Abstract: The invention generally provides methods of treating or preventing aspergillosis disease and/or its symptoms associated with infection by the Aspergillus pathogenic fungus. The methods involve administering an Aspergillus Kexin peptide, or a composition comprising an Aspergillus peptide, to a mammalian subject in need thereof, such as a subject afflicted with aspergillus, or a subject susceptible to or at risk of infection by Aspergillus and ensuing aspergillosis disease. In some aspects, the Aspergillus Kexin peptide is an A. fumigatus Kexin peptide. In some aspects, the mammalian subject is a human patient. In some aspects, the patient is immunosuppressed or immunocompromised. The Aspergillus Kexin peptide as immunogen or vaccine generates a potent and robust immune response, e.g., antibody response, in the immunized subject. The methods afford therapeutic and protective treatment against aspergillosis and its symptoms, as well as a reduction in the severity of aspergillosis in the treated subjects.