Monday, 7 September 2009

Clever cloak prevents immune recognition of airborne fungal spores


Recent scientific work published in Nature in August, has illuminated the means by which inhaled spores of aspergillus avoid recognition by the immune system. The air we breathe is loaded with many types of fungal spores but it is not known why inhaling these spores does not continuously activate the host's immune system and promote a detrimental immune inflammation. So the spores (or conidia) must have a means of evading the immune system.

The spore surface of many fungi is covered with a layer of regularly arranged fibres known as the rodlet layer - in Aspergillus species this layer is responsible for a high level of hydrophobicity - composed of the hydrophobic RodA protein covalently bound to the conidial cell wall.
In laboratory studies, RodA when extracted from aspergillus conidia, did not induce activation of immune cells in vivo - it appears to be immunologically inactive. However when the rodlet layer was removed either chemically or genetically using a mutant strain - the modified conidia stimulated immune responses. All the scientist's observations indicate that the rodlet layer on the conidial surface acts as an invisibility cloak - so far as the human immune system is concerned.

Interestingly during germination of conidia, the RodA protein appears to be degraded, exposing the underlying immunogenic cell wall components usually masked by this rodlet layer. So germinating spores will evoke immune responses in an individual.

Aspergillus makes it to the movies

In the newly released Pedro Almodovar film "Broken Embraces" a young boy is treated in Madrid for aspergillosis. The film is an intense tale of passion and tragedy - a Spanish film with subtitles.

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