The emerging D b NPN3A + CD8 + T cell population was characterised by different Va and Vb preference, distinct CDR3b sequences and a lower overall TCR diversity in comparison to wt D b NP 366 + CD8 + T cells. These findings suggest that a very limited spectrum of CD8 + T cells can recognise the D b NPN3A mutant structure. Interestingly, a similar P3 substitution in the influenza virus D b PA 224 epitope had no affect on D b PA 224 + CD8 + T cell recognition and recruited a diverse array of TCR clones comparable to the spectrum found for the wt response [21] . This suggests that the partially-exposed P3 residue plays a greater structural and/or TCR recognition role for the ''featureless'' D b NP 366 than for the ''featured'' D b PA 224 complex reflecting, in turn, the more limited spectrum of TCRs that bind D b NP 366 [21] . Taken together, it appears that partially-exposed residues within viral peptides can provide important contacts with the MHC-I, which can in turn cause remote effects that modify antigenicity for the TCR-pMHC-I complex and impact on both TCR repertoire selection and the magnitude of CD8 + T cell responses.