Polygenic risk score for acute rejection based on donor-recipient non-HLA genotype mismatch

BACKGROUND

Acute rejection (AR) after kidney transplantation is an important allograft complication. To reduce the risk of post-transplant AR, determination of kidney transplant donor-recipient mismatching focuses on blood type and human leukocyte antigens (HLA), while it remains unclear whether non-HLA genetic mismatching is related to post-transplant complications.

METHODS

We carried out a genome-wide scan (HLA and non-HLA regions) on AR with a large kidney transplant cohort of 784 living donor-recipient pairs of European ancestry. An AR polygenic risk score (PRS) was constructed with the non-HLA single nucleotide polymorphisms (SNPs) filtered by independence (r2 < 0.2) and P-value (< 1×10-3) criteria. The PRS was validated in an independent cohort of 352 living donor-recipient pairs.

RESULTS

By the genome-wide scan, we identified one significant SNP rs6749137 with HR = 2.49 and P-value = 2.15×10-8. 1,307 non-HLA PRS SNPs passed the clumping plus thresholding and the PRS exhibited significant association with the AR in the validation cohort (HR = 1.54, 95% CI = (1.07, 2.22), p = 0.019). Further pathway analysis attributed the PRS genes into 13 categories, and the over-representation test identified 42 significant biological processes, the most significant of which is the cell morphogenesis (GO:0000902), with 4.08 fold of the percentage from homo species reference and FDR-adjusted P-value = 8.6×10-4.

CONCLUSIONS

Our results show the importance of donor-recipient mismatching in non-HLA regions. Additional work will be needed to understand the role of SNPs included in the PRS and to further improve donor-recipient genetic matching algorithms. Trial registry: Deterioration of Kidney Allograft Function Genomics (NCT00270712) and Genomics of Kidney Transplantation (NCT01714440) are registered on ClinicalTrials.gov.

Impact of Immunosenescence in Older Kidney Transplant Recipients: Associated Clinical Outcomes and Possible Risk Stratification for Immunosuppression Reduction

The number of older individuals receiving a kidney transplant as replacement therapy has significantly increased in the past decades and this increase is expected to continue. Older patients have a lower rate of acute rejection but an increased incidence of death with a functioning graft. Several factors, including an increased incidence of infections, post-transplant malignancy and cardiovascular comorbidity and mortality, contribute to this increased risk. Notwithstanding, kidney transplantation is still the best form of kidney replacement therapy in all patients with chronic kidney disease, including in older individuals. The best form of immunosuppression and the optimal dose of these medications in older recipients remains a topic of discussion. Pharmacological studies have usually excluded older patients and when included, patients were highly selected and their numbers insignificant to draw a reasonable conclusion. The reduced incidence of acute rejection in older recipients has largely been attributed to immunosenescence. Immunosenescence refers to the aging of the innate and adaptive immunity, accumulating in phenotypic and functional changes. These changes influences the response of the immune system to new challenges. In older individuals, immunosenescence is associated with increased susceptibility to infectious pathogens, a decreased response after vaccinations, increased risk of malignancies and cardiovascular morbidity and mortality. Chronic kidney disease is associated with premature immunosenescent changes, and these are independent of aging. The immunosenescent state is associated with low-grade sterile inflammation termed inflammaging. This chronic low-grade inflammation triggers a compensatory immunosuppressive state to avoid further tissue damage, leaving older individuals with chronic kidney disease in an immune-impaired state before kidney transplantation. Immunosuppression after transplantation may further enhance progression of this immunosenescent state. This review covers the role of immunosenescence in older kidney transplant recipients and it details present knowledge of the changes in chronic kidney disease and after transplantation. The impact of immunosuppression on the progression and complications of an immunosenescent state are discussed, and the future direction of a possible clinical implementation of immunosenescence to individualize/reduce immunosuppression in older recipients is laid out.

Clinical relevance of the living kidney donor profile index in Korean kidney transplant recipients

BACKGROUND

The Living Kidney Donor Profile Index (LKDPI) was developed in the United States to predict graft outcomes based on donor characteristics. However, there are significant differences in donor demographics, access to transplantation, proportion of ABO incompatibility, and posttransplant mortality in Asian countries compared with the United States.

