Real-time PCR expression profiling of genes encoding potential virulence factors in Candida albicans biofilms: identification of model-dependent and -independent gene expression

Abstract

BackgroundCandida albicans infections are often associated with biofilm formation. Previous work demonstrated that the expression of HWP1 (hyphal wall protein) and of genes belonging to the ALS (agglutinin-like sequence), SAP (secreted aspartyl protease), PLB (phospholipase B) and LIP (lipase) gene families is associated with biofilm growth on mucosal surfaces. We investigated using real-time PCR whether genes encoding potential virulence factors are also highly expressed in biofilms associated with abiotic surfaces. For this, C. albicans biofilms were grown on silicone in microtiter plates (MTP) or in the Centres for Disease Control (CDC) reactor, on polyurethane in an in vivo subcutaneous catheter rat (SCR) model, and on mucosal surfaces in the reconstituted human epithelium (RHE) model.ResultsHWP1 and genes belonging to the ALS, SAP, PLB and LIP gene families were constitutively expressed in C. albicans biofilms. ALS1-5 were upregulated in all model systems, while ALS9 was mostly downregulated. ALS6 and HWP1 were overexpressed in all models except in the RHE and MTP, respectively. The expression levels of SAP1 were more pronounced in both in vitro models, while those of SAP2, SAP4 and SAP6 were higher in the in vivo model. Furthermore, SAP5 was highly upregulated in the in vivo and RHE models. For SAP9 and SAP10 similar gene expression levels were observed in all model systems. PLB genes were not considerably upregulated in biofilms, while LIP1-3, LIP5-7 and LIP9-10 were highly overexpressed in both in vitro models. Furthermore, an elevated lipase activity was detected in supernatans of biofilms grown in the MTP and RHE model.ConclusionsOur findings show that HWP1 and most of the genes belonging to the ALS, SAP and LIP gene families are upregulated in C. albicans biofilms. Comparison of the fold expression between the various model systems revealed similar expression levels for some genes, while for others model-dependent expression levels were observed. This suggests that data obtained in one biofilm model cannot be extrapolated to other model systems. Therefore, the need to use multiple model systems when studying the expression of genes encoding potential virulence factors in C. albicans biofilms is highlighted.

Susceptibility To Caspofungin And Fluconazole And Als1/Als3 Gene Expression In Biofilm And Dispersal Cells Of Candida Albicans / Profil Osjetljivosti Na Kaspofungin I Flukonazol I Ekspresija Gena Als1 I Als3 U Stanicama Biofilma Te Planktonskim Stanicama Vrste Candida Albicans

“…To date, only a few genes participating in dispersion have been profi led (15,32). Our study has provided new data on the expression of two important genes encoding for adhesins Als1 and Als3, completing the earlier fi ndings (11,16,19). In agreement with them the Als1 gene was signifi cantly up-regulated in the early biofi lm stage, and the Als3 gene in the mature one.…”

“…During the development of C. albicans biofilm, many specific genes are expressed. C. albicans adhesins Als1 and Als3 play an important role and are highly expressed in in vitro (16) as well as in vivo biofi lms (17,18). While the Als1 gene is expressed in the earlier stages of biofi lm formation (19), the Als3 gene is mainly up-regulated in the mature biofi lm (11).…”

Detailed comparison of Candida albicans and Candida glabrata biofilms under different conditions and their susceptibility to caspofungin and anidulafungin

“…We therefore analysed the changes in expression of genes participating significantly in adhesion and biofilm formation, such as C. glabrata EPA6 (Iraqui et al, 2005) and C. albicans ALS1, ALS3 and EAP1 (Nailis et al, 2010;Nobile et al, 2006). The results are displayed in Figs 3 and 4(a, b, c), respectively.…”

“…For instance, C. albicans adhesins Als1, Als3 and Eap1 are highly expressed in biofilms in vitro (Li et al, 2007;Nailis et al, 2010) and in vivo (Nett et al, 2009;Ř ičicová et al, 2010). In C. glabrata, Epa6 has been shown to be involved in mature biofilm development (Iraqui et al, 2005).…”

Genetic and phenotypic characterization of Candida albicans strains isolated from infectious disease patients in Shanghai

“…Cells within a biofilm structure display a reduced susceptibility to commonly used antifungals, such as fluconazole and amphotericin B, and host immune defences (Mathé & Van Dijck, 2013;Seneviratne et al, 2008). Several genes are reported to orchestrate the formation of biofilms, including ALS3 and HWP1 (Nailis et al, 2010).…”