Analysis of pathogenic factors of Candida albicans and the effect of vaginal immunization on recurrent vulvovaginal candidiasis in mice.

Background: The role of fungal pathogenic factors and the immune response of the vaginal epithelium in vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC) are still unclear. Our study wants to clarify whether there are differences in pathogenic factors between VVC and RVVC strains, confirm the roles of pathogenic factors in the pathogenesis of RVVC, and analyze the influence of pathogenic factors on vaginal host immunity.

Methods: VVC- and RVVC-causing Candida albicans strains were genotyped with 25S rDNA. Drug susceptibility assays using a modified alamarBlue broth microdilution method were carried out. Milk culture medium and egg yolk culture medium were used to measure the secreted aspartate protease (Sap) and phospholipase (Plb) activity of the samples. We used C. albicans with different Sap activity levels to induce RVVC in mice and measured interleukin 4 (IL4), interleukin 8 (IL8), and interleukin 17 (IL17) in vaginal lavage fluid at different stages of RVVC infection.

Results: There were no significant differences between VVC and RVVC fungi except that the Sap activity was lower for RVVC-causing C. albicans than for VVC-causing C. albicans. C. albicans with both strong Sap and weak Sap induced RVVC in mice. C. albicans with strong Sap had a reduced RVVC infection rate. In addition, C. albicans with strong Sap stimulated the vaginal epithelium to secrete more IL4, IL8, and IL17.

Conclusion: Compared with that of VVC-causing C. albicans, the Sap activity of RVVC-causing C. albicans was lower. C. albicans with strong Sap was less capable of causing repeated vaginal infections than that with weak Sap and stimulated the vaginal epithelium to produce more cytokines.