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UBC Theses and Dissertations

Assessing exposure to Cryptococcus gattii Griffiths, Andrea


Cryptococcus gattii is an encapsulated basidomycetous yeast that is capable of causing cryptococcosis in humans and animals. The disease caused by C. gattii frequently begins with pneumonia which in some cases can disseminate into fatal form of meningitis. Traditionally, this organism was thought to occur globally in tropical and subtropical regions, however recently it has been isolated from the Coastal Douglas Fir Zone on Vancouver Island, British Columbia (BC), a coastal temperate zone. From 1999 to present, there have been more than 130 human cases of Cryptococcosis caused by C. gattii on Vancouver Island and numerous cases in companion animals and wildlife. The aim of this study was to develop an assay to identify biomarkers of exposure to C. gattii which could be used to determine the extent of exposure of residents of BC. A Western blot analysis was developed to identify cytoplasmic antigens isolated from C. gattii which are recognized by antibodies in test sera. The sera of 77 Vancouver Island residents were tested following the 1999 outbreak of C. gattii and greater than 80% of those tested (at a 1 in 250 dilution of serum) were found to have antibodies against cytoplasmic antigens unique to the organism. Conversely, at the same dilution only 25% of those tested (n=51) from other areas of BC, the Yukon and Northwest Territories prior to the 1999 outbreak had antibodies against C. gattii antigens. The most commonly recognized antigens were 20 kDa and 50 kDa in size and their identity is presently unknown. This Western blot analysis has proven to be a useful means of suggesting potential biomarkers of exposure to C. gattii in a population.

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