FIG. 2.

Multicycle viral replication in MDCK cells transfected with TMPRSS2 (left column), HAT (middle column), or proteolytically inactive protease mutant TMPRSS2(S441A) (right column). Ten hours after transfection with protease-encoding plasmids, the cultures were infected with influenza viruses A/Memphis/14/96 (H1N1) (top row), A/Mallard/Alberta/205/98 (H2N9) (middle row), and A/Texas/6/96 (H3N2) (bottom row) at a multiplicity of infection of 0.01. We incubated infected cultures for 24 h and immunostained them for viral nucleoprotein as described previously (16).