Abstract
Chlamydia psittaci is an important pathogenic zoonotic pathogen that infects birds and can be transmitted to humans and other animals. This research focused on creating an mRNA vaccine targeting C. psittaci and assessing its immunogenic and protective effects in BALB/c mice. We carried out a trial to prepare and assess an mRNA vaccine targeting C. psittaci. This study involves an mRNA vaccine encoding the major outer membrane protein (MOMP), produced via an in vitro transcription system and encapsulated in lipid nanoparticles (LNPs). The mRNA vaccine was constructed by synthesizing non-replicating mRNA encoding MOMP. LNPs were produced and characterized for their particle morphology, size, and cytotoxicity. Histopathological analysis and indirect immunofluorescence assay of lung tissue demonstrated that mRNA vaccines effectively reduce chlamydial infection and shedding in BALB/c mice. The western blot assay confirmed the successful expression of the recombinant MOMP mediated by the target mRNA in HeLa cells. Immunization with the LNP-Opt-mRNA vaccine induced a strong immune response in mice. Mice immunized with the LNP-Opt-mRNA vaccine exhibited lower levels of C. psittaci load and decreased concentrations of interferon-γ, TNF-α, and IL-6 in the lungs compared to the PBS group. The study successfully constructed and developed the LNP-mRNA vaccine expressing the MOMP of C. psittaci. The vaccine demonstrated strong immunogenicity, inducing effective humoral and cellular immune responses that significantly decreased pulmonary C. psittaci burden in mice. These findings provide a basis for designing mRNA vaccines against C. psittaci and similar respiratory pathogens.IMPORTANCEChlamydia psittaci is a significant threat to public health due to its zoonotic nature and capability to spread from birds to humans and other animals. It is necessary to develop an effective preventive measure. This study introduces an innovative strategy against C. psittaci using an mRNA vaccine that encodes the major outer membrane protein, demonstrating potential in eliciting robust immune responses in mice. The work emphasizes the efficacy of mRNA vaccines in inducing humoral and cellular immune responses, significantly decreasing the lung C. psittaci burden in mice and underscoring their potential against respiratory pathogens. The study indicates that lipid nanoparticle-mRNA vaccines may be a useful technique for treating and preventing C. psittaci infections, providing valuable insights for developing vaccines against other Chlamydia species and respiratory pathogens. Finally, this study provides a theoretical foundation and practical experience for the production of C. psittaci vaccines, paving the way for further exploration of mRNA vaccine platforms and co-delivery strategies to enhance immune responses.