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(236-244) showed the strongest HLA-A*0201-binding affinity. The percentages of HLA-A*0201-MLAA-34(236-244) tetramer(+) CD8(+) T cells in MLAA-34(236-244)-induced CTLs were raised apparently. Enzyme-linked immunospot showed that MLAA-34(236-244) and MLAA-34(324-332)-specific CTLs produced a higher amount of interferon-gamma. 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(236-244) peptide 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(236-244) vaccine had increased percentages of MLAA-34(236-244) tetramer(+) 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-gamma and interleukin (IL)-2 and decreased IL-10 and IL-4 were seen in the MLAA-34(236-244) peptide vaccine group. MLAA-34(236-244) peptide (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.

Automated summary

Our research identified the HLA-A*0201-restricted cytotoxic T-lymphocyte (CTL) epitope MLAA-34(236-244) as having strong binding affinity and inducing significant interferon-gamma production. CTLs targeting this epitope showed potent cytotoxicity against leukemia cells and inhibited tumor growth. Additionally, immunization with the MLAA-34(236-244) peptide vaccine resulted in elevated levels of interferon-gamma and enhanced survival in mouse models of leukemia.