The effect of low and ultra-low dosages Thymoglobulin on peripheral T, B and NK cells in kidney transplant recipients

Alemtuzumab Exposure and T Lymphocyte Depletion: A Population Pharmacokinetic-Pharmacodynamic Model of Alemtuzumab Induction Therapy for Kidney Transplantation

Alemtuzumab is a T cell-depleting monoclonal antibody that is used for the prevention of kidney transplant rejection. The duration of lymphodepletion after the current standard induction therapy dose is likely longer than necessary, resulting in prolonged T cell lymphopenia with the associated risk of infections. Here, the interplay between alemtuzumab exposure and T cell dynamics was quantitatively evaluated, and the influence of different doses on T cell recovery was investigated. A population pharmacokinetic-pharmacodynamic model describing the interplay between 30 mg alemtuzumab induction therapy and T cell dynamics in kidney transplantation was developed using NONMEM, using pharmacodynamic data from the Triton study (NCT02057965). The developed model was used to perform an exposure-response analysis and investigate dose optimization with model-derived simulations. In total, 418 peripheral blood T cell measurements from 61 adult kidney transplant recipients were included for model development. A single-compartment turnover Emax model with a first-order T cell influx with feedback and a first-order T cell efflux with parallel alemtuzumab-stimulated T cell removal best described the data. Higher alemtuzumab exposure was associated with lower individual-predicted T cells 4 weeks after administration and longer T cell recovery (> 200 cells/μL). In the simulations, a fixed dose of 15 mg improved median recovery times by 19 days as compared to the standard 30 mg dose without influencing early T cell depletion. A population pharmacokinetic-pharmacodynamic model adequately described T cell dynamics after alemtuzumab induction therapy in kidney transplant recipients. This model can be used to inform future dose-optimization studies of alemtuzumab in different clinical settings.

Effects of two immunosuppression regimens on T-lymphocyte subsets in elderly kidney transplant recipients

Background

Despite the growing number of elderly kidney transplant (Ktx) recipients, few studies have examined the effects of immunosuppression on their lymphocyte profiles.

Methods

We evaluated the early conversion from mycophenolate sodium (MPS) to everolimus (EVL) after rabbit antithymocyte globulin (rATG) 2 mg/kg induction in elderly kidney recipients. Three groups of KTx patients were compared: (a) Young (n=20, 36 ± 7 y) receiving standard immunosuppression (Group A1) (prednisone, tacrolimus, and MPS), (b) Elderly (n=35, 65 ± 3 y) receiving standard immunosuppression (Group B1), and (c) Elderly (n=16, 65 ± 3 y) with early (mean 30 d) conversion from MPS to EVL (Group B2). Naive, memory, and regulatory peripheral blood TCD4+ lymphocytes were quantified at 0, 30, and 365 d.

Results

Results are reported as [mean(p25-p75)]. Young recipients had higher lymphocyte counts at baseline [2,100(1,630-2,400) vs. 1,310 (1,000-1,600)/mm3, p<0.0001] maintained higher counts within 365 d [1,850(1,590-2,120) vs. 1,130(460-1,325)/mm3, p=0.018 and vs. 1,410(805-1,895)/mm3, p=0.268]. Elderly recipients showed a decrease in lymphocytes within 30 d [1,310(1,000-1,600) vs. 910(700-1,198)/mm3, p=0.0012] with recovery within 365 d. The same pattern was observed in total lymphocytes and TCD4+ counts. Rabbit antithymocyte globulin induced a reduction in central memory T-cell percentages at 30 d in both young recipients [6.2(3.77-10.8) vs. 5.32(2.49-7.28)% of CD4+, p=0.036] and in elderly recipients [8.17(5.28-12.88) vs. 6.74(4.36-11)% of CD4+, p=0.05] on standard immunosuppression, returning to baseline at 365 d in elderly recipients but not in young recipients. Regulatory T CD39+ cells (Treg) percentages decreased at 30 d in elderly recipients [2.1(1.23-3.51) vs. 1.69(0.8-2.66)% of CD4+, p=0.0028] and in young recipients [1.29(0.45-1.85) vs. 0.84(0.18-1.82)% of CD4+, p=0.0038], returning to baseline at 365 d in elderly recipients [2.1(1.23-3.51) vs. 2.042(0.88-2.42)% of CD4+], but not in young recipients [1.29(0.45-1.85) vs. 0.86(0.7-1.34) % of CD4+]. The elderly everolimus conversion group did not show significant changes in cell profile over time or compared to elderly recipients with standard immunosuppression.

Conclusion

Aging favored the maintenance of Treg during the late transplantation period despite ongoing immunosuppression. Lymphocyte depletion due to rATG was more prominent in elderly recipients and affected memory subsets with a temporary reduction in central memory T cells. However, conversion to everolimus did not impact Treg profile. Reducing the dose of rATG in elderly recipients seems necessary for the expected lymphocyte changes with EVL to occur.

Clinical trial registration

nEverOld Trial, identifier NTC01631058.

Single-dose antithymocyte globulin in standard immunological risk kidney transplant recipients: efficacy and kinetics of peripheral blood CD3+ T lymphocyte modulation

BACKGROUND

Polyclonal anti-T cell antibodies (ATG or thymoglobulin®) are used as induction therapy in kidney transplant recipients. This study evaluates the safety, efficacy, and CD3+ T lymphocyte modulation of two ATG regimens.

METHODS

The trial included two cohorts of kidney transplant recipients that were followed for one year. The study group, including standard immunological risk recipients, received one 3 mg/kg dose of ATG. The comparator group, including standard and high immunological risk kidney transplant recipients, received a fractionated dose regimen (up to four 1.5 mg/kg doses). Patient and graft outcomes and the kinetics of CD3+ T lymphocyte modulation in the peripheral blood were evaluated.

RESULTS

One hundred kidney transplant recipients were included in each group. The one-year incidence of treated acute rejection, and patient and graft survival did not differ between groups. Bacterial infections were significantly more frequent in fractionated-dose group patients (66% versus 5%; P = 0.0001). At one-year follow-up, there was no difference in the incidence of cytomegalovirus infection (P = 0.152) or malignancies (P = 0.312). CD3+ T lymphocyte immunomodulation in the single-dose group was more effective in the first two days after transplantation. After the third post-transplant day, CD3+ T lymphocyte modulation was more efficient in the fractionated dose group.

CONCLUSION

Both regimens resulted in low rejection rates and equivalent survival. The single and reduced dose regimen protects from the occurrence of bacterial infections. CD3+ T lymphocyte modulation occurred with different kinetics, although it did not result in distinct outcomes.

Efficacy and safety of single-dose anti-thymocyte globulin versus basiliximab induction therapy in pediatric kidney transplant recipients: A retrospective comparative cohort study

BACKGROUND

This study aimed to compare the efficacy and safety of basiliximab (BAS) versus a single dose of anti-thymocyte globulin (r-ATG) induction therapy in pediatric kidney transplant recipients (KTRs).

METHODS

This single-center retrospective comparative cohort study included all pediatric KTRs from May 2013 to April 2018 and followed up to 12 months. In the first period, all recipients received BAS, while from May 2016, a single 3 mg/kg dose of r-ATG was instituted. Maintenance therapy consisted of a calcineurin inhibitor plus prednisone plus azathioprine or mycophenolate.

RESULTS

A total of 227 patients were included (BAS, n = 113; r-ATG, n = 114). The main combination of immunosuppressive drugs was tacrolimus, prednisone, and azathioprine in both groups (87% vs. 88%, p = .718). Patients receiving r-ATG showed superior survival-free of the composite endpoint (acute rejection, graft loss, or death; 76% vs. 61%, p = .003; HR 2.08, 1.29-3.34, p = .003) and lower incidence of biopsy-proven acute rejection (10% vs. 21%, p = .015). There was no difference in the overall incidence of CMV infection (33% vs. 37%, p = .457), PTLD (1% vs. 3%, p = .309), 30-day hospital readmissions (24% vs. 23%, p = .847), and kidney function at 12 months (86 ± 29 vs. 84 ± 30 mL/min/1.73m2, p = .614).

CONCLUSIONS

These data suggest that induction therapy with a single 3 mg/kg dose of r-ATG is associated with higher efficacy for preventing acute rejection and similar safety profile compared to BAS.

