Macrophage-inducible C-type lectin activates B cells to promote T cell reconstitution in heart allograft recipients.

Diminishing homeostatic proliferation of memory T cells is essential for improving the efficacy of lymphoablation in transplant recipients. Our previous studies in a mouse heart transplantation model established that B lymphocytes secreting proinflammatory cytokines are critical for T cell recovery after lymphoablation. The goal of the current study was to identify mediators of B cell activation following lymphoablation in allograft recipients. Transcriptome analysis revealed that macrophage-inducible C-type lectin (Mincle, Clec4e) expression is up-regulated in B cells from heart allograft recipients treated with murine anti-thymocyte globulin (mATG). Recipient Mincle deficiency diminishes B cell production of pro-inflammatory cytokines and impairs T lymphocyte reconstitution. Mixed bone marrow chimeras lacking Mincle only in B lymphocytes have similar defects in T cell recovery. Conversely, treatment with a synthetic Mincle ligand enhances T cell reconstitution after lymphoablation in non-transplanted mice. Treatment with agonistic CD40 mAb facilitates T cell reconstitution in CD4 T cell-depleted, but not in Mincle-deficient, recipients indicating that CD40 signaling induces T cell proliferation via a Mincle-dependent pathway. These findings are the first to identify an important function of B cell Mincle as a sensor of damage-associated molecular patterns released by the graft and demonstrate its role in clinically relevant settings of organ transplantation.

CTOTC-08: A multicenter randomized controlled trial of rituximab induction to reduce antibody development and improve outcomes in pediatric lung transplant recipients.

We conducted a randomized, placebo-controlled, double-blind study of pediatric lung transplant recipients, hypothesizing that rituximab plus rabbit anti-thymocyte globulin induction would reduce de novo donor-specific human leukocyte antigen antibodies (DSA) development and improve outcomes. We serially obtained clinical data, blood, and respiratory samples for at least one year posttransplant. We analyzed peripheral blood lymphocytes by flow cytometry, serum for antibody development, and respiratory samples for viral infections using multiplex PCR. Of 45 subjects enrolled, 34 were transplanted and 27 randomized to rituximab (n = 15) or placebo (n = 12). No rituximab-treated subjects versus five placebo-treated subjects developed de novo DSA with mean fluorescence intensity >2000. There was no difference between treatment groups in time to the primary composite outcome endpoint (death, bronchiolitis obliterans syndrome [BOS] grade 0-p, obliterative bronchiolitis or listing for retransplant). A post-hoc analysis substituting more stringent chronic lung allograft dysfunction criteria for BOS 0-p showed no difference in outcome (p = .118). The incidence of adverse events including infection and rejection episodes was no different between treatment groups. Although the study was underpowered, we conclude that rituximab induction may have prevented early DSA development in pediatric lung transplant recipients without adverse effects and may improve outcomes (Clinical Trials: NCT02266888).

Age-related effects on thymic output and homeostatic T cell expansion following depletional induction in renal transplant recipients.

Thymic output and homeostatic mature cell proliferation both influence T cell repopulation following depletional induction, though the relative contribution of each and their association with recipient age have not been well studied. We investigated the repopulating T cell kinetics in kidney transplant recipients who underwent alemtuzumab induction followed by belatacept/rapamycin-based immunosuppression over 36-month posttransplantation. We focused specifically on the correlation between repopulating T cell subsets and the age of patients. Substantial homeostatic Ki67-expressing T cell proliferation was seen posttransplantation. A repertoire enriched for naïve T (TNaïve ) cells emerged posttransplantation. Analysis by generalized estimating equation linear models revealed a strong negative linear association between reconstituting TNaïve cells and advancing age. A relationship between age and persistence of effector memory cells was shown. We assessed thymic output and found an increase in the frequency of recent thymic emigrants (RTEs, CD4+ CD31+ ) at 12-month posttransplantation. Patients under 30 years of age showed significantly higher levels of CD4+ CD31+ cells than patients over 55 years of age pre- and posttransplantation. IL-7 and autologous mature dendritic cells (mDCs) induced CD57- cell proliferation. In contrast, mDCs, but not IL-7, induced CD57+ cell proliferation. This study establishes the relationship between age and thymic output during T cell homeostatic repopulation after alemtuzumab induction. Trial Registration: ClinicalTrials.gov - NCT00565773.