METHODS

We evaluated the clinical relevance of the LKDPI score in a Korean kidney transplant cohort by analyzing 1860 patients who underwent kidney transplantation between 2000 and 2019. Patients were divided into three groups according to LKDPI score: <0, 1-19.9, and ≥20.

RESULTS

During a median follow-up of 119 months, 232 recipients (12.5%) experienced death-censored graft loss, and 98 recipients (5.3%) died. High LKDPI scores were significantly associated with increased risk of death-censored graft loss independent of recipient characteristics (LKDPI 1-19.9: HR 1.389, 95% CI 1.036-1.863; LKDPI ≥20: HR 2.121, 95% CI 1.50-2.998). High LKDPI score was also significantly associated with increased risk of biopsy-proven acute rejection and impaired graft renal function. By contrast, overall patient survival rates were comparable among the LKDPI groups.

CONCLUSION

High LKDPI scores were associated with an increased risk of death-censored graft loss, biopsy-proven acute rejection, and impaired graft renal function among a Korean kidney transplant cohort.

Alloimmune Risk Stratification for Kidney Transplant Rejection

Different types of kidney transplantations are performed worldwide, including biologically diverse donor/recipient combinations, which entail distinct patient/graft outcomes. Thus, proper immunological and non-immunological risk stratification should be considered, especially for patients included in interventional randomized clinical trials. This paper was prepared by a working group within the European Society for Organ Transplantation, which submitted a Broad Scientific Advice request to the European Medicines Agency (EMA) relating to clinical trial endpoints in kidney transplantation. After collaborative interactions, the EMA sent its final response in December 2020, highlighting the following: 1) transplantations performed between human leukocyte antigen (HLA)-identical donors and recipients carry significantly lower immunological risk than those from HLA-mismatched donors; 2) for the same allogeneic molecular HLA mismatch load, kidney grafts from living donors carry significantly lower immunological risk because they are better preserved and therefore less immunogenic than grafts from deceased donors; 3) single-antigen bead testing is the gold standard to establish the repertoire of serological sensitization and is used to define the presence of a recipient's circulating donor-specific antibodies (HLA-DSA); 4) molecular HLA mismatch analysis should help to further improve organ allocation compatibility and stratify immunological risk for primary alloimmune activation, but without consensus regarding which algorithm and cut-off to use it is difficult to integrate information into clinical practice/study design; 5) further clinical validation of other immune assays, such as those measuring anti-donor cellular memory (T/B cell ELISpot assays) and non-HLA-DSA, is needed; 6) routine clinical tests that reliably measure innate immune alloreactivity are lacking.

Polymorphisms in the CYP3A5 gene significantly affect the pharmacokinetics of sirolimus after kidney transplantation

Aim: Sirolimus (SIR) is an immunosuppressant with limitations, including a narrow treatment window, multiple adverse reactions and large differences within and among individuals. Objective: The correlation between numerous SNPs and SIR in terms of trough concentration in the early stage after kidney transplantation was analyzed. Materials & methods: A retrospective cohort study involving 69 kidney transplantation recipients was designed. Blood samples were collected to extract total DNAs, and trough SIR concentrations were measured. Logistic regression was used to analyze the association between SNPs and SIR trough concentrations. Results: At 7 days, 1 month and 3 months, the mean SIR trough concentration of patients in the CYP3A5 rs4646453-CC group was significantly higher than that in the CYP3A5 rs4646453-AA and CYP3A5 rs4646453-CA groups (p < 0.001) and CYP3A5 rs15524-AA group was significantly higher than that in the CYP3A5 rs15524-AG and CYP3A5 rs15524-GG groups (p < 0.001). Conclusion: Our study indicated that both CYP3A5 rs4646453 and CYP3A5 rs15524 had a certain influence on SIR trough concentration at 7 days, 1 month and 3 months.

