Monday, 30 July 2012

Chronic Granulomatous Disorder and Aspergillus nidulans - the Odd Couple

A granuloma as seen using a microscope -
darker dots are the nuclei of cells
Chronic Granulomatous Disorder (CGD) is an inherited disorder of the immune system effecting a specific part of the the immune system - rendering individuals that suffer from this unable to produce a group of chemicals (ie. reactive oxygen) that is used by our bodies to attack invading microrganisms such as Aspergillus. As a result infection tends to persist and form granulomas as other cells of the immune system accumulate around the infection in an attempt to prevent it spreading throughout the body.

Although they are mainly vulnerable to Aspergillus fumigatus, intruigingly CGD patients tend to be infected by another species - Aspergillus nidulans. This is unusual as A. nidulans is not a common pathogen elswhere - in fact it almost never infects people other than CGD patients. This is interesting from the point of view of why this happens and may tell us something about the importance of some parts of our bodies immune system in fighting off fungi, but more importantly A. nidulans tend to behave quite aggressively in these patients so needs to be identified and  treated promptly.

Diagnosing aspergillosis can be a slow process as our current tests are quite time consuming, and identifying  which Aspergillus species is infecting is also slow. We desperately need to develop new, faster tests so that we can start treatment as early as possible.

Just as importantly we need to study the interaction between A. nidulans and CGD patients as our current understanding is clearly not complete as we cannot explain why A.nidulans can attack these individuals, so consequently we do no fully understand how our immune systems currently prevent infection by Aspergillus. A better understanding is vital to help us fight infecton. This recent review is aimed at summarising the current evidence and infection model theories in the hope of improving future research in this area.

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