Interferons Induce STAT1-Dependent Expression of Tissue Plasminogen Activator, a Pathogenicity Factor in Puumala...

Hantaviruses are zoonotic viruses that show various degrees of vasculopathy in humans. In this study, we analyzed the regulation of 2 fibrinolytic parameters, tissue plasminogen activator (tPA) and its physiological inhibitor, plasminogen activator inhibitor 1 (PAI-1), in Puumala hantavirus (PUUV)-infected patients and in human microvascular endothelial cells. We detected strong upregulation of tPA in the acute phase of illness and in PUUV-infected macaques and found the tPA level to positively correlate with disease severity. The median levels of PAI-1 during the acute stage did not differ from those during the recovery phase. In concordance, hantaviruses induced tPA but not PAI-1 in microvascular endothelial cells, and the induction was demonstrated to be dependent on type I interferon. Importantly, type I and II interferons directly upregulated tPA through signal transducer and activator of transcription 1 (STAT1), which regulated tPA gene expression via a STAT1-responsive enhancer element. These results suggest that tPA may be a general factor in the immunological response to viruses.