Pre-transplant donor-reactive IL-21 producing T cells as a tool to identify an increased risk for acute rejection

Pre-transplant screening focuses on the detection of anti-HLA alloantibodies. Previous studies have shown that IFN-γ and IL-21 producing T cells are associated with the development of acute rejection (AR). The aim of this study, was to assess whether pre-transplant donor-reactive T cells and/or B cells are associated with increased rejection risk. Samples from 114 kidney transplant recipients (transplanted between 2010 and 2013) were obtained pre-transplantation. The number of donor-reactive IFN-γ and IL-21 producing cells was analyzed by ELISPOT assay. The presence of donor specific antibodies (DSA) was also determined before transplantation. Numbers of donor-reactive IFN-γ producing cells were similar in patients with or without AR whereas those of IL-21 producing cells were higher in patients with AR (p = 0.03). Significantly more patients with AR [6/30(20%)] had detectable DSA compared to patients without AR [5/84(5.9%), p = 0.03]. Multivariate logistic regression showed that donor age (OR 1.06), pre-transplant DSA (OR 5.61) and positive IL-21 ELISPOT assay (OR 2.77) were independent predictors of an increased risk for the development of AR. Aside from an advanced donor-age and pre-transplant DSA, also pre-transplant donor-reactive IL-21 producing cells are associated with the development of AR after transplantation.

CYP and SXR gene polymorphisms influence in opposite ways acute rejection rate in pediatric patients with renal transplant

Background

We evaluated the role of CYP3A5, ABCB1 and SXR gene polymorphisms in the occurrence of acute kidney rejection in a cohort of pediatric renal transplant recipients.

Methods

Forty-nine patients were genotyped for CYP3A5, ABCB1 and SXR polymorphisms and evaluated with tacrolimus through levels in a retrospective monocenter study.

Results

Patients with the A allele of CYP3A5 treated with tacrolimus had a higher risk of acute rejection than those without the A allele, while patients carrying the homozygous GG variant for SXR A7635GG did not show any episode of acute rejection.

Conclusion

Genetic analysis of polymorphisms implicated in drug metabolism and tacrolimus trough levels may help to forecast the risk of acute rejection and individualize drug dosage in children undergoing renal transplantation.

[Application of immunosuppressants in patients with autosomal dominant polycystic kidney disease after kidney transplantation]

OBJECTIVE

To investigate the optimal dose range of immunosuppressants in patients with autosomal dominant polycystic kidney disease (ADPKD) after renal transplantation.

METHODS

A cohort of 68 patients with ADPKD who received their first renal transplantation between March, 2000 and January, 2018 in our institute were retrospectively analyzed, with 68 non-ADPKD renal transplant recipients matched for gender, age and date of transplant as the control group. We analyzed the differences in patient and renal survival rates, postoperative complications and concentrations of immunosuppressive agents between the two groups at different time points within 1 year after kidney transplantation. The concentrations of the immunosuppressants were also compared between the ADPKD patients with urinary tract infections (UTI) and those without UTI after the transplantation.

RESULTS

The recipients with ADPKD and the control recipients showed no significantly difference in the overall 1-, 5-, and 10- year patient survival rates (96.6% vs 96.0%, 94.1% vs 93.9%, and 90.6% vs 93.9%, respectively; P > 0.05), 1-, 5-, and 10-year graft survival rates (95.2% vs 96.0%, 90.8% vs 87.2%, and 79.0% vs 82.3%, respectively; P > 0.05), or the incidences of other post- transplant complications including acute rejection, gastrointestinal symptoms, cardiovascular events, pneumonia, and neoplasms (P > 0.05). The plasma concentrations of both tacrolimus and mycophenolate mofetil (MPA) in ADPKD group were significantly lower than those in the control group at 9 months after operation (P < 0.05). The incidence of UTI was significantly higher in ADPKD patients than in the control group (P < 0.05). In patients with ADPKD, those with UTI after transplantation had a significantly higher MPA plasma concentration (P < 0.05).

CONCLUSIONS

In patients with ADPKD after renal transplant, a higher dose of MPA is associated with a increased risk of UTI, and their plasma concentrations of immunosuppressants for long-term maintenance of immunosuppression regimen can be lower than those in other kidney transplantation recipients.

Evidence of Interleukin-2-Receptor-Antibody Induction in Low-Risk Living Donor Kidney Transplantation: A Single-Center Pilot Study

BACKGROUND

The recommended standard immunosuppressive therapy for renal transplant recipients comprises an initial induction therapy mainly with an interleukin-2-receptor antibody (IL2-RA) and a triple maintenance therapy. With tacrolimus and mycophenolate acid it is unknown whether IL2-RA application affects the short- and long-term results. This question is addressed in the present analysis.

