Lower tacrolimus exposure and time in therapeutic range increase the risk of de novo donor‐specific antibodies in the first year of kidney transplantation

De novo donor‐specific antibodies (dnDSAs) have been associated with reduced graft survival. Tacrolimus (TAC)–based regimens are the most common among immunosuppressive approaches used in in clinical practice today, yet an optimal therapeutic dose to prevent dnDSAs has not been established. We evaluated mean TAC C₀ (tacrolimus trough concentration) and TAC time in therapeutic range for the risk of dnDSAs in a cohort of 538 patients in the first year after kidney transplantation. A mean TAC C₀ < 8 ng/mL was associated with dnDSAs by 6 months (odds ratio [OR] 2.51, 95% confidence interval [CI] 1.32–4.79, P = .005) and by 12 months (OR 2.32, 95% CI 1.30–4.15, P = .004), and there was a graded increase in risk with lower mean TAC C₀. TAC time in the therapeutic range of <60% was associated with dnDSAs (OR 2.05, 95% CI 1.28‐3.30, P = .003) and acute rejection (hazard ratio [HR] 4.18, 95% CI 2.31–7.58, P < .001) by 12 months and death‐censored graft loss by 5 years (HR 3.12, 95% CI 1.53–6.37, P = .002). TAC minimization may come at a cost of higher rates of dnDSAs, and TAC time in therapeutic range may be a valuable strategy to stratify patients at increased risk of adverse outcomes.     

Efficacy and safety of everolimus with reduced tacrolimus in living‐donor liver transplant recipients: 12‐month results of a randomized multicenter study

In a multicenter, open‐label, study, 284 living‐donor liver transplant patients were randomized at 30 ± 5 days posttransplant to start everolimus+reduced tacrolimus (EVR+rTAC) or continue standard tacrolimus (TAC Control). EVR+rTAC was non‐inferior to TAC Control for the primary efficacy endpoint of treated BPAR, graft loss or death at 12 months posttransplant: difference –0.7% (90% CI ?5.2%, 3.7%); P < .001 for non‐inferiority. Treated BPAR occurred in 2.2% and 3.6% of patients, respectively. The key secondary endpoint, change in estimated glomerular filtration rate (eGFR) from randomization to month 12, achieved non‐inferiority (P < .001 for non‐inferiority), but not superiority and was similar between groups overall (mean ?8.0 vs. ?12.1 mL/min/1.73 m², P = .108), and in patients continuing randomized treatment (?8.0 vs. ?13.3 mL/min/1.73 m², P = .046). In the EVR+rTAC and TAC control groups, study drug was discontinued in 15.5% and 17.6% of patients, adverse events with suspected relation to study drug occurred in 57.0% and 40.4%, and proteinuria ≥1 g/24 h in 9.3% and 0%, respectively. Everolimus did not negatively affect liver regeneration. At 12 months, hepatocellular recurrence was only seen in the standard TAC‐treated patients (5/62; 8.1%). In conclusion, early introduction of EVR+rTAC was non‐inferior to standard tacrolimus in terms of efficacy and renal function at 12 months, with hepatocellular carcinoma recurrence only in TAC Control patients. ClinicalTrials.gov Identifier: NCT01888432.     

Spectrum of chronic lung allograft pathology in a mouse minor‐mismatched orthotopic lung transplant model

Chronic lung allograft dysfunction (CLAD) is a fatal condition that limits survival after lung transplantation (LTx). The pathological hallmark of CLAD is obliterative bronchiolitis (OB). A subset of patients present with a more aggressive CLAD phenotype, called restrictive allograft syndrome (RAS), characterized by lung parenchymal fibrosis (PF). The mouse orthotopic single LTx model has proven relevant to the mechanistic study of allograft injury. The minor‐alloantigen‐mismatched strain combination using C57BL/10(B10) donors and C57BL/6(B6) recipients reportedly leads to OB. Recognizing that OB severity is a spectrum that may coexist with other pathologies, including PF, we aimed to characterize and quantify pathologic features of CLAD in this model. Left LTx was performed in the following combinations: B10→B6, B6→B10, B6→B6. Four weeks posttransplant, blinded pathologic semi‐quantitative assessment showed that OB was present in 66% of B10→B6 and 30% of B6→B10 grafts. Most mice with OB also had PF with a pattern of pleuroparenchymal fibroelastosis, reminiscent of human RAS‐related pathology. Grading of pathologic changes demonstrated variable severity of airway fibrosis, PF, acute rejection, vascular fibrosis, and epithelial changes, similar to those seen in human CLAD. These assessments can make the murine LTx model a more useful tool for further mechanistic studies of CLAD pathogenesis.     

