Chlamydia recombinant MOMP encapsulated in PLGA 85/15 nanoparticles admixed with Escherichia coli dmLT mucosal adjuvant enhanced protection against a genital challenge in subcutaneously immunized BALB/c mice

Abstract

Abstract There is an urgent need to develop a vaccine against Chlamydia trachomatis, the most reported bacterial-sexually transmitted infection globally. We developed a Chlamydia nanovaccine by employing PLGA [poly (D, L-lactic-co-glycolic acid) 85/15 nanoparticles encapsulated with recombinant MOMP (major outer membrane protein) of Chlamydia](named PLGA-rMOMP) that partially protected mice against a genital challenge. Here we hypothesized that admixing PLGA-rMOMP with the Escherichia coli dmLT (double-mutant heat-labile enterotoxin (LT)-R192G/L211A) mucosal adjuvant will improve the protective efficacy. Six groups of BALB/c mice were subcutaneously immunized three-times at two-week intervals with various immunogens and then challenged intravaginally with 105 inclusions forming units (IFUs) of C. muridarum. Vaginal swabs were collected every three days up to three weeks from all mice and analyzed by indirect immunofluorescence to compare the IFUs between groups of mice. Our results showed maximal protection provided in mice immunized with PLGA-rMOMP admixed with dmLT evidently by their lower IFUs as compared with the other mice groups. Moreover, the PLGA-rMOMP adjuvanted mice produced elevated MOMP-specific serum IgG2b (Th1) as compared to IgG1 (Th2) antibodies, which is indicative of an effective Th1 immune response. Interestingly splenic T-cells from these mice also produced enhanced IL-17 and IL-2 MOMP-specific cytokines after the genital challenge in comparison to the other groups of mice. Our results indicate that the E. coli dmLT mucosal adjuvant improves the immunogenicity and the protective efficacy of the PLGA-rMOMP nanovaccine against a genital challenge in mice.