METHODS

From July 2007 to June 2019 a total of 127 living donor kidney transplant recipients meeting the center-specific definition of immunologic low risk situation (first transplantation, HLA-mismatch ≤3, panel reactive antibody ≤10%) were identified. In 83 recipients with a first-degree relationship to the donor we omitted the IL2-RA induction (IL2-RA-). The remaining 44 recipients, mostly not first-degree relatives, served as controls (IL2-RA+). Biopsy-proven acute rejection and long-term patient and graft survival rates were compared.

RESULTS

Biopsy-proven acute rejection rates after 3 months were similar in both groups with 4.8% (IL2-RA-) vs 13.7% (IL2-RA+; P = .0937), including borderline rejection rates of 18.0% (IL2-RA-) vs 18.3% (IL2-RA+; P = 1.000), respectively. Ten-year long-term survival rates were comparable between the IL2-RA- and the IL2-RA+ group with 95.6% vs 93.5% (patient survival; P = .5465) and 92.1% vs 90.6% (death-censored graft survival; P = .8893).

CONCLUSION

For low-risk living donor kidney transplant recipients with first-degree relationship to the donor, it is safe to omit induction therapy with IL2-RA.

Association of polymorphisms in leptin and adiponectin genes with long-term outcomes in renal transplant recipients

The effect of polymorphims in leptin and adiponectin genes on long-term outcomes of renal transplantation is unknown. In 349 renal transplant recipients (RTR), we aimed to determine associations between five SNPs in the leptin receptor (LEPR) and adiponectin (ADIPOQ) genes and these outcomes. Follow-up time ranged from 2 to 25 years (mean 10.29 ± 5.16 years). Two SNPs showed associations with long-term outcomes and their statistical significance greatly increased after 39 RTR with a history of cardiovascular events prior to transplantation were removed from the analysis. Adjusted odds ratios (OR) for LEPR rs1805094 and ADIPOQ rs1501299 and risk of graft loss were 0.35 (0.16-0.74) p = 0.006 and 2.37 (1.28-4.37) p = 0.006, respectively. The assessment of risk for global mortality revealed OR values of 0.20 (0.06-0.62), p = 0.005, and 2.43 (1.08-5.44), p = 0.031 for LEPR rs1805094 and ADIPOQ rs1501299, respectively. Our results show that polymorphism in genes involved in leptin and adiponectin function modify long-term outcomes in renal transplantation.

CD45RC Expression of Circulating CD8+ T Cells Predicts Acute Allograft Rejection: A Cohort Study of 128 Kidney Transplant Patients

Predictive biomarkers of acute rejection (AR) are lacking. Pre-transplant expression of CD45RC on blood CD8⁺ T cells has been shown to predict AR in kidney transplant (KT) patients. The objective of the present study was to study CD45RC expression in a large cohort of KT recipients exposed to modern immunosuppressive regimens. CD45RC expression on T cells was analyzed in 128 KT patients, where 31 patients developed AR, of which 24 were found to be T-cell mediated (TCMR). Pre-transplant CD4⁺ and CD8⁺ CR45RC^high T cell proportions were significantly higher in patients with AR. The frequency of CD45RC^high T cells was significantly associated with age at transplantation but was not significantly different according to gender, history of transplantation, pre-transplant immunization, and de novo donor specific anti-Human Leucocyte Antigen (HLA) antibody. Survival-free AR was significantly better in patients with CD8⁺ CD45RC^high T cells below 58.4% (p = 0.0005), but not different according to CD4⁺ T cells (p = 0.073). According to multivariate analysis, CD8⁺ CD45RC^high T cells above 58.4% increased the risk of AR 4-fold (HR 3.96, p = 0.003). Thus, pre-transplant CD45RC expression on CD8⁺ T cells predicted AR, mainly TCMR, in KT patients under modern immunosuppressive therapies. We suggest that CD45RC expression should be evaluated in a prospective study to validate its usefulness to quantify the pre-transplant risk of AR.

Comparison of Transplant Outcomes for Low-level and Standard-level Tacrolimus at Different Time Points after Kidney Transplantation

BACKGROUND

Optimal tacrolimus (TAC) trough levels for different periods after kidney transplantation (KT) has not been definitely established. This study aimed to investigate transplant outcomes of low-level (LL) and standard-level (SL) TAC according to post-transplant period.

