Wild-type and MBL KO mice infected with pdmH1N1 or H9N2/G1 virus were sacrificed on days 3, 7, and 14 after infection. Virus titers in lung homogenates were determined by TCID 50 . As shown in Figure 3 , these 2 strains of influenza virus were detectable in the lung homogenates collected from MBL WT and KO mice on day 3 and day 7, confirming viral lung infection. On day 14, titers for both strains of virus were undetectable, which was consistent with the regain of body weight by MBL WT and MBL KO mice and suggested recovery from the infection. For pdmH1N1 virus infection, there was no significant difference in the lung virus titer between MBL KO and MBL WT mice on days 3 and 7 after infection ( Figure 3A ). In contrast, significantly less virus titer was detected in MBL KO mice on day 7 but not on day 3 after H9N2/G1 virus infection compared to that in MBL WT mice ( Figure 3B ). 