T cell receptor CDR3 sequences and recombinant T cell receptors. Prerequisites for developing ligands to interfere with T cell receptor binding to the MHC/peptide complex.

Background: The interaction of T cell receptors (TCRs) with peptide fragments bound to major histocompatibility complex (MHC) molecules is central to the initiation and propagation of most immune responses. In order to understand and control the molecular interactions underlying T cell recognition of MHC/peptide complexes, recent efforts have focused on the production of recombinant soluble forms of the TCR heterodimer. Methods: TCRA variable (TCRAV) and TCRBV sequences used by human T cell clones were amplified by PCR, cloned and sequenced. The deduced amino acid sequences of the complementarity determining region (CDR) 3 loops of TCRs specific for the same allergenic epitope were compared. V region genes of a selected TCR were expressed as a single-chain (sc) molecule in the periplasm of Escherichia coli. Results: Conserved amino acid motifs specific for allergenic peptides of Bet v 1 and Phl p 1 were identified in CDR3 sequences of TCRs. A recombinant scTCR was produced. The ratio of insoluble to soluble material was 1:1. The recombinant protein was of the correct size and showed no signs of degradation. Conclusions: Conservation of amino acid motifs in CDR3 loops of TCRs specific for the same allergen fragments indicated that the three-dimensional structure of the CDR3 was determined by the presented peptide. The recombinant scTCR will be used to identify ligands for the CDR3s from random peptide libraries to interfere with TCR binding to the MHC/peptide complex.