↵Influenza matrix (M1) protein mRNA expression in lung and brain tissue. Influenza M1 mRNA expression was measured in lung and hippocampal tissue at days 1, 4, and 7 following inoculation with influenza virus. As viral M1 was non-detectable (ND) in control lung samples, data are expressed as fold change in mRNA expression from day 1 after inoculation. Influenza M1 expression was elevated in the lungs of infected mice at day 4 and 7 after inoculation (*p < 0.05 compared with day 1 after inoculation). Influenza M1 mRNA was nondetectable (ND) in hippocampal tissue from control or influenza- infected mice at any timepoint.