Highly conserved pattern of recognition of influenza A wild-type and variant CD8+ CTL epitopes in HLA-A2+ humans and transgenic HLA-A2+/H2 class I-deficient mice.

As an in vivo model for studying human MHC (HLA) class I-restricted CTL responses to viral infection, we established a series of HLA Tg mice expressing HLA-A2, -B7 or -B27 human/mouse hybrid genes on a background deficient for H2 class I (Tg HLA(hyb)/H2 class I DKO). To determine whether CTL recognition of influenza A (flu) infection in Tg HLA-A2(hyb)/H2 DKO mice is similar to HLA-A2+ humans, we compared the HLA-A2-restricted Tg mouse and human CD8+ T-cell responses to an immunodominant flu epitope (wild-type [WT] M1 58-66), as well as a variant of this peptide (var. M1 58-66). Similar to HLA-A2+ humans, our results show WT M1 58-66 is likely the dominant CTL epitope recognized in infected Tg HLA-A2(hyb)/H2 DKO mice. Var. M1 58-66 was also recognized by WT peptide-reactive T cells from both HLA-A2+ humans and Tg mice, although slightly less efficiently than WT M1 58-66 in both cases. Reduced variant recognition was shown to be associated with reduced peptide/A2 binding, as well as a more limited repertoire of utilized TCR Vbeta chains. The similar pattern of recognition and cross reaction observed here for the WT and variant M1 58-66 epitopes with HLA-A2 by human and Tg HLA mouse CTLs indicates that A2-dependent events of Ag processing, presentation and recognition are well-conserved between species. These findings demonstrate that this Tg HLA-A2/H2 DKO model will aid identification and development of epitopes as vaccines for numerous viral and tumor antigens for the HLA-A2 supertype.