Addition of Anti-thymocyte Globulin in Allogeneic Stem Cell Transplantation With Peripheral Stem Cells From Matched Unrelated Donors Improves Graft-Versus-Host Disease and Relapse Free Survival.

Anti-thymocyte globulin (ATG) is commonly used to prevent graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). To evaluate the impact of ATG as part of the GvHD prophylaxis in our institution, we report the outcome of 415 patients with matched unrelated donors (MUD) transplanted for hematological malignancies with or without ATG from 2005 to 2019 at Oslo University Hospital, Norway. The following groups were compared: (1) 154 patients transplanted with peripheral blood stem cells (PBSC) without ATG 2005-2014. (2) 137 patients transplanted with bone marrow stem cells (BMSC) 2005-2019. (3) 124 patients transplanted with PBSC and ATG (PBSC + ATG) 2014-2019. Three years survival was similar in the groups, 61% following allografting with PBSC, 54% with BMSC, and 59% with PBSC + ATG. Acute GvHD grade III-IV was 14%, 14%, and 7%; chronic GvHD was 81%, 32, and 26%; and extensive cGvHD 44%, 15%, and 6% in the corresponding groups. Both acute and chronic GvHD were significantly reduced in the PBSC + ATG-versus the PBSC group (p < 0.05 and p < 0.001 respectively).Transplant-related mortality (TRM) was 33%, 25%, and 17% (p = 0.18). Graft versus host disease and relapse free survival (GRFS) at 3 years was 43 %, 43%, and 64% in the groups. Adding ATG to the GvHD prophylaxis regimen of MUD allo-HSCT with PBSC resulted in a substantial reduction of both acute and chronic GvHD without compromising the disease control, reflected in a superior 3 years GRFS.

Antithymocyte globulin administration in patients with profound lymphopenia receiving a PBSC purine analog/busulfan-based conditioning regimen allograft.

Graft-versus host disease (GVHD) remains one of the main causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (ASCT). Prophylactic T cell depletion via antithymocyte globulin (ATG) during ASCT conditioning is one of the standards of care for GVHD prophylaxis, although the optimal dosing strategy is still unclear. Recent studies have reported that absolute lymphocyte count at the time of ATG administration could predict survivals in ASCT from unrelated donors. Here this issue was examined in 116 patients receiving peripheral blood stem cells (PBSC) ASCT with purine analog/busulfan-based conditioning regimens between 2009 and 2019 in our department. The impact of lymphopenia at the time of ATG administration was evaluated in terms of overall survival, disease-free survival and GVHD-free/relapse-free survival. After a median follow-up of 4 years, no adverse effect of a profound lymphopenia was observed on patients' outcome. Notably, a reduced dose of ATG in patients with profound lymphopenia did not translate into better survivals. This study indicates that ATG can be administered whatever the recipient's lymphocyte counts in patients receiving a PBSC purine analog/busulfan-based conditioning regimen ASCT.

Outcomes of kidney transplantation from elderly deceased donors of a Korean registry.

To overcome organ shortage, expanded criteria donors, including elderly deceased donors (DDs), should be considered. We analyzed outcomes of kidney transplantation (KT) from elderly DDs in a nationwide study. In total, data of 1049 KTs from DDs using the database of Korean Organ Transplantation Registry (KOTRY) were retrospectively analyzed based on the age of DDs: age ≥60 years vs. <60 years. Clinical information, graft status, and adverse events were reviewed in DDs and recipients. The mean age of the 1006 DDs was 51.04±10.54 years, and 21.5% of donors were aged ≥60 years. Elderly DDs had a significantly higher prevalence of diabetes and hypertension and higher Kidney Donor Risk Index (KDRI) and Kidney Donor Profile Index (KDPI). The mean age of the recipients was 47.45±14.87 years. Patients who received KT from elderly DDs were significantly older (53.12±15.14 vs. 45.88±14.41, P<0.001) and had a higher rate of diabetes (41.9 vs. 24.4%, P<0.001). Graft outcomes were not significantly different. Renal function was similar between the groups at the time of discharge and at 6 months, 1 year, and 2 years after KT. The rate of delayed graft function (DGF) was not significantly different. Risk factors of DGF were significantly different in DDs aged ≥60 years and <60 years. In the multivariable model, male sex (odds ratio: 3.99, 95% confidence interval: 1.42-11.22; P = 0.009) and KDRI (12.17, 2.23-66.34; P = 0.004) were significant risk factors for DGF in DDs aged ≥60 years. In DDs aged <60 years, thymoglobulin induction (2.62, 1.53-4.48; P<0.001) and continuous renal replacement therapy (3.47, 1.52-7.96; P = 0.003) were significant factors. Our data indicated that graft outcomes, including renal function and DGF, were similar for elderly DDs and DDs aged <60 years. Elderly DDs might be considered tolerable donors for KT, with active preoperative surveillance.