Liver transplantation for acute liver failure in a SARS-CoV-2 PCR-positive patient.

Current guidelines recommend deferring liver transplantation (LT) in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection until clinical improvement occurs and two PCR tests collected at least 24 hours apart are negative. We report a case of an 18-year-old, previously healthy African-American woman diagnosed with COVID-19, who presents with acute liver failure (ALF) requiring urgent LT in the context of SARS-CoV-2 polymerase chain reaction (PCR) positivity. The patient was thought to have acute Wilsonian crisis on the basis of hemolytic anemia, alkaline phosphatase:bilirubin ratio <4, AST:ALT ratio >2.2, elevated serum copper, and low uric acid, although an unusual presentation of COVID-19 causing ALF could not be excluded. After meeting criteria for status 1a listing, the patient underwent successful LT, despite ongoing SARS-CoV-2 PCR positivity. Remdesivir was given immediately posttransplant, and mycophenolate mofetil was withheld initially and the SARS-CoV-2 PCR test eventually became negative. Three months following transplantation, the patient has made a near-complete recovery. This case highlights that COVID-19 with SARS-CoV-2 PCR positivity may not be an absolute contraindication for transplantation in ALF. Criteria for patient selection and timing of LT amid the COVID-19 pandemic need to be validated in future studies.

Idiopathic pulmonary fibrosis lung transplant recipients are at increased risk for EBV-associated posttransplant lymphoproliferative disorder and worse survival.

Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disorder (EBV-PTLD) is a serious complication in lung transplant recipients (LTRs) associated with significant mortality. We performed a single-center retrospective study to evaluate the risks for PTLD in LTRs over a 7-year period. Of 611 evaluable LTRs, we identified 28 cases of PTLD, with an incidence of 4.6%. Kaplan-Meier analysis showed a decreased freedom from PTLD in idiopathic pulmonary fibrosis (IPF)-LTRs (P < .02). Using a multivariable Cox proportional hazards model, we found IPF (hazard ratio [HR] 3.51, 95% confidence interval [CI] 1.33-8.21, P = .01) and alemtuzumab induction therapy (HR 2.73, 95% CI 1.10-6.74, P = .03) as risk factors for PTLD, compared to EBV mismatch (HR: 34.43, 95% CI 15.57-76.09, P < .0001). Early PTLD (first year) was associated with alemtuzumab use (P = .04), whereas IPF was a predictor for late PTLD (after first year) (P = .002), after controlling for age and sex. Kaplan-Meier analysis revealed a shorter time to death from PTLD in IPF LTRs compared to other patients (P = .04). The use of alemtuzumab in EBV mismatch was found to particularly increase PTLD risk. Together, our findings identify IPF LTRs as a susceptible population for PTLD. Further studies are required to understand the mechanisms driving PTLD in IPF LTRs and develop strategies to mitigate risk.

B cell reconstitution following alemtuzumab induction under a belatacept-based maintenance regimen.

Lymphocyte depletion has been shown to control costimulation blockade-resistant rejection but, in some settings, to exacerbate antibody-mediated rejection (AMR). We have used alemtuzumab, which depletes T and B cells, combined with belatacept and rapamycin and previously reported control of both costimulation blockade-resistant rejection and AMR. To evaluate this regimen's effect on B cell signatures, we investigated 40 patients undergoing this therapy. B cell counts and phenotypes were interrogated using flow cytometry, and serum was analyzed for total IgG, IgM, and donor-specific alloantibody (DSA). Alemtuzumab induction produced pan-lymphocyte depletion; B cells repopulated faster and more completely than T cells. Reconstituting B cells were predominantly naïve, and memory B cells were significantly reduced (P = .001) post repopulation. Two B cell populations with potential immunomodulatory effects-regulatory (CD38hi CD24hi IgMhi CD20hi ) and transitional B cells (CD19+ CD27- IgD+ CD38hi )-were enriched posttransplant (P = .001). Total serum IgG decreased from baseline (P = .016) while IgM levels remained stable. Five patients developed DSAs within 36 months posttransplant, but none developed AMR. Baseline IgG levels in these patients were significantly higher than those in patients without DSAs. These findings suggest that belatacept and rapamycin together limit homeostatic B cell activation following B cell depletion and may lessen the risk of AMR. This regimen warrants prospective, comparative study. ClinicalTrials.gov NCT00565773.

