Sex-Specific Cytokine Profiles Associated with Viral Load and Disease Severity in Patients with Severe Fever with Thrombocytopenia Syndrome

Abstract

Background: Severe fever with thrombocytopenia syndrome (SFTS) is a severe tick-borne viral disease characterized by dysregulated host immune responses. Although previous studies have suggested sex-related differences in immune responses in SFTS, the sex-specific magnitude of cytokine changes and their relationships with viral load and laboratory parameters have not been fully characterized. Methods: We investigated sex differences in cytokine profiles and their associations with viral load and disease severity in 100 confirmed SFTS patients and 60 healthy controls. Nineteen cytokines, viral load, and clinical and laboratory parameters were assessed in acute-phase sera. Correlation analyses were performed to assess the relationships of cytokine changes with viral load and clinical parameters. Multivariable regression analyses were used to evaluate the association between sex and cytokine changes after adjustment for potential confounders, and sex-stratified ROC analyses were conducted to assess the ability of cytokines to discriminate disease severity. Results: Cytokine levels were generally higher in SFTS patients than in controls and increased with disease severity. After normalization to sex-matched controls, females showed higher normalized cytokine ratios for CCL4, IL-17, IL-8, and FGF2, whereas males showed higher normalized ratios for IL-5 and PDGF-AB. Cytokine changes were associated with viral load in both sexes, but these associations did not differ significantly between males and females. After adjustment for potential confounders, FGF2 and IL-17 showed higher normalized cytokine ratios in females, whereas IL-5 and CXCL10 showed higher normalized ratios in males. Exploratory sex-stratified ROC analyses identified several cytokines with relatively high AUCs for discriminating concurrent mild and severe disease, including CXCL10 and CCL4. Conclusions: These findings provide preliminary indications of sex-related differences in cytokine responses during acute SFTS and suggest that the magnitude of cytokine changes may help better characterize sex-specific cytokine responses and their associations with disease severity.