Computational design of orthogonal membrane receptor-effector switches for rewiring signaling pathways.

Membrane receptors regulate numerous intracellular functions. However, the molecular underpinnings remain poorly understood because most receptors initiate multiple signaling pathways through distinct interaction interfaces that are structurally uncharacterized. We present an integrated computational and experimental approach to model and rationally engineer membrane receptor-intracellular protein systems signaling with novel pathway selectivity. We targeted the dopamine D2 receptor (D2), a G-protein-coupled receptor (GPCR), which primarily signals through Gi, but triggers also the Gq and beta-arrestin pathways. Using this approach, we designed orthogonal D2-Gi complexes, which coupled with high specificity and triggered exclusively the Gi-dependent signaling pathway. We also engineered an orthogonal chimeric D2-Gs/i complex that rewired D2 signaling from a Gi-mediated inhibitory into a Gs-dependent activating pathway. Reinterpreting the evolutionary history of GPCRs in light of the designed proteins, we uncovered an unforeseen hierarchical code of GPCR-G-protein coupling selectivity determinants. The results demonstrate that membrane receptor-cytosolic protein systems can be rationally engineered to regulate mammalian cellular functions. The method should prove useful for creating orthogonal molecular switches that redirect signals at the cell surface for cell-engineering applications.

Review: Insights into molecular mechanisms of disease in neurodegeneration with brain iron accumulation: unifying theories.

Neurodegeneration with brain iron accumulation (NBIA) is a group of disorders characterized by dystonia, parkinsonism and spasticity. Iron accumulates in the basal ganglia and may be accompanied by Lewy bodies, axonal swellings and hyperphosphorylated tau depending on NBIA subtype. Mutations in 10 genes have been associated with NBIA that include Ceruloplasmin (Cp) and ferritin light chain (FTL), both directly involved in iron homeostasis, as well as Pantothenate Kinase 2 (PANK2), Phospholipase A2 group 6 (PLA2G6), Fatty acid hydroxylase 2 (FA2H), Coenzyme A synthase (COASY), C19orf12, WDR45 and DCAF17 (C2orf37). These genes are involved in seemingly unrelated cellular pathways, such as lipid metabolism, Coenzyme A synthesis and autophagy. A greater understanding of the cellular pathways that link these genes and the disease mechanisms leading to iron dyshomeostasis is needed. Additionally, the major overlap seen between NBIA and more common neurodegenerative diseases may highlight conserved disease processes. In this review, we will discuss clinical and pathological findings for each NBIA-related gene, discuss proposed disease mechanisms such as mitochondrial health, oxidative damage, autophagy/mitophagy and iron homeostasis, and speculate the potential overlap between NBIA subtypes.

The immunogenicity of virus-derived 2A sequences in immunocompetent individuals.

Genetic engineering of T cells for adoptive immunotherapy in cancer patients has shown significant promise. To ensure optimal antitumor activity and safety, the simultaneous expression of multiple genes is frequently required, and short viral-derived 2A sequences are increasingly preferred for this purpose. Concerns exist, however, that these virus-derived sequences may induce unwanted immune responses, and thus diminish persistence of the gene-modified cells after adoptive transfer. Whereas such responses were absent in immunocompromised recipients, potential immunogenicity in immunocompetent individuals remains a concern. We now address whether ex vivo T cell responses can be elicited against the most widely used 2A sequences (2A-Thosea asigna virus (TAV) or 2A-equine rhinitis virus (ERAV), specifically) in immunocompetent individuals. We used a potent ex vivo culture system previously validated to induce T cell responses even against weakly immunogenic antigens. Of the sixteen donors tested, only five released very low levels of interferon-γ in response to 2A-TAV peptide mixtures (single peptide specificity in three donors, adjacent self-antigen peptide specificity in one donor and nonspecific reactivity in one donor). None of them produced cytotoxic activity or responded to 2A-ERAV. These results suggest that exposure to viral-derived 2A sequences is unlikely to produce unwanted T cell responses in immunocompetent individuals and further supports their continued use for studies of human gene therapy.