T Cells Promote Bronchial Epithelial Cell Secretion of Matrix Metalloproteinase‐9 via a C‐C Chemokine Receptor Type 2 Pathway: Implications for Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is the major limitation of long‐term survival after lung transplantation. CLAD manifests as bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS). Alloimmune reactions and epithelial‐to‐mesenchymal transition have been suggested in BOS. However, little is known regarding the role of allogenicity in epithelial cell differentiation. Primary human bronchial epithelial cells (BECs) were treated with activated T cells in the presence or absence of transforming growth factor (TGF)‐β. The expression of epithelial and mesenchymal markers was investigated. The secretion of inflammatory cytokines and matrix metalloproteinase (MMP)‐9 was measured in culture supernatants and in plasma from lung transplant recipients (LTRs): 49 stable, 29 with BOS, and 16 with RAS. We demonstrated that C‐C motif chemokine 2 secreted by T cells supports TGF‐β–induced MMP‐9 production by BECs after binding to C‐C chemokine receptor type 2. Longitudinal investigation in LTRs revealed a rise in plasma MMP‐9 before CLAD onset. Multivariate analysis showed that plasma MMP‐9 was independently associated with BOS (odds ratio [OR] = 6.19, p = 0.002) or RAS (OR = 3.9, p = 0.024) and predicted the occurrence of CLAD 12 months before the functional diagnosis. Thus, immune cells support airway remodeling through the production of MMP‐9. Plasma MMP‐9 is a potential predictive biomarker of CLAD.     

Efficacy and safety of prolonged‐release tacrolimus in stable pediatric allograft recipients converted from immediate‐release tacrolimus – a Phase 2, open‐label,single‐arm,one‐way crossover study

There are limited clinical data regarding prolonged‐release tacrolimus (PR‐T) use in pediatric transplant recipients. This Phase 2 study assessed the efficacy and safety of PR‐T in stable pediatric kidney, liver, and heart transplant recipients (aged ≥5 to ≤16 years) over 1 year following conversion from immediate‐release tacrolimus (IR‐T), on a 1:1 mg total‐daily‐dose basis. Endpoints included the incidence of acute rejection (AR), a composite endpoint of efficacy failure (death, graft loss, biopsy‐confirmed AR, and unknown outcome), and safety. Tacrolimus dose and whole‐blood trough levels (target 3.5–15 ng/ml) were also evaluated. Overall, 79 patients (kidney, n = 48; liver, n = 29; heart, n = 2) were assessed. Following conversion, tacrolimus dose and trough levels remained stable; however, 7.6–17.7% of patients across follow‐up visits had trough levels below the target range. Two (2.5%) patients had AR, and 3 (3.8%) had efficacy failure. No graft loss or deaths were reported. No new safety signals were identified. Drug‐related treatment‐emergent adverse events occurred in 28 patients (35.4%); most were mild, and all resolved. This study suggests that IR‐T to PR‐T conversion is effective and well tolerated over 1 year in pediatric transplant recipients and highlights the importance of therapeutic drug monitoring to maintain target tacrolimus trough levels.     

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.     

Immunosuppressive effect of the gut microbiome altered by high‐dose tacrolimus in mice

The alterations induced in gut microbiota by tacrolimus may affect immune function and organ transplantation. Mice were treated with high‐dose tacrolimus for 14 days. The fecal microbiota were analyzed by pyrosequencing the 16S rRNA genes, and the effect on metabolism was predicted using the sequence data. The subgroups of T cells in the serum, gut‐associated lymphoid tissue, and draining lymph nodes were determined by flow cytometry. Tacrolimus treatment significantly altered the relative abundance of Allobaculum, Bacteroides, and Lactobacillus and CD4⁺CD25^hiFoxP3⁺ regulatory T cells in the colonic mucosa and the circulation. These were significantly increased after either tacrolimus treatment or treatment by fecal microbiota transfer from tacrolimus‐treated donors. Further, treatment with low‐dose tacrolimus plus fecal microbiota transfer from high‐dose tacrolimus–altered mice increased skin allograft survival rate in a skin transplantation model. Thus, high‐dose tacrolimus alters the compositions and taxa of the gut microbiota. Administration of these conditioned gut microbiota plus low‐dose tacrolimus resulted in regulation of colonic and systemic immune responses and an increased allograft survival rate. This study demonstrated a new strategy for controlling allograft rejection by combining an immunosuppressive agent with gut microbiome transplantation.     

