Lung tissues were homogenized in DMEM using the bead-beating technology (Precellys Lysing kits; Bertin Technologies, Aix-en-Provence, France). Following centrifugation, supernatants were stored in small aliquots. Viral titers were determined using a plaque assay following a previously described methodology [12 (link)]. For western analysis, thawed supernatants were mixed with equal amounts of RIPA buffer containing lysozyme and proteinase inhibitors. The protein content was measured with a protein assay kit (Bio-Rad, Richmond, CA, USA). Equal amounts of cellular proteins were separated by SDS-PAGE and subsequently transferred onto polyvinylidene fluoride membranes. Subsequently, the membranes were immunoblotted with specific primary antibodies and subsequently exposed to horseradish peroxidase (HRP)-conjugated secondary antibodies. The Immobilon Western HRP Chemiluminescence Substrate (Millipore, Burlington, MA, USA) was used for blot development. Mouse monoclonal anti-nucleocapsid (GTX632269, 1:2000 dilution) and anti-GAPDH (GTX627408, 1:5000 dilution) antibodies were obtained from Genetex (Hsinchu, Taiwan).