Background Trichomonas vaginalis is an underreported STD known to increase HIV transmission. Development of a vaccine against T vaginalis could greatly affect transmission of T vaginalis and HIV as well as reducing their global prevalence. Herein, we aim to investigate the feasibility of developing a T vaginalis vaccine using the human-safe adjuvant Alhydrogel compared against an already established Freund's adjuvanted vaccine in a BALB/c vaginal infection mouse model.

Methods A prime-boost vaccination schedule was employed with live, whole cell T vaginalis (1×107 Tv/ml) is injected in 2–200 ul aliquots 4 weeks apart and prior to vaginal infection challenge. Either Freund's, 0.5 mg Al/ml Alyhydrogel, or 0.75 mg Al/ml Alhydrogel were applied as adjuvants. Additionally, 0.75 mg Al/ml Alhydrogel sham and non-vaccinated groups serve as controls. The BALB/c vaginal environment was modified to mimic humans by adjustment of vaginal flora and estrogenisation prior to vaginal infection. The total IgG, IgG1 and IgG2a levels in serum were tested 3 weeks post each vaccine injection, then 2 and 4 weeks post-vaginal infection by ELISA. Groups were compared using Tukey's MCT (Post-Hoc one-way ANOVA; α<0.05).

Results Alhydrogel adjuvanted groups showed comparable total IgG and IgG1 levels to Freund's adjuvanted group. These levels for all adjuvanted groups were significantly different from control groups at all time points following boost-vaccination. IgG2a levels were not as consistent with large SD seen within Freund's adjuvanted mice. Alhydrogel adjuvanted groups were not significantly different from control groups at any time point for IgG2a levels suggesting no induction of IgG2. Controls and sham vaccines showed no Ig response.

Conclusions Our data suggest that in line with expected Th2 skewed response from Alhydrogel adjuvant and Th1 skewed response from Freund's adjuvant there was a difference in IgG2a antibody production. Additionally, the Alhydrogel adjuvanted vaccines are otherwise similar to Freund's adjuvant in terms of total IgG and IgG1 levels suggesting the feasibility to pursue Alhydrogel as a vaccine candidate. Alhydrogel induces a significantly elevated immune response compared to natural infection antibody production (non-vaccinated control) and does not induce a nonspecific immune response.