Frequency and Species Distribution of Gliotoxin-Producing Aspergillus Isolates Recovered from Patients at a Tertiary-Care Cancer Center

Abstract

Aspergillus isolates (n ‫؍‬ 103) collected from cancer patients were screened to determine the taxonomic distribution and quantity of gliotoxin production. Gliotoxin was detected in 93% of Aspergillus fumigatus, 75% of A. niger, 25% of A. terreus, and 4% of A. flavus cultures. Gliotoxin concentrations were highest in cultures of A. fumigatus.Aspergillus fumigatus produces several secondary metabolites during invasive hyphal growth (4, 12). One of the most abundantly produced metabolites is the epipolythiodioxopiperazine metabolite gliotoxin, which exhibits a diverse array of biologic effects on the immune system. Gliotoxin inhibits macrophage and polymorphonuclear cell function and the generation of alloreactive cytotoxic T cells (2,3,7,13,14) and suppresses activation of the nuclear transcription factor NFB-the central regulator of gene transcription for inflammatory cytokines, growth factor receptors, and cell adhesion molecules (9). In immunocompetent mice, the administration of gliotoxin results in a level of immunosuppression sufficient to render animals susceptible to fatal invasive aspergillosis after challenge with A. fumigatus conidia (11). These immunosuppressive properties, in conjunction with the release of the mycotoxin by the invasive hyphal form, suggest that gliotoxin production in situ could aid the evasion of fungal hyphae from professional effector cells of the host immune response and contribute to the pathobiology of invasive aspergillosis (12).Little is known about the biosynthesis or primary role of gliotoxin production in Aspergillus species. Interestingly, not all Aspergillus species appear to be capable of producing gliotoxin (3). Horizontal transmission of gene clusters involved in epipolythiodioxopiperazine synthesis has been proposed as a possible reason for the discontinuous evolution of mycotoxin production in fungi (3). Clearly, the ability to produce immunosuppressive secondary metabolites could have advantages for the growth and persistence of a saprophytic mold in humans. However, no published studies have examined the frequency and distribution of gliotoxin production among Aspergillus isolates recovered from patients at risk for invasive aspergillosis. To this end, we screened 103 consecutive Aspergillus isolates from cancer patients for the production of gliotoxin.( Collection of clinical isolates and of corresponding patient data from electronic medical records was carried out in accordance with institution standards and with the approval of the internal review committees. Consecutive Aspergillus isolates (n ϭ 103) recovered from respiratory and tissue specimens from 1998 to 2003 at The University of Texas M. D. Anderson Cancer Center Clinical Microbiology Laboratory were collected and stored using routine microbiological methods. All isolates were subcultured twice on potato dextrose agar slants (Remel, Lenexa, KS) and incubated at 37°C for 5 days. Conidia were then harvested from slants by flooding agar with 0.85% NaCl/0.2% Tween 80 and filtering the suspension through st...

Galleria mellonellaas a host model to studyAspergillus terreusvirulence and amphotericin B resistance

“…32,33 The production of gliotoxin and fumagillin was also proved in infected G. mellonella larvae. 31,34 A study by Lewis et al 35 detected gliotoxin in culture medium of A. terreus, but as we did not test gliotoxin production, or any other secondary metabolites, of the 5 different isolates we can only speculate its contribution to differences in virulence potential. The same effect may account for the variable production of proteases by the ATR and ATS strains.…”

Gliotoxin Is a Virulence Factor of Aspergillus fumigatus : gliP Deletion Attenuates Virulence in Mice Immunosuppressed with Hydrocortisone

“…Of about 20 species of Aspergillus reported to cause IA, Aspergillus fumigatus is the most frequently isolated species regardless of the underlying risk factors (6,15). A. fumigatus produces a variety of secondary metabolites, including gliotoxin (13), and this mycotoxin has received considerable attention for over 2 decades as a putative virulence factor based on the following observations: (i) up to 93% of A. fumigatus strains recovered from cancer patients with IA produced gliotoxin (17) compared to less than 20% of the environmental isolates (8); (ii) A. fumigatus is the most prolific producer of gliotoxin among the pathogenic Aspergillus species tested (17); (iii) gliotoxin is immunosuppressive and proapoptotic for mammalian cells (9, 19-21, 30, 39); (iv) gliotoxin inhibits the NADPH oxidase activity responsible for the neutrophil oxidative burst (38); (v) circulating gliotoxin is readily detected in experimental aspergillosis and in sera from patients with IA, while it is only occasionally detected in patients without any evidence of IA (16); (vi) mice infected with a nongliotoxin-producing strain survived longer than those infected with a genetically unrelated gliotoxin producer (36).…”

Impact of Enzymes and Toxins Potentiality of Four Aspergillus Species to Cause Aspergillosis

“…Gliotoxin is a potent immunosuppressive mycotoxin and belongs to the epipolythiodioxopiperazine family with an active disulfide bridge in its structure. Gliotoxin is abundantly produced by A. fumigatus and is the only toxin isolated in vivo from invasive aspergillosis [65,66]. In the in vitro assays, gliotoxin inhibits phagocotosis by thymocytes, macrophages, induction of cytotoxic T cells, and stimulation of lymphocytes with mitogen.…”

“…It has been detected in tissue samples from animals and humans, where it may facilitate fungal persistence and colonization of tissue. In addition, gliotoxin has been implicated in the destruction of lung parenchyma in invasive aspergillosis and the penetration of blood vessels in angioinvasive aspergillosis [65]. Gliotoxin is a potent immunosuppressive mycotoxin and belongs to the epipolythiodioxopiperazine family with an active disulfide bridge in its structure.…”