ABSTRACT: Purpose of the study The encounter between Candida albicans and phagocytes (macrophages) is considered the initial step in the development of host immune defenses. The single utility of proteomic and genomic approaches to study host - pathogen interaction has been previously described in the literature (1, 2, 3); but up to now few studies have employed both techniques as complementary approaches. Because of the importance of the macrophages in the innate immune response against fungal infectious, we have investigated the transcriptional profiling and the differential protein expression (using a proteomic approach) of C. albicans after the interaction with these phagocytes. Description We have developed an in vitro system by employing the murine macrophage cell line RAW264.7 and the wild-type Candida albicans yeast strain SC5314. The study of the differential C. albicans protein expression in these conditions (3h. of interaction) has been performed by 2D-PAGE. The comparative analyse of the bidimensional silver stained gels obtained, was performed using the bioinformatic software Melanie 3. A complementary approach for this proteomic work is the study of the yeast transcriptional profiling after two time points of interaction (1.5 and 3h). We have analyzed differential C. albicans gene expression using Microarrays from Eurogentec. Results and conclusions A total of 132 protein species differentially expressed have been detected; 79 with increased expression and 53 with their expression decreased. The most interesting proteins up and down regulated, have been identified by MALDI-TOF TOF (59 proteins) and classified according to their biological function.The majority of these proteins belong to different metabolic pathways. Up-regulated proteins belong to oxidation of fatty acids and detoxification, meanwhile, other metabolic proteins belonging to glycolysis, fermentation and gluconeogenesis are clearly down-regulated. Proteins belonging to cell rescue, defence and virulence, proteosome and oxidative stress response are also up-regulated. A total of 240 C. albicans differentially expressed genes have been detected after 1,5 and 3h of macrophage interaction (122 over-expressed and 118 under-expressed). The yeast transcriptional response pointed out an increase in genes belonging to oxidative stress, metal homeostasis, DNA damage repair, lipid metabolism and pathogenesis and a down-regulation profile in genes belonging to cytoskeleton, morphogenesis, metabolism (carbohydrate, amino acid and nucleotide) and vesicular-vacuolar transport. The results obtained after this proteomic/genomic analyses indicate that a great percent of these proteins/genes belong to different cellular pathways showing the attempt of C. albicans to avoid being engulfed by macrophages, and once inside, points out the hostile environment that surrounds the yeast. References 1-Lorenz MC, Bender JA, Fink GR. Transcriptional response of Candida albicans upon internalization by macrophages. Eukaryot Cell. 2004 Oct;3(5):1076-87. 2-Fradin C, De Groot P, MacCallum D, Schaller M, Klis F, Odds FC, Hube B. Granulocytes govern the transcriptional response, morphology and proliferation of Candida albicans in human blood. Mol Microbiol. 2005 Apr;56(2):397-415. 3- Martínez-Solano L, Nombela C, Molero G, and Gil C. Differential protein expression of murine macrophages upon interaction with Candida albicans. Proteomics, in press. Keywords: stress response
