Lactobacillus casei bacterial ghost-based DNA vaccine enhances the immune protection effect by stimulating macrophages to regulate intestinal mucosal immunity.

Porcine rotavirus is a major threat to the swine industry, yet effective vaccines are still lacking. Lactobacillus casei bacterial ghosts (L. casei BGs) as DNA vaccine delivery vehicles represent a promising approach, providing a safe and structurally intact platform that enhances antigen presentation and elicits intestinal mucosal immunity. To elucidate how L. casei BGs regulate macrophage function and amplify mucosal immune responses, we investigated the response of macrophages and the intestinal mucosal immune system to an L. casei BG-based DNA vaccine encoding VP7. Using genetically engineered L. casei BGs, we performed in vitro macrophage stimulation and in vivo oral/intramuscular immunization in murine models, assessing phagocytic efficiency, TLR/MyD88/NF-κB pathway activation, M1 polarization, antigen presentation, serum IgG, fecal IgA, T cell proliferation, intestinal viral load, virus neutralization, and intestinal histopathology. Compared with a naked DNA vaccine, the L. casei BG-based vaccine significantly enhanced phagocytosis and antigen presentation and promoted M1 polarization via the TLR/MyD88/NF-κB pathway. Furthermore, oral administration of the vaccine proved superior to intramuscular injection in inducing mucosal immunity, preserving intestinal villus integrity, and enhancing antiviral protection. Collectively, this study establishes L. casei BGs as an effective DNA vaccine delivery system that enhances immunogenicity by modulating macrophage function and activating mucosal immunity, and offers a promising strategy for the control of porcine rotavirus infection.