Partial characterization of a rapidly released antigenic/allergenic component (Ag 5) of Aspergillus fumigatus

An antigenic component of Aspergillus fumigatus, which was responsible for inducing an initial early antibody response in rabbits immunized with A. fumigatus germlings, has been identified and partially characterized. By immunofluorescent antibody and ELISA techniques, this antigen was demonstrated to be present on the germling surface, although it was also detected in supernatants of conidia/germlings within 1 hour and was present in all shake and stationary culture-filtrate extracts. By incorporation of a monospecific antiserum to this component in an intermediate gel of the reference self-crossed radioimmunoelectrophoresis pattern for allergic bronchopulmonary aspergillosis sera, it was recognized as Ag 5 and was also demonstrated to bind specific IgE. Further immunochemical analyses have revealed that Ag 5 is relatively heat labile, does not bind to concanavalin A, and has a molecular weight of approximately 35 kd. This rapidly released antigenic/allergenic component may play an important role in the initiation of immunologic responses in patients with allergic bronchopulmonary aspergillosis.