FIG 5.
66Y facilitated infection in the presence of human mucus. Reverse genetics (rg) analysis of 6+2 viruses on an A/WSN/33 (H1N1) background and containing the hemagglutinin (HA) and neuraminidase (NA) genes of pH1N1low-1 and the D66Y mutation in NA showed increased infectivity of Madin-Darby canine kidney (MDCK) cells in the presence of human mucus compared to rg pH1N1low-1 (A, C, G, and H). The infectivity of rg pH1N1low-1 was also less than that of pH1N1-1 in the presence of mucus (panels A and B, respectively). In the absence of mucus, the infectivities of these viruses were similar to those of each other and to that of the rg pH1N1low-1 virus (D, E, F, J, and K). The infectivity of rg pH1N1low-1 was also less than the infectivity of the rg virus containing the HA of pH1N1low-1 and the NA of pH1N1-1 in the presence of mucus (panels A and I, respectively) but similar in the absence of mucus (panels D and L, respectively). Scale bars, 100 μm. Blue, DAPI nuclear stain; green, influenza nucleoprotein. Images are representative of the results of three replicates of each experimental condition.