Comparison of the clinical outcomes of hematologic malignancies after myeloablative haploidentical transplantation with G-CSF/ATG and posttransplant cyclophosphamide: results from the Chinese Bone Marrow Transplantation Registry Group (CBMTRG).

This study compared G-CSF/ATG and PTCy in myeloablative haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for hematologic malignancies between January 2013 and March 2018 reporting to the Chinese Bone Marrow Transplantation Registry Group (CBMTRG). For each PTCy, G-CSF/ATG subjects (1:4) were selected using the nested case-pair method. In total, 220 patients including 176 in G-CSF/ATG group and 44 in PTCy group were analyzed. The incidences of 30-day neutrophil engraftment (88.6% vs. 96.6%, P=0.001), 90-day platelet engraftment (84.1% vs. 94.2%, P=0.04), the median time to neutrophil engraftment (17 days vs. 12 days, P=0.000) and platelet engraftment (22 days vs. 17 days, P=0.001) were significantly inferior in PTCy group. The incidences of grades 2-4 and 3-4 acute graft-versus-host disease (GVHD), chronic GVHD and severe chronic GVHD were comparable. Among G-CSF/ATG and PTCy groups, the 3-year progression-free survival, overall survival, cumulative incidences of nonrelapse mortality and relapse was 74.3% vs. 61% (P=0.045), 78.3% vs. 65.2% (P=0.039), 12% vs. 27.3% (P=0.008), and 14.9% vs. 11.7% (P=0.61), respectively. G-CSF/ATG can achieve better engraftment, PFS and OS, and lower incidence of NRM compared to PTCy in myeloablative haplo-HSCT for hematologic malignancies.

Inhibition of HIV-1 envelope-dependent membrane fusion by serum antilymphocyte autoantibodies is associated with low plasma viral load.

The HIV-1 envelope protein (Env) mediates the membrane fusion process allowing virus entry to target cells and the efficiency to induce membrane fusion is an important determinant of HIV-1 pathogenicity. In addition to virus receptors, other adhesion/signaling molecules on infected and target cells and virus particles can enhance fusion. The presence of antilymphocyte autoantibodies (ALA) in HIV patients' serum suggests that they may contribute to the inhibition of Env-mediated membrane fusion. Here, sera from 38 HIV-1 infected treatment-naïve men and 30 healthy donors were analyzed for the presence of IgG and IgM able to bind to CD4-negative Jurkat cells. The use of CD4-negative cells precluded the binding of virus-antibody immune complexes, and allowed detection of ALA different from anti-CD4 antibodies. IgG and IgM antibodies binding to Jurkat CD4-negative cells was detected in 74% and 84% of HIV-positive sera, respectively. Then, the activity of sera on fusion of CD4+ with HIV Env+ Jurkat cells was determined before and after their adsorption on CD4-negative Jurkat cells to remove ALA. Sera inhibited fusion at variable extents, and inhibitory activity decreased in 58% of serum samples after adsorption, indicating that ALA contributed to fusion inhibition in these sera (herein called fusion inhibitory ALA). The contribution of ALA to fusion inhibition in individual sera was highly variable, with an average of 33%. IgG purified from a pool of HIV+ sera inhibited fusion of primary CD4 T lymphocytes with Jurkat Env+, and adsorption of IgG on CD4-negative Jurkat cells diminished the fusion inhibitory activity. Thus, the inhibitory activity of sera was related to IgG ALA. Our observations suggest that fusion inhibitory ALA other than anti-CD4 antibodies may contribute significantly to the inhibition of Env-mediated cell-cell fusion. Fusion inhibitory ALA, but not total ALA levels, associated with low plasma viral loads, suggesting that specific ALA may participate in virus containment by inhibiting virus-cell fusion in a significant fraction of HIV-infected patients.

Antirelapse effect of pretransplant exposure to rabbit antithymocyte globulin.