Excellent efficacy and beneficial safety during observational 5-year follow-up of rapid steroid withdrawal after renal transplantation (Harmony FU study)

BACKGROUND

We previously reported excellent efficacy and improved safety aspects of rapid steroid withdrawal (RSWD) in the randomized controlled 1-year "Harmony" trial with 587 predominantly deceased-donor kidney transplant recipients randomized either to basiliximab or rabbit antithymocyte globulin induction therapy and compared with standard immunosuppressive therapy consisting of basiliximab, low tacrolimus once daily, mycophenolate mofetil and corticosteroids.

METHODS

The 5-year post-trial follow-up (FU) data were obtained in an observational manner at a 3- and a 5-year visit only for those Harmony patients who consented to participate and covered clinical events that occurred from the second year onwards.

RESULTS

Biopsy-proven acute rejection and death-censored graft loss rates remained low and independent of RSWD. Rapid steroid withdrawal was an independent positive factor for patient survival (adjusted hazard ratio 0.554, 95% confidence interval 0.314-0.976; P = .041).The reduced incidence of post-transplantation diabetes mellitus in RSWD patients during the original 1-year study period was not compensated by later incidences during FU. Incidences of other important outcome parameters such as opportunistic infections, malignancies, cardiovascular morbidity/risk factors, donor-specific antibody formation or kidney function did not differ during FU period.

CONCLUSIONS

With all the limitations of a post-trial FU study, the Harmony FU data confirm excellent efficacy and beneficial safety aspects of RSWD under modern immunosuppressive therapy over the course of 5 years after kidney transplantation in an immunologically low-risk, elderly population of Caucasian kidney transplant recipients. Trial registration: Clinical trial registration number: Investigator Initiated Trial (NCT00724022, FU study DRKS00005786).

The use of lymphocyte-depleting antibodies in specific populations of kidney transplant recipients: A systematic review and meta-analysis

BACKGROUND

Recommendations of the use of antibody induction treatments in kidney transplant recipients (KTR) are based on moderate quality and historical studies. This systematic review aims to reevaluate, based on actual studies, the effects of different antibody preparations when used in specific KTR subgroups.

METHODS

We searched MEDLINE and CENTRAL and selected randomized controlled trials (RCT) and observational studies looking at different antibody preparations used as induction in KTR. Comparisons were categorized into different KTR subgroups: standard, high risk of rejection, high risk of delayed graft function (DGF), living donor, and elderly KTR. Two authors independently assessed the risk of bias.

RESULTS

Thirty-seven RCT and 99 observational studies were finally included. Compared to anti-interleukin-2-receptor antibodies (IL2RA), anti-thymocyte globulin (ATG) reduced the risk of acute rejection at two years in standard KTR (RR 0.74, 95%CI 0.61-0.89) and high risk of rejection KTR (RR 0.55, 95%CI 0.43-0.72), but without decreasing the risk of graft loss. We did not find significant differences comparing ATG vs. alemtuzumab or different ATG dosages in any KTR group.

CONCLUSIONS

Despite many studies carried out on induction treatment in KTR, their heterogeneity and short follow-up preclude definitive conclusions to determine the optimal induction therapy. Compared with IL2RA, ATG reduced rejection in standard-risk, highly sensitized, and living donor graft recipients, but not in high DGF risk or elderly recipients. More studies are needed to demonstrate beneficial effects in other KTR subgroups and overall patient and graft survival.

Evaluating anti-thymocyte globulin induction doses for better allograft and patient survival in Asian kidney transplant recipients

Anti-thymocyte globulin (ATG) is currently the most widely prescribed induction regimen for preventing acute rejection after solid organ transplantation. However, the optimal dose of ATG induction regimen in Asian kidney recipients is unclear. Using the Korean Organ Transplantation Registry, we performed a retrospective cohort study of 4579 adult patients who received renal transplantation in South Korea and divided them into three groups according to the induction regimen: basiliximab group (n = 3655), low-dose ATG group (≤ 4.5 mg/kg; n = 467), and high-dose ATG group (> 4.5 mg/kg; n = 457). We applied the Toolkit for Weighting and Analysis of Nonequivalent Groups (TWANG) package to generate high-quality propensity score weights for intergroup comparisons. During four-year follow-ups, the high-dose ATG group had the highest biopsy-proven acute rejection rate (basiliximab 20.8% vs. low-dose ATG 22.4% vs. high-dose ATG 25.6%; P < 0.001). However, the rates of overall graft failure (4.0% vs. 5.0% vs. 2.6%; P < 0.001) and mortality (1.7% vs. 2.8% vs. 1.0%; P < 0.001) were the lowest in the high-dose ATG group. Our results show that high-dose ATG induction (> 4.5 mg/kg) was superior to basiliximab and low-dose ATG induction in terms of graft and patient survival in Asian patients undergoing kidney transplant.

A prospective, randomized, non-blinded, non-inferiority pilot study to assess the effect of low-dose anti-thymocyte globulin with low-dose tacrolimus and early steroid withdrawal on clinical outcomes in non-sensitized living-donor kidney recipients

BACKGROUND

The optimal dose of anti-thymocyte globulin (ATG) as an induction regimen in Asian living-donor kidney recipients is unclear.

METHODS

This is a pilot study in which 36 consecutive patients undergoing living-donor kidney transplantation were randomly assigned to receive either 4.5 mg/kg (n = 19) or 6.0 mg/kg (n = 17) of ATG; all patients had corticosteroid withdrawal within 7 days. The primary end point was a composite of biopsy-proven acute rejection, de novo donor-specific antibody formation, and graft failure.

RESULTS

At 12 months post-transplant, biopsy-proven acute rejection was more common in the ATG4.5 group (21.1%) than in the ATG6.0 group (0%)(P = .048). Importantly, the rate of the composite end point was significantly higher in the ATG4.5 group (36.8% vs 0%)(P = .006). There were significant differences in neither the renal function nor adverse events between the two groups. One case of death-censored graft failure occurred in the ATG4.5 group and no mortality was observed overall. Compared with pre-transplantation, T cells, natural killer (NK) cells, and natural killer T (NKT) cells were significantly decreased in the first week post-transplantation except for B cells. Although T and NKT cells in both groups and NK cells in the ATG4.5 group had recovered to the pre-transplant levels, NK cells in the ATG6.0 group remained suppressed until six months post-transplant.

CONCLUSIONS

Compared with ATG 6.0 mg/kg, ATG 4.5 mg/kg with early corticosteroid withdrawal and low dose maintenance regimen was associated with higher rates of acute rejection in non-sensitized Asian living-donor kidney recipients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02447822.

Very Low Dose Anti-Thymocyte Globulins Versus Basiliximab in Non-Immunized Kidney Transplant Recipients

The choice between Basiliximab (BSX) or Anti-Thymocyte Globulin (ATG) as induction therapy in non-immunized kidney transplant recipients remains uncertain. Whilst ATG may allow steroid withdrawal and a decrease in tacrolimus, it also increases infectious complications. We investigated outcomes in non-immunized patients receiving a very low dosage of ATG versus BSX as induction. Study outcomes were patient/graft survival, cumulative probabilities of biopsy proven acute rejection (BPAR), infectious episode including CMV and post-transplant diabetes (PTD). Cox, logistic or linear statistical models were used depending on the studied outcome and models were weighted on propensity scores. 100 patients received ATG (mean total dose of 2.0 mg/kg) and 83 received BSX. Maintenance therapy was comparable. Patient and graft survival did not differ between groups, nor did infectious complications. There was a trend for a higher occurrence of a first BPAR in the BSX group (HR at 1.92; 95%CI: [0.77; 4.78]; p = 0.15) with a significantly higher BPAR episodes (17% vs 7.3%, p = 0.01). PTD occurrence was significantly higher in the BSX group (HR at 2.44; 95%CI: [1.09; 5.46]; p = 0.03). Induction with a very low dose of ATG in non-immunized recipients was safe and associated with a lower rate of BPAR and PTD without increasing infectious complications.

