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Background Hantavirus causes hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Strong inflammatory responses and vascular leakage are important hallmarks of these often fatal diseases. The mechanism behind pathogenesis is unknown and no specific treatment is available. IL-6 was recently highlighted as a biomarker for HPS/HFRS severity. IL-6 signaling is complex and context dependent: while classical signaling generally provide protective responses, trans-signaling can cause severe pathogenic responses. Here, we investigated a potential role for IL-6 trans-signaling in hantavirus pathogenesis.

Methods Effects of IL-6 trans-signaling during in vitro hantavirus infection were assessed using primary human endothelial cells treated with recombinant soluble IL-6 receptor (sIL-6R). Plasma from Puumala orthohantavirus-infected HFRS patients (n=28) were analyzed for IL-6 trans-signaling potential and its associations to severity.

Findings In vitro, sIL-6R treatment of infected cells enhanced IL-6 and CCL2 secretion, upregulated ICAM-1, and affected VE-cadherin leading to a disrupted cell barrier integrity. HFRS patients showed altered plasma levels of sIL-6R and soluble gp130 (sgp130) resulting in an increased sIL-6R/sgp130 ratio suggesting enhanced IL-6 trans-signaling potential. Plasma sgp130 levels negatively correlated with number of interventions and positively with albumin levels. Patients receiving oxygen treatment displayed a higher sIL-6R/sgp130 ratio compared to patients that did not.

Interpretation IL-6 trans-signaling is linked to hantavirus pathogenesis. Targeting IL-6 trans-signaling might provide a therapeutic strategy for treatment of severe HFRS and perhaps also HPS.