Harnessing Chlorella vulgaris-derived extracellular vesicles for potentiated cancer immunotherapy

Plant-derived extracellular vesicles (EVs) have emerged as promising drug delivery vehicle due to their inherent biocompatibility, high stability and large-scale production. Chlorella vulgaris (C. vulgaris) has been increasing application in the food industry and biomedical fields. Nevertheless, the biogenesis and immunomodulatory functions of EVs from Chlorella species remain poorly understood. Herein, we found that the EVs in C. vulgaris originated from "vacuolar structures", a process analogous to the biogenesis of exosomes which originates from endosomes in mammalian cells. Therefore, we further isolated and characterized EVs secreted by Chlorella vulgaris (C.V-EVs). Afterwards, we investigated the regulatory effects of C.V-EVs on immune cells, with a particular emphasis on their capacity to promote dendritic cell (DC) maturation, enhance antigen presentation, and improve T-cell priming efficiency. Furthermore, we developed C.V-EVs as multifunctional biomimetic nanocarriers for co-delivering gemcitabine (Gem) and a programmed cell death-1/ligand-1 checkpoint inhibitor (PD-1/PD-L1 checkpoint inhibitor, PD-1/L1i), and conjugated these drug-loaded C.V-EVs with platelet (Platelet-C.V-EVs-Gem&PD-1/L1i) to enhance tumor-targeted delivery. Simultaneously, the release of PD-1/L1i could block the PD-1/PD-L1 signaling axis, reinvigorating tumor specific-T cell activity, to trigger robust antitumor immune responses. In addition, C. vulgaris could generate oxygen in situ to alleviate hypoxia in the tumor microenvironment, synergistically with preloaded C. V-EVs to promote the infiltration and activation of immune cells to prevent the tumor relapse and metastasis.