Human parvovirus B19NS1 protein modulates inflammatory signaling by activation of STAT3/PIAS3 in human endothelial cells

The pathogenic mechanism by which parvovirus B19 may induce inflammatory cardiomyopathy (WNW) is complex but is known to involve inflammatory processes, possibly including activation of JAK/STAT signaling. The nonstructural B19 protein NSI acts as a transactivator triggering signaling cascades that eventually lead to activation of interleukin 6 (11,6). We examined the impact of NS1 on modulation of STAT signaling in human endothelial cells (HMEC-1). The NS1 sequences were identified from B19 DNA isolated from the myocardia of patients with fatal iCMP. B19 infection as well as NS1 overexpression in HMEC-1 cells produced a significant upregulation in the phosphorylation of both tyrosine' and serine727 STAT3 (P < 0.05). The increased STAT3 phosphorylation was accompanied by dirnerization, nuclear translocation, and DNA binding of pSTAT3. In contrast, NS1 expression did not result in increased STATI activation. Notably, the expression levels of the negative regulators of STAT activation, SOCS1 and SOCS3, were not altered by NS1. However, the level of PIAS3 was upregulated in NSI-expressing HMEC-1 cells. Analysis of the transcriptional activation of target genes revealed that NS1-induced STAT3 signaling was associated with upregulation of genes involved in immune response (e.g., the 11FNAR1 and IL-2 genes) and downregulation of genes associated with viral defense (e.g., the OASI and TYK2 genes). Our results demonstrate that B19 NSI modulates the STAT/PIAS pathway. The NS1-induced upregulation of STAT3/PIAS3 in the absence of STATI. phosphorylation and the lack of SOCSI/SOCS3 activation may contribute to the mechanisms by which B19 evades the immune response and establishes persistent infection in human endothelial cells. Thus, NS1 may play a critical role in the mechanism of viral pathogenesis in B19-associated iCNW.