Nanostructured lipid carriers overcome the low immunogenicity of M2e peptide via surface click chemistry conjugation, improving the anti-M2e antibody response

Influenza vaccines are considered the most effective measure for preventing influenza. The key antigen of commercial vaccines is hemagglutinin (HA), the main protein on the surface of influenza viruses. This protein is genetically variable, necessitating the annual redefinition of the vaccine formulation. Furthermore, these vaccines do not offer protection against pandemic viral strains. The M2e peptide, a small surface protein conserved among influenza type A strains, could enable cross-immunity when used as an antigen. Nevertheless, its limited immunogenicity has restricted its application in universal influenza vaccines. To enhance the immune responses to M2e, we associated it with Nanostructured Lipid Carriers (NLCs). These NLCs are stable over time and their small diameter (<100 nm) enhances interactions with antigen-presenting cells and improve lymphatic drainage, facilitating their uptake by the immune system. The M2e specific antibody response in mice was enhanced by using 'click' chemistry to conjugate the M2e peptide to the NLC surface. Also, the incorporation of PADRE-specific CD4+ T cells stimulating peptide between M2e peptide and its linking region greatly enhanced the specific antibody response to M2e and generated immune response levels that could be compatible with influenza protection. This promising M2e formulation vectorized by NLC represents a potential universal influenza vaccine candidate warranting further preclinical investigations and clinical evaluation.