The Role of Innate Immune Cells in the Prediction of Early Renal Allograft Injury Following Kidney Transplantation

Background: Despite recent advances and refinements in perioperative management of kidney transplantation (KT), early renal graft injury (eRGI) remains a critical problem with serious impairment of graft function as well as short- and long-term outcome. Serial monitoring of peripheral blood innate immune cells might be a useful tool in predicting post-transplant eRGI and graft outcome after KT. Methods: In this prospective study, medical data of 50 consecutive patients undergoing KT at the University Hospital of Leipzig were analyzed starting at the day of KT until day 10 after the transplantation. The main outcome parameter was the occurrence of eRGI and other outcome parameters associated with graft function/outcome. eRGI was defined as graft-related complications and clinical signs of renal IRI (ischemia reperfusion injury), such as acute tubular necrosis (ATN), delayed graft function (DGF), initial nonfunction (INF) and graft rejection within 3 months following KT. Typical innate immune cells including neutrophils, natural killer (NK) cells, monocytes, basophils and dendritic cells (myeloid, plasmacytoid) were measured in all patients in peripheral blood at day 0, 1, 3, 7 and 10 after the transplantation. Receiver operating characteristics (ROC) curves were performed to assess their predictive value for eRGI. Cutoff levels were calculated with the Youden index. Significant diagnostic immunological cutoffs and other prognostic clinical factors were tested in a multivariate logistic regression model. Results: Of the 50 included patients, 23 patients developed eRGI. Mean levels of neutrophils and monocytes were significantly higher on most days in the eRGI group compared to the non-eRGI group after transplantation, whereas a significant decrease in NK cell count, basophil levels and DC counts could be found between baseline and postoperative course. ROC analysis indicated that monocytes levels on POD 7 (AUC: 0.91) and NK cell levels on POD 7 (AUC: 0.92) were highly predictive for eRGI after KT. Multivariable analysis identified recipient age (OR 1.53 (95% CI: 1.003−2.350), p = 0.040), recipient body mass index > 25 kg/m2 (OR 5.6 (95% CI: 1.36−23.9), p = 0.015), recipient cardiovascular disease (OR 8.17 (95% CI: 1.28−52.16), p = 0.026), donor age (OR 1.068 (95% CI: 1.011−1.128), p = 0.027), <0.010), deceased-donor transplantation (OR 2.18 (95% CI: 1.091−4.112), p = 0.027) and cold ischemia time (CIT) of the renal graft (OR 1.005 (95% CI: 1.001−1.01), p = 0.019) as clinically relevant prognostic factors associated with increased eRGI following KT. Further, neutrophils > 9.4 × 103/μL on POD 7 (OR 16.1 (95% CI: 1.31−195.6), p = 0.031), monocytes > 1150 cells/ul on POD 7 (OR 7.81 (95% CI: 1.97−63.18), p = 0.048), NK cells < 125 cells/μL on POD 3 (OR 6.97 (95% CI: 3.81−12.7), p < 0.01), basophils < 18.1 cells/μL on POD 10 (OR 3.45 (95% CI: 1.37−12.3), p = 0.02) and mDC < 4.7 cells/μL on POD 7 (OR 11.68 (95% CI: 1.85−73.4), p < 0.01) were revealed as independent biochemical predictive variables for eRGI after KT. Conclusions: We show that the combined measurement of immunological innate variables (NK cells and monocytes on POD 7) and specific clinical factors such as prolonged CIT, increased donor and recipient age and morbidity together with deceased-donor transplantation were significant and specific predictors of eRGI following KT. We suggest that intensified monitoring of these parameters might be a helpful clinical tool in identifying patients at a higher risk of postoperative complication after KT and may therefore help to detect and—by diligent clinical management—even prevent deteriorated outcome due to IRI and eRGI after KT.

Harnessing the B Cell Response in Kidney Transplantation - Current State and Future Directions

Despite dramatic improvement in kidney transplantation outcomes over the last decades due to advent of modern immunosuppressive agents, long-term outcomes remain poor. Antibody-mediated rejection (ABMR), a B cell driven process, accounts for the majority of chronic graft failures. There are currently no FDA-approved regimens for ABMR; however, several clinical trials are currently on-going. In this review, we present current mechanisms of B cell response in kidney transplantation, the clinical impact of sensitization and ABMR, the B cell response under current immunosuppressive regimens, and ongoing clinical trials for ABMR and desensitization treatment.

Effects of Reduced-Dose Anti-Human T-Lymphocyte Globulin on Overall and Donor-Specific T-Cell Repertoire Reconstitution in Sensitized Kidney Transplant Recipients

Background

Pre-sensitized kidney transplant recipients have a higher risk for rejection following kidney transplantation and therefore receive lymphodepletional induction therapy with anti-human T-lymphocyte globulin (ATLG) whereas non-sensitized patients are induced in many centers with basiliximab. The time course of lymphocyte reconstitution with regard to the overall and donor-reactive T-cell receptor (TCR) specificity remains elusive.

Methods/Design

Five kidney transplant recipients receiving a 1.5-mg/kg ATLG induction therapy over 7 days and five patients with 2 × 20 mg basiliximab induction therapy were longitudinally monitored. Peripheral mononuclear cells were sampled pre-transplant and within 1, 3, and 12 months after transplantation, and their overall and donor-reactive TCRs were determined by next-generation sequencing of the TCR beta CDR3 region. Overall TCR repertoire diversity, turnover, and donor specificity were assessed at all timepoints.

Results

We observed an increase in the donor-reactive TCR repertoire after transplantation in patients, independent of lymphocyte counts or induction therapy. Donor-reactive CD4 T-cell frequency in the ATLG group increased from 1.14% + -0.63 to 2.03% + -1.09 and from 0.93% + -0.63 to 1.82% + -1.17 in the basiliximab group in the first month. Diversity measurements of the entire T-cell repertoire and repertoire turnover showed no statistical difference between the two induction therapies. The difference in mean clonality between groups was 0.03 and 0.07 pre-transplant in the CD4 and CD8 fractions, respectively, and was not different over time (CD4: F(1.45, 11.6) = 0.64 p = 0.496; CD8: F(3, 24) = 0.60 p = 0.620). The mean difference in R20, a metric for immune dominance, between groups was -0.006 in CD4 and 0.001 in CD8 T-cells and not statistically different between the groups and subsequent timepoints (CD4: F(3, 24) = 0.85 p = 0.479; CD8: F(1.19, 9.52) = 0.79 p = 0.418).

Conclusion

Reduced-dose ATLG induction therapy led to an initial lymphodepletion followed by an increase in the percentage of donor-reactive T-cells after transplantation similar to basiliximab induction therapy. Furthermore, reduced-dose ATLG did not change the overall TCR repertoire in terms of a narrowed or skewed TCR repertoire after immune reconstitution, comparable to non-depletional induction therapy.

Rabbit antithymocyte globulin dose and early subclinical and clinical rejections in kidney transplantation

Antithymocyte globulin (ATG) is a commonly used induction agent in kidney transplant recipients. However, the optimal dosing has not been well defined. Our protocol aims for a 5-6 mg/kg cumulative dose. It is unclear if a dose lower than 5 mg/kg is associated with more rejection. We performed a retrospective cohort study of patients who received a kidney transplant at our center between January 1, 2013 and December 31, 2016. Primary outcome was biopsy proven acute rejection (clinical and subclinical) in the first six months after kidney transplant. CMV viremia in high risk(D+/R-) recipients and BK viremia was compared as a secondary endpoint. Of the 543 patients, the Low Dose (LD) group (n = 56) received <5 mg/kg ATG and Regular Dose (RD) group (n = 487) received ≧5 mg/kg. Patients in RD were more sensitized (higher PRA and CPRA). LD received a dose of 4 ± 1.1 mg/kg ATG whereas RD received 5.6 ± 0.3 mg/kg ATG (p < 0.001). TCMR(Banff 1A or greater) was present in 34% of patients in LD vs. 22% in RD (p = 0.04) (OR 2.1;95%CI 1.12-3.81;p = 0.019). There was no difference in the incidence of CMV or BK viremia. ATG doses lower than 5 mg/kg may be associated with a heightened risk of rejection despite a low degree of sensitization. This article is protected by copyright. All rights reserved.

Effect of Kidney Transplantation on Accelerated Immunosenescence and Vascular Changes Induced by Chronic Kidney Disease

Kidney transplantation is the best option for patients with end-stage renal disease. Despite the improvement in cardiovascular burden (leading cause of mortality among patients with chronic kidney disease), cardiovascular adverse outcomes related to the inflammatory process remain a problem. Thus, the aim of the present study was to characterize the immune profile and microvesicles of patients who underwent transplantation. We investigated the lymphocyte phenotype (CD3, CD4, CD8, CD19, and CD56) and monocyte phenotype (CD14, CD16, CD86, and CD54) in peripheral blood, and endothelium-derived microvesicles (annexin V+CD31+CD41–) in plasma of patients with advanced chronic kidney disease (n = 40), patients with transplantation (n = 40), and healthy subjects (n = 18) recruited from the University Hospital “12 de Octubre” (Madrid, Spain). Patients with kidney transplantation had B-cell lymphopenia, an impairment in co-stimulatory (CD86) and adhesion (CD54) molecules in monocytes, and a reduction in endothelium-derived microvesicles in plasma. The correlations between those parameters explained the modifications in the expression of co-stimulatory and adhesion molecules in monocytes caused by changes in lymphocyte populations, as well as the increase in the levels of endothelial-derived microvesicles in plasma caused by changes in lymphocyte and monocytes populations. Immunosuppressive treatment could directly or indirectly induce those changes. Nevertheless, the particular characteristics of these cells may partly explain the persistence of cardiovascular and renal alterations in patients who underwent transplantation, along with the decrease in arteriosclerotic events compared with advanced chronic kidney disease. In conclusion, the expression of adhesion molecules by monocytes and endothelial-derived microvesicles is related to lymphocyte alterations in patients with kidney transplantation.