Belatacept-based immunosuppression with simultaneous calcineurin inhibitor avoidance and early corticosteroid withdrawal: A prospective, randomized multicenter trial.

Simultaneous calcineurin inhibitor avoidance (CNIA) and early corticosteroid withdrawal (ESW) have not been achieved primarily due to excessive acute rejection. This trial compared 2 belatacept-based CNIA/ESW regimens with a tacrolimus-based ESW regimen. Kidney transplant recipients were randomized to receive alemtuzumab/belatacept, rabbit anti-thymocyte globulin (rATG)/belatacept, or rATG/tacrolimus. The combinatorial primary endpoint consisted of patient death, renal allograft loss, or a Modification of Diet in Renal Disease-calculated eGFR of <45 mL/min/1.73 m2 at 12 months. Results are reported by treatment group (alemtuzumab/belatacept, rATG/belatacept, and rATG/tacrolimus). Superiority was not observed at 1 year for the primary endpoint (9/107 [8.4%], 15/104 [14.4%], and 14/105 [13.3%], respectively; P = NS) for either belatacept-based regimen. Differences were not observed for secondary endpoints (death, death-censored graft loss, or estimated glomerular filtration rates < 45 mL/min/1.73 m2 ). Differences were observed in biopsy-proved acute cellular rejection (10.3%, 18.3%, and 1.9%, respectively) (P < .001), but not in antibody-mediated rejection, mixed acute rejection, or de novo donor-specific anti-HLA antibodies. Neurologic and electrolyte abnormality adverse events were less frequent under belatacept. Belatacept-based CNIA/ESW regimens did not prove to be superior for the primary or secondary endpoints. Belatacept-treated patients demonstrated an increase in biopsy-proved acute cellular rejection and reduced neurologic and metabolic adverse events. These results demonstrate that simultaneous CNIA/ESW is feasible without excessive acute rejection.

The use of induction therapy in liver transplantation is highly variable and is associated with posttransplant outcomes.

The use of induction immunosuppression in liver transplantation (LT) remains controversial. This was a retrospective cohort study of adult, first-time liver-alone recipients (N = 69 349) at 114 US centers between 2005 and 2018 using data from the United Network for Organ Sharing. The comparative effectiveness of nondepleting and depleting induction (NDI and DI) was assessed. Overall, 27% of recipients received induction with 65.7% of the variance in the receipt of induction being attributed to transplant center alone. NDI and DI were associated with a lower risk of death/graft failure compared to no induction (adjusted hazard ratio 0.90 [95% confidence interval (CI): 0.86-0.95] and 0.91 [95% CI: 0.85-0.97], respectively; P < .001). In nondialysis recipients at the mean transplant estimated glomerular filtration rate (eGFR), NDI was associated with an adjusted gain in eGFR by 6 months of +3.8 mL/min per 1.73 m2 and DI of +3.33 mL/min per 1.73 m2 compared to no induction (P < .001). Recipients with lower eGFR at LT had greater predicted improvement in eGFR (interaction P < .001). Only NDI was associated with a reduced risk of acute rejection in the first year post-LT (odds ratio 0.87, 95% CI: 0.8-0.94). Significant variability in induction practices exists, with center being a major determinant. The absolute incremental benefits of NDI and DI over no induction were small.

Rabbit anti-thymocyte globulin for the prevention of acute rejection in kidney transplantation.

