Characterization of Scedosporium apiospermum glucosylceramides and their involvement in fungal development and macrophage functions

PLoS One. 2014 May 30;9(5):e98149. doi: 10.1371/journal.pone.0098149. eCollection 2014.

Abstract

Scedosporium apiospermum is an emerging fungal pathogen that causes both localized and disseminated infections in immunocompromised patients. Glucosylceramides (CMH, GlcCer) are the main neutral glycosphingolipids expressed in fungal cells. In this study, glucosylceramides (GlcCer) were extracted and purified in several chromatographic steps. Using high-performance thin layer chromatography (HPTLC) and electrospray ionization mass spectrometry (ESI-MS), N-2'-hydroxyhexadecanoyl-1-β-D-glucopyranosyl-9-methyl-4,8-sphingadienine was identified as the main GlcCer in S. apiospermum. A monoclonal antibody (Mab) against this molecule was used for indirect immunofluorescence experiments, which revealed that this CMH is present on the surface of the mycelial and conidial forms of S. apiospermum. Treatment of S. apiospermum conidia with the Mab significantly reduced fungal growth. In addition, the Mab also enhanced the phagocytosis and killing of S. apiospermum by murine cells. In vitro assays were performed to evaluate the CMHs for their cytotoxic activities against the mammalian cell lines L.929 and RAW, and an inhibitory effect on cell proliferation was observed. Synergistic in vitro interactions were observed between the Mab against GlcCer and both amphotericin B (AmB) and itraconazole. Because Scedosporium species develop drug resistance, the number of available antifungal drugs is limited; our data indicate that combining immunotherapy with the available drugs might be a viable treatment option. These results suggest that in S. apiospermum, GlcCer are most likely cell wall components that are targeted by antifungal antibodies, which directly inhibit fungal development and enhance macrophage function; furthermore, these results suggest the combined use of monoclonal antibodies against GlcCer and antifungal drugs for antifungal immunotherapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amphotericin B / pharmacology
  • Animals
  • Antibodies, Monoclonal / immunology
  • Cell Line
  • Culture Media, Conditioned / metabolism
  • Glucosylceramides / chemistry
  • Glucosylceramides / immunology
  • Glucosylceramides / metabolism*
  • Itraconazole / pharmacology
  • Macrophages / microbiology*
  • Male
  • Mice
  • Scedosporium / drug effects
  • Scedosporium / growth & development*
  • Scedosporium / metabolism*
  • Scedosporium / physiology

Substances

  • Antibodies, Monoclonal
  • Culture Media, Conditioned
  • Glucosylceramides
  • Itraconazole
  • Amphotericin B

Grants and funding

This work was supported by Grants from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Conselho de Pesquisa da UFRJ, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ and Programa de Núcleos de Excelência (PRONEX). LCLL and EBB are supported by CAPES/FAPERJ and CNPq. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.