Identification of HLA-A*0201-restricted CTL Epitopes for MLAA-34-specific Immunotherapy for Acute Monocytic Leukemia

Our previous research has shown that monocytic leukemia-associated antigen-34 (MLAA-34) was a novel antiapoptotic molecule with unique expression in acute monocytic leukemia (M5), making it an ideal target for T-cell-based immunotherapy. Here, we sought to identify HLA-A*0201-restricted cytotoxic T-lymphocyte (CTL) epitope of MLAA-34 by reverse immunology. In all, 10 HLA-A*0201 restricted epitopes of MLAA-34 were predicted by bioinformatics. MLAA-34_324-332, MLAA-34_293-301, and MLAA-34_236-244showed the strongest HLA-A*0201-binding affinity. The percentages of HLA-A*0201-MLAA-34_236-244tetramer⁺CD8⁺T cells in MLAA-34_236-244-induced CTLs were raised apparently. Enzyme-linked immunospot showed that MLAA-34_236-244and MLAA-34_324-332-specific CTLs produced a higher amount of interferon-?. MLAA-34_236-244-induced CTLs presented a stronger cytotoxic effect on THP-1 cells (HLA-A*0201⁺MLAA-34⁺) at various effector to target ratios. MLAA-34_236-244peptide vaccine could inhibit the tumor growth and improve mean survival time of leukemia-bearing human peripheral blood lymphocyte reconstituting severe combined immunodeficient mice. Mice immunized with MLAA-34_236-244vaccine had increased percentages of MLAA-34_236-244tetramer⁺CD8⁺T cells in the spleen after each round of immunization. High-purity CD8⁺and CD4⁺T cells were sorted by Dynabeads as effector cells. The killing activity of CD8⁺T cells was higher than that of CD4⁺T cells. CTLs derived from the MLAA-34 peptide vaccine group were significantly higher than other therapeutic groups and showed specific cytotoxicity to THP-1 cells. Increased interferon-? and interleukin (IL)-2 and decreased IL-10 and IL-4 were seen in the MLAA-34_236-244peptide vaccine group. MLAA-34_236-244peptide (ILDRHNFAI) is an effective HLA-A*0201-restricted CTL epitope and that it may serve as a promising strategy in designing antigen-specific immunotherapy against MLAA-34-positive acute monocytic leukemia.