Expression of Aspergillus fumigatus virulence-related genes detected in vitro and in vivo with competitive RT-PCR.

We have measured the transcription of several genes that have been implicated as virulence factors in Aspergillus fumigatus, including fos-1, a histidine kinase, two-component signal protein, rhbA, a ras-related protein required for signaling, pksP, a polyketide synthase involved in biosynthesis of melanin, pabA synthetase, an enzyme catalyzing a late step in the biosynthesis of folate, lysF, a homoconitase related to lysine biosynthesis, and cpcA, the transcriptional activator of the cross-pathway control system of amino acid biosynthesis. Transcription levels were determined from in vitro grown organism as well as from lung tissue from mice infected with A. fumigatus. Our data indicate that fos-1 and rhbA transcription increased significantly during the infection in mice, compared to the other genes whose transcription remained the same (pksP, cpcA, pabA) or decreased slightly (lysF). In vitro measurements of transcription compared to transcription in infected lung tissue demonstrated low levels of fos-1 and rhbA, 20-40-fold increases (cpcA, lysF, pabA), while pksP was not detected from cultures. Our data demonstrate that transcription of these genes differs in vitro versus during disease.