Crystallization and preliminary X-ray crystallographic characterization of a public CMV-specific TCR in complex with its cognate antigen.

The T-cell response to human cytomegalovirus is characterized by a dramatic reduction of clonal diversity in patients undergoing chronic inflammation or immunodepression. In order to check whether all the selected high-avidity T-cell clones recognize the immunodominant pp65 peptide antigen pp65(495-503) (NLVPMVATV) presented by the major histocompatibility complex (MHC) molecule HLA-A2 in a similar manner, several public high-affinity T-cell receptors (TCRs) specific for the pp65(495-503)-HLA-A2 complex have been investigated. Expression, purification and crystallization were performed and preliminary crystallographic data were collected to 4.7 angstrom resolution for the RA15 TCR in complex with the pp65(495-503)-HLA-A2 complex. Comparison of the RA15-pp65(495-503)-HLA-A2 complex molecular-replacement solution with the structure of another high-affinity pp65(495-503)-HLA-A2-specific TCR, RA14, shows a shared docking mode, indicating that the clonal focusing could be accompanied by the selection of a most favoured peptide-readout mode. However, the position of the RA15 V beta domain is significantly shifted, suggesting a different interatomic interaction network.