It remains unknown why rabbit antithymocyte globulin (ATG; Thymoglobulin) has not affected relapse after hematopoietic cell transplantation (HCT) in randomized studies. We hypothesized that high pre-HCT ATG area under the curve (AUC) would be associated with a low incidence of relapse, whereas high post-HCT AUC would be associated with a high incidence of relapse. We measured serum levels of ATG capable of binding to mononuclear cells (MNCs), lymphocytes, T cells, CD4 T cells, or CD33 cells. We estimated pre- and post-HCT AUCs in 152 adult recipients of myeloablative conditioning and blood stem cells. High pre-HCT AUCs of MNC- and CD33 cell-binding ATG were associated with a low incidence of relapse and high relapse-free survival (RFS). There was a trend toward an association of high post-HCT AUC of lymphocyte-binding ATG with a high incidence of relapse and low RFS. High pre-HCT AUCs were also associated with faster engraftment and had no impact on graft-versus-host disease (GVHD) or fatal infections. High post-HCT AUCs were associated with a low risk of GVHD, seemed associated with an increased risk of fatal infections, and had no impact on engraftment. In conclusion, pre-HCT AUC seems to have a positive, whereas post-HCT AUC seems to have a negative, impact on relapse.

Effect of plasmapheresis on ATG (Thymoglobulin) clearance prior to adoptive T cell transfer.

The effect of anti-thymocyte globulin (ATG) on the outcome of hematopoietic stem cell transplantation (SCT) is dependent on formulation, dose and exposure. However, ATG levels are not routinely measured and therapeutic levels are not well defined. In ex vivo T cell-deplete SCT, the potential effect of residual ATG has important implications on the timing of adoptive T cell transfer. Here we measured active rabbit ATG concentration using a flow cytometry-based method that can be implemented in any laboratory. Three adult patients received 6 mg/kg Thymoglobulin over 4 days, leading to peak plasma active ATG concentration of 20.8 ± 1.4 µg/mL, suggesting volume of distribution of 16-19 L. The half-life of active ATG was 6.1 ± 0.7 days and plasmapheresis at Day 25 ± 1 post-transplant reduced mean plasma concentration from 1.25 to 0.61 µg/mL. Total ATG and active ATG do not have a constant relationship because of differences in volumes of distribution and half-lives. Thymoglobulin can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro at concentrations as low as 0.03 µg/mL, with a log-linear relationship between ATG concentration and ADCC. Plasmapheresis can remove ATG but likely has modest biological impact when performed 4 weeks after 6 mg/kg ATG.

Midterm Results of Renal Transplantation From Controlled Cardiac Death Donors Are Similar to Those From Brain Death Donors.

BACKGROUND: The systematic use of grafts from controlled donors after cardiac death (cDCD) started in our country in 2012 and expanded with the strategic support of National Transplant Organization. We present our experience in kidney transplantation with organs from cDCD donors with a mean follow-up of 3 years. METHODS: Observational prospective study of all transplants performed in our center in 2012-2013 followed to 2016. The immunosuppression protocols were triple therapy for low-risk recipients from a standard brain death donor (DBD), adding basiliximab or thymoglobulin induction for extended-criteria donor or high-risk recipient, respectively, and thymoglobulin induction plus triple therapy for all cDCD recipients. RESULTS: A total of 42 donors were included (84 grafts in total, but 1 discarded due to multiple cysts); 25 DBD and 17 cDCD without differences in age or sex. The graft use rate was 98.9% for cDCD; 55 grafts were implanted in our hospital (26 DBD and 29 cDCD), and the remaining 28 grafts were transferred to other centers. There were no differences in primary failure (3.4% cDCD vs 7.4% DBD), but the cDCD organs had a higher incidence of delayed graft function (51.7% vs 25.9%). Despite that, graft and patient survivals, as well as glomerular filtration rate (66.3 vs 59.6 mL/min) were similar in both groups. Only 1 patient died at home with a functioning graft in the cDCD group. CONCLUSIONS: Despite a higher rate of delayed graft function with cDCD, the midterm outcomes are at least similar to those with DBD. The cDCD programs should be promoted to increase the chances of a transplant in our patients.

Impact of in vivo T-cell depletion on outcome of AML patients in first CR given peripheral blood stem cells and reduced-intensity conditioning allo-SCT from a HLA-identical sibling donor: a report from the Acute Leukemia Working Party of the European Group for Blood and Marrow Transplantation.

