Nanocrystalline alloy-mediated delivery of mosaic epitope peptides for universal influenza vaccine†

Seasonal influenza infection poses great threat to public health systems. The flu vaccine remains the most effective method to reduce transmission and mortality. However, its effectiveness is limited due to the challenges in protecting against all influenza variants, as well as the weaker immune response observed in the adult population. Here, combining machine learning, synchrotron small angle X-ray scattering, we design an adjuvanted influenza vaccine composing mosaic epitope peptides selected from the hemagglutinin proteins of influenza A and B virus. These epitopes share similar physiochemical properties cognate to host antimicrobial peptides (AMPs) allowing them to form supramolecular assembly with poly(I:C), a synthetic toll-like receptor 3 (TLR3) agonist, through electrostatic interaction. The poly(I:C) is arranged into columnar lattice with the average inter-poly(I:C) distance commensurate with TLR3 and thereby capable of inducing multivalent TLR3 binding and hyperactivating the downstream inflammatory pathway. Interestingly, multiple AMP-like epitopes (Ampitopes) with compatible lattice parameter can co-crystalize into the same lattice to form 'alloy'-like composite with better poly(I:C) arrangement which allows the co-delivery of mosaic Ampitopes. The designed Ampitope-poly(I:C) nanocrystalline (and alloy) successfully activates interferon regulatory factor 3 (IRF3)-mediated pathway in antigen presenting cells. The intramuscular delivery of the nanocrystalline to the mice strongly trigger IL-6 and IFN-α release, which well-mimics the cytokines release pattern in influenza infected patients. After the third boost, the antigen-specific T cell response is 55 times higher compared to the free Ampitopes treatment group. Together, this vaccine offers a versatile way of eliciting strong and broad anti-flu protection.