CD5-Positive B Lymphocytes after Kidney Transplantation

Kidney transplantation is the treatment of choice for end-stage kidney diseases. Unfortunately, kidney allograft recipients rarely develop tolerance or accommodation and require life-long immunosuppression. Among many other regulatory mechanisms, CD5+ B lymphocytes (mainly B-1a) seem to be involved in the process of allograft acceptance. These cells are the major source of natural, low-affinity antibodies, which are polyreactive. Thus, we hypothesized that CD5+ B cells could be referred to as a biomarker in those patients who developed accommodation towards kidney allotransplant. In this study, 52 low-immunized kidney transplant recipients were evaluated for transplant outcome up to 8 y post-transplant. The follow up included anti-HLA antibodies, B cells phenotype and cytokines. We have identified a cohort of recipients who produced alloantibodies (Abs+), which was associated with increased levels of CD5+ B cells, mainly during the first year after transplantation but also later on. Importantly, creatinine levels were comparable between Abs+ and Abs− allorecipients at 2 years after the transplantation and graft survival rate was comparable between these groups even eight years post-transplant. So, it seems that despite the presence of alloantibodies the graft function was sustained when the level of CD5+ B cells was increased. Targeting CD5+ B cells may be a valuable therapeutic option to increase transplant success. The phenotype can be also tried as a biomarker to increase the effectiveness of individualized post-transplant treatments.

Association between cumulative rATG induction doses and kidney graft outcomes and adverse effects in kidney transplant patients: a systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis were performed to explore the association between rabbit thymoglobulin (rATG) doses and transplant-related efficacy and safety outcomes.

METHODS

We searched PubMed and Scopus databases from inception up to June 2020. The primary efficacy and safety endpoints in kidney transplant recipients were evaluated.

RESULTS

Data of 23 cohort studies (3457 patients) and three RCTs (154 patients) were extracted and analyzed. rATG doses of ≤4.5 m/kg was associated with lower rates of biopsy proven acute rejection, cytomegalovirus infection, BK virus infection, and malignancy with a comparable rate of delayed graft function, patients' mortality, and death-censored graft loss compared to rATG total doses of 4.5-6 mg/kg or more than 6 mg/kg. The rATG doses of 3-4.5 mg/kg was associated with better outcomes in dose-response analysis.

EXPERT OPINION

Cumulative rATG induction doses as much as 3-4.5 mg/kg is as effective as higher doses regarding to allograft and patient outcomes while minimizing potential adverse effects in kidney transplant recipients.

Relationship Between Antithymocyte Globulin Concentrations and Lymphocyte Sub-Populations in Kidney Transplant Patients

BACKGROUND

Rabbit antithymocyte globulins (rATGs) are polyclonal antibodies used to prevent acute cellular rejection in kidney transplantation. Their dosing remains largely empirical and the question of an individualized dose is still unresolved.

METHODS

Data from a prospective study in 17 kidney transplant patients were used to develop a model describing the dose-concentration-response relationship of rATG with T-lymphocyte subpopulation counts over time. The model was validated using an independent cohort of kidney transplant patients treated by rATG in the same center.

RESULTS

Pharmacokinetics of rATG was described using a two-compartment model integrating a third compartment and a target-mediated elimination for active rATG. The kinetics of CD3⁺, CD4⁺, CD8⁺, and CD3^-CD56⁺ cell counts over time were described by a pharmacokinetic-pharmacodynamic model with transit compartments, integrating both CD3^-CD56⁺-independent and CD3^-CD56⁺-dependent rATG-mediated lymphocyte depletion, and a positive feedback. Elimination of rATG was influenced by age and body surface area, while its distribution was also influenced by body surface area. CD3⁺ proliferation rate decreased with age and CD3^-CD56⁺-mediated elimination was influenced by the V158F-FCGR3A polymorphism. Binary efficacy and tolerance endpoints were defined as a CD3⁺ count < 20 mm^-3 for at least 7 days and a CD4⁺ count > 200 mm^-3 at 1 year, respectively. Simulations showed that increasing or decreasing the standard 6-mg/kg dose will impact both tolerance and efficacy, while a dose decrease may be beneficial in elderly patients.

CONCLUSIONS

Our results can be used to design prospective clinical trials testing dose individualization based on patients' characteristics.

CLINICAL TRIAL REGISTRATION

Eudract No. 2009-012673-35.

HLA Class I Molecules as Immune Checkpoints for NK Cell Alloreactivity and Anti-Viral Immunity in Kidney Transplantation

Natural killer (NK) cells are innate lymphocytes that can kill diseased- or virally-infected cells, mediate antibody dependent cytotoxicity and produce type I immune-associated cytokines upon activation. NK cells also contribute to the allo-immune response upon kidney transplantation either by promoting allograft rejection through lysis of cells of the transplanted organ or by promoting alloreactive T cells. In addition, they protect against viral infections upon transplantation which may be especially relevant in patients receiving high dose immune suppression. NK cell activation is tightly regulated through the integrated balance of signaling via inhibitory- and activating receptors. HLA class I molecules are critical regulators of NK cell activation through the interaction with inhibitory- as well as activating NK cell receptors, hence, HLA molecules act as critical immune checkpoints for NK cells. In the current review, we evaluate how NK cell alloreactivity and anti-viral immunity are regulated by NK cell receptors belonging to the KIR family and interacting with classical HLA class I molecules, or by NKG2A/C and LILRB1/KIR2DL4 engaging non-classical HLA-E or -G. In addition, we provide an overview of the methods to determine genetic variation in these receptors and their HLA ligands.

The influence of the antithymocyte globulin dose on clinical outcomes of patients undergoing kidney retransplantation

Optimizing antithymocyte globulin (rATG) dosage is critical for high immunological risk patients undergoing a repeat kidney transplant. This natural retrospective cohort study compared clinical outcomes of two successive cohorts of consecutive recipients of retransplants receiving 5 x 1 mg/kg (rATG-5, n = 100) or a single 3 mg/kg (rATG-3, n = 110) dose of rATG induction therapy. All patients had negative complement-dependent cytotoxicity crossmatch and no anti-HLA A, B, DR donor-specific antibodies (DSA). The primary endpoint was efficacy failure (first biopsy-proven acute rejection, graft loss, or death) at 12 months. There was no difference in the cumulative incidence of efficacy failure (18.0% vs. 21.8%, HR = 1.22, 95% CI 0.66–2.25), respectively. There were no differences in 3-years freedom from biopsy proven acute rejection, and patient, graft, and death-censored graft survivals. There were no differences in the incidence of surgical complications (25.0% vs. 18.2%; p 0.151), early hospital readmission (27.8% vs. 29.5%; p = 0.877) and CMV infections (49% vs. 40%; p = 0.190). There were also no differences in the incidence (59.6% vs. 58.7%, p = 0.897) and duration of delayed graft function but a stable difference in estimate glomerular filtration rate was observed from month 1 (54.7±28.8 vs. 44.1±25.3 ml/min/1.73 m², p = 0.005) to month 36 (51.1±27.7 vs. 42.5±24.5, p = 0.019). Mean urinary protein concentration (month 36: 0.38±0.81 vs. 0.70±2.40 g/ml, p = 0.008) and mean chronic glomerular Banff score in for cause biopsies (months 4–36: 0.0±0.0 vs. 0.04±0.26, p = 0.044) were higher in the rATG-3 group. This cohort analysis did not detect differences in the incidence of efficacy failure and in safety outcomes at 12 months among recipients of kidney retransplants without A, B, and DR DSA, receiving induction therapy with a single 3 mg/kg rATG dose or the traditional 5 mg/kg rATG.