The impact of in vivo T-cell depletion on transplantation outcomes in patients transplanted with reduced-intensity conditioning (RIC) remains controversial. This study assessed the outcome of 1250 adult patients with de novo AML in first CR (CR1) given PBSC from HLA-identical siblings after chemotherapy-based RIC. A total of 554 patients did not receive any form of in vivo T-cell depletion (control group), whereas antithymocyte globulin (ATG) and alemtuzumab were given in 444 and 252 patients, respectively. The incidences of grade II-IV acute GVHD were 21.4, 17.6 and 10.2% in control, ATG and alemtuzumab patients, respectively (P<0.001). In multivariate analysis, the use of ATG and the use of alemtuzumab were each associated with a lower risk of chronic GVHD (P<0.001 each), but a similar risk of relapse, and of nonrelapse mortality, and similar leukemia-free survival and OS. Further, among patients given BU-based RIC, the use of <6 mg/kg ATG did not increase the risk of relapse (hazard ratio, HR=1.1), whereas there was a suggestion for higher relapse risk in patients given 6 mg/kg ATG (HR=1.4, P=0.08). In summary, these data suggest that a certain amount of in vivo T-cell depletion can be safely used in the conditioning of AML patients in CR1 given PBSC after chemotherapy-based RIC.

Synergies of phosphatidylserine and protein disulfide isomerase in tissue factor activation.

Tissue factor (TF), the cellular receptor and cofactor for factor VII/VIIa, initiates haemostasis and thrombosis. Initial tissue distribution studies suggested that TF was sequestered from the circulation and only present at perivascular sites. However, there is now clear evidence that TF also exists as a blood-borne form with critical contributions not only to arterial thrombosis following plaque rupture and to venous thrombosis following endothelial perturbation, but also to various other clotting abnormalities associated with trauma, infection, or cancer. Because thrombin generation, fibrin deposition, and platelet aggregation in the contexts of haemostasis, thrombosis, and pathogen defence frequently occur without TF de novo synthesis, considerable efforts are still directed to understanding the molecular events underlying the conversion of predominantly non-coagulant or cryptic TF on the surface of haematopoietic cells to a highly procoagulant molecule following cellular injury or stimulation. This article will review some of the still controversial mechanisms implicated in cellular TF activation or decryption with particular focus on the coordinated effects of outer leaflet phosphatidylserine exposure and thiol-disulfide exchange pathways involving protein disulfide isomerase (PDI). In this regard, our recent findings of ATP-triggered stimulation of the purinergic P2X7 receptor on myeloid and smooth muscle cells resulting in potent TF activation and shedding of procoagulant microparticles as well as of rapid monocyte TF decryption following antithymocyte globulin-dependent membrane complement fixation have delineated specific PDI-dependent pathways of cellular TF activation and thus illustrated additional and novel links in the coupling of inflammation and coagulation.

Impact of thymoglobulin prior to pediatric unrelated umbilical cord blood transplantation on immune reconstitution and clinical outcome.

In vivo T-cell depletion might contribute to the delayed immune reconstitution observed after unrelated umbilical cord blood transplantation (UCBT). We studied the impact of early, late, and no antithymocyte globulin (ATG) on immune reconstitution and outcome. One hundred twenty seven children receiving UCBT in London or Utrecht were divided into 3 groups: early ATG (days -9 to -5; n = 33), late ATG (days -5 to 0; n = 48), and no ATG (n = 46). The no-ATG group received mycophenolate mofetile + cyclosporin A as graft-versus-host disease (GVHD) prophylaxis, while the ATG groups received cyclosporin A + prednisone. End points studied were survival, immune recovery, infections, and GVHD. The probability of survival was similar in all groups: no ATG, 71% ± 8%; early ATG, 68% ± 9%; and late ATG, 61% ± 7%. CD3(+), CD4(+), and CD4(+)-naive T-cell counts were significantly higher (P < .001) in the no-ATG group at 1, 2, 3, 6, and 12 months post-UCBT. In the no-ATG group, significantly fewer viral reactivations (P = .021) were noted. A higher probability of severe acute GVHD (aGVHD; 31%) was found in the no-ATG group compared with 18% (P = .018) for early-ATG and 5% (P < .001) for late-ATG groups. This was not associated with more chronic GVHD (cGVHD).

