A targeted single mutation in influenza A virus universal epitope transforms immunogenicity and protective immunity via CD4 + T cell activation.
Hulin-Curtis, S., Geary, J.K., MacLachlan, B.J., Altmann, D.M., Baillon, L., Cole, D.K., Greenshields-Watson, A., Hesketh, S.J., Humphreys, I.R., Jones, I.M., Lauder, S.N., Mason, G.H., Smart, K., Scourfield, D.O., Scott, J., Sukhova, K., Stanton, R.J., Wall, A., Rizkallah, P.J., Barclay, W.S., Gallimore, A., Godkin, A.(2024) Cell Rep 43: 114259-114259
- PubMed: 38819988 
- DOI: https://doi.org/10.1016/j.celrep.2024.114259
- Primary Citation of Related Structures:  
8PJE, 8PJF, 8PJG - PubMed Abstract: 
CD4 + T cells are central to adaptive immunity. Their role in cross-protection in viral infections such as influenza and severe acute respiratory syndrome (SARS) is well documented; however, molecular rules governing T cell receptor (TCR) engagement of peptide-human leukocyte antigen (pHLA) class II are less understood. Here, we exploit an aspect of HLA class II presentation, the peptide-flanking residues (PFRs), to "tune" CD4 + T cell responses within an in vivo model system of influenza. Using a recombinant virus containing targeted substitutions at immunodominant HLA-DR1 epitopes, we demonstrate limited weight loss and improved clinical scores after heterosubtypic re-challenge. We observe enhanced protection linked to lung-derived influenza-specific CD4 + and CD8 + T cells prior to re-infection. Structural analysis of the ternary TCR:pHLA complex identifies that flanking amino acids influence side chains in the core 9-mer peptide, increasing TCR affinity. Augmentation of CD4 + T cell immunity is achievable with a single mutation, representing a strategy to enhance adaptive immunity that is decoupled from vaccine modality.
Organizational Affiliation: 
Division of Infection and Immunity/Systems Immunity University Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.