Natural Killer Cells in Post-Transplant Lymphoproliferative Disorders

Post-transplant lymphoproliferative disorders (PTLDs) are life-threatening complications arising after solid organ or hematopoietic stem cell transplantations. Although the majority of these lymphoproliferations are of B cell origin, and are frequently associated with primary Epstein-Barr virus (EBV) infection or reactivation in the post-transplant period, rare cases of T cell and natural killer (NK) cell-originated PTLDs have also been described. A general assumption is that PTLDs result from the impairment of anti-viral and anti-tumoral immunosurveillance due to the long-term use of immunosuppressants in transplant recipients. T cell impairment is known to play a critical role in the immune-pathogenesis of post-transplant EBV-linked complications, while the role of NK cells has been less investigated, and is probably different between EBV-positive and EBV-negative PTLDs. As a part of the innate immune response, NK cells are critical for protecting hosts during the early response to virus-induced tumors. The complexity of their function is modulated by a myriad of activating and inhibitory receptors expressed on cell surfaces. This review outlines our current understanding of NK cells in the pathogenesis of PTLD, and discusses their potential implications for current PTLD therapies and novel NK cell-based therapies for the containment of these disorders.

Sebaceous Carcinoma Incidence and Survival Among Solid Organ Transplant Recipients in the United States, 1987-2017

Importance

Risk of sebaceous carcinoma (SC), a rare skin cancer associated with Muir-Torre syndrome, is elevated among solid organ transplant recipients (SOTRs). However, population studies evaluating this association and assessing survival for posttransplant cases are lacking, and further understanding of SC epidemiology in this immunosuppressed population could provide etiologic and clinical insights.

Objective

To assess SC incidence and patient survival after solid organ transplantation.

Design, Setting, and Participants

This cohort study, conducted from January 1, 1987, to December 31, 2017, used data from the Transplant Cancer Match Study, which links transplant and cancer registry data for 17 states and 1 metropolitan area in the United States. Altogether, these registries account for approximately 46% of all US transplants. Data on demographic and transplant characteristics as well as induction and initial maintenance immunosuppressive therapies were obtained from the transplant registry. Standardized incidence ratios (SIRs) comparing SC incidence among SOTRs to the general population were calculated. Incidence rate ratios (IRRs) comparing SC risk between SOTR subgroups were calculated using multivariate Poisson regression. Cox regression was used to compare overall survival between SC cases in SOTRs and other individuals.

Main Outcomes and Measures

Sebaceous carcinoma incidence and overall patient survival after transplantation compared with the general population.

Results

A total of 326 282 transplant procedures were performed for 301 075 patients (No. [%] age at transplant, 126 550 [38.8%] aged 0-44 years; 82 394 [25.3%] aged 45-54 years; 82 082 [25.5%] aged 55-64 years; 35 256 [10.8%] aged ≥65 years; 201 354 male patients [61.7%]; 202 557 White patients [62.1%]). A total of 102 SCs were diagnosed in 301 075 SOTRs, corresponding to a 25-fold increased incidence (SIR, 24.8; 95% CI, 20.2-30.1). Incidence was especially elevated among lung recipients (SIR, 47.7; 95% CI, 20.6-94.0) and after a posttransplant diagnosis of cutaneous squamous cell carcinoma (SIR, 104.0; 95% CI, 62.8-163.0). Among SOTRs, factors independently associated with SC risk included male sex (IRR, 2.46; 95% CI, 1.48-4.07; P < .001), race/ethnicity (non-Hispanic Black vs non-Hispanic White, IRR, 0.28; 95% CI, 0.10-0.77; P = .01), older age (IRR, 7.85; 95% CI, 3.85-16.0; ≥65 vs 0-44 years; P < .001 for trend), use of thymoglobulin induction (IRR, 1.82; 95% CI, 1.16-2.86; P = .009), posttransplant cutaneous squamous cell carcinoma (IRR, 4.60; 95% CI, 2.67-7.94; P < .001), and longer time since transplant (IRR, 8.40; 95% CI, 3.94-17.90; ≥10 vs 0-1.9 years; P < .001 for trend). Muir-Torre syndrome-associated cancers were rare among both SOTRs and others with SC (3.3%-4.1%). Among patients with SC, prior transplantation was associated with increased overall mortality (adjusted hazard ratio, 2.09; 95% CI, 1.45-3.01), although few deaths were attributed to SC (4 of 92 SOTRs [4.3%]; 235 of 3585 non-SOTRs [6.6%]).

Conclusions and Relevance

Among SOTRs, results of this large cohort study suggest that SC was associated with measures of immunosuppression, and overall survival was worse than for other patients with SC. Findings also suggest a possible role for UV radiation in carcinogenesis.

Comparison of Alemtuzumab and Anti-thymocyte Globulin Treatment for Acute Kidney Allograft Rejection

Rabbit anti-thymocyte globulin (rATG) is currently the treatment of choice for glucocorticoid-resistant, recurrent, or severe acute allograft rejection (AR). However, rATG is associated with severe infusion-related side effects. Alemtuzumab is incidentally given to kidney transplant recipients as treatment for AR. In the current study, the outcomes of patients treated with alemtuzumab for AR were compared with that of patients treated with rATG for AR. The patient-, allograft-, and infection-free survival and adverse events of 116 alemtuzumab-treated patients were compared with those of 108 patients treated with rATG for AR. Propensity scores were used to control for differences between the two groups. Patient- and allograft survival of patients treated with either alemtuzumab or rATG were not different [hazard ratio (HR) 1.14, 95%-confidence interval (CI) 0.48–2.69, p = 0.77, and HR 0.82, 95%-CI 0.45–1.5, p = 0.52, respectively). Infection-free survival after alemtuzumab treatment was superior compared with that of rATG-treated patients (HR 0.41, 95%-CI 0.25–0.68, p < 0.002). Infusion-related adverse events occurred less frequently after alemtuzumab treatment. Alemtuzumab therapy may therefore be an alternative therapy for glucocorticoid-resistant, recurrent, or severe acute kidney transplant rejection.

Efficacy of ATG and Rituximab in capuchin monkeys (a New World monkey)-An in vitro study relevant to xenotransplantation

While Old World monkeys, for example, baboons, have antibodies against triple-knockout (TKO) pig cells, thus complicating pig organ transplantation studies, capuchin monkeys (a New World monkey) do not, thus more closely mimicking humans in respect to the response to TKO pig cells. Whether drugs such as anti-thymocyte globulin (ATG) and Rituximab are effective in capuchin monkeys remains uncertain. We measured the binding and cytotoxicity of ATG and Rituximab to human (n = 7), baboon (n = 7), and capuchin monkey (n = 5) peripheral blood mononuclear cells (PBMCs), T cells or B cells by flow cytometry.The effect in vitro of ATG in depleting PBMCs in capuchin monkeys and baboons was significantly less than in humans, but the depletion in capuchin monkeys was not significantly different from that in baboons. In contrast, the effect in vitro of Rituximab in depleting B cells in capuchin monkeys was very limited, and significantly less than in humans and baboons.Although capuchin monkeys mimic the human antibody response to TKO pig cells more closely than baboons, Rituximab had a minimal effect in capuchin monkeys in vitro. This observation may limit the value of New World Monkeys as recipients of pig organs, tissues, or cells in experimental studies of xenotransplantation or, indeed, in allotransplantation.

Thymoglobulin vs. ATG-Fresenius as Induction Therapy in Kidney Transplantation: A Bayesian Network Meta-Analysis of Randomized Controlled Trials

Background: Thymoglobulin (THG) and antithymocyte globulin-Fresenius (ATG-F) have not been compared directly as induction therapies in kidney transplantation. Materials and Methods: We performed a Bayesian network meta-analysis to compare THG with ATG-F by pooling direct and indirect evidence. Surface under the cumulative ranking curve (SUCRA) values were used to compare the superiority of one method over the other. Results: A total of 27 randomized controlled trials (RCT) were eligible for the network meta-analysis. Efficacy endpoints, as well as safety indicators, were statistically comparable. For efficacy endpoints, THG seemed inferior to ATG-F in preventing delayed graft function [odds ratio (OR): 1.27; SUCRA: 78% vs. 58%], patient deaths (OR: 2.78; SUCRA: 83% vs. 34%), and graft loss (OR: 1.40; SUCRA: 83% vs. 59%), but superior to ATG-F in biopsy-proven acute rejection (BPAR; OR: 0.59; SUCRA: 78% vs. 39%) and steroid-resistant BPAR prevention (OR: 0.61; SUCRA: 76% vs. 49%) within the first year. For safety endpoints, THG was associated with higher risk of infection (OR: 1.49, SUCRA: 79% vs. 54%), cytomegalovirus infection (OR: 1.04; SUCRA: 40% vs. 37%), de novo diabetes (OR: 1.10; SUCRA: 90% vs. 30%), and malignancy (OR: 8.40; SUCRA: 89% vs. 6%) compared to ATG-F. A subgroup analysis of patients at high risk for immunologic complications revealed similar results, but THG performed better for graft loss (OR: 0.82; SUCRA: 68% vs. 54%). Conclusion: ATG-F seemed to be more effective than THG in improving the short-term kidney transplantation outcomes. Prospective head-to-head comparison of THG and ATG-F with larger sample sizes and longer follow-up is still required.