Immunosuppression regimen and the risk of acute rejection in HIV-infected kidney transplant recipients.

BACKGROUND: Kidney transplantation (KT) is the treatment for end-stage renal disease in appropriate HIV-positive individuals. However, acute rejection (AR) rates are over twice those of HIV-negative recipients. METHODS: To better understand optimal immunosuppression for HIV-positive KT recipients, we studied associations between immunosuppression regimen, AR at 1 year, and survival in 516 HIV-positive and 93,027 HIV-negative adult kidney-only recipients using Scientific Registry of Transplant Recipients data from 2003 to 2011. RESULTS: Consistent with previous reports, HIV-positive patients had twofold higher risk of AR (adjusted relative risk [aRR], 1.77; 95% confidence interval [CI], 1.45-2.2; P<0.001) than their HIV-negative counterparts as well as a higher risk of graft loss (adjusted hazard ratio, 1.51; 95% CI, 1.18-1.94; P=0.001), but these differences were not seen among patients receiving antithymocyte globulin (ATG) induction (aRR for AR, 1.16; 95% CI, 0.41-3.35, P=0.77; adjusted hazard ratio for graft loss, 1.54; 95% CI, 0.73-3.25; P=0.26). Furthermore, HIV-positive patients receiving ATG induction had a 2.6-fold lower risk of AR (aRR, 0.39; 95% CI, 0.18-0.87; P=0.02) than those receiving no antibody induction. Conversely, HIV-positive patients receiving sirolimus-based therapy had a 2.2-fold higher risk of AR (aRR, 2.15; 95% CI, 1.20-3.86; P=0.01) than those receiving calcineurin inhibitor-based regimens. CONCLUSION: These findings support a role for ATG induction, and caution against the use of sirolimus-based maintenance therapy, in HIV-positive individuals undergoing KT.

The effect of rabbit antithymocyte globulin on human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) possess immunomodulatory properties which are of key interest for their application in autoimmunity and transplantation. In transplantation, administration of MSCs has shown promising results in preclinical models and has recently moved to clinical trials. Therefore, it is important to study the interactions between MSCs and immunosuppressive drugs currently used in transplantation. We aimed to analyze the effect of rabbit antithymocyte globulin (rATG) MSCs. MSCs were obtained from perirenal fat of kidney donors and exposed to ranging doses of rATG (Thymoglobulin(®) , Genzyme; 0.5-100 µg/ml). Binding of rATG, effects on viability and susceptibility to be killed by cytotoxic lymphocytes as well as effects on their immunosuppressive potential of MSCs were tested. rATG binds dose-dependently to MSCs. This binding was associated with slightly impaired viability after 48 and 72 h when compared with nonexposed MSCs. In contrast to nontreated MSCs, rATG preexposed MSCs were susceptible to be lysed by cytokine-activated CD8(+) cytotoxic cells and NKT cells. The capacity of MSCs to suppress the proliferation of anti-CD3/CD28 activated CD4 and CD8 T cells were reduced by the presence of rATG in the culture. rATG reduces the viability and antiproliferative capacity of MSCs in a dose-dependent manner and converts them into targets for CD8 T cells and NKT cell lysis.

Influence of maintenance steroids on the outcomes in deceased-donor kidney transplant recipients exposed to prolonged pretransplantation dialysis.

BACKGROUND: Pre-transplant dialysis duration exerts a graded negative influence on outcomes after kidney transplantation. Higher immune reactivity associated with prolonged dialysis with consequent increased acute rejection could be contributory. METHODS: Using the Organ Procurement and Transplant Network/United Network of Organ Sharing database, we identified patients ≥ 18 years of age who received deceased-donor kidney (DDK) transplants from 2000 to 2008 after being on maintenance dialysis for ≥ 4 years. Patients received induction therapy with rabbit antithymocyte globulin (r-ATG), alemtuzumab, or an interleukin-2 receptor blocker (IL-2B) and were discharged on calcineurin inhibitor (CNI)/mycophenolate mofetil (MMF)-based immunosuppression with or without steroid. Unadjusted and adjusted graft/patient survivals were compared in steroid versus no-steroid groups by induction type. RESULTS: A total of 14,459 patients were identified, of which 7,684 received r-ATG (steroid, 6,098; no-steroid, 1,586), 1,292 alemtuzumab (steroid, 362; no-steroid, 930), and 5,483 an IL-2B agent (steroid, 5,107; no-steroid, 376). Adjusted graft survivals were similar for steroid versus no-steroid groups in r-ATG (hazard ratio [HR] 1.10, 95% confidence interval (CI) 0.96-1.26, P = .16), alemtuzumab (HR 0.88, 95% CI 0.65-1.19; P = .40), and IL-2B (HR 0.91, 95% CI 0.73-1.13; P = .38) groups. Adjusted patient survival for steroid versus no-steroid groups was inferior in r-ATG (HR 1.41, 95% CI 1.17-1.71; P < .001) but similar in alemtuzumab (HR 1.05, 95% CI 0.70-1.59; P = .80) and IL-2B (HR 1.17, 95% CI 0.86-1.58; P = .32) groups. CONCLUSIONS: Our analysis failed to show a graft survival benefit for the addition of steroid to a CNI/MMF-based immunosuppression after induction with r-ATG, alemtuzumab, or an IL-2B agent in DDK recipients exposed to prolonged pretransplantation dialysis.

