The present invention relates to the field of immunotherapy, in particular adoptive T cell therapy or T cell receptor (TCR) gene therapy of cancer. The invention provides a nucleic acid encoding at least one T cell receptor alpha chain construct and/or TCR beta chain construct of a TCR construct capable of specifically binding to an epitope from NY-ESO-1 (also designated CTAG-1) in complex with a human MHC, wherein the TCR alpha chain construct and/or the TCR beta chain construct comprises a complementarity determining region 3 (CDR3) having at least 90% sequence identity to an amino acid selected from SEQ ID NO: 1-20. The invention provides TCR constructs restricted to an epitope from NY-ESO-1 presented on MHC I, and, for the first time, TCR constructs restricted to an epitope from NY-ESO-1 presented on MHC II molecules, and thus enables a combined adoptive T cell therapy with both recombinant CD4+ and recombinant CD8+ T cells. The invention also provides proteins and host cells corresponding to said TCR constructs, as well as the medical use of such constructs, in particular, in the diagnosis, prevention and/or treatment of a proliferative or viral disease, wherein, preferably, both TCR constructs restricted to MHC I and MHC II molecules are provided in a kit. The invention also relates to a mouse transgenic for the human TCR loci and human HLA-DR4, ABabDR4 mouse.
