Acanthamoeba healyi: expressed gene profiles with enhanced virulence after mouse-brain passage.

The virulence of Acanthamoeba can be attenuated by long-term in vitro cultivation, and can be recovered by serial mouse-brain passage via intranasal inoculation. Recovery is concomitant with changes in expression of virulence-related genes. To investigate the virulence factors of Acanthamoeba, expressed sequence tags (ESTs) from two kinds of cDNA libraries-long-term in vitro cultivated A. healyi (OLD) and three times mouse-brain passaged A. healyi (MBP)-were compared using reciprocal BLAST analysis, eukaryotic orthologous groups (KOG) assignment, and gene annotation. A total of 938 (OLD) and 1033 (MBP) ESTs were sequenced and resulted in the assembling of 718 OLD and 833 MBP unique sequences. Comparison of the KOG analysis revealed a relatively higher percentage of MBP ESTs in genes related to transcription (K group), amino acid transport and metabolism (E group), coenzyme transport and metabolism (H group), and secondary metabolites biosynthesis, transport and metabolism (Q group). However, a higher percentage of unidentified MBP ESTs (57.9%) than OLD ESTs (28.9%) was evidence of the limited understanding of virulence-related factors of Acanthamoeba. Characterization of the genes expressed during brain passage in mice will be useful in clarifying the pathogenesis of granulomatous amoebic encephalitis by Acanthamoeba.