Generation of cytotoxic T lymphocytes specific for B-cell acute lymphoblastic leukemia family-shared peptides derived from immunoglobulin heavy chain framework region

Background Immunoglobulin heavy chain variable region（IgHV）is a well-characterized tumor antigen for B-cellmalignancies.It can function as a target for T cell-mediated immune response.Clinical trials of IgHV protein vaccinesagainst lymphoma have demonstrated induction of tumor-specific cytotoxic T lymphocyte（CTL）responses.However,complementary determining regions-based individual vaccines have disadvantages for wide clinical application.Althougha recent study demonstrated that immunogenic peptides are derived from framework regions（FR）shared amongpatients with B-cell lymphoma,how to choose the appropriate peptides for each patient is still unsolved.The aim of thisstudy was to investigate whether immunoglobulin heavy chain FR-derived peptides shared in each IgHV family arepotential CTL epitopes presented by B-cell acute lymphoblastic leukemia（B-ALL）.Such CTL epitopes might be beneficialto shifting vaccination strategies against B-ALL from individual specificity to family specificity.Methods Seven IgHV gene families were amplified respectively by PCR and sequenced directly from 71 childhoodB-ALL cases.Bioinformatics was applied in analyzing characteristics of sequences available and predictingHLA-A0201-restricted CTL epitopes for each IgHV family.An antigen-specific T cell expansion system was used togenerate peptide-specific CTLs.The cytotoxicity of CTLs against B-ALL cells was assessed in the lactate dehydrogenaserelease assay.Results Complete IgHV rearrangements were identified in all of the 71 B-ALL cases.All of 40 sequences availableshowed ≥98% homology with the nearest germline IgHV genes,indicating IgHV genes in B-ALL of germline nature.Twelve nonapeptides of high HLA-A0201-binding scores were obtained from 26 productive IgHV protein sequences.Ten（83%）of the peptides were located in FR1 and FR3 shared among the corresponding IgHV family.CTLs specific for thepeptide QLVQSGAEV located in FR1（3-11）shared among the IgHV1 family could be successfully generated fromperipheral blood mononuclear cells of two HLA-A0201+healthy donors in vitro and were capable of killing HLA-matchedB-ALL cell clones belonging to the IgHV1 family.Conclusion Anti-B-ALL CTLs against immunoglobulin heavy chain FR-derived peptides have family-specificcytotoxicity.