Determining the efficacy of a ChAdOx1-vectored Chlamydia vaccine (2024)

Undergraduate: Aakash Bhardwaj

Faculty Advisor: Taylor Poston
Department: Biology, Microbiology and Immunology, Pediatrics

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Chlamydia trachomatis is the causative agent of chlamydia, the most common sexually transmitted bacterial infection worldwide, which is estimated to infect 336 million people globally. These infections are often asymptomatic and can lead to serious sequelae like pelvic inflammatory disease, pregnancy complications, and infertility, making a vaccine urgently needed. We have developed a vaccine against the mouse pathogen C. muridarum that uses a modified chimpanzee adenovirus, to express the candidate antigen chlamydial protease-like activity factor (ChAdOx1.CPAF). Our preliminary data revealed that high-dose intramuscular ChAdOx1.CPAF prime-boost immunization reduced the amount of infectious Chlamydia 10-fold over the course of infection in mice. As part of our ongoing NIH U19-funded Chlamydia Vaccine Initiative, we further determined that ChAdOx1.CPAF is effective at reducing burden in C57BL/6 mice (P=0.0448). Further, we demonstrated that IFN-γ producing CD4 T cells are a main correlate of protective immunity against Chlamydia in mice, while CD8 T cells are less essential. These data suggest future vaccines should elicit high frequencies of IFN-γ producing CD4 T cells to reduce Chlamydia burden and protect against oviduct disease.