α-galactosylceramide-stimulated invariant natural killer T-cells play a protective role in murine vulvovaginal candidiasis by Candida albicans

Background Vulvovaginal candidiasis is a common superficial candidiasis; however, a host’s immunological mechanism against vaginal Candida infection remains unknown. Objectives In this study, we aimed to elucidate the effect of iNKT cell activation on vulvovaginal candidiasis. Methods Using a vulvovaginal candidiasis model with estrogenized mice, we evaluated the fungal burden and number of leukocyte infiltrations in the vaginal lavage of wild-type C57BL/6J mice after Candida albicans inoculation. One day before C. albicans inoculation, α-galactosylceramide (the α-GalCer group) or sterile phosphate-buffered saline (the sham group) was intraperitoneally injected into the mice. We also evaluated the level of antimicrobial peptide S100A8 in the vaginal lavage and analyzed the correlation between S100A8 concentration and the number of vaginal leukocyte infiltrations. Moreover, the number of uterine and vaginal immune cells were evaluated using flow cytometry. Results The number of vaginal leukocyte infiltrations was significantly higher in the α-GalCer group than in the sham group 3 days after C. albicans inoculation. In addition, the fungal burden was significantly lower in the α-GalCer group than the sham group at 7 days after inoculation. In the analysis of S100A8 concentration of vaginal lavage, there were no significant differences between these two groups, although S100A8 concentration and the number of vaginal leukocyte infiltrations were positively correlated in the α-GalCer group. Moreover, the number of vaginal iNKT cells, NK cells and CD8+ T-cells was significantly higher in the α-GalCer group 3 days after inoculation. Conclusions α-GalCer-stimulated iNKT cells likely play a protective role against vulvovaginal candidiasis.