Regulation of encephalitogenic T cells with recombinant TCR ligands

We have previously described recombinant MHC class II beta i and alpha l do mains loaded with free antigenic peptides with potent inhibitory activity o n encephalitogenic T cells. We have now produced single-chain constructs in which the peptide Ag is genetically encoded within the same exon as the li nked pi and al domains, overcoming the problem of displacement of peptide A g from the peptide binding cleft. We here describe clinical effects of reco mbinant TCR ligands (RTLs) comprised of the rat RT1.B beta 1 alpha 1 domain s covalently linked to the 72-89 peptide of guinea pig myelin basic protein (RTL-201), to the corresponding 72-89 peptide from rat myelin basic protei n (RTL-200), or to cardiac myosin peptide CM-2 (RTL-203). Only RTL-201 poss essed the ability to prevent and treat active or passive experimental autoi mmune encephalomyelitis, Amelioration of experimental autoimmune encephalom yelitis was associated with a selective inhibition of proliferation respons e and cytokine production by Ag-stimulated lymph node T cells and a drastic reduction in the number of encephalitogenic and recruited inflammatory cel ls infiltrating the CNS, The exquisitely selective inhibition could be obse rved between molecules that differ by a single methyl group (the single ami no acid residue difference between RTL-200 (threonine) and RTL-20 (serine) at position 80 of the myelin basic protein peptide), These novel RTLs provi de a platform for developing potent and selective human diagnostic and ther apeutic agents for treatment of autoimmune disease.