Influenza virus proteins modulate hemostasis in vitro and in vivo

: We studied the effect of influenza virus proteins--hemagglutinin, neuraminidase, nucleoprotein, and membrane protein--on hemostasis in vitro and in vivo. The obtained data demonstrated that the envelope proteins hemagglutinin and neuraminidase increased the plasma fibrinolytic and anticoagulant activities and the activity of human tissue plasminogen activator. Among the core proteins of influenza virus, membrane protein proved to have the highest activity; in contrast to hemagglutinin and neuraminidase, it inhibited fibrinolysis, increased the coagulation activity of the plasma, and decreased the activity of human tissue plasminogen activator. Combined action of hemagglutinin and neuraminidase increased the plasma fibrinolytic and anticoagulant activities exceeding their individual effects. Combined action of an envelope protein hemagglutinin and membrane protein also increased the plasma fibrinolytic and anticoagulant activities although to a lesser extent as compared to hemagglutinin alone. The obtained data indicate that the viral proteins are physiologically active and can induce hemostatic changes specific for influenza.