IMMUNOLOGICAL SIGNIFICANCE OF A COLLAGEN-DERIVED CULTURE FILTRATE CONTAINING PROTEOLYTIC ACTIVITY IN ASPERGILLUS-RELATED DISEASES

Background: Despite increasing evidence implicating fungal proteases i n the virulence of pulmonary fungal diseases, routine fungal culture m edia do not favor protease production. Hence, filtrates that serve as the source of antigen for serologic determinations are poor in proteas es, and consequently the immunologic significance of these enzymes is unknown. Methods: A clinical isolate of Aspergillus fumigatus was cult ured on collagen medium, resulting in excretion of high levels of fung al proteases in the culture filtrate. This was compared with standard culture filtrates by diverse analytic techniques including immunoblott ing with sera of patients with pulmonary aspergilloma (PA) and allergi c bronchopulmonary aspergillosis (ABPA). Results: Protein profiles of collagen medium filtrate showed several (glyco)proteins not found in c onventional culture filtrates, including a prominent 32 kd glycoprotei n, which coisolated in gel filtration and ion-exchange chromatography with elastase activity, as well as 67 kd and 94 kd (glyco)proteins. In tense IgG binding was seen with the 32 kd glycoprotein when ABPA and P A sera were used. The 94 kd protein showed intense binding with PA ser a but not with ABPA sera, whereas for the 67 kd glycoprotein the rever se tended to be the case. Conclusion: Fungal culture on collagen media results in the production of filtrates with high pretense activity, c ontaining unique (glyco)proteins of which at least one (32 kd) is clos ely associated with fungal elastase activity. These constituents are i mmunologically relevant, eliciting IgG production in patients with PA and ABPA, suggesting production of these (glyco)proteins during diseas e in vivo. The use of collagen media filtrates may enhance our serodia gnostic capacity in patients with fungal pulmonary diseases.