Human Phagocytic Cell Responses to Scedosporium apiospermum (Pseudallescheria boydii): Variable Susceptibility to Oxidative Injury

Cristina Gil-Lamaignere, Emmanuel Roilides, Caron A. Lyman, Maria Simitsopoulou, Theodouli Stergiopoulou, Avgi Maloukou, Thomas J. Walsh

Research output: Contribution to journalArticlepeer-review


Scedosporium apiospermum (Pseudallescheria boydii) is an emerging opportunistic filamentous fungus that causes serious infections in both immunocompetent and immunocompromised patients. To gain insight into the immunopathogenesis of infections due to S. apiospermum, the antifungal activities of human polymorphonuclear leukocytes (PMNs), mononuclear leukocytes (MNCs), and monocyte-derived macrophages (MDMs) against two clinical isolates of S. apiospermum were evaluated. Isolate SA54A was amphotericin B resistant and was the cause of a fatal disseminated infection. Isolate SA1216 (cultured from a successfully treated localized subcutaneous infection) was susceptible to amphotericin B. MDMs exhibited similar phagocytic activities against conidia of both isolates. However, PMNs and MNCs responded differently to the hyphae of these two isolates. Serum opsonization of hyphae resulted in a higher level of superoxide anion (O2-) release by PMNs in response to SA54A (amphotericin B resistant) than that seen in response to SA1216 (amphotericin B susceptible; P < 0.001). Despite this increased O 2- production, PMNs and MNCs induced less hyphal damage to SA54A than to SA1216 (P < 0.001). To investigate the potential mechanisms responsible for these differences, hyphal damage was evaluated in the presence of antifungal oxidative metabolites as well as in the presence of a series of inhibitors and scavengers of antifungal PMN function. Mannose, catalase, superoxide dismutase, dimethyl sulfoxide, and heparin had no effect on PMN-induced hyphal damage to either of the two isolates. However, azide, which inhibits PMN myeloperoxidase activity, significantly reduced hyphal damage to SA1216 (P < 0.01) but not to SA54A. Hyphae of SA1216 were slightly more susceptible to oxidative pathway products, particularly HOCI, than those of SA54A. Thus, S. apiospermum is susceptible to antifungal phagocytic function to various degrees. The selective inhibitory pattern of azide with respect to hyphal damage and the parallel susceptibility to HOCI suggests an important difference in susceptibilities to myeloperoxidase products that may be related to the various levels of pathogenicity and amphotericin B resistance of S. apiospermum.

Original languageEnglish (US)
Pages (from-to)6472-6478
Number of pages7
JournalInfection and immunity
Issue number11
StatePublished - Nov 2003
Externally publishedYes

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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