Analysisofthefrequencyofantigen-specificcytotoxicTlymphocytes(CTLs)exvivoislargelydependentontheuseofMHC/peptidetetramers.However,thelatterreagentshavenotbeenwidelyavailable,mostlikelybecauseoftheircostlyandtime-consumingproduction.InthisreportweutilizedaneconomicstrategytoconstructHLA/peptidetetramerswithrecombinantpeptide-linkedβ2microglobulin(β2m).TheHLA-A2-restricted,melanomaantigenMARTl-derivedpeptideMARTI27-35(AAGIGILTV)wasfusedtotheNterminusofhumanβ2mthrougha15-aminoacid(aa)-longlinkerbeforebeingrefoldedwiththerecombinantbiotinylatedHLA-A2heavychainectodomain.Theresulted2-component(2C)monomerwasthentetramerizedwithphycoerythin-labeledstreptavidin.Theexperimentalresultshowedthatthe2CHLA-A2/MARTI27-35monomerwasshowntobindtotheHLAclassⅠcomplex-specificmonoclonalantibodyW6/32andtheHLA-A2/MARTI27-35complex-specificsinglechainantibodyfragment(scFv)8.3,suggestingthecorrectnessofitsspecificity.Furthermore,the2CHLA-A2/MARTI27-35tetramerdetectedaspecificCD8^+TcellpopulationinHLA-A2-restrictedmelanomainfiltratinglymphocytesastheconventional3CHLA-A2/MARTI27-35tetramer.Theyieldof2CHLA-A2/MARTI27-35monomerwas2.5timesmorethanthatoftheconventional3Cmonomer.Takentogether,thesedataindicatethattheHLA-A2/MARTI27-35tetramercanbegeneratedconvenientlythroughtheuseofMARTI27-35peptide-β2mfusionproteins,whichcanfacilitatethemonitoringofHLA-A2-restricted,MARTl-specificCTLresponsesinpatientswithmelanoma.
