title: Ex vivo alloanergization with belatacept: a strategy to selectively modulate alloresponses after transplantation.
abstract: Ex vivo alloanergization of human immune cells, via allostimulation in the presence of costimulatory blockade with either a combination of anti-B7.1 and anti-B7.2 antibodies or first-generation cytotoxic T-lymphocyte antigen 4-immunoglobulin (CTLA4-Ig), induces alloantigen-specific  hyporesponsiveness and expands alloantigen-specific regulatory T cells (Treg). We have successfully used this approach in the clinical setting of haploidentical hematopoietic stem cell transplantation. Recently, the in vivo use of a new second-generation CTLA4-Ig, belatacept, has shown promise  in controlling alloresponses after transplantation of both human kidneys and islet cells. We therefore compared the efficiency of first- and second-generation CTLA4-Ig in alloanergizing human peripheral blood mononuclear cells (PBMCs) and investigated whether ex vivo alloanergization with  belatacept could be used to engineer an alloantigen-specific immunoregulatory population of autologous cells suitable for administration to recipients of cellular or solid organ transplant recipients. Alloanergization of HLA-mismatched human PBMCs with belatacept resulted in a greater reduction  in subsequent alloresponses than alloanergization with first generation CTLA4-Ig. Moreover, subsequent ex vivo re-exposure of alloanergized cells to alloantigen in the absence of belatacept resulted in a significant expansion of Tregs with enhanced alloantigen-specific suppressive function.  Alloanergized PBMCs retained functional Epstein-Barr virus (EBV)-specific T-cell responses, and expanded Tregs did not suppress EBV-specific proliferation of autologous cells. These results suggest that ex vivo alloanergization with belatacept provides a platform to engineer populations of  recipient Treg with specificity for donor alloantigens but without nonspecific suppressive capacity. The potential advantages of such cells for solid organ transplantation include (1) reduction of the need for nonspecific immunosuppression, (2) retention of pathogen-specific immunity, and  (3) control of graft rejection, if used as an intervention.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
authors.forename: Jeff K
authors.initials: JK
authors.lastname: Davies
authors.forename: Christine M
authors.initials: CM
authors.lastname: Barbon
authors.forename: Annie
authors.initials: A
authors.lastname: Voskertchian
authors.forename: Lee M
authors.initials: LM
authors.lastname: Nadler
authors.forename: Eva C
authors.initials: EC
authors.lastname: Guinan
mesh_terms: D000069594:Abatacept; D000939:Epitopes; D006680:HLA Antigens / Q000276:immunology; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods; D006801:Humans; D018796:Immunoconjugates / Q000008:administration & dosage*; D007166:Immunosuppressive Agents / Q000008:administration & dosage*; D007519:Isoantigens / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology; D014181:Transplantation Immunology
chemical_list: D000939:Epitopes; D006680:HLA Antigens; D018796:Immunoconjugates; D007166:Immunosuppressive Agents; D007519:Isoantigens; D000069594:Abatacept