Elevated CD4 CD8 double-negative T cells in the peripheral blood of SFTS patients are associated with disease severity.

Background: Severe fever with thrombocytopenia syndrome (SFTS), caused by the Dabie bandavirus, is a fatal infectious disease with no specific vaccines or antiviral treatments. Early diagnosis and severity assessment are critical for clinical management.

Methods: This study analyzed peripheral blood samples from 81 SFTS patients and healthy controls, focusing on the distribution of CD4, CD8, CD4CD8 double-positive T (DPT) cells, and CD4CD8 double-negative T (DNT) cells. The relationship between T cell subsets, clinical parameters, viral load, and cytokine levels was examined for diagnostic and prognostic potential.

Results: DPT cells were lower and DNT cells higher in SFTS patients compared to controls. DNT cell proportions were higher in severe and fatal cases, correlating positively with viral load, APTT, TT, D-dimer, ferritin, and LDH, and negatively with platelet count, HDL, and fibrinogen. DNT cells were also positively correlated with IFN-α and IFN-γ levels, and higher in patients with complications like shock and sepsis. Furthermore, Cox regression analysis revealed that an elevated DNT cell proportion was an independent risk factor for poor prognosis in SFTS patients.

Conclusion: DNT cell proportion changes are linked to SFTS severity and prognosis, suggesting DNT cells as potential biomarkers for early diagnosis and prognosis assessment.