Mice were infected with 10⁵ of AH1 or 10⁶ PFU of CK1, at day 1, 2, 4 and 6 p.i., 3–5 mice from each group were sacrificed. The left side of the lung was homogenized in 1 ml of MEM culture medium. Viral loads were determined by amplification of viral M gene copy numbers by real time RT-PCR (top panel), and infectious viral titre were determined by TCID₅₀ assay on MDCK cells (bottom panel). **<i>P</i><0.01; * <i>P</i><0.05.