Low-dose Thymoglobulin vs Basiliximab Induction Therapy in Low-Risk Living Related Kidney Transplant Recipients: A Prospective Randomized Trial

CONTEXT

Thymoglobulin is used effectively as induction agent in kidney transplantation but the optimal dose is not well established.

OBJECTIVE

Demonstrate that low-dose thymoglobulin (3 mg/kg) has similar efficacy and safety compared to basiliximab induction in low-risk kidney transplantation under standard maintenance immunosuppression DESIGN, SETTING, PARTICIPANTS: Prospective randomized study in kidney transplant patients (12/2016-05/2018).

INCLUSION CRITERIA

Recipients > 18 years, first living donor transplant.

EXCLUSION CRITERIA

Second and multiorgan transplant, ABO incompatibility, positive cross-match, panel reactive antibodies (PRA) > 30%, positive donor-specific antibody, human immunodeficiency virus, hepatitis B surface antigen, hepatitis C virus positive, white blood cells < 2000 cells/mm³, platelets < 75,000 cells/mm³ and malignancy.

INTERVENTION

Group A: basiliximab (20 mg D0 and D4). Group B: thymoglobulin (3 mg/kg total). Maintenance immunosuppression: tacrolimus, mycophenolate mofetil, and steroids.

MAIN OUTCOME MEASURES

Biopsy-proven acute rejection (BPAR), delayed graft function, slow graft function, leukopenia, infections, adverse events, graft loss, estimated glomerular filtration rate, and death within 12 months.

RESULTS

100 patients (basiliximab, n = 53) (thymoglobulin, n = 47) were included. Donor and recipient characteristics were similar except for longer dialysis (basiliximab), PRA class I (1.2% basiliximab, 4.5% thymoglobulin), HLA match (basiliximab 2.8, thymoglobulin 2.2), and cytomegalovirus status. BPAR rate was basiliximab 3.8% and thymoglobulin 6.4% (P = ns). Delayed graft function (basiliximab 3.8%; thymoglobulin 4.3%), slow graft function, and 12-month leukopenia (basiliximab 11.3%, thymoglobulin 21.3%) were similar between groups (P = ns). There was no difference in infections and adverse events between groups. Patient and graft survival were as follows: basiliximab 98.1% and 92.5%, thymoglobulin 100% and 93.6% (P = ns).

CONCLUSION

Low-dose thymoglobulin induction (3 mg/kg) can be used effectively and safely in low-risk kidney transplantation with good results during the first year post-transplant.

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 (CD38^hi CD24^hi IgM^hi CD20^hi ) and transitional B cells (CD19⁺ CD27^- IgD⁺ CD38^hi )-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.

Reconstitution of T-Cell Subsets Following Thymoglobulin-Induced Depletion in High Immunologic Risk and Donation After Cardiac Death Renal Transplant Recipients

INTRODUCTION

Depletion therapy in high immunologic risk (HR) patients by antithymocyte globulin (rATG) induces lymphopenia and subsequent compartmental repopulation of T-cell subsets. rATG is also given to patients receiving kidneys from donations after cardiac death (DCDs) to mitigate innate immune activation associated with the DCD process.

METHODS

We compared the T-cell response with rATG in both HR and DCD kidney recipients. We examined the reconstitution of T-cell subsets after rATG treatment in HR and DCD recipients (n = 19 per group) by multicolor flow cytometry.

RESULTS

Following treatment, there was a rapid drop in the frequency of T cells in both groups, which persisted over 28 days. HR patients had an early surge in the frequency of CD4⁺ naïve, effector-memory, and regulatory T cells. Although we found a significant proliferation of the T cells in both groups, the DCD cohort had a blunted response as well as reduced CD4⁺ T-cell immune-reactivity compare with the HR group.

CONCLUSIONS

Our data suggest that there is a lack of significant homeostatic proliferative response in DCD recipients following rATG, and CD4⁺ T cells may be less reactive in the DCD group than previously thought, indicating that rATG treatment may not have to be considered a first-line induction therapy in DCD recipients.

Induction Therapy in Elderly Kidney Transplant Recipients With Low Immunological Risk

BACKGROUND

In nonimmunized patients, similar rejection rates are observed for patients who have undergone thymoglobulin (antithymocyte globulins [ATG]) or basiliximab (BSX) therapy. While ATG may improve delayed graft function, it may also be associated with higher infection rates and malignancy risk. We compared survival and clinical outcomes in elderly recipients with low immunological risk according to their induction therapy.

METHODS

We conducted a multicentric study on nonimmunized patients ≥65 years of age receiving a first kidney transplant between 2010 and 2017. The principal outcome was patient and graft survival. Secondary outcomes were cumulative probabilities of infection, first acute rejection episode, malignancy, de novo donor specific antibody, posttransplant diabetes (PTD), cardiac complications, estimated glomerular filtration rate, and occurrence of delayed graft function. Cox, logistic, or linear statistical models were used depending on the outcome studied, and models were weighted on the propensity scores.

RESULTS

Two hundred and four patients were included in the BSX group and 179 in the ATG group with the average age of 71.0 and 70.5 years, respectively. Patient and graft survival at 3 years posttransplantation were 74% (95% CI, 65%-84%) and 68% (95% CI, 60%-78%) in ATG and BSX group, respectively, without significant difference. Occurrence of PTD was significatively higher in BSX group (23% versus 15%, P = 0.04) due to higher trough levels of Tacrolimus on month 3 (9.48 versus 7.30 ng/mL, P = 0.023). There was no difference in other evaluated outcomes.

CONCLUSIONS

In elderly recipients, ATG does not lead to poorer outcomes compared with BSX and could permit lower trough levels of Tacrolimus, thus reducing occurrence of PTD.

Regulatory and Effector B Cells: A New Path Toward Biomarkers and Therapeutic Targets to Improve Transplant Outcomes?

B cells shape the alloimmune response through polarized subsets. These cells inhibit or promote immune responses by expressing suppressive or proinflammatory cytokines. Their summed activity dictates the influence of B cells on the alloimmune response. We review the evidence for regulatory B cells and effector B cells in mice and humans, discuss current limitations in their phenotypic identification, and discuss regulatory B cells as a signature for clinical renal allograft tolerance and predictive markers for allograft outcomes. We discuss the effects of therapeutic agents on regulatory B cells and potential approaches to augment their numbers as a therapeutic tool.

The Efficacy of Rabbit Anti-Thymocyte Globulin for Acute Kidney Transplant Rejection in Patients Using Calcineurin Inhibitor and Mycophenolate Mofetil-Based Immunosuppressive Therapy

Background

T cell depleting antibody therapy with rabbit anti-thymocyte globulin (rATG) is the treatment of choice for glucocorticoid-resistant acute kidney allograft rejection (AR) and is used as first-line therapy in severe AR. Almost all studies investigating the effectiveness of rATG for this indication were conducted at the time when cyclosporine A and azathioprine were the standard of care. Here, the long-term outcome of rATG for AR in patients using the current standard immunosuppressive therapy (i.e., tacrolimus and mycophenolate mofetil) is described.

Material/Methods

Between 2002 to 2012, 108 patients were treated with rATG for AR. Data on kidney function in the year following rATG and long-term outcomes were collected.

Results

Overall survival after rATG was comparable to overall survival of all kidney transplantation patients (P=0.10). Serum creatinine 1 year after rATG was 179 μmol/L (interquartile range (IQR) 136–234 μmol/L) and was comparable to baseline serum creatinine (P=0.22). Early AR showed better allograft survival than late AR (P=0.0007). In addition, 1 year after AR, serum creatinine was lower in early AR (157 mol/L; IQR 131–203) compared to late AR (216 mol/L; IQR 165–269; P<0.05). The Banff grade of rejection, kidney function at the moment of rejection, and reason for rATG (severe or glucocorticoid resistant AR) did not influence the allograft survival.

Conclusions

Treatment of AR with rATG is effective in patients using current standard immunosuppressive therapy, even in patients with poor allograft function. Early identification of AR followed by T cell depleting treatment leads to better allograft outcomes.

