Human leukocyte antigen DR-presented BCR-ABL b3a2 fusion-junction peptide (HLA-DR-presented BCR-ABL b3a2 peptide)

The HLA-DR–presented BCR-ABL b3a2 fusion-junction peptide is a tumor-specific neoantigen derived from the b3a2 isoform of the BCR-ABL1 fusion protein. This fusion protein results from the reciprocal translocation between chromosomes 9 and 22, known as the Philadelphia chromosome, which is the primary driver of chronic myeloid leukemia (CML) and some cases of acute lymphoblastic leukemia (ALL) (Ten Bosch et al., 1996). The b3a2 junction creates a unique amino acid sequence at the breakpoint that does not exist in normal cells, providing a highly specific target for immunotherapy (Oertli et al., 2000). When these junctional peptides are processed and presented by HLA-DR (MHC class II) molecules, they are recognized by CD4+ T helper cells, which are essential for coordinating a durable anti-tumor immune response (Masuko et al., 2011). Therapeutic approaches targeting this complex include peptide-based vaccines and dendritic cell therapies aimed at eradicating minimal residual disease in patients who do not achieve a complete molecular response with tyrosine kinase inhibitors (Nieda et al., 1998). Because the target is unique to the malignant clone, it minimizes the risk of off-target toxicity to healthy tissues. However, the efficacy of such therapies is often limited by the specific HLA alleles of the patient, as the peptide must bind effectively to the HLA-DR molecule to be presented (Yasukawa et al., 2001). Monitoring of BCR-ABL transcript levels and T-cell responses serves as a key biomarker for assessing the success of targeting this neoantigen.

Other names

BCR-ABL b3a2 neoantigenMHC class II-restricted BCR-ABL b3a2 junctional peptidePhiladelphia chromosome b3a2 fusion peptideb3a2 breakpoint peptidep210 BCR-ABL b3a2 peptideBCR-ABL b3a2 junctional peptide

Stimulation of specific CD4+ T-helper cells to recognize and eliminate leukemic cells expressing the BCR-ABL b3a2 fusion protein through cytokine production and coordination of the adaptive immune response.