Abstract
AbstractPneumocystisspp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainablein vitroculture system poses challenges in understanding their metabolism and the acquisition of essential nutrients from host lungs remains unexplored.Transmission electron micrographs show Extracellular Vesicles (EVs) are found nearPneumocystisspp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs fromP. cariniiandP. murinainfected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicatingPneumocystismay release EVs. Notably, EV uptake byP. cariniiindicated their potential involvement in nutrient acquisition and indicate a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added toP. carinii in vitro, did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels, but did not affect macrophages’ ability to kill or phagocytoseP. carinii. These findings provide vital insights intoP. cariniiand host EV interactions, yet the mechanisms underlyingP. carinii’s survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs fromPneumocystis-infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.
Publisher
Cold Spring Harbor Laboratory