共生细菌通过溶血素调控白念珠菌EFG1基因参与复发性念珠菌性阴道炎机制的研究

Recurrent vaginitis (RVVC) is a vaginal mucosal infectious disease caused by Candida albicans. The inbalance of vaginal microecological is one of the important causes. However, the pathogenesis has not been elucidated yet. Our previous work found that Streptococcus agalactiae can specifically inhibit hyphal development in C. albicans and the bacterial hemolysin was the virulence factor. We speculate that bacterial hemolysin inhibits C. albicans morphological transformation and down-regulate the vaginal mucosa immune response. This promote vaginal C. albicans colonization inducing persistent vaginal mucosal infection. The project is intended to carry out the following studies: 1) To study the molecular mechanism of C. albicans morphological transformation by means of Westernblot, CHIP and co-IP and other methods; 2) To study the co-infection of bacteria and C. albicans infection in vaginal mucosa basis. The research of this subject is expected to deepen the understanding of bacterial-fungal infection mechanism of interaction and reveal the mechanism of RVVC recurrence, providing new ideas for the treatment of this disease.

复发性念珠菌性阴道炎(RVVC)是一种由念珠菌主要是白念珠菌引起的阴道粘膜感染性疾病，阴道微生态平衡被破坏是其重要病因之一，但其致病机制尚未阐明。我们前期工作发现无乳链球菌通过菌丝调控基因EFG1调控白念珠菌菌丝生长，下调阴道粘膜Th17免疫反应，并发现细菌溶血素是其毒力因子。我们推测：细菌溶血素通过下调菌丝调控基因EFG1抑制白念珠菌形态转换,下调阴道粘膜免疫反应，促进白念珠菌阴道粘膜定植诱发持续感染。本项目拟开展如下研究：1）利用Westernblot、Chip和Co-IP等方法研究溶血素作用下，白念珠菌形态转换的分子机制；2）通过FACS, ELISA及组织化学染色等方法研究小鼠阴道炎模型中，细菌分泌溶血素影响白念珠菌形态转换，参与阴道粘膜感染的致病及免疫机制。本研究预期将加深粘膜感染中细菌-真菌相互作用机制的研究。

白念珠菌与其他微生物菌群体间也存在相互作用，与宿主的相互作用复杂，可诱发机体持续感染，机制不明。研究工作初步阐明细菌溶血素（α-Hemolysin， Hla）作用后损伤白色念珠菌（C. albicans）细胞壁糖基磷脂酰肌醇（GPI）锚定蛋白，从而破坏白念珠菌细胞壁机构。进一步诱发白念珠菌线粒体氧化呼吸爆发，大量的活性氧（ROS）生成损伤白念珠菌线粒体。为了对抗这种氧化损伤，白念珠菌细胞周期停滞在G0/G1期，细胞合成修复增加。当细胞周期停滞在G0/G1期，表达在白念珠菌芽管顶端的CDC42的蛋白表达下降，从而抑制白念珠菌出芽和菌丝生长，粘附力下降；同时白念珠菌表面Ywp1的蛋白表达增加，从而降低了白色念珠菌细胞的聚集。小鼠皮肤、外阴阴道念珠菌病 (VVC)模型中，证明感染 Hla 预处理的白色念珠菌的小鼠粘膜上的白色念珠菌定植较少，同时IL-1、IL-17细胞因子生成减少，提示宿主抗白念珠菌反应下降。本研究结果证明细菌分泌的活性蛋白会降低白念珠菌致病性，伴随宿主抗真菌免疫反应降低,从而引起机体的长期持续感染，疾病迁延不愈，诱发RVVC发生。该研究结果同时提示黏膜中定植的细菌和真菌共生平衡被打破，会导致真菌感染性疾病的发生。