Ibrutinib suppresses alloantibody responses in a mouse model of allosensitization

Desensitization Strategies for Donor-Specific Antibodies in HLA-Mismatched Stem Cell Transplantation Recipients: What We Know and What We Do Not Know

In human leukocyte antigen (HLA)-mismatched allogeneic stem cell transplantation settings, donor-specific anti-HLA antibodies (DSAs) can independently lead to graft failure, including both primary graft rejection and primary poor graft function. Although several strategies, such as plasma exchange, intravenous immunoglobulin, rituximab, and bortezomib, have been used for DSA desensitization, the effectiveness of desensitization and transplantation outcomes in some patients remain unsatisfactory. In this review, we summarized recent research on the prevalence of anti-HLA antibodies and the underlying mechanism of DSAs in the pathogenesis of graft failure. We mainly focused on desensitization strategies for DSAs, especially novel methods that are being investigated in the preclinical stage and those with promising outcomes after preliminary clinical application.

Translating B cell immunology to the treatment of antibody-mediated allograft rejection

Antibody-mediated rejection (AMR), including chronic AMR (cAMR), causes ~50% of kidney allograft losses each year. Despite attempts to develop well-tolerated and effective therapeutics for the management of AMR, to date, none has obtained FDA approval, thereby highlighting an urgent unmet medical need. Discoveries over the past decade from basic, translational and clinical studies of transplant recipients have provided a foundation for developing novel therapeutic approaches to preventing and treating AMR and cAMR. These interventions are aimed at reducing donor-specific antibody levels, decreasing graft injury and fibrosis, and preserving kidney function. Innovative approaches emerging from basic science findings include targeting interactions between alloreactive T cells and B cells, and depleting alloreactive memory B cells, as well as donor-specific antibody-producing plasmablasts and plasma cells. Therapies aimed at reducing the cytotoxic antibody effector functions mediated by natural killer cells and the complement system, and their associated pro-inflammatory cytokines, are also undergoing evaluation. The complexity of the pathogenesis of AMR and cAMR suggest that multiple approaches will probably be required to treat these disease processes effectively. Definitive answers await results from large, double-blind, multicentre, randomized controlled clinical trials.

Screening and Management of PTLD

Posttransplant lymphoproliferative disorder (PTLD) represents a heterogeneous group of lymphoproliferative diseases occurring in the setting of immunosuppression following hematopoietic stem cells transplant and solid organ transplantation. Despite its overall low incidence, PTLD is a serious complication following transplantation, with a mortality rate as high as 50% in transplant recipients. Therefore, it is important to establish for each transplant recipient a personalized risk evaluation for the development of PTLD based on the determination of Epstein-Barr virus serostatus and viral load following the initiation of immunosuppression. Due to the dynamic progression of PTLD, reflected in the diverse pathological features, different therapeutic approaches have been used to treat this disorder. Moreover, new therapeutic strategies based on the administration of virus-specific cytotoxic T cells have been developed. In this review, we summarize the available data on screening and treatment to suggest a strategy to identify transplant recipients at a higher risk for PTLD development and to review the current therapeutic options for PTLD.

Validation of a Mathematical Model Describing the Dynamics of Chemotherapy for Chronic Lymphocytic Leukemia In Vivo

In recent years, mathematical models have developed into an important tool for cancer research, combining quantitative analysis and natural processes. We have focused on Chronic Lymphocytic Leukemia (CLL), since it is one of the most common adult leukemias, which remains incurable. As the first step toward the mathematical prediction of in vivo drug efficacy, we first found that logistic growth best described the proliferation of fluorescently labeled murine A20 leukemic cells injected in immunocompetent Balb/c mice. Then, we tested the cytotoxic efficacy of Ibrutinib (Ibr) and Cytarabine (Cyt) in A20-bearing mice. The results afforded calculation of the killing rate of the A20 cells as a function of therapy. The experimental data were compared with the simulation model to validate the latter’s applicability. On the basis of these results, we developed a new ordinary differential equations (ODEs) model and provided its sensitivity and stability analysis. There was excellent accordance between numerical simulations of the model and results from in vivo experiments. We found that simulations of our model could predict that the combination of Cyt and Ibr would lead to approximately 95% killing of A20 cells. In its current format, the model can be used as a tool for mathematical prediction of in vivo drug efficacy, and could form the basis of software for prediction of personalized chemotherapy.

The effect of rapamycin and ibrutinib on antibody responses to adeno-associated virus vector-mediated gene transfer

Adeno-associated virus (AAV) vector-mediated gene transfer is lessening the impact of monogenetic disorders. Human AAV gene therapy recipients commonly mount immune responses to AAV or the encoded therapeutic protein, which requires transient immunosuppression. Most efforts to date have focused on blunting AAV capsid-specific T cell responses, which have been implicated in elimination of AAV transduced cells. Here we explore the use of immunosuppressants, rapamycin given alone or in combination with ibrutinib to inhibit AAV vector- or transgene product-specific antibody responses. Our results show that rapamycin or ibrutinib given alone reduce primary antibody responses against AAV capsid but the combination of rapamycin and ibrutinib is more effective, blunts recall responses, and reduces numbers of circulating antibody-secreting plasma cells. The drugs fail to lower B cell memory formation or to reduce the inhibitory effects of pre-existing AAV capsid-specific antibodies on transduction efficiency.

Novel Therapeutic Approaches to Allosensitization and Antibody-mediated Rejection

Modification of pathogenic antibodies for autoimmune diseases illuminated the biologic relevance of B cells, plasma cells, and pathogenic antibodies in autoimmunity. They have also rejuvenated interest in how B cells mediate multiple effector functions that include antibody production, antigen presentation to T cells, costimulation, and the production of immune stimulating and immune modulatory cytokines. Repurposing these drugs from autoimmunity and cancer immunotherapy has yielded important advancements in the care of antibody-mediated rejection patients and novel drug development aimed at HLA desensitization have recently emerged. We now stand on an important threshold that promises many advances in the care of our allosensitized patients. We hope that these initial advances will encourage basic scientist, clinical investigators, industry, National Institutes of Health, our academic societies, and the Food and Drug Administration to continue support of these important objectives. These advances clearly have implications for sensitized patients receiving solid organ transplants and antibody-mediated rejection treatment. Modification of alloimmunity and alloantibodies will also have relevance to xenotransplantation where the xenoantibodies present a formidable obstacle to advancement of this important therapy. Working together, we can advance transplant therapeutics where biologic agents are likely to play novel and important roles. Here, we discuss novel drugs emerging in this area.