Minor Histocompatibility Antigen DBY Elicits a Coordinated B and T Cell Response after Allogeneic Stem Cell Transplantation

We examined the immune response to DBY, a model H-Y minor histocompatibility antigen (mHA) in a male patient with chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplant from a human histocompatibility leukocyte antigen (HLA)-identical female sibling. Patient peripheral blood mononuclear cells were screened for reactivity against a panel of 93 peptides representing the entire amino acid sequence of DBY. This epitope screen revealed a high frequency CD4(+) T cell response to a single DBY peptide that persisted from 8 to 21 mo after transplant. A CD4(+) T cell clone displaying the same reactivity was established from posttransplant patient cells and used to characterize the T cell epitope as a 19-mer peptide starting at position 30 in the DBY sequence and restricted by HLA-DRB1*1501. Remarkably, the corresponding X homologue peptide was also recognized by donor T cells. Moreover, the T cell clone responded equally to mature HLA-DRB1*1501 male and female dendritic cells, indicating that both DBY and DBX peptides were endogenously processed. After transplant, the patient also developed antibodies that were specific for recombinant DBY protein and did not react with DBX. This antibody response was mapped to two DBY peptides beginning at positions 118 and 536. Corresponding DBX peptides were not recognized. These studies provide the first demonstration of a coordinated B and T cell immune response to an H-Y antigen after allogeneic transplant. The specificity for recipient male cells was mediated by the B cell response and not by donor T cells. This dual DBX/DBY antigen is the first mHA to be identified in the context of chronic GVHD

Identification of FAM111A as an SV40 Host Range Restriction and Adenovirus Helper Factor

The small genome of polyomaviruses encodes a limited number of proteins that are highly dependent on interactions with host cell proteins for efficient viral replication. The SV40 large T antigen (LT) contains several discrete functional domains including the LXCXE or RB-binding motif, the DNA binding and helicase domains that contribute to the viral life cycle. In addition, the LT C-terminal region contains the host range and adenovirus helper functions required for lytic infection in certain restrictive cell types. To understand how LT affects the host cell to facilitate viral replication, we expressed full-length or functional domains of LT in cells, identified interacting host proteins and carried out expression profiling. LT perturbed the expression of p53 target genes and subsets of cell-cycle dependent genes regulated by the DREAM and the B-Myb-MuvB complexes. Affinity purification of LT followed by mass spectrometry revealed a specific interaction between the LT C-terminal region and FAM111A, a previously uncharacterized protein. Depletion of FAM111A recapitulated the effects of heterologous expression of the LT C-terminal region, including increased viral gene expression and lytic infection of SV40 host range mutants and adenovirus replication in restrictive cells. FAM111A functions as a host range restriction factor that is specifically targeted by SV40 LT

The Fe-MAN Challenge:Ferrates-Microkinetic Assessment of Numerical Quantum Chemistry

Organometallic species, such as organoferrate ions, are prototypical nucleophiles prone to reacting with a wide range of electrophiles, including proton donors. In solution, the operation of dynamic equilibria and the simultaneous presence of several organometallic species severely complicate the analysis of these fundamentally important reactions. This can be overcome by gas-phase experiments on mass-selected ions, which allow for the determination of the microscopic reactivity of the target species. In this contribution, we focus on the reactivity of a series of trisarylferrate complexes toward 2,2,2-trifluoroethanol and 2,2-difluoroethanol. By means of mass-spectrometric measurements, we determined the experimental bimolecular rate constants kexp of the gas-phase protolysis reactions of the trisarylferrate anions FePh3- and FeMes3- with the aforementioned acids. Based on these experiments, we carried out a dual blind challenge, inviting theoretical groups to submit their best predictions for the activation barriers and/or theoretical rate constants ktheo. This provides a unique opportunity to evaluate different computational protocols under minimal bias and sets the stage for further benchmarking of quantum chemical methods and data-driven approaches in the future. </p

Antibody response to DBY minor histocompatibility antigen is induced after allogeneic stem cell transplantation and in healthy female donors

Minor histocompatibility antigens (mHAs) recognized by donor T cells play a central role as immunologic targets of graft-versus-host disease (GVHD) and graft versus leukemia after allogeneic hematopoietic stem cell transplantation (HSCT). Men who have undergone sex-mismatched allogeneic HSCT are at high risk for GVHD because of immune responses directed against mHAs encoded by genes on the Y chromosome (termed H-Y antigens). We hypothesized that the immunogenicity of mHAs results in a coordinated response involving B cells as well as T cells. To test this, we measured antibody responses to a well-characterized H-Y antigen, dead box RNA helicase Y (DBY), and its homolog, DBX, in 150 HSCT patients. Using Western blot and enzyme-linked immunosorbent assay (ELISA), we found that 50% of male patients who received stem cell grafts from female donors developed antibody responses to recombinant DBY protein. Antibodies to DBY were also detected in 17% of healthy women, but not in healthy men. Antibody responses were directed primarily against areas of amino acid disparity between DBY and DBX. These studies demonstrate that the immune response to mHA includes the generation of specific antibodies and suggests that the serologic response to these antigens may also be useful in the identification of new mHAs