A bivalent multi-adjuvant Chlamydia vaccine targeting secreted and outer membrane antigens reduces genital infection and pathology in mice 2257258

Abstract Introduction Chlamydia trachomatis is the most common bacterial STI and a major cause of hydrosalpinx and infertility, making a vaccine urgently needed. We developed a vaccine by conjugating the secreted Chlamydial Protease-like Activity Factor (CPAF) to the STING agonist CL1151 (CPAF-CL1151). Although intramuscular (i.m.) immunization elicited strong Th1 responses, it did not prevent oviduct pathology following C. muridarum infection. We hypothesized that co-delivery of CPAF-CL1151 with the Major Outer Membrane Protein (MOMP) and additional adjuvants (CpG1826 and QS-21) via combined i.m./intranasal (i.n.) routes would enhance mucosal and systemic Th1 immunity and protection. Methods Female C57BL/6 mice were immunized with CPAF-CL1151 ± QS-21 (i.m.) or CPAF-CL1151 + QS-21 ± MOMP ± CpG1826 (i.m.+i.n.). Antigen-specific T-cell responses were assessed by IFNγ/IL-17A ELISpot and flow cytometry, and serum IgG by ELISA. After challenge, cervical chlamydia burden was quantified by inclusion forming unit assay, and oviduct hydrosalpinx was assessed macroscopically. Results CPAF-CL1151 + QS-21 i.m. immunization increased IFNγTNFα CD4+ T cells 2.4-fold compared to CPAF-CL1151 alone. The combined i.m.+i.n. CPAF-CL1151 + MOMP + CpG + QS-21 regimen further doubled this population. MOMP-specific CD4+ T-cell responses were modest (0.75% of CD4+ cells) compared to CPAF (28.7%), but high anti-Chlamydia IgG titers (∼106 endpoint) were generated. The bivalent triple-adjuvant vaccine reduced cervical burden by 1.3 log10 (P < 0.0001) and shortened infection by 11 days compared to PBS controls (P = 0.0002), and decreased hydrosalpinx by ∼50% relative to CPAF-CL1151 + QS-21. Conclusion Thus, a bivalent CPAF-MOMP vaccine delivered via i.m.+i.n. routes induces robust Th1 immunity, accelerates clearance, and reduces oviduct pathology. Ongoing studies aim to define the minimal antigen, adjuvant, and route combinations required for optimal protection. Funding Source NIAID F31AI194796, NIAID U01AI182180 Topic Categories Vaccines and Immunotherapy (VAC)