To expand the breadth and extent of current multiple myeloma (MM)-specific immunotherapy,we have identified various antigens on CD138+ tumor cells from newly diagnosed MM patients (n = 616) and confirmed B-cell maturation antigen (BCMA) as a key myeloma-associated antigen. The aim of this study is to target the BCMA,which promotes MM cell growth and survival,by generating BCMA-specific memory CD8+ CTL that mediate effective and long-lasting immunity against MM. Here we report the identification of novel engineered peptides specific to BCMA,BCMA72-80 (YLMFLLRKI),and BCMA54-62 (YILWTCLGL),which display improved affinity/stability to HLA-A2 compared to their native peptides and induce highly functional BCMA-specific CTL with increased activation (CD38,CD69) and co-stimulatory (CD40L,OX40,GITR) molecule expression. Importantly,the heteroclitic BCMA72-80 specific CTL demonstrated poly-functional Th1-specific immune activities [IFN-gamma/IL-2/TNF-alpha production,proliferation,cytotoxicity] against MM,which were correlated with expansion of Tetramer+ and memory CD8+ CTL. Additionally,heteroclitic BCMA72-80 specific CTL treated with anti-OX40 (immune agonist) or anti-LAG-3 (checkpoint inhibitor) display increased immune function,mainly by central memory CTL. These results provide the framework for clinical application of heteroclitic BCMA72-80 peptide,alone and in combination with anti-LAG3 and/or anti-OX40 therapy,in vaccination and/or adoptive immunotherapeutic strategies to generate long-lasting anti-tumor immunity in patients with MM or other BCMA expressing tumors.
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