Determining the efficacy and protective mechanism of a bivalent Chlamydia vaccine

The proposed study focuses on developing a novel bivalent vaccine to combat Chlamydia trachomatis (CT), a leading sexually transmitted bacterial infection which can spread to the upper genital tract of women and cause pelvic inflammatory disease, infertility, and chronic pelvic pain. No FDA-approved vaccine exists for CT, and due to its largely asymptomatic nature, many infections go undetected and untreated, increasing prevalence and risk for sequelae. This project builds on promising preliminary findings using a vaccine formulation combining Chlamydial Protease Activity Factor (CPAF), a conserved and immunodominant antigen, with a Stimulator of Interferon Genes (STING) agonist, ADU-S100, in murine models. This vaccine elicited robust CD4 T cell responses and significantly reduced bacterial burden but fell short in preventing oviduct pathology. To enhance efficacy, the study proposes a bivalent vaccine incorporating CPAF and the chlamydial Major Outer Membrane Protein (MOMP), a key target for opsonizing antibodies, conjugated with a novel STING agonist (CL1151) via click-chemistry. The central hypothesis posits that the bivalent vaccine will generate synergistic Th1 immunity and antibody responses critical for reducing bacterial load and preventing pathology. Specific aims include: (1) Determining whether a bivalent CL1151-conjugated vaccine improves protection over monovalent CPAF-CL1151, and elucidating the contribution of CD4 T cells and opsonizing antibody to protection. (2) Determine the downstream molecular mechanisms induced by the STING adjuvant, CL1151, in protection, including assessment of the roles of TNFα and type I interferon signaling. Experimental methods involve priming and boosting mice with various vaccine formulations, monitoring bacterial burden, and evaluating immunological responses via ELISpot and intracellular cytokine assays. Additional studies will investigate protective mechanisms through adoptive transfer experiments and gene knockout mouse models. Findings aim to clarify mechanisms of vaccine-induced immunity and establish a foundation for advancing a protective CT vaccine. This work addresses critical gaps in CT vaccine development and holds potential to mitigate the global burden of chlamydial infections.