The Study On Pathogenicity Of HOG Gene In Candida Albicans

ObjectiveTo understand the differences of pathogenicity between Candida albicans parental control strain(strain CAF2),CHK21(CHK null strain) and HOG21(HOG null strain) and the relationship between HOG and CHK, we compared the cell walls`ultrastructures in these three stains,the susceptibility with FIuconazole and the pathogenic roles in systemic candidiasis in murine model. These works may offer theoretical supports for screening systemic candidiasis related genes and exploring effective,low toxic and broad-spectrum antifungal agent.Methods1.Three groups of mice: CAF2, HOG21 and CHK21 were set up in murine model with systemic candidasis.Mortality and survival curves were abtained.Colony forming units(CFUs) of C.albicans were determined in infected kidney and spleen with plating dilution method.Histopathological changes of infected kidneys were measured.2.Three groups of strains were performed to observe the ultrastructructures under scanning electron microscope (SEM) and transmission electron microscope (TEM).3.Broth macrodilution assay were performed to investigate the susceptibility of three groups of strains with FIuconazole.Result1. in vivo(1) The murine model of hematogenously disseminated candidiasis were successfully established.(2) The results of mortality and survival studies:the mortality of group mice infected with CAF-2,CHK21 and HOG21 was 100%,0 and 0 respectively.The live time of mice infected with HOG21 and CHK21 were longer than CAF-2,have statistical significance.(3) CFUs of spleen and kidney organization: CFUs of C.albicans were significantly higher in kidney and spleen in the 1st ,2nd and 3rd day after infection in CAF2 group than those in the other two groups:HOG21 group and CHK21 group, have statistical significance.The results between HOG21 group and CHK21 group have no statistical significance.(4) Renal histopathology and transmission electron microscopy results: CAF-2 group formed more extensive hyphae and fungal cells with centripetal spread into the medulla.Candida cells formed bundles within tubule lumens.Plenty of neutrophilics were often observed associated with fungal colonies and the structures of kidney were destroyed heavily. In contrast, HOG21 group only formed microabscess in infected tissues and small amounts of mycelial and fungal cells were observed. CHK21 group showed large amounts of neutrophilics accumulated in the tubule lumens.Under transmission electron microscopy ,we found that the tubular epithelial cells infected with CAF-2 lost microvilli,even shown focal necrosis. The ultrastructures of renal tissue in mice infected with HOG21 and CHK21 change less than CAF-2.The spores phagocytized by neutrophilics infectd by HOG21 were observed.2. in vitro(1) Under scanning electron microscope, three groups of cells appeared round or ellipse with multilateral buds.But the surface of cells were different.The HOG21 group appeared punctiform enation ,CHK21 showed rough and uneven surface while CAF-2 cells appeared smooth with much more budding scars. Under transmission electron microscope,the walls of CHK21 showed incomplete cell wall structure with electron dense layers disappeared somewhere and HOG21 cells with incomplete electron parent layers and the cytoplasmic membrane of cell showed several changes,such as presence of evaginations,discontinuity,budding of small vesicles accumulated with the cell membrane.In contrast CAF-2 cells wall were integrity.(2) The MIC of CAF-2,CHK21 and HOG21 with Fluconazole were:1ug/ml; 0.125~0.25ug/ml and 0.25ug/ml, respectly. Conclusion1.HOG gene may play an important role in the pathogenicity of C.albicans.2.HOG gene may regulate the biosynthesis of cell wall in Candida albicans.3.HOG gene may play a role in the susceptibility of C.albicans with FIuconazole,and this result may offer experimental supports for screening systemic candidiasis related genes,and maybe a base for new inhibitor combined with Fluconazole treating candidiasis effectively and avirulently.4.CHK gene also play a role in virulence,biosynthesis of cell wall and susceptibility of C.albicans with Fluconazole.But the mechanism maybe different from HOG gene.