METHODS

A total of 278 consecutive kidney transplant recipients (KTRs) receiving TAC-based immunosuppression were divided into LL and SL-TAC groups (4-7 and 7-12 ng/mL for 0-2 months, 3-6 and 6-10 ng/mL for 3-6 months, 2-5 and 5-8 ng/mL for 7-12 months, respectively) according to TAC trough level at each period. We compared estimated glomerular filtration rate (eGFR), biopsy-proven acute rejection (BPAR), de novo donor-specific antibody (dnDSA), calcineurin inhibitor (CNI) toxicity, opportunistic infection, and allograft survival.

RESULTS

SL-TAC group showed significantly higher mean eGFR at 0-2 months than LL-TAC group (72.1 ± 20.3 vs. 64.2 ± 22.7 mL/min/1.73m²; P = 0.003). Incidence of BPAR at 7-12 months was significantly lower in SL-TAC group than in LL-TAC group (0.0% vs. 3.9%; P = 0.039). Patients with persistent SL-TAC lasting 12 months showed higher eGFR at 7-12 months than those with persistent LL-TAC (65.5 ± 13.0 vs. 57.9 ± 13.9 mL/min/1.73m²; P = 0.007). No significant differences in dnDSA, CNI toxicity, serious infections, or allograft survival were observed.

CONCLUSIONS

Maintenance of proper TAC trough level after 6 months could reduce BPAR without adverse drug toxicities in KTRs. Moreover, persistent SL-TAC during the first year after KT might have a beneficial effect on a trend for a lower incidence of dnDSA and better renal allograft function.

Immunological Alterations due to Hemodialysis Might Interfere with Early Complications in Renal Transplantation

BACKGROUND

Chronic or intercurrent alterations of the immune system in patients with end-stage renal disease (CKD) and intermittent hemodialysis (CKD5D, HD) have been attributed to an acute rejection of renal allograft.

METHODS

Leukocyte subsets in flow cytometry, complement activation, and concentrations of TGFβ, sCD30 (ELISA), and interleukins (CBA) of fifteen patients eligible for renal transplantation were analyzed before, during, and after a regular HD.

RESULTS

Before HD, the median proportion of CD8+ effector cells, CD8+ CCR5+ effector cells, and HLA-DR+ regulatory T cells as well as the median concentration of soluble CD30 increased and naive CD8+ T cells decreased. During HD, there was a significant decrease in CD4- CD8- T cells (p < 0.001) and an increase in CD25+ T cells (p = 0.026), sCD30 (p < 0.001), HLA-DR+ regulatory T cells (p = 0.005), and regulatory T cells (p = 0.003). TGFβ and sCD30 increased significantly over time. The activity of the classical complement pathway started to slightly increase after the first hour of HD and lasted until fifteen minutes after finishing dialysis. The decrease in the functional activity of the alternative pathway was only transient and was followed by a significant increase within 15 minutes after finishing the treatment.

CONCLUSION

HD might interact with the allograft outcome by influencing T cell subsets and activation of the complement system in a biphasic course.

The clinicopathological relevance of pretransplant anti-angiotensin II type 1 receptor antibodies in renal transplantation

Background

Anti-angiotensin II type 1 receptor antibodies (AT1R-Abs) have been suggested as a risk factor for graft failure and acute rejection (AR). However, the prevalence and clinical significance of pretransplant AT1R-Abs have seldom been evaluated in Asia.

Methods

In this multicenter, observational cohort study, we tested the AT1R-Abs in pretransplant serum samples obtained from 166 kidney transplant recipients. Statistical analysis was used to set a threshold AT1R-Abs level at 9.05 U/mL.

Results

Pretransplant AT1R-Abs were detected in 98/166 (59.0%) of the analyzed recipients. No graft loss or patient death was reported during the study period. AT1R-Abs (+) patients had a significantly higher incidence of biopsy-proven AR than AT1R-Abs (-) patients (27.6 versus 10.3%, P = 0.007). Recipients with pretransplant AT1R-Abs had a 3.2-fold higher risk of AR within a year of transplantation (P = 0.006). Five study subjects developed microcirculation inflammation (score ≥2). Four of them were presensitized to AT1R-Abs. In particular, three patients had a high titer of anti-AT1R-Abs (>22.7 U/mL).

