Extracellular vesicles recovered from plasma of severe dengue patients induce CD4+T cell suppression through PD-L1/PD-1 interaction

Extracellular vesicles (EVs) are small membrane vesicles secreted into biological fluids, which play crucial roles in influencing the cellular function in different pathological processes. However, there is less clarity on how plasma EVs influence proliferation activation and functions of immune cells during dengue virus (DV) infection. In this study, we aimed to characterize circulating EVs from different categories of dengue patients and examined the consequence of naive CD4+ T cells to EVs isolated from the plasma of mild or severe dengue patients. We observed that severe dengue infection was associated with an increased release of CD41a+ platelet extracellular vesicles compared with that from patients with mild disease or healthy donors. These EVs carried an increased level of pro- and anti-inflammatory cytokines along with immunoregulatory proteins on the surface that caused CD4+ T cell suppression. Treatment of purified naive CD4+ T cells with EVs derived from severe dengue plasma drove CD4+ proliferation toward specific subtypes and modulated surface receptor CXCR3 and CCR6 expression. Subsequent studies indicated a notable rise in programmed cell death ligand 1 (PD-L1) expression within CD41a+ severe DV (SDV) EVs. Additionally, CD4+ T cells showed an elevated increase in programmed cell death 1 (PD-1) after incubating with SDV-EVs. We also demonstrated that blocking PD-L1 on SDV-EVs or PD-1 on late-activating CD4+ T cells partially reversed the SDV-EV-induced suppression of CD4+ T cell proliferation. Overall, our study highlights the immunosuppressive property of EVs derived from plasma of severe dengue patients, which might contribute to immune pathogenesis by shaping the immune response.IMPORTANCESevere dengue manifestations caused by the dengue virus are a global health problem. Studies suggest that severe dengue disease depends on uncontrolled immune cell activation, and excessive inflammation adds to the pathogenesis of severe dengue disease. Therefore, it is important to understand the process that triggers the uncontrolled activation of the immune cells. The change in immune response in mild to severe dengue may be due to direct virus-to-cell interaction or it could be a contact-independent process through the extracellular vesicles (EVs) released from infected cells. The importance of circulating EVs in the context of dengue virus infection and pathogenesis remains unexplored. Therefore, understanding the possible biological function of circulating EVs may help to delineate the role of EVs in the progression of disease. Our present study highlights that EVs from plasma of severe dengue patients can have immunosuppressive properties on CD4+ T cells which may contribute to T cell suppression and may contribute to dengue disease progression. Severe dengue manifestations caused by the dengue virus are a global health problem. Studies suggest that severe dengue disease depends on uncontrolled immune cell activation, and excessive inflammation adds to the pathogenesis of severe dengue disease. Therefore, it is important to understand the process that triggers the uncontrolled activation of the immune cells. The change in immune response in mild to severe dengue may be due to direct virus-to-cell interaction or it could be a contact-independent process through the extracellular vesicles (EVs) released from infected cells. The importance of circulating EVs in the context of dengue virus infection and pathogenesis remains unexplored. Therefore, understanding the possible biological function of circulating EVs may help to delineate the role of EVs in the progression of disease. Our present study highlights that EVs from plasma of severe dengue patients can have immunosuppressive properties on CD4+ T cells which may contribute to T cell suppression and may contribute to dengue disease progression.