High-dose melphalan with or without stem cell support before myeloablative allo-SCT for remission induction in patients with advanced relapsed or refractory AML.

Treatment strategies for relapsed/refractory AML are limited and disappointing. Recently, high-dose melphalan (HDM) chemotherapy and autologous hematopoietic SCT (HSCT) has been proposed for AML re-induction. We investigated the impact of HDM remission induction in highly advanced relapsed/refractory AML patients planned for allogeneic HSCT. A total of 23 patients with relapsed/refractory AML were prospectively scheduled for HDM with or without stem cell support followed by myeloablative allogeneic HSCT. Patients included nine individuals with a history of previous HSCT (seven allogeneic, two autologous). A total of 18 patients (78%) achieved a leukemia-free state and an additional four had substantial reduction of the initial leukemia burden warranting treatment continuation. There were no differences between patients with or without immediate stem cell support regarding mucositis or other organ toxicity. A total of 20 patients proceeded to myeloablative allogeneic HSCT. Outcome of allogeneic HSCT was poor: 11 patients (55%) relapsed, 7 patients (35%) died from TRM and only 2 patients (10%) were alive at the last follow-up. Our study shows that HDM is effective in inducing a leukemia-free state in patients with highly advanced relapsed/refractory AML. Leukemia burden reduction with HDM, however, did not translate into improved OS.

Cyclosporine levels and rate of graft rejection following non-myeloablative conditioning for allogeneic hematopoietic SCT.

Hematopoietic SCT (HSCT) after non-myeloablative conditioning is associated with reduced TRM, and increased risk of graft rejection. Although preclinical data have shown the importance of post transplant immunosuppression in achieving engraftment, little is known about the role of CSA in the clinical setting of non-myeloablative transplantation. In a retrospective analysis of patients treated with allogeneic HSCT after fludarabine and 2 Gy TBI, 15 of 77 evaluable patients (20%) experienced primary (n=2) or secondary graft rejection at a median of 66 days post transplant. Mean day 1-28 CSA trough levels were inversely associated with day 28 chimerism (median 99, 85 and 70% for mean CSA <300, 300-600 and >600 ng/mL, respectively; P=0.003). A similar association was observed for the cumulative incidence of graft rejection, which occurred in 8% (<300 ng/mL), 26% (300-600 ng/mL) and 50% (>600 ng/mL, P=0.005) of patients. The detrimental effect of high CSA levels on engraftment was confirmed in multivariable models and was found to operate comparably in sibling and unrelated donor transplants. Impairment of donor T-cell function by high serum levels of CSA might account for this finding, which should be verified in a larger patient group to better understand the role of CSA in non-myeloablative transplantation.

Graft source determines human hematopoietic progenitor distribution pattern within the CD34(+) compartment.

The CD34(+) compartment of grafts for clinical allogeneic hematopoietic cell transplantation (HCT) is very heterogeneous. It contains hematopoietic stem cells and several different progenitor cell populations. This study assesses (1) the content of these populations in clinical grafts from G-CSF-mobilized PBMCs, BM and cord blood, (2) the functional correlation of the graft composition with time to engraftment of neutrophils, platelets and reticulocytes and (3) donor age-related changes. Quantitative flow cytometry showed that the distribution of the progenitor subsets differed significantly between the graft sources and that donor age-related changes occur. In patients after myeloablative allogeneic HCT, accelerated platelet and reticulocyte engraftment correlated with the content of common myeloid and/or megakaryocyte erythroid progenitors in the graft. These findings show that a better understanding of the progenitor compartment in human hematopoietic grafts could lead to improved strategies for the development of cellular therapies, for example in situations where platelet engraftment is delayed.

Sideroblastic changes of the bone marrow can be predicted by the erythrogram of peripheral blood.