Anti-thymocyte globulins capable of binding to T and B cells reduce graft-vs-host disease without increasing relapse.

Anti-thymocyte globulin (ATG) is polyclonal, containing Ab specificities capable of binding to various immune-cell subsets implicated in the pathogenesis of GVHD, including T cells, B cells, natural killer cells, monocytes/macrophages, neutrophils and DC. We wished to determine which ATG specificities are important for GVHD prevention. We measured day 7 serum levels of 23 ATG specificities in 120 hematopoietic cell transplant recipients whose myeloablative conditioning included 4.5 mg/kg ATG (thymoglobulin). High levels of ATG specificities capable of binding to T- and B-cell subsets were associated with a low likelihood of acute GVHD (aGVHD). High levels of these ATG specificities were associated with increased rates of viral but not bacterial or fungal infections. They were not associated with an increased risk of malignancy relapse; on the contrary, high levels of ATG specificities capable of binding to regulatory T cells and invariant NKT cells were associated with a low risk of relapse. In conclusion, high levels of ATG antibodies to Ag(s) expressed on T and B cells are associated with a low risk of aGVHD and a high risk of viral but not bacterial or fungal infections. These antibodies have neutral or beneficial effects on relapse.

The role of Thymoglobulin induction in kidney transplantation: an update.

The rabbit antithymocyte globulin Thymoglobulin first became available over 25 yr ago and is the most widely used lymphocyte-depleting preparation in solid organ transplantation. Thymoglobulin targets a wide range of T-cell surface antigens as well as natural killer-cell antigens, B-cell antigens, plasma cell antigens, adhesion molecules and chemokine receptors, resulting in profound, long-lasting T-cell depletion. Randomized studies have established the anti-rejection efficacy of Thymoglobulin in kidney transplantation. Experimental and clinical data suggest that Thymoglobulin administration may ameliorate ischemia reperfusion injury, thus reducing the incidence of delayed graft function (DGF). Studies have demonstrated the benefit of using Thymoglobulin to facilitate immunosuppression minimization, both for corticosteroid and calcineurin inhibitor (CNI) withdrawal or avoidance, with potential improvement in cardiovascular and renal outcomes. The optimal cumulative dose for Thymoglobulin induction is 6-7.5 mg/kg, with vigilant short- and long-term monitoring of hematological status. Induction with Thymoglobulin is now indicated in immunologically high-risk patients, in those at increased risk of DGF and to maintain efficacy in low-risk transplant recipients receiving steroid or CNI minimization or avoidance regimens. We suggest that in future trials Thymoglobulin be tested with costimulation signal blockers and other immunosuppressants with the objective of establishing operational tolerance.

Immunopharmacologic response of patients with B-lineage acute lymphoblastic leukemia to continuous infusion of T cell-engaging CD19/CD3-bispecific BiTE antibody blinatumomab.

