Outer Membrane Vesicles Coating Nano-Glycyrrhizic Acid Confers Protection Against Borderella bronchiseptica Through Th1/Th2/Th17 Responses

Abstract

Purpose Outer membrane vesicles (OMVs) are spherical nano-sized proteolipids secreted by numerous pathogenic Gram-negative bacteria. Due to the immunostimulatory properties and protective efficacy, OMVs have received increasing attention as a candidate for the vaccine to prevent and treat bacterial infections. However, the immune response remains elusive due to the low structural stability and poor size homogeneity of the vesicles. In this study, OMVs were used to coat self-assembled glycyrrhizic acid nanoparticles (GANs) and obtain a stable OMV vaccine. The immunoprotective effects and anti-infection efficacy were evaluated in vivo and in vitro. Methods The OMVs were prepared by ultrafiltration method and fused with GAN through mechanical extrusion. The characteristics, including morphology, hydrodynamic size, zeta potential, and stability were evaluated. The in vitro immunological function of GAN-OMV on the macrophages and in vivo immune efficacy and anti-infection effect were examined and compared. Results The results showed that the GAN-OMV were homogenous with a size of 130 nm and a stable core-shell structure. Micropinocytosis-dependent and clathrin-mediated endocytotic pathways effectively internalized the GAN-OMV into the macrophages and promoted cell proliferation, cytokine secretion, and M1 polarization. Furthermore, subcutaneous GAN-OMV vaccination contributed to significantly higher Borderella bronchiseptica (Bb)-specific antibody production and lymphocyte proliferation. The splenic lymphocytes of mice immunized with GAN-OMVs displayed a higher ratio of CD4+/CD8+ T cells and CD19+ B cells and produced significantly higher levels of Th1/Th2/Th17 cytokines. GAN-OMV also effectively prevented Bb reinfection. Conclusion In this study, GAN-OMV was developed successfully to stimulate Th1/Th2/Th17 immune responses against Bb and provide a promising strategy for novel vaccine development against the microbial pathogen.

Emerging nanoparticle designs against bacterial infections

“…Therefore, by varying the size of the gold core, researchers modulated bacterium‐specific immune activation in mice (Gao et al, 2015; Figure 8). In another study, a nanovaccine was made by coating Borderella bronchiseptica (Bb) outer membrane onto self‐assembled glycyrrhizic acid nanoparticles (Huang et al, 2022). In this case, the outer membrane mimicked their natural antigen presentation, while the glycyrrhizic acid core maintained OMV stability and acted as an additional adjuvant.…”

“…Outer membrane vesicle Nonspecific • Vaccines made from OMV from N. meningitidis or S. typhimurium (Arnold et al, 2011, Fiorino et al, 2021, Micoli et al, 2020 Bacterial membrane-coated nanoparticle Nonspecific • Bacterial outer membrane coated onto gold nanoparticles (Gao et al, 2015) • S. aureus outer membrane onto ICG-loaded magnetic mesoporous silica cores (Chen et al, 2020;Huang et al, 2022) • Bb outer membrane coated onto self-assembled glycyrrhizic acid nanoparticles (Huang et al, 2022).…”