The diagnosis of sideroblastic anemia is based on bone marrow aspiration, and the detection of ring sideroblasts (RS) in iron staining. The finding of laboratory parameters to approach this diagnosis still remains a great challenge. In this study, we analyzed the value of a specific erythrogram pattern from peripheral blood, produced by the ADVIA120 cell counter, to predict sideroblastic changes in the bone marrow. In a two step-design study, we first showed that 32/38 consecutive patients reporting > or =15% RS had such a pattern in the erythrogram. In the second step, we prospectively identified over a period of 32 months 21 patients with this typical erythrogram; 20/21 had > or =15% RS in the bone marrow. Hence, by this validation, we confirm that the erythrogram is highly predictive of RS in the bone marrow. The interpretation of the erythrogram should become daily practice in hematology to improve the efficacy to detect sideroblastic changes.

Double allogeneic hematopoietic SCT as a rescue therapy for poor-risk hematological malignancies.

The prognosis of patients with poor-risk or relapsed hematological malignancies is dismal. The dose intensification necessary to achieve subsequent CR is limited by the toxicity of chemotherapy. Treatment intensification with double allogeneic HSCT (dHSCT) may enhance the antileukemic effect and reduces treatment-related toxicity associated with prolonged aplasia during reinduction. We evaluated this approach in 23 patients, nine with primary refractory disease or relapse after conventional chemotherapy (group I) and 14 with relapses after allogeneic HSCT (group II). Double HSCT was feasible in all patients. At the end of the observation period, 6 of 23 (26%) patients were still alive and in remission with a median observation time of 60 months (1-153). The overall survival probability at 1 year was 41% (95% confidence interval (CI), 21-62%), transplant-related mortality (TRM) 28% (9-47%) and the incidence of relapse 42% (18-66%). The TRM in groups I and II were 22 and 36% and the relapse rate 33 and 50%, respectively. In conclusion, we have shown the feasibility of dHSCT with an acceptable TRM, irrespective of a previous allogeneic HSCT. Whether this approach offers a survival benefit for patients with poor-risk leukemias has to be tested in larger prospective trials.

Impaired B-cell reconstitution in lymphoma patients undergoing allogeneic HSCT: an effect of pretreatment with rituximab?

Allogeneic hematopoietic SCT (HSCT) is increasingly considered an option in refractory or relapsing lymphoma. Today, most patients with B-cell lymphoma are treated with the monoclonal anti-CD20 antibody rituximab before HSCT. We hypothesized that prior therapy with rituximab might alter immune reconstitution after allogeneic transplantation due to in vivo depletion of B cells at the time of graft infusion. We studied B-cell immune reconstitution in 12 patients with lymphoma receiving rituximab 1-12 months before HSCT. Compared to an age- and sex-matched population of patients transplanted for myeloid malignancies, lymphoma patients with rituximab pretreatment showed significantly reduced B-cell counts at time of HSCT at +3, +6 and +12 months; B-cell counts reached values comparable to controls only 24 months after HSCT. In parallel, levels of immunoglobulins were markedly reduced for up to 2 years post transplant in patients with prior rituximab treatment. Two patients suffered from severe late bacterial infections to which the impaired humoral immunity may have contributed. In contrast, T- and NK-cell reconstitution was not different compared to control patients.In conclusion, B-cell reconstitution can be significantly delayed in allogeneic HSCT recipients with prior rituximab treatment. Rituximab appears to have clinical consequences beyond the immediate early post-transplant period.

Visceral leishmaniasis: a threat to immunocompromised patients in non-endemic areas?

Visceral leishmaniasis is rare in western Europe, but may be life-threatening in immunocompromised patients. It is therefore important to understand the incidence of the disease in a non-endemic area and its relationship with immunosuppressive conditions. Between 1990 and 2005, 12 patients were diagnosed with leishmaniasis at Basel University Hospital, Switzerland. Eleven presented with visceral symptoms and ten had an underlying immunosuppressive condition. Since increasing numbers of immunosuppressed patients have a history of travel to endemic countries, an association of visceral leishmaniasis with cellular immunosuppression (other than that associated with human immunodeficiency virus) might become more frequent in non-endemic areas.