Sepsis is associated with lack of monocyte HLA-DR expression recovery without modulating T-cell reconstitution after lung transplantation

BACKGROUND

Immunosuppressive strategy targets mainly adaptive immunity after solid organ transplantation. We assessed the influence of early post-operative sepsis on T cell and monocyte reconstitution in anti-thymocyte globulin (ATG)-treated lung transplant recipients.

METHODS

We retrospectively included recipients who underwent a first lung transplant at our Lung Transplant Center (Marseille, France) between July 2011 and February 2013. Peripheral blood T-lymphocyte subset counts and monocyte HLA-DR (mHLA-DR) expression routinely performed by flow cytometry within 60 days post-transplant were analyzed. We compared the immune kinetics of patients who did or did not develop sepsis during the post-operative intensive care unit stay.

RESULTS

Among the 37 recipients included, 19 patients (51%) developed at least one episode of sepsis. At the ICU admission, septic recipients had higher SOFA score (9 [7.5-9] versus 6 [4-7]), p = .01), higher primary graft dysfunction score (1.4 ± 1.4 versus 0.3 ± 0.7, p = .008) and more frequent use of ECMO (47% versus 0%, p = .003). Whereas both groups had similar T-lymphocytes reconstitution in the post-operative period, mHLA-DR reconstitution was dramatically affected in septic patients after day 14, median mHLA-DR expression at 2.3 MFI [1.3-3.5] in the septic versus 8.0 MFI [5.1-10.5] in the non-septic group, p = .02.

CONCLUSION

We found that sepsis is negatively correlated with the mHLA-DR expression but not adaptive T cell immune reconstitution. This finding highlights the importance of immunomonitoring after lung transplantation and questions the strategy of a lower immunosuppression therapy in context of sepsis.

The effect of anti-thymocyte globulin and everolimus on the kinetics of cytomegalovirus viral load in seropositive kidney transplant recipients without prophylaxis

BACKGROUND

The use of mTOR inhibitors is associated with lower incidence of CMV infections but its effect on viral load has not been investigated.

AIMS, MATERIALS AND METHODS

This post-hoc analysis included data from 273 CMV seropositive kidney transplant recipients randomized to receive anti-thymocyte globulin and everolimus (rAGT/TAC/EVR, n = 81), basiliximab and everolimus (BAS/TAC/EVR, n = 97) or basiliximab and mycophenolate (BAS/TAC/MPS, n = 95). All patients received tacrolimus (TAC) and corticosteroids. Preemptive CMV therapy based on weekly pp65 antigenemia test was used during the first 6 months. Blinded weekly CMV DNAemia was compared among the groups.

RESULTS

The proportion of patients with undetectable CMV DNAemia (23.4% vs 56.7% vs 22.1%, P < .001) was higher in the BAS/TAC/EVR. The median number of study visits with positive CMV DNAemia (2.0 vs 0.0 vs 4.6, rATG/EVR vs BAS/MPS, P = .354; BAS/EVR vs BAS/MPS, P < .0001; rATG/EVR vs BAS/EVR, P < .001) were lower in the BAS/TAC/EVR. The proportion of patients with positive CMV DNAemia who were not treat for CMV infection/disease based on pp65 antigenemia was higher in rATG/TAC/EVR group (74.1% vs 36.1% vs 44.2%, P < .001) but mean CMV DNAemia was comparable to BAS/TAC/EVR and lower than BAS/TAC/MPS (8536 ± 15 899 vs 7975 ± 17 935 vs 16 965 ± 37 694 copies/mL, P < .05), respectively. The proportion of patients with CMV DNAemia below 5000 copies/mL was higher in patients receiving EVR (74.1% vs 83.5% vs 50.0%, P = .000), respectively.

DISCUSSION AND CONCLUSION

These data suggest that mTOR inhibitors reduce the incidence of CMV infection by limiting CMV viral replication.

Highly Diluted Acetylcholine Promotes Wound Repair in an In Vivo Model

Objective: Wound healing is a dynamic, interactive, and complex process that involves a series of events, including inflammation, migration, proliferation, granulation tissue formation, and matrix remodeling. Despite the high frequency of serious slow-healing wounds, there is still no adequate therapy. The aim of this study is to evaluate a new highly diluted acetylcholine (Ach) formulation obtained through a sequential kinetic activation (SKA) method applied to a wound healing in vivo model to verify the hypothesis that a low dose of Ach could be a more physiological stimulus for healing, by stimulating muscarinic and nicotinic receptors and their related intracellular pathways.

Approach: Two different concentrations (10 fg/mL and 1 pg/mL) and two formulations (either kinetically or nonkinetically activated) of Ach were used to verify the wound healing process. Area closure, histological aspect, and nicotinic and muscarinic receptors, matrix metalloproteinase 9 (MMP-9), Nestin, and von Willebrand's factor have been assessed by Western blot or ELISA and compared to 147 ng/mL Ach, used as positive control. Moreover, the systemic effect through plasmatic radical oxygen species (ROS) production and Ach concentration has been evaluated.

Results: Ach SKA 1 pg/mL revealed a significant capacity to restore the integrity of tissue compared to other formulation and this effect was more evident after a single administration.

Innovation: Topical application on skin of Ach SKA 1 pg/mL accelerates wound closure stimulating non-neuronal cholinergic system.

Conclusion: Our results demonstrate for the first time the importance in an in vivo model of highly diluted SKA Ach during wound healing, suggesting a potential use in skin disease.

Effect of Immunosuppression on Target Blood Immune Cells Within 1 Year After Lung Transplantation: Influence of Age on T Lymphocytes

Background

Lymphocytes are targeted by immunosuppressive therapy in solid organ transplantation and they influence allograft outcome.

Material/Methods

Peripheral blood lymphocyte subsets (PBLS) determined by flow cytometry during the first year post-transplant from patients who underwent a first lung transplantation in a French University Hospital between December 2011 and July 2013 were retrospectively analyzed according to recipient characteristics and allograft outcome.

Results

Fifty-seven recipients were enrolled and 890 PBLS were collected. T lymphocytes and NK cells were rapidly decreased, below normal range, from the first postoperative days. B cells decreased more gradually, remaining within normal range, with the lowest level reached after day 100. In multivariate analysis, greater T lymphopenia was found in older recipients (−414 [−709 to −119] cells/μL, p=0.007). According to the outcome, multivariate analysis evidenced lower levels of lymphocytes when bacterial and viral infection occurred (−177 [−310 to −44] cells/μL, p=0.009 and (−601 [−984 to −218] cells/μL, p=0.002, respectively), higher CD8+ T lymphocytes with BOS (+324 [+94 to +553] cells/μL, p=0.006), and higher leukocytes with restrictive allograft syndrome (+3770 [+418 to +7122] cells/μL, p=0.028).

Conclusions

Aging is associated in our cohort with more severe T lymphopenia after induction therapy for lung transplantation. The analysis of leukocytes and PBLS is associated with specific profile according to the allograft outcome.

Rabbit anti-human thymocyte immunoglobulin for the rescue treatment of chronic antibody-mediated rejection after pediatric kidney transplantation

BACKGROUND

Chronic antibody-mediated rejection (cAMR) is the leading cause of late kidney graft loss, but current therapies are often ineffective. Rabbit anti-human thymocyte immunoglobulin (rATG) may be helpful, but its use is virtually undocumented.

METHODS

Data were analyzed retrospectively from nine pediatric kidney transplant patients with cAMR were treated with rATG (1.5 mg/kg × 5 days) at our center after non-response to pulsed prednisolone, intravenous immunoglobulin, rituximab, and increased immunosuppressive intensity (including switching to belatacept in some cases), with or without bortezomib.

RESULTS

The median time from diagnosis to cAMR was 179 days. rATG was started 5-741 days after diagnosis. Median estimated glomerular filtration rate (eGFR) increased from 40 mL/min/1.73 m² when rATG was started to 62 mL/min/1.73 m² 9 months later (p = 0.039). Four patients showed substantially higher eGFR after 9 months and 2 patients showed a small improvement; eGFR continued to decline in 3 patients after starting rATG. No grafts were lost during follow-up. At last follow-up, donor-specific antibodies (DSAs) were no longer detectable in 4 out of 8 patients for whom data were available, median fluorescence intensity had decreased substantially in 1 out of 8 patients; anti-HLA DQ DSAs persisted in 2 out of 8 patients. No adverse events with a suspected relation to rATG, including allergic reactions, leukocytopenia or infections, were observed in any of the patients.

