Platelet immune modulation under DENV-2 and NS1 stimulation: a focus on antigen presentation markers

Dengue represents the most prevalent human arboviral disease worldwide, with endemic transmission in tropical and subtropical regions. Platelets, beyond their established role in hemostasis and coagulation, are increasingly recognized as important modulators of the immune response. Platelets contribute to pathogen recognition and response, including dengue virus (DENV) and its non-structural protein 1 (NS1). However, platelet responses regarding the expression of costimulatory and coinhibitory molecules following NS1 stimulation or DENV infection remain to be elucidated. This study aimed to evaluate the expression of platelet markers associated with antigen presentation, including human leukocyte antigen class I (HLA-I), the costimulatory molecules CD80, CD86, and CD40, and the coinhibitory molecule CD274 (PD-L1), after stimulation with free or liposome-encapsulated DENV NS1, or DENV infection. Platelets isolated from healthy volunteers (IRB: 85978925.4.1001.5147) were used to evaluate antigen presentation-related responses following DENV-2 infection (strain 2861 D7K; multiplicity of infection = 1) for 3, 6, and 24 hours, as well as upon stimulation with free or liposome-encapsulated NS1 (0.5, 5, or 50 μg/mL) for 1.5, 3, or 6 hours. Subsequently, the expression of platelet markers was evaluated by flow cytometry. DENV-2 infection induced platelet activation, but not HLA-I expression, while inducing increased expression of the costimulatory molecule CD80 in an endosomal TLR-independent manner. Increased platelet activation, HLA-I, and CD80 expression were also induced by free NS1, but not by encapsulated NS1. Encapsulating NS1 resulted in decreased platelet activation, as well as reduced PD-L1 and CD80 expression. Together, these data indicate that DENV and its NS1 modulates HLA-I and co-stimulatory molecules especially through surface signaling, and suggest that platelets may contribute to antigen presentation-related immune responses during dengue infection.