Conclusions

Pretransplant AT1R-Abs is an independent risk factor for AR, especially acute cellular rejection, and is possibly associated with the risk of antibody-mediated injury. Pretransplant assessment of AT1R-Abs may be useful for stratifying immunologic risks.

Risk Factors for Acute Rejection After Deceased Donor Kidney Transplantation in China

OBJECTIVES

This study aimed to identify the potential risk factors of acute rejection after deceased donor kidney transplantation in China.

METHODS

Adult kidney transplantations from deceased donors in our center from February 2004 to December 2015 were enrolled for retrospective analysis. All deceased donations complied with China's Organ Donation Program. No organs from executed prisoners were used. The incidence of clinical and biopsy-proved acute rejection was assessed with the Kaplan-Meier method, and the Cox proportional hazard model was used for multivariate analysis.

RESULTS

One-year, 2-year, 3-year and 5-year incidences of acute rejection were 12.4%, 14.2%, 14.8%, and 17.1%, respectively. Multivariate analysis demonstrated that longer pre-transplant dialysis duration (hazard ratio [HR] 1.009 per month; 95% confidence interval, 1.003-1.015; P = .003), positive pre-transplant panel reactive antibody (PRA) (positive vs negative HR 3.266; 1.570-6.793; P = .023), and increasing HLA mismatches (≥4 vs < 4 HR 2.136; 1.022-4.465; P = .044) increased the risk of acute rejection, while tacrolimus decreased acute rejection risk compared to cyclosporine (HR 0.317; 0.111-0.906; P = .032).

CONCLUSION

Longer pre-transplant dialysis duration, HLA mismatch, and positive pre-transplant PRA increase the risk of acute rejection, while tacrolimus helps prevent acute rejection compared to cyclosporine in deceased donor kidney transplantation.

Polymorphisms in genes involved in vasoactive eicosanoid synthesis affect cardiovascular risk in renal transplant recipients

OBJECTIVE

Arachidonic acid metabolism by cytochrome P450 (CYP) epoxygenases leads to epoxyeicosatrienoic acids (EETs), which are eicosanoids with vasodilator and anti-inflammatory properties. We aim to determine whether genetic variability in these routes may contribute to cardiovascular (CV) risk in renal transplant recipients.

METHODS

In a cohort of 355 patients, we determined the presence of two polymorphisms, CYP2C8*3 and CYP2J2*7, known to affect eicosanoid levels. Associations with CV mortality, CV event-free long-term survival and graft survival were retrospectively investigated by logistic regression models.

RESULTS

CYP2J2*7 showed a statistical trend towards higher CV mortality (p = .06) and lower cardiac or cerebral event-free long-term survival (p = .05), whilst CYP2C8*3 displayed a significant inverse association with the risk of CV event (hazard ratio [HR] = 0.34 [0.15-0.78], p = .01). The association of CYP2J2*7 with CV mortality became significant when the analysis was restrained to 316 patients without a history of CV events prior to transplantation (HR = 15.72 [2.83-91.94], p = .005). In this subgroup of patients both single nucleotide polymorphisms (SNPs) were significantly associated with event-free survival. HR values were 5.44 (1.60-18.51), p = .007 and 0.26 (0.09-0.75), p = .012 for CYP2J2*7 and CYP2C8*3, respectively.

CONCLUSIONS

Our results show, for the first time to our knowledge, that two SNPs in CYP2C8 and CYP2J2, which synthesize EETs, may modify CV outcomes in renal transplant recipients, a population that is already at a high risk of suffering these events.

Role of B and T Lymphocyte Attenuator in Renal Transplant Recipients with Biopsy-Proven Acute Rejection

Background

Acute rejection is a common predisposing cause of allograft dysfunction in kidney transplantation. Recently, the B and T lymphocyte attenuator (BTLA)/herpes virus entry mediator (HVEM)/lymphotoxin (LIGHT)/CD160 pathway was found to be potentially involved in the regulation of T cell activation. This could mean that this pathway is involved in graft rejection in kidney transplantation; the present study aimed to explore this possibility.

