Surface hydrophobin prevents immune recognition of airborne fungal spores

Aimanianda V. et al. Nature. 460: 1117-21. (2009).

Speaker: I-ping Lin (林宜平)                                                Time: 13:10~14:00, Mar. 17, 2010

Commentator: Dr. Chi-Chang Shieh (謝奇璋醫師)             Place: Room 601

Abstract:

Thousands of fungal spores are spread in air. Aspergillus species is one of the mainly airborne spores [1]. In Aspergillus genera, A. fumigatus is the major human fungal pathogens that caused invasive aspergillosis in immunocompromised patients. In previous study, different species of airborne fungal conidia, including A. fumigates, contains vary of antigens and allergen that can elicit strong immune response [2]. But the reason why most people can normally breathe with no inflammatory response in airway even inhale these fungal spores is still unknown. RodA is a glycosylphosphatidylinositol-anchored hydrophobic protein that makes the rodlet layer outside the cell wall of A. fumigatus conidia [3]. The authors discovered that RodA proteins cannot induce human dendritic cell activation, including cell surface markers expression and cytokines production, even in high concentration. Dormant conidia, which contain RodA in rodlet layer, cannot activate human dendritic cells, too. As compared to wild type dormant conidia, DrodA conidia, hydrofluoric acid treated conidia and germinating conidia induce both human and murine antigen-presenting cells activation. Intranasally inoculation mice with DrodA conidia or germinating conidia elicit inflammatory cytokines production and neutrophils infiltration in lung, compared with wild type dormant conidia. In addition, adoptive transfer RodA-pulsed dendritic cells in mice with aspergillosis cannot decrease fugal growth and induce protective immune response as germinating conidia-pulsed dendritic cells. In summaries, RodA hydrophobin masks and lets fungal spores cannot be recognized by human immune systems, so that we can safely breathe without any improper immune response.

Reference:

1. Codina R. et al. A. Typical levels of airborne fungal spores in houses without obvious moisture problems during a rainy season in Florida, USA. J. Investig. Allergol. Clin. Immunol. 18: 156–62. (2008).

2. Glaser A. G. et al. Molecular and immunological characterization of Asp f 34, a novel major cell wall allergen of Aspergillus fumigatus. Allergy. 64: 1144–51. (2009).

3. Latge J. P. The cell wall: a carbohydrate armour for the fungal cell. Mol. Microbiol. 66: 279–90. (2007).