CpG-mediated TLR9 signalling enhances the efficacy of the OprF/PcrV DNA vaccine with cGAS-STING-activating properties

Background Pseudomonas aeruginosa (PA) infection poses a major global threat to health care. DNA vaccines, which induce humoral and cellular immunity, are promising for preventing and treating PA infection. However, the low immunogenicity of DNA vaccines has limited its clinical application. Therefore, this study seeks to explore whether the OprF/PcrV DNA vaccine can activate the cGAS-STING pathway and boost the immunogenicity of the OprF/PcrV DNA vaccine by combining a CpG adjuvant which presumably activates the TLR9 pathway. Results We found that the DNA-OprF/PcrV + CpG could activate the cGAS-STING and TLR9 pathways, activate innate immune responses, and stimulate BMDC maturation. In addition, in vivo data revealed that the vaccine could induce strong antigen-specific cellular and humoral immune responses and protect mice with pneumonia from PAO1 infection by reducing the bacterial burden in the lungs and reducing lung inflammation. Finally, the DNA-OprF/PcrV + CpG vaccine showed reliable biosafety. Conclusion This study conclusively demonstrated that the DNA-OprF/PcrV vaccine, when combined with CpG, effectively stimulated the innate immune response through the cGAS-STING and TLR9 pathways, subsequently enhancing the adaptive immune response. This synergistic combination not only triggers robust humoral immunity but also enhances cellular immune responses, indicating that the DNA-OprF/PcrV + CpG vaccine may serve as a promising option against PA infection both intracellularly and extracellularly.