High-dose chemotherapy using BEAM without autologous rescue followed by reduced-intensity conditioning allogeneic stem-cell transplantation for refractory or relapsing lymphomas: a comparison of delayed versus immediate transplantation.

Patients with refractory/relapsing lymphoma are rarely cured by chemotherapy. High-dose chemotherapy (HDC) for tumor debulking followed by reduced-intensity conditioning (RIC) hematopoietic stem-cell transplantation (HSCT) has been advocated as a concept. We previously treated 10 patients (group A) with BEAM chemotherapy followed by delayed RIC HSCT at day 28. We now report on the subsequent 11 patients receiving BEAM followed immediately by fludarabine/total body irradiation and allogeneic HSCT (group B), and compare the outcome to group A patients. Non-hematological toxicity before engraftment was comparable, only gut toxicity was higher in group B. Days in aplasia, days on antibiotics and length of hospital stay were significantly longer in group A. Cumulative incidence of acute (GvHD) >or=grade II and incidence of chronic GvHD were lower in group B. At last follow-up, seven patients in group A were alive, with six of them in complete remission. In group B, nine patients were alive, seven of them in complete remission. No significant difference in estimated 3-year overall survival was seen. These data challenge the initial concept of debulking first and delaying allogeneic RIC HSCT. Allogeneic HSCT with standard BEAM conditioning is a valid alternative for patients with resistant/relapsed lymphoma, which might be considered earlier in the disease course.

C-reactive protein and fever in neutropenic patients.

The predictive value of daily C-reactive protein (CRP) monitoring to distinguish causes of fever in neutropenic patients was studied retrospectively. A total of 143 fever episodes during 113 consecutive hospitalizations were studied in 71 patients who had been referred for chemotherapy or haemopoietic stem cell transplantation (HSCT). There were, on average, 1.3 fever episodes per hospital stay, attributed to: infection (55, 27 invasive bacterial, 5 fungal, 3 viral and 20 probable infections); acute graft vs host disease (GvHD) (20); drugs (22); transfusions (7); and not attributable (39). 130 (91%) fever episodes were accompanied by a rise in CRP, 6 (4%) episodes were fatal. Maximal CRP levels (CRPmax) and maximal temperature (Tmax) were higher in invasive bacterial infections than in aGvHD and higher in aGvHD than in drug- or transfusion-related fever (p < 0.0001). Temperature and CRP rose in parallel. A total of 16 patients developed grade II-IV aGvHD by day 11 (9-21) (median, range) after allogeneic HSCT. Acute GvHD was preceded by fever for 3 d (1-7), and by CRP increase for 5 d (0-15) (p < 0.0001). CRP monitoring may be useful to distinguish between causes of fever. Very high CRP levels tend to be associated with invasive bacterial infections. CRP is not an early warning sign. An increase in CRP and fever may precede other clinical manifestations of aGvHD.

Dissociation of parathyroid hormone bioactivity and immunoreactivity in pseudohypoparathyroidism type I.

Circulating levels of parathyroid hormone (PTH) in six patients with pseudohypoparathyroidism type I (PSPI) have been measured by two immunoassays and by cytochemical bioassay and compared with measurements in normal subjects and patients with clinically defined hyper- and hypoparathyroidism. In all PSPI patients, the levels of immunoreactive PTH were in the hyperparathyroid range, whereas the bioactive levels were either in the normal or close to the normal range. In one patient from whom the dihydrotachysterol therapy was withdrawn, both immunoreactive and bioactive PTH concentrations increased. The finding that the PTH measured by RIA in these PSPI patients may have reduced biological activity may explain some of the clinical findings of hypoparathyroidism in this syndrome.