Friday, 12 August 2011

Yeast as a Universal Antifungal Vaccine?

We mentioned a few weeks ago that a research group in the US was working on a vaccine to help prevent aspergillosis. This is an alternative to attempts to identify and isolate specific antigens on the Aspergillus fungus which might form a viable basis for a vaccine that specifically prevents infection by Aspergillus. Developing specific vaccines is a long process and although they are very precise and well worth the time and effort it takes to make them there will be a long delay before they are available.

Liu et. al. set out to test which pieces of Aspergillus were most suitable to act as a vaccine by cloning them into yeast, but then realised that the yeast controls without any cloned Aspergillus were acting as a good vaccine!
To use killed yeast as a vaccine could be available relatively quickly as it is far simpler to achieve than a specific vaccine and already has a good safety record with regard to toxicity.

The researchers have shown that using yeast as a protective vaccine works well against aspergillosis in a mouse model system, so we must assume that a component of yeast is so similar to Aspergillus (both are of course fungi) that it stimulates our immune system in the same way as Aspergillus. Work so far indicates that the important components are cell wall components glucan and mannan.

Other fungi share these cell wall components so we seem to have the makings of a pan-fungal vaccine that would be useful for a wide variety of fungal infections.
What would normally happen now is that the component of the heat killed yeast that is active in providing a protective effect would be isolated and subcloned, but in this case the crude preparation is already known to be safe and lacks toxicity so the possibility remains that the crude preparation could be used as a rapidly available vaccine to provide protection against aspergillosis and a variety of other fungal infections - a remarkable discovery if hopes are borne out.

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