Aspergillosis is increasing in frequency, as is the immunocompromised patient population most susceptible to the infection. Invasive pulmonary aspergillosis is initiated by inhaling the air-borne conidia of the ubiquitous Aspergillus species. The histopathology of the lesion has been well described: following germination, the hyphae elongate and spread rapidly, penetrating vessels and bronchi in their path. The phagocytic cell defects required to establish experimental aspergillosis in mice have been carefully documented and are presumed to be analogous to the situation in man. However, little is known about virulence mechanisms used by the fungi. The report that elastase production by A. fumigatus is correlated with virulence in mice is supported by our data on elastase production in clinical isolates of Aspergillus. Indeed, these data stimulated preliminary investigation of the A. flavus elastinolytic proteinase. The conditions of production and a preliminary isolation protocol have been devised. The active peak, following ion-exchange on carboxymethyl cellulose, gel filtration chromatography, and adsorption (hydroxyapatite) chromatography, is homogeneous on SDS-PAGE (MW 27 kD). Initial experiments to elucidate the class of proteinase the Aspergillus elastase represents suggest that it is a cysteine proteinase. From this background and preliminary data, the following aims are proposed: (1) to isolate and to characterize both physically and biochemically the elastase of A. flavus, (2) to establish the role of elastase in the pathogenesis of invasive aspergillosis in mice by studying the enzyme's effect on virulence in an isogenic set (wild type, deficient mutant, wild type revertant), (3) to produce mouse monoclonal antibodies to Aspergillus elastase which inhibit its activity in vitro and are suitable for immunohistology, and to evaluate in the murine model the therapeutic efficacy of inhibiting the enzyme in vivo with the antibodies and non-antibody inhibitors, and (4) to compare the physicochemical profiles of the A. flavus and A. fumigatus elastases to identify common susceptibilities to inhibitors. From these studies, a better understanding of a virulence mechanism used by the opportunistic fungus Aspergillus in the pathogenesis of an important clinical problem, invasive aspergillosis, will emerge.
| Rhodes, J C; Amlung, T W (1991) The elastinolytic proteinase of Aspergillus flavus is not glycosylated. J Med Vet Mycol 29:407-11 |
| Eisenstein, D J; Biddinger, P W; Rhodes, J C (1990) Experimental murine invasive pulmonary aspergillosis. Am J Clin Pathol 93:510-5 |
| Rhodes, J C; Amlung, T W; Miller, M S (1990) Isolation and characterization of an elastinolytic proteinase from Aspergillus flavus. Infect Immun 58:2529-34 |
| Rhodes, J C (1988) Virulence factors in fungal pathogens. Microbiol Sci 5:252-4 |