Material/Methods

The expression of BTLA, HVEM, LIGHT and CD160 on peripheral CD4+, CD8+ and CD19+ lymphocytes were analyzed by flow cytometry in recipients with biopsy-proven acute rejection (BPAR) or stable allograft function, as well as in healthy volunteers. Moreover, we performed HE staining and immunohistochemical staining to assess the expression of BTLA and HVEM in kidney samples from recipients with BPAR and patients who underwent the surgery of radical nephrectomy.

Results

We observed the significantly lower expression of BTLA on CD4+ T cells in recipients from the BPAR group than in recipients from the stable group. The expression of BTLA on CD8+ T cells among recipients both from the BPAR and stable group was statistically increased than that in the healthy volunteers. A significant difference in the expression of CD160 in the stable group was found when compared with the BPAR group or control group. Moreover, there was no significance in the expression of HVEM, LIGHT or CD160 on other subtypes of T cells between the 3 groups or in the expression of BTLA on CD4+ T cells between the BPAR and control group.

Conclusions

The findings indicate that the BTLA/HVEM pathway does be involved in pathogenesis of acute rejection following kidney transplantation, as well as the induction of transplant tolerance. This pathway may therefore be a useful target for therapy against acute rejection after kidney transplantation.

Renal Transplant Acute Rejection with Lower Mycophenolate Mofetil Dosing and Proton Pump Inhibitors or Histamine-2 Receptor Antagonists

BACKGROUND

Pharmacokinetic data show reduced mycophenolic acid levels in renal transplant recipients taking mycophenolate mofetil (MMF) and proton pump inhibitors (PPIs) concomitantly. This reduced exposure could increase rejection risk. The typical initial MMF dose post renal transplantation is 2 g/day, which often requires dose reduction secondary to side effects. Existing studies have not shown significant acute rejection differences for patients taking MMF-PPI versus patients taking MMF-ranitidine.

OBJECTIVE

The purpose of this study was to evaluate clinical outcomes in renal transplant recipients receiving a lower MMF dose than previously studied (1.5 g/day) and either a PPI or histamine-2 receptor antagonist (H2RA).

METHODS

This retrospective cohort study included adult subjects receiving a renal transplant between January 1, 2009, and June 30, 2013. Comparison groups were defined based on acid-suppressing therapy class prescribed at discharge from transplantation. The primary outcome was acute rejection incidence within 1 year posttransplantation.

RESULTS

Of 728 renal transplant recipients screened, 522 were included: 183 taking a PPI and 339 taking an H2RA. There was no significant difference in acute rejection within 1 year (H2RA 19% versus PPI 14%, p=0.12) or 3 months (4% vs 5%, p=0.44, respectively) posttransplantation. Maintenance immunosuppression (MMF dose and tacrolimus troughs) was similar between groups at 3 months and 1 year. Graft and patient survivals were favorable (> 95%), and graft function at 1 year was stable and similar between groups.

CONCLUSION

Despite taking lower MMF doses than previously studied, subjects on a PPI compared to an H2RA were not at increased risk of acute rejection within 1 year posttransplantation.

Precision Transplant Medicine: Biomarkers to the Rescue

The concept that individuals with the same disease and a similar clinical presentation may have very different outcomes and need very different therapies is not novel. With the development of many innovative tools derived from the omics technologies, transplant medicine is slowly entering the era of precision medicine. Biomarkers are the cornerstone of precision medicine, which aims to integrate biomarkers with traditional clinical information and tailor medical care to achieve the best outcome for an individual patient. Here, we discuss the basic concepts of precision medicine and biomarkers, with a specific focus on progress in renal transplantation. We delineate the different types of biomarkers and provide a general assessment of the current applications and shortcomings of previously proposed biomarkers. We also outline the potential of precision medicine in transplantation. Moving toward precision medicine in the field of transplantation will require transplant physicians to embrace the increased complexity and expanded decision algorithms and therapeutic options that are associated with improved disease nosology.

Cytolytic Induction Therapy Improves Clinical Outcomes in African-American Kidney Transplant Recipients

OBJECTIVE

Determine the impact of cytolytic versus IL-2 receptor antibody (IL-2RA) induction on acute rejection, graft loss and death in African-American (AA) kidney transplant (KTX) recipients.

BACKGROUND

AAs are underrepresented in clinical trials in transplantation; thus, there is controversy regarding the optimal choice of perioperative antibody induction in KTX to improve outcomes.