CONCLUSIONS

In this small series of patients, rATG appears a promising treatment for unresponsive cAMR. Further evaluation, including earlier introduction of rATG, is warranted.

Inflammatory Conditions Dictate the Effect of Mesenchymal Stem or Stromal Cells on B Cell Function

The immunomodulatory capacity of mesenchymal stem or stromal cells (MSC) makes them a promising tool for treatment of immune disease and organ transplantation. The effects of MSC on B cells are characterized by an abrogation of plasmablast formation and induction of regulatory B cells (Bregs). It is, however, unknown how MSC interact with B cells under inflammatory conditions. In this study, adipose tissue-derived MSC were pretreated with 50 ng/ml IFN-γ for 96 h (MSC–IFN-γ) to simulate inflammatory conditions. Mature B cells were obtained from spleens by CD43⁻ selection. B cells were co-cultured with MSC and stimulated with anti-IgM, anti-CD40, and IL-2; and after 7 days, B cell proliferation, phenotype, Immunoglobulin-G (IgG), and IL-10 production were analyzed. MSC did not inhibit B cell proliferation but increased the percentage of CD38^high CD24^high B cells (Bregs) and IL-10 production, while MSC–IFN-γ significantly reduced B cell proliferation and inhibited IgG production by B cells in a more potent fashion but did not induce Bregs or IL-10 production. Both MSC and MSC–IFN-γ required proximity to target cells and being metabolically active to exert their effects. Indoleamine 2,3 dioxygenase expression was highly induced in MSC–IFN-γ and was responsible of the anti-proliferative and Breg reduction since addition of tryptophan (TRP) restored MSC properties. Immunological conditions dictate the effect of MSC on B cell function. Under immunological quiescent conditions, MSC stimulate Breg induction; whereas, under inflammatory conditions, MSC inhibit B cell proliferation and maturation through depletion of TRP. This knowledge is useful for customizing MSC therapy for specific purposes by appropriate pretreatment of MSC.

Dual Role of Natural Killer Cells on Graft Rejection and Control of Cytomegalovirus Infection in Renal Transplantation

Allograft rejection constitutes a major complication of solid organ transplantation requiring prophylactic/therapeutic immunosuppression, which increases susceptibility of patients to infections and cancer. Beyond the pivotal role of alloantigen-specific T cells and antibodies in the pathogenesis of rejection, natural killer (NK) cells may display alloreactive potential in case of mismatch between recipient inhibitory killer-cell immunoglobulin-like receptors (KIRs) and graft HLA class I molecules. Several studies have addressed the impact of this variable in kidney transplant with conflicting conclusions; yet, increasing evidence supports that alloantibody-mediated NK cell activation via FcγRIIIA (CD16) contributes to rejection. On the other hand, human cytomegalovirus (HCMV) infection constitutes a risk factor directly associated with the rate of graft loss and reduced host survival. The levels of HCMV-specific CD8⁺ T cells have been reported to predict the risk of posttransplant infection, and KIR-B haplotypes containing activating KIR genes have been related with protection. HCMV infection promotes to a variable extent an adaptive differentiation and expansion of a subset of mature NK cells, which display the CD94/NKG2C-activating receptor. Evidence supporting that adaptive NKG2C⁺ NK cells may contribute to control the viral infection in kidney transplant recipients has been recently obtained. The dual role of NK cells in the interrelation of HCMV infection with rejection deserves attention. Further phenotypic, functional, and genetic analyses of NK cells may provide additional insights on the pathogenesis of solid organ transplant complications, leading to the development of biomarkers with potential clinical value.

Rabbit-ATG or basiliximab induction for rapid steroid withdrawal after renal transplantation (Harmony): an open-label, multicentre, randomised controlled trial

BACKGROUND

Standard practice for immunosuppressive therapy after renal transplantation is quadruple therapy using antibody induction, low-dose tacrolimus, mycophenolate mofetil, and corticosteroids. Long-term steroid intake significantly increases cardiovascular risk factors with negative effects on the outcome, especially post-transplantation diabetes associated with morbidity and mortality. In this trial, we examined the efficacy and safety parameters of rapid steroid withdrawal after induction therapy with either rabbit antithymocyte globulin (rabbit ATG) or basiliximab in immunologically low-risk patients during the first year after kidney transplantation.

METHODS

In this open-label, multicentre, randomised controlled trial, we randomly assigned renal transplant recipients in a 1:1:1 ratio to receive either basiliximab induction with low-dose tacrolimus, mycophenolate mofetil, and steroid maintenance therapy (arm A), rapid corticosteroid withdrawal on day 8 (arm B), or rapid corticosteroid withdrawal on day 8 after rabbit ATG (arm C). The study was done in 21 centres across Germany. Only participants aged between 18 and 75 years with a low immunological risk who were scheduled to receive a single-organ renal transplant from either a living donor or a deceased donor were considered for enrolment. Patients receiving a second renal transplant were eligible, provided that the first allograft was not lost due to acute rejection within the first year after transplantation. Donor and recipient had to be ABO compatible. Grafts with pre-transplant existing donor-specific human leukocyte antigen (HLA) antibodies were not eligible and the recipients had to have a panel-reactive antibody concentration of 30% or less. Pregnant women and nursing mothers were excluded from the study. The primary endpoint was the incidence of biopsy-proven acute rejection (BPAR) at 12 months. All analyses were done by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT00724022.

FINDINGS

Between Aug 7, 2008, and Nov 30, 2013, 615 patients were randomly assigned to arm A (206), arm B (189), and arm C (192). BPAR rates were not reduced by rabbit ATG (9·9%) compared with either treatment arm A (11·2%) or B (10·6%; A versus C: p=0·75, B versus C p=0·87). As a secondary endpoint, rapid steroid withdrawal reduced post-transplantation diabetes in arm B to 24% and in arm C to 23% compared with 39% in control arm A (A versus B and C: p=0·0004). Patient survival (94·7% in arm A, 97·4% in arm B, and 96·9% in arm C) and censored graft survival (96·1% in arm A, 96·8% in arm B, and 95·8% in arm C) after 12 months were excellent and equivalent in all arms. Safety parameters such as infections or the incidence of post-transplantation malignancies did not differ between the study arms.

INTERPRETATION

Rabbit ATG did not show superiority over basiliximab induction for the prevention of BPAR after rapid steroid withdrawal within 1 year after renal transplantation. Nevertheless, rapid steroid withdrawal after induction therapy for patients with a low immunological risk profile can be achieved without loss of efficacy and is advantageous in regard to post-transplantation diabetes incidence.

FUNDING

Investigator Initiated Trial; financial support by Astellas Pharma GmbH, Sanofi, and Roche Pharma AG.

A Comparison of Two Types of Rabbit Antithymocyte Globulin Induction Therapy in Immunological High-Risk Kidney Recipients: A Prospective Randomized Control Study

BACKGROUND

Induction treatment with rabbit polyclonal antithymocyte globulins (ATGs) is frequent used in kidney transplant recipients with donorspecific HLA antibodies and shows acceptable outcomes. The two commonly used ATGs, Thymoglobulin and ATG-F have slightly different antigen profile and antibody concentrations. The two compounds have never been directly compared in a prospective trial in immunological high-risk recipients. Therefore we performed a prospective randomized controlled study comparing the two compounds in immunological high-risk kidney recipients in terms of safety and efficacy.

METHODS

Immunological high-risk kidney recipients, defined as the presence of HLA DSA but negative CDC-B and T-cell crossmatches were randomized 1:1 to receive ATG-F or Thymoglobulin. Maintenance immunosuppressive therapy consisted of tacrolimus, mycophenolate mofetil and steroids.

RESULTS

The per-protocol analysis included 35 patients. There was no immediate infusion reaction observed with both compounds. No PTLD or malignancy occurred during the follow-up in both groups. The incidence of viral and bacterial infections was similar in both groups (p = 0.62). The cumulative incidence of clinical and subclinical antibody mediated allograft rejection as well as T-cell mediated allograft rejection during the first year between ATG-F and Thymoglobulin was similar (35% versus 19%; p = 0.30 and 11% versus 18%; 0.54 respectively). The two-year graft function was similar with a median eGFR of 56 ml/min/1.73m2 (range 21-128) (ATG-F-group) and 51 ml/min/1.73m2 (range 22-132) (Thymo-group) (p = 0.69).

CONCLUSION

We found no significant differences between the compared study drugs for induction treatment in immunological high-risk patients regarding safety and efficacy during follow-up with good allograft function at 2 years after transplantation.