This report describes the results of 2 international randomized trials (total of 508 kidney transplant recipients). The primary objective was to assess the noninferiority of rabbit anti-thymocyte globulin (rATG, Thymoglobulin® ) versus interleukin-2 receptor antagonists (IL2RAs) for the quadruple endpoint (treatment failure defined as biopsy-proven acute rejection, graft loss, death, or loss to follow-up) to serve as the pivotal data for United States (US) regulatory approval of rATG. The pooled analysis provided an incidence of treatment failure of 25.1% in the rATG and 36.0% in the IL2RA treatment groups, an absolute difference of -10.9% (95% confidence interval [CI] -18.8% to -2.9%) supporting noninferiority (noninferiority margin was 10%) and superiority of rATG to IL2RA. In a meta-analysis of 7 trials comparing rATG with an IL2RA, the difference in the proportion of patients with BPAR at 12 months was -4.8% (95% CI -8.6% to -0.9%) in favor of rATG. In conclusion, a rigorous reanalysis of patient-level data from 2 prior randomized, controlled trials comparing rATG versus IL-2R monoclonal antibodies provided support for regulatory approval for rATG for induction therapy in renal transplant, making it the first T cell-depleting therapy approved for the prophylaxis of acute rejection in patients receiving a kidney transplant in the United States.

Long-term survival in visceral transplant recipients in the new era: A single-center experience.

There is a paucity of data on long-term outcomes following visceral transplantation in the contemporary era. This is a single-center retrospective analysis of all visceral allograft recipients who underwent transplant between November 2003 and December 2013 with at least 3-year follow-up data. Clinical data from a prospectively maintained database were used to assess outcomes including patient and graft survival. Of 174 recipients, 90 were adults and 84 were pediatric patients. Types of visceral transplants were isolated intestinal transplant (56.3%), combined liver-intestinal transplant (25.3%), multivisceral transplant (16.1%), and modified multivisceral transplant (2.3%). Three-, 5-, and 10-year overall patient survival was 69.5%, 66%, and 63%, respectively, while 3-, 5-, and 10-year overall graft survival was 67%, 62%, and 61%, respectively. In multivariable analysis, significant predictors of survival included pediatric recipient (P = .001), donor/recipient weight ratio <0.9 (P = .008), no episodes of severe acute rejection (P = .021), cold ischemia time <8 hours (P = .014), and shorter hospital stay (P = .0001). In conclusion, visceral transplantation remains a good option for treatment of end-stage intestinal failure with parenteral nutritional complications. Proper graft selection, shorter cold ischemia time, and improvement of immunosuppression regimens could significantly improve the long-term survival.

IL-7 receptor heterogeneity as a mechanism for repertoire change during postdepletional homeostatic proliferation and its relation to costimulation blockade-resistant rejection.

Kidney transplant patients treated with belatacept without depletional induction experience higher rates of acute rejection compared to patients treated with conventional immunosuppression. Costimulation blockade-resistant rejection (CoBRR) is associated with terminally differentiated T cells. Alemtuzumab induction and belatacept/sirolimus immunotherapy effectively prevent CoBRR. We hypothesized that cells in late phases of differentiation would be selectively less capable than more naive phenotypes of repopulating postdepletion, providing a potential mechanism by which lymphocyte depletion and repopulation could reduce the risk of CoBRR. Lymphocytes from 20 recipients undergoing alemtuzumab-induced depletion and belatacept/sirolimus immunosuppression were studied longitudinally for markers of maturation (CCR7, CD45RA, CD57, PD1), recent thymic emigration (CD31), and the IL-7 receptor-α (IL-7Rα). Serum was analyzed for IL-7. Alemtuzumab induction produced profound lymphopenia followed by repopulation, during which naive IL-7Rα+ CD57- PD1- cells progressively became the predominant subset. This did not occur in a comparator group of 10 patients treated with conventional immunosuppression. Serum from depleted patients showed markedly elevated IL-7 levels posttransplantation. Sorted CD57- PD1- cells demonstrated robust proliferation in response to IL-7, whereas more differentiated cells proliferated poorly. These data suggest that differences in IL-7-dependent proliferation is one exploitable mechanism that distinguishes CoB-sensitive and CoB-resistant T cell populations to reduce the risk of CoBRR. (ClinicalTrials.gov - NCT00565773.).