STAT1 and infection: The phosphorylation of STAT1 was first detected in control siRNA-transfected cells within 2 h of infection and peaked at 12 h of infection, then subsided at 24 h of infection almost to the level of 2 h (Figure 5A); potentially due to the antagonism by IAV or caspase-mediated cleavage of total STAT1 (King and Goodbourn, 1998).