Extracellular Vesicles from the Probiotic Yeast Pichia kudriavzevii: Proteomic Characterization and Modulation of Immune and Defense Responses in an Induced Inflammation Model of Intestinal Epithelial Cells

<b>Background/Objectives</b>: Extracellular vesicles (EVs) derived from probiotics represent a new and exciting frontier in host-microbe therapeutics. These nanoscale carriers are not merely cellular byproducts but are sophisticated mediators of intercellular communication, capable of modulating immune responses, reducing inflammation, and inhibiting pathogens through a rich cargo of bioactive molecules. <b>Methods</b>: The EVs isolated from the culture supernatants of the yeast probiotic candidate <i>Pichia kudriavzevii</i> were characterized for their dimensions, protein composition, and targeting both the gut pathogen virulence and the host inflammatory response. <b>Results:</b> The vesicles had a size distribution from 100 to 150 nm, which is consistent with previous reports on fungal EVs. Proteomic analysis of the purified EVs identified a complex array of 189 proteins, hypothesized to be responsible for some of the antimicrobial and immunomodulatory properties observed. Safety was a key consideration, and the isolated EVs demonstrated no cytotoxicity in human Caco-2 cells and no in vivo toxicity in the <i>Galleria mellonella</i> larval model, confirming their potential for safe use. <b>Conclusions</b>: The field is moving towards a new era of "postbiotics," where cell-free therapies offer a safer, more stable alternative to live probiotics.