Minor histocompatibility antigen HA-1 (Rho GTPase-activating protein 45) (HA-1)

Minor histocompatibility antigen HA-1 (HA-1) is a well-defined target for immunotherapy in the context of allogeneic hematopoietic stem cell transplantation (HSCT). It is encoded by the ARHGAP45 gene and is characterized by its restricted expression in hematopoietic tissues, including leukemic cells, while being absent from most non-hematopoietic tissues (UniProt: Q92619). This tissue-specific expression pattern makes HA-1 an ideal target for inducing a graft-versus-leukemia (GvL) effect without causing severe systemic graft-versus-host disease (GvHD) (Goulmy et al., Science, 1996). The antigenicity arises from a single nucleotide polymorphism (SNP) in the ARHGAP45 gene, where a histidine (H) at position 168 creates the immunogenic peptide VLHDDLLEA, which is presented by HLA-A*02:01 (Mutis et al., Blood, 1999). Therapeutic interventions targeting HA-1 include the development of HA-1-specific T-cell receptor (TCR) engineered T-cells and peptide-based vaccines designed to boost the donor-derived immune response against residual leukemic cells (PubMed: 21636734). Clinical trials have explored these modalities to prevent or treat relapse in HLA-matched, HA-1-mismatched transplant recipients. The biological function of the parent protein, ARHGAP45, involves acting as a GTPase-activating protein that regulates Rho-family GTPases, thereby influencing cytoskeleton organization and cell motility (UniProt: Q92619).

Other names

HMHA1ARHGAP45Rho GTPase-activating protein 45Minor histocompatibility antigen HA1

T-cell receptor-mediated recognition of the HA-1 peptide presented by HLA-A*02:01, leading to cytotoxic T-lymphocyte activation and lysis of hematopoietic cells.