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From the * Microbiology and Tumor Biology Center, Karolinska Institute, S-171 77, Stockholm,
Sweden; and The T cell receptor (TCR) repertoires of cytotoxic responses to the immunodominant and
subdominant HLA A11-restricted epitopes in the Epstein-Barr virus (EBV) nuclear antigen-4
were investigated in four healthy virus carriers. The response to the subdominant epitope
(EBNA4 399-408, designated AVF) was highly restricted with conserved V
Institute of Biochemistry and Molecular Biology, University of Ferrara Medical School,
44100 Ferrara, Italy
usage and identical length and amino acid motifs in the third complementarity-determining regions (CDR3),
while a broad repertoire using different combinations of TCR-
/
V and J segments and
CDR3 regions was selected by the immunodominant epitope (EBNA4 416-424, designated
IVT). Distinct patterns of interaction with the A11-peptide complex were revealed for each AVF- or IVT-specific TCR clonotype by alanine scanning mutagenesis analysis. Blocking of
cytotoxic function by antibodies specific for the CD8 coreceptor indicated that, while AVF-specific TCRs are of high affinity, the oligoclonal response to the IVT epitope includes both
low- and high-affinity TCRs. Thus, comparison of the memory response to two epitopes derived from the same viral antigen and presented through the same MHC class I allele suggests that immunodominance may correlate with the capacity to maintain a broad TCR repertoire.
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