An in vitro assay to study the transcriptional response during adherence of Candida albicans to different human epithelia.

Adhesion to mammalian epithelia is one of the prerequisites that are essential to accomplish pathogenesis of Candida albicans in the mammalian host. In this context C. albicans is able to adhere to a plethora of different cell types providing different microenvironments for colonization. To study the response of C. albicans adhering to different surfaces on the transcriptional level we have established an in vitro adhesion assay exploiting confluent monolayers of the human colorectal carcinoma cell line Caco-2 or epidermoid vulvo-vaginal A-431 cells. Candida albicans very efficiently adheres to these epithelia growing as hyphae. Using whole-genome DNA microarrays comprising probes for almost 7000 predicted ORFs we found that transcriptional profiles of C. albicans adhering to Caco-2 or to A-431 cells, although very similar, still significantly differ from those of Candida cells adhering to plastic surfaces. Differences became even more obvious when comparing C. albicans cells either growing in an adherent manner or in suspension culture. Correspondingly, we found for several cell surface genes, including PRA1, PGA23, PGA7 and HWP1, an adhesion-dependent induction of transcription. Obviously, C. albicans is able to respond specifically to very subtle differences in the environment during adhesion to various growth substrates.