Prediction and identification of HLA-A2 restricted CTL epitope derived from the leukemia-associated antigen MLAA-34

Objective: To predict and identify the leukemia-associated antigen MLAA-34 HLA-A2 restricted cytotoxic T lymphocyte (CTL) epitopes by bio-informatic methods so as to provide the probability of MLAA-34-based target for leukemia immunotherapy. Methods: MLAA-34 specific HLA-A2 restricted CTL epitopes were predicted by computer supermotif algorithm combined with quantitative motif algorithm. Candidate epitopes were verified when their scores were relatively high and in the top 10, and then artificially synthesized. Affinity of the candidate epitope was examined by HLA-A2 binding assay combined with flow cytometry applying T2 cells (shown as fluorescence index, FI). Four selected candidates with higher affinity were detected by lactate dehydrogenase (LDH) release assay kit to determine their ability to induce the generation of specific CTLs in vitro. Results: Among the top 10 candidate CTL epitope peptide derived from MLAA-34, MLAA2 (ILLKNQPKL), MLAA3 (LLTRHKVLV), MLAA5 (LLVTLIADL) and MLAA9 (YLIKQIRDL) had a higher affinity of HLA-A2; the FI values were 1.65, 1.73, 1.82 and 1.05, respectively. These epitope peptides could be candidates for further analysis. The analysis of the CTLs cytotoxicity showed that the peptide MLAA5 (LLVTLIADL) could effectively induce specific CTLs in vitro, and the CTLs could lyse not only the human leukemia cell line THP-1 but also the cell line T2 pulsed with MLAA3 (LLTRHKVLV). Conclusion: MLAA5 (LLVTLIADL) is a CTL epitope of the leukemia-associated antigen MLAA-34 presented by HLA-A2. This study provides an experimental basis for design and preparation of therapeutic vaccines based on MLAA-34.