TMPRSS2 isoform 1 cleaves and activates the influenza virus hemagglutinin.

<p>(A) Expression plasmids encoding FLUAV HA subtypes H1 (left) and H3 (right) and the indicated proteases or empty plasmid (pCAGGS) were transiently cotransfected into 293T cells. At 48 h post transfection the cells were treated with PBS or trypsin, and HA cleavage was determined by Western blotting. Similar results were obtained in three independent experiments. The HA₀ precursor (upper arrow) and the HA₁ (middle arrow) and HA₂ (lower arrow) subunits are indicated. (B) The indicated proteases were transiently expressed in 293T cells and the cells infected with FLUAV A/PR/8/34 (H1N1) at an MOI 0.01 (left) or FLUAV A/Panama/2007/99 (H3N2) at an MOI of 0.1 (right) and treated with either trypsin or PBS. At 48 h post infection, the virus release was measured by determination of infectious particles (ffu/ml) in the culture supernatant. The results of representative experiments performed with triplicate samples are shown. Error bars indicate standard deviations. Similar results were obtained in three independent experiments. ffu, focus forming units.