Multipotent Vδ2-negative γδT-cells after CMV-reactivation in allogeneic stem cell transplantation (162.36)

Human cytomegalovirus (CMV) infections and relapse of disease remain major problems after allogeneic stem cell transplantation (allo-SCT). Great promise as an alternative strategy, with a potential use for very broad patient population, arises from the non-MHC-restricted target-recognition of cancer cells and virally-infected cells by γδT-cells. Therefore, we investigated the role of γδT-cells after allo-SCT and CMV infection. An increase in selectively Vδ1-positive γδT-cells was observed in CMV-reactivating patients from CMV-positive conventional donors. Even more important, γδT-cell expansions were also observed after CMV-negative cordblood transplantation. However, in contrast to expansions from CMV-positive donors, γδT-cells from cordblood donors did not only include Vδ1-positive but also Vδ3-positive cells. Expanded Vδ2-negative γδT-cells were not only able to lyse CMV-infected fibroblasts, but also to partially mature dendritic cells (DCs) and to kill primary leukemic blasts. CMV- and leukemia-reactivity were restricted to the same clonal population and separated from DC-maturation capacities of Vδ2-negative T-cells. Vδ2-negative γδTCRs selectively mediated anti-leukemia-reactivity. This makes CMV-reactive γδT-cells e.g. from cordblood donors as well as individual Vδ2-negative γδTCRs interesting candidates for adoptive immunotherapy strategies

The immunological phenotype of rituximab-sensitive chronic graft-versus-host disease: a phase II study

Chronic graft-versus-host disease is the major long-term complication after allogeneic stem cell transplantation with a suboptimal response rate to current treatments. Therefore, clinical efficacy and changes in lymphocyte subsets before and after rituximab treatment were evaluated in a prospective phase II study in patients with steroid-refractory chronic graft-versus-host disease. Overall response rate was 61%. Only responding patients were found to have increased B-cell numbers prior to treatment. B cells had a naïve-antigen-presenting phenotype and were mainly CD5 negative or had a low CD5 expression. Normal B-cell homeostasis was reestablished in responding patients one year after ritxumab treatment and associated with a significant decline in skin-infiltrating CD8(+) T cells, suggesting that host B cells play a role in maintaining pathological CD8(+) T-cell responses. Imbalances in B-cell homeostasis could be used to identify patients a priori with a higher chance of response to rituximab treatment (Eudra-CT 2008-004125-42).

Rituximab treatment before reduced-intensity conditioning transplantation associates with a decreased incidence of extensive chronic GVHD

Chronic graft-versus-host-disease (cGVHD) is the major cause of late morbidity and mortality after allogeneic stem cell transplantation. B cells have been reported to be involved in mediating cGVHD. To assess whether preemptive host B cell depletion prevents extensive cGVHD after allogeneic reduced-intensity conditioning transplantation (RICT), 173 patients treated with RICT for various hematologic diseases, who had or had not received Rituximab (Rtx) within 6 month prior to RICT, were analyzed retrospectively. Rtx treatment within 6 months prior to RICT reduced extensive cGVHD significantly from 45.8% to 20.1%. We hypothesize that most likely host B cells initiate cGVHD, and thus, host B cell depletion prior to RICT by Rtx might be a valuable strategy to reduce extensive cGVHD after RICT.

Immune surveillance of EBV-infected B cells and the development of non-Hodgkin lymphomas in immunocompromised patients

After infection with the Epstein - Barr virus, a common gammaherpes virus which infects and persists in the B cells, an equilibrium is established in which newly infected and differentiating B cells are controlled by cytotoxic T cell (CTL) responses. Disturbance of this equilibrium, which can occur in immunocompromised situations, can lead to uncontrolled lymphoproliferation and subsequent development of non-Hodgkin Lymphomas (NHL). Here, we review the role of immunesurveillance of EBV-infected B cells and two situations where immunesurveillance is altered because of immunodeficiencies, transplantation recipients and HIV infection, which can lead to EBV-mediated NHL. In transplant recipients, immunosuppression prior and during transplantation can lead to lack of immunesurveillance and results in proliferation of infected B cells, which would normally be controlled by CTL responses. Interestingly, in HIV infection both deregulation of the normal B cell biology and a reduction in immunity play a role in developing NHL. Therefore, the nature of EBV infection in HIV-positive subjects is very different from that in transplanted individuals, in whom (re-)appearance of EBV-specific CD8(+) T cells - either by a decrease in immune suppression or infusion of donor lymphocytes - immediately leads to a decrease in EBV load.