Extracellular Vesicle Release from Immune Cells in Cutaneous Leishmaniasis: Modulation by Leishmania (V.) braziliensis and Reversal by Antimonial Therapy

Human cutaneous leishmaniasis (CL) caused by <i>Leishmania (Viannia) braziliensis</i> is a complex parasitic disease marked by dynamic host-parasite interactions and immunomodulation. Extracellular vesicles (EV) derived from immune cells have emerged as key mediators of intercellular communication and potential biomarkers in infectious diseases. In this study, we combined a modified lymphocyte proliferation assay with nano-flow cytometry to quantify and phenotype EV released by CD4⁺, CD8⁺, and CD14⁺ cells in PBMC cultures from CL patients at different clinical stages: before treatment (PBT), during treatment (PDT), and post-treatment (PET) with antimonial. Healthy individuals (HI) were included as physiological controls. Upon stimulation with <i>L. (V.) braziliensis</i> antigens, we observed a distinct modulation of EV subsets. In the PBT group, CD4⁺ and CD14⁺ EV were significantly reduced, while CD8⁺ EV remained elevated. During PDT and PET, EV concentrations were restored across all subsets. These findings suggest that <i>L. (V.) brazilie</i>nsis selectively modulates the release of immune cell-derived EV, possibly as an immune evasion mechanism. The restoration of EV release following antimonial therapy highlights their potential as sensitive biomarkers for disease activity and treatment monitoring. This study offers novel insights into the immunoregulatory roles of EV in CL and underscores their relevance in host-parasite interactions.