Extracellular vesicles promote transkingdom nutrient transfer during viral-bacterial co-infection.

Extracellular vesicles (EVs) are increasingly appreciated as a mechanism of communication among cells that contribute to many physiological processes. Although EVs can promote either antiviral or proviral effects during viral infections, the role of EVs in virus-associated polymicrobial infections remains poorly defined. We report that EVs secreted from airway epithelial cells during respiratory viral infection promote secondary bacterial growth, including biofilm biogenesis, by Pseudomonas aeruginosa. Respiratory syncytial virus (RSV) increases the release of the host iron-binding protein transferrin on the extravesicular face of EVs, which interact with P. aeruginosa biofilms to transfer the nutrient iron and promote bacterial biofilm growth. Vesicular delivery of iron by transferrin more efficiently promotes P. aeruginosa biofilm growth than soluble holo-transferrin delivered alone. Our findings indicate that EVs are a nutrient source for secondary bacterial infections in the airways during viral infection and offer evidence of transkingdom communication in the setting of polymicrobial infections.