Assessment of tacrolimus intrapatient variability in stable adherent transplant recipients: Establishing baseline values

The purpose of this study was to determine the intrapatient (within the same patient) variability of tacrolimus in adherent patients. Daily tacrolimus trough levels were obtained at home using dried blood spot technology in kidney and liver transplant recipients. Patients were randomized to receive 3 formulations of tacrolimus, each for two 1‐week periods. Adherence was monitored by patient diary, pill counts, and use of the Medication Event Monitoring System (MEMS). Variability was quantified as the coefficient of variation (CV). Comparison of CV between groups was by independent t test or one‐way ANOVA as appropriate. The population was found to be adherent with a rate of 99.9% with a mean interval between the evening and morning dose of tacrolimus of 11.86 hours. The median CV for the entire population was 15.2% (range 4.8%‐110%). There were no differences in CV by allograft type or tacrolimus formulation. The multivariate analysis did not identify any demographic characteristics associated with a CV > 30%. In a highly adherent population, tacrolimus did not display high intrapatient variability. Given the association between IPV and poor allograft outcomes, future studies are needed to quantitate the influence of adherence and establish target IPV goals.     

A randomized trial of everolimus‐based quadruple therapy vs standard triple therapy early after lung transplantation

Calcineurin inhibitor (CNI) therapy after lung transplantation increases risk of kidney failure. Early everolimus‐based quadruple low CNI immunosuppression may improve renal function without compromising efficacy or safety. A prospective, randomized, open‐label, 12‐month multicenter trial was conducted at 8 German sites. Patients 3‐18 months after lung transplantation were randomized (1:1), stratified by baseline estimated glomerular filtration rate (eGFR). In the quadruple low CNI regimen, patients received everolimus (target trough level 3‐5 ng/mL) with reduced CNI (tacrolimus 3‐5 ng/mL or cyclosporine 25‐75 ng/mL) and a cell cycle inhibitor plus prednisone. In the standard triple CNI regimen, patients received tacrolimus (target trough level >5 ng/mL) or cyclosporine (>100 ng/mL) and a cell cycle inhibitor plus prednisone. Of the 180 patients screened, 130 were randomized: 67 in the quadruple low CNI group and 63 in the standard triple CNI group. The primary endpoint (eGFR after 12 months) demonstrated superiority of the quadruple low CNI regimen: 64.5 mL/min vs 54.6 mL/min for the standard triple group (least squares mean, analysis of covariance; P < .001). Key efficacy parameters (biopsy‐proven acute rejection, chronic lung allograft dysfunction, and death) and safety endpoints were similar between both groups. Quadruple low CNI immunosuppression early after lung transplantation was demonstrated to be efficacious and safe. Clinical trials registry: ClinicalTrials.gov NCT01404325.     

Reduction of Extended‐Release Tacrolimus Dose in Low‐Immunological‐Risk Kidney Transplant Recipients Increases Risk of Rejection and Appearance of Donor‐Specific Antibodies: A Randomized Study

The aim of this study (ClinicalTrials.gov, NCT01744470) was to determine the efficacy and safety of two different doses of extended‐release tacrolimus (TacER) in kidney transplant recipients (KTRs) between 4 and 12 mo after transplantation. Stable steroid‐free KTRs were randomized (1:1) after 4 mo: Group A had a 50% reduction in TacER dose with a targeted TacER trough level (C₀) >3 μg/L; group B had no change in TacER dose (TacER C₀ 7–12 μg/L). The primary outcome was estimated GFR at 1 year. Of 300 patients, the intent‐to‐treat analysis included 186 patients (group A, n = 87; group B, n = 99). TacER C₀ was lower in group A than in group B at 6 mo (4.1 ± 2.7 vs. 6.7 ± 3.9 μg/L, p < 0.0001) and 12 mo (5.6 ± 2.0 vs. 7.4 ± 2.1 μg/L, p < 0.0001). Estimated GFR was similar in both groups at 12 mo (group A, 56.0 ± 17.5 mL/min per 1.73 m²; group B, 56.0 ± 22.1 mL/min per 1.73 m²). More rejection episodes occurred in group A than group B (11 vs. 3; p = 0.016). At 1 year, subclinical inflammation occurred more frequently in group A than group B (inflammation score [i] >0: 21.4% vs. 8.8%, p = 0.047; tubulitis score [t] >0: 19.6% vs. 8.7%, p = 0.076; i + t: 1.14 ± 1.21 vs. 0.72 ± 1.01, p = 0.038). Anti‐HLA donor‐specific antibodies appeared only in group A (6 vs. 0 patients, p = 0.008). TacER C₀ should be maintained >7 μg/L during the first year after transplantation in low‐immunological‐risk, steroid‐free KTRs receiving a moderate dose of mycophenolic acid.     

