TMPRSS2, TMPRSS4 and HAT of non-human primate origin cleave and activate influenza virus hemagglutinin.

<p>(A) 293T cells were transiently cotransfected with plasmids encoding FLUAV HA of the 1918 H1N1 FLUAV and the indicated proteases or empty plasmid (pCAGGS). At 48 h post transfection the cells were treated with PBS or trypsin, and HA cleavage was determined by Western blotting. The HA precursor HA0 (filled triangle) and the surface unit HA1 (empty triangle) are indicated. The expression of β-actin was determined as a loading control. Similar results were obtained in three independent experiments. (B) The indicated proteases were expressed in 293T cells and the cells infected with FLUAV A/PR/8/34 (H1N1) at an MOI 0.01 and treated with either trypsin or PBS. At 48 h post infection, the virus titers were determined by focus formation assay. The average of three to five independent experiments is shown; error bars indicate standard error of the mean. Virus titers measured upon trypsin treatment were set as 100%.