Polymorphonuclear granulocytes (PMNs) are indispensable for controlling life-threatening
fungal infections. In addition to various effector mechanisms, PMNs also produce extracellular
vesicles (EVs). Their contribution to antifungal defense has remained unexplored.
We reveal that the clinically important human-pathogenic fungus Aspergillus fumigatus
triggers PMNs to release a distinct set of antifungal EVs (afEVs). Proteome analyses
indicated that afEVs are enriched in antimicrobial proteins. The cargo and the release
kinetics of EVs are modulated by the fungal strain confronted. Tracking of afEVs indicated
that they associated with fungal cells and even entered fungal hyphae, resulting in
alterations in the morphology of the fungal cell wall and dose-dependent antifungal
effects. To assess as a proof of concept whether the antimicrobial proteins found
in afEVs might contribute to growth inhibition of hyphae when present in the fungal
cytoplasm, two human proteins enriched in afEVs, cathepsin G and azurocidin, were
heterologously expressed in fungal hyphae. This led to reduced fungal growth relative
to that of a control strain producing the human retinol binding protein 7. In conclusion,
extracellular vesicles produced by neutrophils in response to A. fumigatus infection
are able to associate with the fungus, limit growth, and elicit cell damage by delivering
antifungal cargo. This finding offers an intriguing, previously overlooked mechanism
of antifungal defense against A. fumigatusIMPORTANCE Invasive fungal infections caused
by the mold Aspergillus fumigatus are a growing concern in the clinic due to the increasing
use of immunosuppressive therapies and increasing antifungal drug resistance. These
infections result in high rates of mortality, as treatment and diagnostic options
remain limited. In healthy individuals, neutrophilic granulocytes are critical for
elimination of A. fumigatus from the host; however, the exact extracellular mechanism
of neutrophil-mediated antifungal activity remains unresolved. Here, we present a
mode of antifungal defense employed by human neutrophils against A. fumigatus not
previously described. We found that extracellular vesicles produced by neutrophils
in response to A. fumigatus infection are able to associate with the fungus, limit
growth, and elicit cell damage by delivering antifungal cargo. In the end, antifungal
extracellular vesicle biology provides a significant step forward in our understanding
of A. fumigatus host pathogenesis and opens up novel diagnostic and therapeutic possibilities.
