The clinical significance of myeloid-derived suppressor cells in dengue fever patients

Background Myeloid-derived suppressor cells (MDSCs) play immunosuppressive roles in cancers and some infectious diseases; however, their role in dengue fever (DF) remains unknown. This study evaluated the clinical significance of MDSCs in DF patients. Methods This study comprised 178 non-severe DF patients, 20 non-dengue fever (NDF) controls, and 30 healthy donors. The DF patients were divided into the following five groups based on the fever duration from its onset to the day of sample collection: fever duration of 1-2, 3-4, 5-6, 7-8, and > 9 days. Among these DF patients, 14 were monitored for eight days, and their peripheral blood samples were collected every two days. The mononuclear cells were isolated and analyzed using flow cytometry. The correlation between the MDSCs and clinical and immunological indicators of the DF patients was evaluated using Spearman analysis. Results The count of the peripheral blood MDSCs, especially monocytic MDSCs, of the 178 DF patients were dramatically higher than those of the NDF and healthy controls, and remarkably decreased with the fever duration. Moreover, the MDSC count correlated with some indicators, including the dengue viral load (rho = 0.367, p < .001), body temperature (rho = 0.263, p = .005), prothrombin time (rho = 0.475, p < .001), CD4(+) T cell number (rho = - 0.317, p < .001), CD8(+) T cell number (rho = - 0.361, p < .001), "programmed cell death protein 1" (PD-1) (rho = - 0.347, p < .001), "T cell immunoglobulin domain and mucin domain-3" (Tim3) (rho = - 0.258, p = .001), interferon-alpha (IFN-alpha) (rho = 0.43, p < .001), and "regulated upon activation normal T-cell expressed and secreted" (RANTES) (rho = 0.278, p = .019). Furthermore, the level of arginase-1, but not nitric oxide, was higher in the DF patients than in the healthy controls and was closely related to the number of MDSCs (rho = 0.265, p = .024). Conclusions Our study reveals a significant correlation between MDSCs and DF clinical indicators, posing MDSCs as potential target cells for DF treatment.