Augmenting influenza-specific T cell memory generation with a NKT cell-dependent glycolipid-peptide vaccine.

The development of a universal vaccine for influenza A virus (IAV) that does not require seasonal modification is a long-standing health goal, particularly in the context of the increasing threat of new global pandemics. Vaccines that specifically induce T cell responses are of considerable interest because they can target viral proteins that are more like-ly to be shared between different virus strains and subtypes and hence provide effective cross-reactive IAV immunity. From a practical perspective, such vaccines should induce T cell responses with long-lasting memory, while also being simple to manufacture and cost-effective. Here we describe the synthesis and evaluation of a vaccine platform based on solid phase peptide synthesis and bio-orthogonal conjugation methodologies. The chemical approach involves cova-lently attaching synthetic long peptides from a virus-associated protein to a powerful adjuvant molecule, α-galactosylceramide (α-GalCer). Strain-promoted azide-alkyne cycloaddition is used as a simple and efficient method for conjugation, and pseudo-proline methodology is used to increase the efficiency of the peptide synthesis. α-GalCer is a glycolipid that stimulates NKT cells, a population of lymphoid-resident immune cells that can provide potent stimula-tory signals to antigen-presenting cells engaged in driving proliferation and differentiation of peptide-specific T cells. When used in mice, the vaccine induced T cell responses that provided effective prophylactic protection against IAV infection, with the speed of viral clearance greater than that seen from previous viral exposure. These findings are sig-nificant because the vaccines are highly defined, quick to synthesize, and easily characterized, and are therefore appro-priate for large scale affordable manufacture.