Immunogenicity and Protective Capacity of a Virus-like Particle Vaccine against Type 3 Secretion System Tip Protein, CT584.

An effective vaccine against is urgently needed as infection rates continue to rise and causes reproductive morbidity. An obligate intracellular pathogen, employs a type 3 secretion system (T3SS) for host cell entry. The tip of the injectosome is composed of the protein CT584, which represents a potential target for neutralization with vaccine-induced antibody. Here, we investigate the immunogenicity and efficacy of a vaccine made of CT584 epitopes coupled to a bacteriophage virus-like particle (VLP), a novel platform for vaccines modeled on the success of HPV vaccines. Female mice were immunized intramuscularly, challenged transcervically with and assessed for systemic and local antibody responses and bacterial burden in the upper genital tract. Immunization resulted in a 3-log increase in epitope-specific IgG in serum and uterine homogenates and in the detection of epitope-specific IgG in uterine lavage at low levels. By contrast, sera from women infected with and virgin controls had similarly low titers to CT584 epitopes, suggesting these epitopes are not systemically immunogenic during natural infection but can be rendered immunogenic by the VLP platform. burden in the upper genital tract of mice varied after active immunization, yet passive protection was achieved when immune sera were pre-incubated with prior to inoculation into the genital tract. These data demonstrate the potential for antibody against the T3SS to contribute to protection against and the value of VLPs as a novel platform for vaccines.