Association of Disparities in Known Minor Histocompatibility Antigens with Relapse-Free Survival and Graft-Versus-Host-Disease Upon Allogeneic Stem Cell Transplantation,

Abstract

4136 Purpose: Allogeneic stem cell transplantation (allo-SCT) can induce remission in patients with hematological malignancies due to graft-versus-tumor (GVT) responses. This, however, is often accompanied by graft-versus-host disease (GVHD). Both the GVT effect and GVHD are mediated by minor histocompatibility antigen (MiHA)-specific T cells recognizing peptide products from polymorphic genes that differ between recipient and donor. Here, we evaluated whether MiHA mismatches are associated with clinical outcome after partial T cell depleted allo-SCT. Patients and Methods: We retrospectively analyzed the impact of MiHA mismatches in a cohort of 327 patients who received a partially T cell-depleted allo-SCT because of a hematological malignancy. MiHA allele genotyping was performed by fluorescence-based competitive allele-specific PCR. Subsequently, a multivariable statistical analysis of immunogenic MiHA disparity rates and association with clinical outcome was performed. In addition, development of MiHA-specific T cell responses was assessed by dual-color tetramer staining. Results: Statistical analysis revealed that an autosomal MiHA disparity on DNA level associates with increased relapse-free survival in sibling transplants, especially in patients transplanted for multiple myeloma. In addition, mismatches for the ubiquitous Y chromosome-encoded MiHA resulted in more acute GVHD (grade 3–4), while other MiHA mismatches, either ubiquitous or restricted to hematopoietic cells, were not associated with GVHD. Finally, we demonstrated considerable differences between MiHA in the capability to induce in vivo T cell responses post-transplantation. Conclusion: These data support that autosomal MiHA contribute to the induction of GVT immunity providing a rationale for MiHA-based post-transplantation immunotherapy to prevent and treat persistent and recurrent cancer following allo-SCT. Disclosures: No relevant conflicts of interest to declare.