Intramuscular All-Trans Retinoic Acid-Adjuvanted Nanovaccine Elicits Robust Mucosal and Systemic Immunity Against Helicobacter pylori.

PURPOSE: Helicobacter pylori (H. pylori) infection, implicated in chronic gastritis, peptic ulcers, and gastric cancer, poses a significant global health burden exacerbated by increasing antibiotic resistance. Traditional intramuscular vaccines often yield limited mucosal immunity, necessitating the development of more effective vaccination strategies capable of robust mucosal and systemic responses. Here, we report a novel nanovaccine (RA-NVs) combining all-trans retinoic acid (RA) and recombinant urease subunit proteins (UreA/UreB), encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles to enhance protective immunity against H. pylori.

METHODS: RA-NVs were synthesized via single emulsion-diffusion-evaporation, with antigens loaded onto the nanoparticle surfaces. Their physicochemical properties, antigen loading capacity, and stability were characterized. In vitro dendritic cell (DC) activation, antigen uptake, and gut-homing receptor expression (C-C chemokine receptor 9, CCR9) were assessed. In vivo distribution was examined using in vivo imaging system (IVIS). BALB/c mice were immunized intramuscularly, and subsequent mucosal (IgA) and systemic (IgG) antibody responses, cytokine profiles, T cell proliferation, and bacterial clearance upon H. pylori challenge were evaluated. Vaccine biosafety was assessed via histopathological and biochemical analyses.

RESULTS: RA-NVs exhibited optimal size, surface charge, and sustained antigen and RA release. In vitro assays demonstrated efficient DC uptake, enhanced CCR9 expression, cytokine secretion (IL-6, IL-10, IL-15), and improved DC migration towards C-C motif chemokine ligand 25 (CCL25). In vivo, RA-NVs significantly elevated serum IgG and mucosal IgA antibodies, promoted CD4+ and CD8+ T cell activation, and elicited robust Th2/Th17-skewed responses. Notably, immunized mice exhibited significantly reduced gastric bacterial colonization and inflammation upon H. pylori challenge, alongside excellent safety profiles with minimal toxicity and organ damage.

CONCLUSION: The RA-adjuvanted nanovaccine effectively induces potent mucosal and systemic immunity via intramuscular administration, representing a promising strategy against mucosal pathogens such as H. pylori. This nanovaccine platform addresses key limitations associated with oral vaccination and with conventional intramuscular approaches that often yield limited mucosal immunity, offering an alternative for enhancing mucosal vaccine efficacy in mice; although a direct head-to-head comparison with an oral formulation remains to be established.