CD8 T-cell responses against the immunodominant Theileria parva peptide Tp249-59 are composed of two distinct populations specific for overlapping 11-mer and 10-mer epitopes.
Immunity against Theileria parva is associated with CD8 T-cell responses that exhibit immunodominance, focusing the response against limited numbers of epitopes. As candidates for inclusion in vaccines, characterization of responses against immunodominant epitopes is a key component in novel vaccine development. We have previously demonstrated that the Tp249-59 and Tp1214-224 epitopes dominate CD8 T-cell responses in BoLA-A10 and BoLA-18 MHC I homozygous animals, respectively. In this study, peptide-MHC I tetramers for these epitopes, and a subdominant BoLA-A10-restricted epitope (Tp298-106 ), were generated to facilitate accurate and rapid enumeration of epitope-specific CD8 T cells. During validation of these tetramers a substantial proportion of Tp249-59 -reactive T cells failed to bind the tetramer, suggesting that this population was heterogeneous with respect to the recognized epitope. We demonstrate that Tp250-59 represents a distinct epitope and that tetramers produced with Tp50-59 and Tp49-59 show no cross-reactivity. The Tp249-59 and Tp250-59 epitopes use different serine residues as the N-terminal anchor for binding to the presenting MHC I molecule. Molecular dynamic modelling predicts that the two peptide-MHC I complexes adopt structurally different conformations and Tcell receptor β sequence analysis showed that Tp249-59 and Tp250-59 are recognized by non-overlapping T-cell receptor repertoires. Together these data demonstrate that although differing by only a single residue, Tp249-59 and Tp250-59 epitopes form distinct ligands for T-cell receptor recognition. Tetramer analysis of T. parva-specific CD8 T-cell lines confirmed the immunodominance of Tp1214-224 in BoLA-A18 animals and showed in BoLA-A10 animals that the Tp249-59 epitope response was generally more dominant than the Tp250-59 response and confirmed that the Tp298-106 response was subdominant.
Division of Immunity and Infection, The Roslin Institute, The University of Edinburgh, Midlothian, UK.
Timothy K
TK
Connelley
Division of Immunity and Infection, The Roslin Institute, The University of Edinburgh, Midlothian, UK.
Xiaoying
X
Li
Division of Immunity and Infection, The Roslin Institute, The University of Edinburgh, Midlothian, UK.
Niall
N
MacHugh
Ludwig Institute for Cancer Research and de Duve Institute, Universite catholique de Louvain, Brussels, Belgium.
Didier
D
Colau
The International Livestock Research Institute, Nairobi, Kenya.
Simon P
SP
Graham
Ludwig Institute for Cancer Research and de Duve Institute, Universite catholique de Louvain, Brussels, Belgium.
Pierre
P
van der Bruggen
The International Livestock Research Institute, Nairobi, Kenya.
Evans L
EL
Taracha
Division of Neurobiology, The Roslin Institute, The University of Edinburgh, Midlothian, UK.
Andy
A
Gill
Division of Immunity and Infection, The Roslin Institute, The University of Edinburgh, Midlothian, UK.
William Ivan
WI
Morrison
D000818:Animals; D000953:Antigens, Protozoan / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002417:Cattle; D002460:Cell Line; D003198:Computer Simulation; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D016056:Immunodominant Epitopes / Q000378:metabolism; D008213:Lymphocyte Activation; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D016052:Protozoan Vaccines / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D016797:Theileria parva / Q000276:immunology*; D013801:Theileriasis / Q000276:immunology*
D000953:Antigens, Protozoan; D018984:Epitopes, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D016056:Immunodominant Epitopes; D010446:Peptide Fragments; D016052:Protozoan Vaccines
CD8 T cell; Theileria parva; cattle; epitope; tetramer