In vivo analysis of secreted aspartyl proteinase expression in human oral candidiasis

Secreted aspartyl proteinases are putative virulence factors in Candida inf ections. Candida albicans possesses at least nine members of a SAP gene fam ily, all of which have been sequenced. Although the expression of the SAP g enes has been extensively characterized under laboratory growth conditions, no studies have analyzed in detail the in vivo expression of these protein ases in human oral colonization and infection. We have developed a reliable and sensitive procedure to detect C. albicans mRNA from whole saliva of pa tients with oral C. albicans infection and those with asymptomatic Candida carriage. The reverse transcription-PCR protocol was used to determine whic h of the SAP1 to SAP7 genes are expressed by C. albicans during colonizatio n and infection of the oral cavity. SAP2 and the SAP4 to SAP6 subfamily wer e the predominant proteinase genes expressed in the oral cavities of both C andida carriers and patients with oral candidiasis; SAP4, SAP5, or SAP6 mRN A was detected in all subjects. SAP1 and SAP3 transcripts were observed onl y in patients,vith oral candidiasis. SAP7 mRNA expression, which has never been demonstrated under laboratory conditions, was detected in several of t he patient samples. All seven SAP genes were simultaneously expressed in so me patients with oral candidiasis. This is the first detailed study showing that the SAP gene family is expressed by C. albicans during colonization a nd infection in humans and that C. albicans infection is associated with th e differential expression of individual SAP genes which may be involved in the pathogenesis of oral candidiasis.