Metal–organic framework–based delivery systems as nanovaccine for enhancing immunity against porcine circovirus type 2

Porcine circovirus type 2 (PCV2) has caused massive economic losses to the global pig farming industry. As emerging nanomaterials, metal-organic frameworks (MOFs) have considerable potential in drug and vaccine delivery because of their unique physicochemical properties. Based on the successful expression and identification of PCV2 antigens (Cap protein), this study exploits MOF platforms to design a nanovaccine delivery system (Cap@ZIF-8-CpG) as a novel subunit vaccine, which effectively enhances the resistance of antigens to denaturation and boosts immune responses against PCV2. Results demonstrate that mice injected with a nanovaccine efficiently incorporating PCV2 antigens (Cap) and an immune enhancer (CpG) elicit robust humoral immune responses. Notably, immunoglobulin G antibody titers are considerably elevated; cytokine secretion is augmented; and the proliferation of CD8⁺ cytotoxic T lymphocytes and CD4⁺ T cells is effectively stimulated. Following a viral challenge, the Cap@ZIF-8-CpG nanovaccine successfully protects the health of the mice, making them resistant to PCV2 infection. This study provides a new promising direction for the development of effective and long-lasting vaccines against PCV2 and other major swine pathogens.