Reasonable permutation of M2e enhances the effect of universal influenza nanovaccine

Influenza A virus (IAV) occasionally cross-species transmission among humans, swine and avian. The ectodomain of matrix protein 2 (M2e) is highly conserved in IAV, and multi-copy M2e from different species are usually displayed on the surface of nanoparticles to improve immunogenicity and constitute universal IAV nanovaccines. In our previous study, three M2e were inserted into the C-terminal of Cap protein of porcine circovirus type 2 (PCV2) to form a universal nanovaccine that provides protection against PCV2 and different subtypes of IAV. However, M2e adopts at least two converted conformations, and the intermolecular linker of M2e enhances the conformational instability, which limits the recognition by B cell receptors and production of high-level antibodies. Here, we report that the permutation of M2e affects effectiveness of nanovaccines. Three M2e derived from humans, swine and avian IAV were inserted into the C-terminal of Cap protein to form nanovaccines. Immunoprotective effects of different M2e arrangements were explored in mice. Results showed that the M2e closest to the surface of nanoparticle induced the most efficient protection against IAV derived from corresponding species. The results will contribute to develop more effective PCV2 and universal IAV bivalent nanovaccines for pigs, as well as species-specific universal IAV vaccines.