Relationship between cytokine level and viral load in severe fever with thrombocytopenia syndrome

Background Severe fever with thrombocytopenia syndrome (SFTS) is a viral hemorrhagic fever caused by the SFTS virus (SFTSV), a tick-borne Phlebovirus. This study investigates the association between viral load and cytokine levels in patients with SFTS. Methods Viral RNA was isolated from plasma collected in EDTA and quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Cytokines in the sera of SFTS patients were measured using cytometric bead array (CBA). Results Viral loads ranged from 2.3×10^3 copies/mL to 7.9×10^11 copies/ml. Of the 46 patients, 10 (21.7%) died during treatment. Viral loads were ≥1×10^8 copies/ml in the patients who died. The concentrations of G-CSF, IFN-α, IFN-γ, IL-1β, IL-6, IL-10, MCP-1, and IP-10 were higher in patients with high viral loads. The levels of IFN-α, IFN-γ, IL-6, MCP-1, and IP-10 positively correlated with SFTSV viral load. Conclusion SFTSV RNA load was significantly correlated with the concentration of IFN-α, as well as other cytokines (IFN-γ, IL-6, MIP-1α, and IP-10).