T cell-engaging CD19/CD3-bispecific BiTE Ab blinatumomab has shown an 80% complete molecular response rate and prolonged leukemia-free survival in patients with minimal residual B-lineage acute lymphoblastic leukemia (MRD(+) B-ALL). Here, we report that lymphocytes in all patients of a phase 2 study responded to continuous infusion of blinatumomab in a strikingly similar fashion. After start of infusion, B-cell counts dropped to < 1 B cell/µL within an average of 2 days and remained essentially undetectable for the entire treatment period. By contrast, T-cell counts in all patients declined to a nadir within < 1 day and recovered to baseline within a few days. T cells then expanded and on average more than doubled over baseline within 2-3 weeks under continued infusion of blinatumomab. A significant percentage of reappearing CD8(+) and CD4(+) T cells newly expressed activation marker CD69. Shortly after start of infusion, a transient release of cytokines dominated by IL-10, IL-6, and IFN-γ was observed, which no longer occurred on start of a second treatment cycle. The response of lymphocytes in leukemic patients to continuous infusion of blinatumomab helps to better understand the mode of action of this and other globally T cell-engaging Abs. The trial is registered with www.clinicaltrials.gov identifier NCT00560794.

Enhanced intrarenal receptor-mediated prorenin activation in chronic progressive anti-thymocyte serum nephritis rats on high salt intake.

Despite suppression of the circulating renin-angiotensin system (RAS), high salt intake (HSI) aggravates kidney injury in chronic kidney disease. To elucidate the effect of HSI on intrarenal RAS, we investigated the levels of intrarenal prorenin, renin, (pro)renin receptor (PRR), receptor-mediated prorenin activation, and ANG II in chronic anti-thymocyte serum (ATS) nephritic rats on HSI. Kidney fibrosis grew more severe in the nephritic rats on HSI than normal salt intake. Despite suppression of plasma renin and ANG II, marked increases in tubular prorenin and renin proteins without concomitant rises in renin mRNA, non-proteolytically activated prorenin, and ANG II were noted in the nephritic rats on HSI. Redistribution of PRR from the cytoplasm to the apical membrane, along with elevated non-proteolytically activated prorenin and ANG II, was observed in the collecting ducts and connecting tubules in the nephritic rats on HSI. Olmesartan decreased cortical prorenin, non-proteolytically activated prorenin and ANG II, and apical membranous PRR in the collecting ducts and connecting tubules, and attenuated the renal lesions. Cell surface trafficking of PRR was enhanced by ANG II and was suppressed by olmesartan in Madin-Darby canine kidney cells. These data suggest the involvement of the ANG II-dependent increase in apical membrane PRR in the augmentation of intrarenal binding of prorenin and renin, followed by nonproteolytic activation of prorenin, enhancement of renin catalytic activity, ANG II generation, and progression of kidney fibrosis in the nephritic rat kidneys on HSI. The origin of the increased tubular prorenin and renin remains to be clarified. Further studies measuring the urinary prorenin and renin are needed.

Allospecific CD154 + T-cytotoxic memory cells as potential surrogate for rejection risk in pediatric intestine transplantation.

Clinical end-points dictate large trial enrollments and exclude children with the rare intestine transplant procedure (ITx), who experience higher drug-related morbidity. We evaluate the novel rejection-risk parameter, allo-(antigen)-specific CD154 + TcMs (i) as surrogates for ACR using Prentice's criteria, (ii) for association with immunosuppression targets to determine Fleming's surrogate end-point designation, and (iii) as time-to-event end-point in a simulated comparison of alemtuzumab (NCT#01208337, n = 14) and rabbit anti-human thymocyte globulin (rATG, n = 16) among 30 children with ITx. CD154 + TcM were measured in MLR before, and at 1-60 and 61-200 days after ITx (NCT#01163578). CD154 + TcM correlate significantly with rejection severity (Spearman r = 0.685, p = 2.03E-5) and associate with biopsy-proven ITx rejection with sensitivity/specificity of 94%/84% [corrected] independent of immunosuppressant. Previously stated sensitivity of 90% is incorrect. [corrected]. The rejection-risk threshold of CD154 + TcM resolves rapidly in 200-day follow-up (46 ± 20 vs. 158 ± 59 days, p = 0.009, K-M) with alemtuzumab, which demonstrates lower 90-day ACR incidence (50% vs. 69%, p=NS, Fisher's exact), and is associated with accelerated prednisone minimization to ≤2.5 mg/day, compared with rATG (120 ± 28 vs. 180 ± 30 days, p = 0.027, K-M). As a surrogate end-point, time-to-rejection-risk resolution measured with CD154 + TcM portends 50% reduction in sample sizes in a simulated trial of alemtuzumab vs. rATG. Rejection-risk assessment with CD154 + TcM may enable informed immunosuppression minimization, and preliminary efficacy comparisons in pediatric ITx.