David Miklos

Research/Lab website:   Bone Marrow Transplantation Site

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure hematologic malignancies. Beneficial alloimmune responses target mHA expressed on hematopoietic tumor cells resulting in graft versus leukemia (GVL) and contribute to the eradication of malignant cells following transplantation. However, when donor T cells target mHA expressed by normal recipient tissues, patients suffer graft-versus-host disease (GVHD). A more extensive characterization of human mHA will establish which mHA mediate GVHD and/or GVL. Thus far, mHA identification has relied on allo-reactive T cells. However, our research has demonstrated that HSCT patients develop clinically relevant allogeneic B cell responses.
1. Antibody Responses to H-Y minor histocompatibility antigens are induced 4-8 months after allogeneic stem cell transplantation and in 40% of normal female donors. In order to determine if antibody responses to mHA occur after HSCT, we focused on H-Y antigens. Males develop tolerance to these self-antigens, but female T cells are capable of recognizing peptides derived from H-Y proteins following transplantation into male recipients. We established a sensitive ELISA to measure antibody responses to 5 recombinant H-Y proteins (DBY, UTY, ZFY, RPS4Y, and EIF1AY) and their X-homologs. Antibodies to at least one H-Y protein were present in 39 of 75 (52%) male HSCT patients with female donors (F-->M HSCT).
2. H-Y antigen DBY elicits a coordinated B and T cell response after allogeneic HSCT. Unstimulated PBMC from a F-->M HSCT patient identified a CD4+ T cell response by ELISpot to a single DBY peptide that persisted for more than a 1-year period after transplant. The T cell epitope was identified as a 19-mer peptide starting at position 30 in the DBY sequence (DBY30-48) and restricted by HLA-DRB1*1501. Remarkably, the corresponding X homolog peptide (DBX30-48) was also recognized by female donor T cells. However this patient developed antibodies after HSCT that were specific for DBY and did not recognize DBX. These studies provided the first demonstration of a coordinated B cell and T cell immune response to an H-Y mHA in the context of chronic graft versus host disease following allogeneic HSCT.
3. Antibody Response to H-Y Minor Histocompatibility Antigens Correlates with Chronic Graft versus Host Disease and Disease Remission.
We examined clinical features of 75 M-->F HSCT patients to determine whether they were associated with the development of antibodies to H-Y proteins. H-Y antibody development strongly correlated with chronic GVHD (Adjusted Odds Ratio: 56.5; p<0.0001). Interestingly, thirteen patients relapsed 5 months to 4 years after transplant. None of these patients had developed antibodies to H-Y and disease relapse was significantly associated with absence of H-Y antibody (p<0.0001).

Our demonstration that patients with chronic GVHD develop antibody responses to mHA suggests new high-throughput serologic screening approaches to identify novel mHA, and suggests that B cell targeted therapies may be effective against chronic GVHD. H-Y antibody detection is a rapid and efficient method to identify female donors who have preexisting immunity to H-Y proteins. Ongoing studies will determine if pre-sensitized female stem cell donors are associated with an increased incidence of GVHD in male stem cell recipients, and would therefore provide useful information in the selection of potential stem cell donors. The overall goal of my laboratory studies is a complete characterization of B cell allogeneic immune response after HSCT, characterizing B and T cell coordinated mHA immune responses, and defining the role of novel mHA in the development of GVHD and prevention of disease relapse.