Enhancing Immunity and Modulating Vaginal Microflora Against Candidal Vaginitis Through Nanoemulsion Supplemented with Oligosaccharide as an Intravaginal Vaccine Adjuvant.

Background: Intravaginal vaccination is an encouraging approach to prevent infectious vaginitis, with nanoemulsions showing effectiveness as mucosal adjuvants.

Purpose: This study aimed to formulate a nanoemulsion incorporating oligosaccharide (PO@NE) and assess its effectiveness as a mucosal adjuvant in intravaginal vaccines against candidal vaginitis.

Materials And Methods: PO@NE was prepared, and the stability, immunomodulatory activity and cytotoxicity were screened in vitro. Further, the preventive effect of PO@NE as adjuvants for heat-killed (HK-CA) vaccines was explored in a murine model of candidal vaginitis, in comparison with those supplemented with polysaccharide (PP@NE). The mice were intravaginally vaccinated with 10 HK-CA cells, suspended in 1% NE without or with either PO or PP at a final concentration of 6.5 μg/mL, in a total volume of 20 μL. This vaccination was intravaginally administered once a week for 3 weeks. One week following the final vaccination, the mice underwent an intravaginal challenge with 10 cells. One week after the challenge, the mice were euthanized to isolate serum, spleen, vaginal washes, and vaginal tissues for analysis.

Results: PP@NE and PO@NE, with diameters approximately around 100 nm, exhibited exceptional stability at 4°C and low cytotoxicity when used at a concentration of 1% (v/v). Intravaginal vaccination with HK-CA adjuvanted with PO@NE effectively protected against candidal vaginitis evidenced by less hyphae colonization, milder mucosal damage and cell infiltration. Moreover, enhanced mucosal antibody production, induction of T helper (Th)1 and Th17-related immune responses, enlarged the population of CD8 cells, and elevated vaginal microflora diversity were observed in vaccinated mice. Interestingly, the potency was rather attenuated when PO@NE was replaced with PP@NE.

Conclusion: These findings indicate PO@NE as a HK-CA vaccine adjuvant for candidal vaginitis prevention via enhancement of both cellular and humoral immunity and modulation of vaginal microflora, emphasizing further intravaginal vaccination development.