Vendor‐specific microbiome controls both acute and chronic murine lung allograft rejection by altering CD4+Foxp3+ regulatory T cell levels

Despite standardized postoperative care, some lung transplant patients suffer multiple episodes of acute and chronic rejection while others avoid graft problems for reasons that are poorly understood. Using an established model of C57BL/10 to C57BL/6 minor antigen mismatched single lung transplantation, we now demonstrate that the recipient microbiota contributes to variability in the alloimmune response. Specifically, mice from the Envigo facility in Frederick, Maryland contain nearly double the number of CD4⁺Foxp3⁺ regulatory T cells (T_regs) than mice from the Jackson facility in Bar Harbor, Maine or the Envigo facility in Indianapolis, Indiana (18 vs 9 vs 7%). Lung graft recipients from the Maryland facility thus do not develop acute or chronic rejection. Treatment with broad‐spectrum antibiotics decreases T_regs and increases both acute and chronic graft rejection in otherwise tolerant strains of mice. Constitutive depletion of regulatory T cells, using Foxp3‐driven expression of diphtheria toxin receptor, leads to the development of chronic rejection and supports the role of T_regs in both acute and chronic alloimmunity. Taken together, our data demonstrate that the microbiota of certain individuals may contribute to tolerance through T_reg‐dependent mechanisms and challenges the practice of indiscriminate broad‐spectrum antibiotic use in the perioperative period.     

The Impact of Alemtuzumab and Basiliximab Induction on Patient Survival and Time to Bronchiolitis Obliterans Syndrome in Double Lung Transplantation Recipients

We examined the effect of alemtuzumab and basiliximab induction therapy on patient survival and freedom from bronchiolitis obliterans syndrome (BOS) in double lung transplantation. The United Network for Organ Sharing database was reviewed for adult double lung transplant recipients from 2006 to 2013. The primary outcome was risk‐adjusted all‐cause mortality. Secondary outcomes included time to BOS. There were 6117 patients were identified, of whom 738 received alemtuzumab, 2804 received basiliximab, and 2575 received no induction. Alemtuzumab recipients had higher lung allocation scores compared with basiliximab and no‐induction recipients (41.4 versus 37.9 versus 40.7, p < 0.001) and were more likely to require mechanical ventilation before to transplantation (21.7% versus 6.5% versus 6.2%, p < 0.001). Median survival was longer for alemtuzumab and basiliximab recipients compared with patients who received no induction (2321 versus 2352 versus 1967 days, p = 0.001). Alemtuzumab (hazard ratio 0.80, 95% confidence interval 0.67–0.95, p = 0.009) and basiliximab induction (0.88, 0.80–0.98, p = 0.015) were independently associated with survival on multivariate analysis. At 5 years, alemtuzumab recipients had a lower incidence of BOS (22.7% versus 55.4 versus 55.9%), and its use was independently associated with lower risk of developing BOS on multivariate analysis. While both induction therapies were associated with improved survival, patients who received alemtuzumab had greater median freedom from BOS.     

COVID‐19 pneumonia in lung transplant recipients: Report of 2 cases

Coronavirus disease 2019 (COVID‐19) has been declared pandemic since March 2020. In Europe, Italy was the first nation affected by this infection. We report anamnestic data, clinical features, and therapeutic management of 2 lung transplant recipients with confirmed COVID‐19 pneumonia. Both patients were in good clinical condition before the infection and were receiving immunosuppression with calcineurin inhibitors (CNI), mycophenolate mofetil, and corticosteroids. Whereas mycophenolate mofetil was withdrawn in both cases, CNI were suspended only in the second patient. The first patient always maintained excellent oxygen saturation throughout hospitalization with no need for additional oxygen therapy. He was discharged with a satisfactory pulmonary function and a complete resolution of radiological and clinical findings. However, at discharge SARS‐CoV‐2 RNA could still be detected in the nasopharyngeal swab and in the stools. The second patient required mechanical ventilation, had a progressive deterioration of his clinical conditions, and had a fatal outcome. Further insight into SARS‐CoV‐2 infection is eagerly awaited to improve the outcome of transplant recipients affected by COVID‐19 pneumonia.     

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.