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Background and objectives: Protothecosis is a rare but severe disease of animals and humans caused by colourless microalgae of the genus Prototheca (P.). P. zopfii, the most common infective species exists as two genotypes (GT), the non-virulent GT1 and GT2 associated with infection. The objective was to create a genotype-specific reference proteome map and identify immunodominant proteins.
Materials and methods: Cells were cultured, harvested and proteins extracted and separated by two-dimensional electrophoresis (2DE). Mass-spectrometry based protein identification was achieved after determining differentially expressed proteins by fluorescence difference gel electrophoresis that matched with the signals of 2DEWestern blotting using sera from experimentally infected rabbits and naturally infected dogs.
Results: A 2DE reference map with 782 spots was established. 107 proteins were identified as differentially expressed (63 up-regulated in GT1 and 44 in GT2), pointing towards an adaptation for intracellular life style. Among the immunodominant proteins we found several (eg, glyceraldehyde-3-phopshate dehydrogenase) described earlier as antigens of eukaryotic pathogens when expressed on the cell surface.
Conclusion: Proteomic analysis indicated that Prototheca possesses infection mechanisms similar to other known eukaryotic pathogens. Prototheca genotypepecific pathways will be defined once the genome sequence becomes available.