Biotinylated surfome profiling of A. fumigatus during early development

Aspergillus fumigatus is one of the most common airborne fungi that cause invasive mycoses in immunocompromised patients and also allergic diseases in immunocompetent individuals. In both cases, the surface proteins mediate the first contact with the human immune system to evade immune responses or to induce hypersensitivity. The peptides exposed on the surface may be reasonable immunotherapy targets or may be used for diagnostic purposes. Several methods have been established to study the surface proteome (surfome) of A. fumigatus, like trypsin shaving, glucanase treatment, or formic acid extraction. Biotinylation coupled with LC-MS/MS identification of peptides is a particularly efficient method to identify the surface exposed regions of proteins that could mediate interaction with the host. After biotinylation of surface proteins during the germination process, we detected 314 surface proteins, including several well-known surface proteins (like RodA, CcpA, and DppV), allergens, heat shock proteins (Hsp), as well as some previously uncharacterized surface proteins. Using immunofluorescence microscopy, we confirmed the surface localization of several chaperone proteins. Collectively, our study generated a comprehensive data set of the A. fumigatus surfome. In addition, for many proteins it uncovers the regions that are exposed on the surface of spores or hyphae. These surface exposed regions could directly interact with host cells and may represent antigenic epitopes that induce protective immune responses.