METHODS

National cohort study using US transplant registry data from January 1, 2000 to December 31, 2009 in adult solitary AA KTX recipients, with at least 5 years of follow-up. Multivariable logistic and Cox regression were utilized to assess the outcomes of acute rejection, graft loss, and mortality, with interaction terms to assess effect modification.

RESULTS

Twenty-five thousand eighty-four adult AAs receiving solitary KTX were included, 16,927 (67.5%) received cytolytic induction and 8157 (32.5%) received IL-2RA induction. After adjustment for recipient sociodemographics, donor, and transplant characteristics, the use of cytolytic induction therapy reduced the risk of acute rejection by 32% (OR 0.68, 0.62-0.75), graft loss by 9% (HR 0.91, 0.86-0.97), and death by 12% (HR 0.88, 0.83-0.94). There were a number of significant effect modifiers, including public insurance, panel reactive antibody, delayed graft function, and steroid withdrawal; in these groups, cytolytic induction substantially improved clinical outcomes.

CONCLUSIONS

These data demonstrate that cytolytic induction therapy, as compared with IL-2RA, reduces the risk of rejection, graft loss, and death in adult AA KTX recipients, particularly in those who are sensitized, receive public insurance, develop delayed graft function, or undergo steroid withdrawal.

Associations Between Posttransplantation Diabetes Mellitus and Renal Graft Survival

BACKGROUND

Previous reports indicate that posttransplantation diabetes mellitus (PTDM) is associated with overall renal graft loss, but not death-censored graft loss.

METHODS

In this single-center retrospective cohort study of 2749 adult Norwegian renal transplant recipients, transplanted between 1999 and 2011, we estimated overall and death-censored renal graft loss hazard ratios in patients diagnosed with PTDM, impaired glucose tolerance and diabetes before transplantation, using multivariable Cox proportional hazard regression analysis.

RESULTS

A total of 893 renal grafts were lost during the study period, either due to recipient death (n = 540) or death-censored graft loss (n = 353).When the observational time started at time of transplantation, diabetes before transplantation was associated with both overall and death-censored graft loss. Pretransplantation diabetes was also associated with a steeper decline in renal graft function, a higher risk of acute rejections and more renal grafts lost due to acute rejection.In patients with a functional renal graft 1 year after transplantation, PTDM was associated with overall graft loss (hazard ratio, 1.46; 95% confidence interval, 1.13-1.88; P < 0.001), but not death-censored graft loss (hazard ratio, 1.25; 95% confidence interval, 0.80-1.96; P = 0.33). We found no significant associations between PTDM and change in renal function during the first 5 years or acute rejection risk during the first year after renal transplantation.Impaired glucose tolerance was not associated with either overall or death-censored graft loss.

CONCLUSIONS

The present study confirms previous findings of an increased risk of overall but not death-censored renal graft loss in renal transplant recipients with PTDM. Longstanding diabetes might increase the risk of acute rejections.

Peritransplant Soluble CD30 as a Risk Factor for Slow Kidney Allograft Function, Early Acute Rejection, Worse Long-Term Allograft Function, and Patients' Survival

BACKGROUND

We aimed to determine whether serum soluble CD30 (sCD30) could identify recipients at high risk for unfavorable early and late kidney transplant outcomes.

METHODS

Serum sCD30 was measured on the day of kidney transplantation and on the 4th day posttransplant. We assessed the value of these measurements in predicting delayed graft function, slow graft function (SGF), acute rejection (AR), pyelonephritis, decline of allograft function after 6 months, and graft and patient survival during 5 years of follow-up in 45 recipients.

RESULTS

We found the association between low pretransplant serum levels of sCD30 and SGF. The absence of significant decrease of sCD30 on the 4th day posttransplant was characteristic for SGF, early AR (the 8th day-6 months), late AR (>6 months), and early pyelonephritis (the 8th day-2 months). Lower pretransplant and posttransplant sCD30 predicted worse allograft function at 6 months and 2 years, respectively. Higher pretransplant sCD30 was associated with higher frequency of early AR, and worse patients' survival, but only in the recipients of deceased-donor graft. Pretransplant sCD30 also allowed to differentiate patients with early pyelonephritis and early AR.

CONCLUSIONS

Peritransplant sCD30 is useful in identifying patients at risk for unfavorable early and late transplant outcomes.

Increase of allosensitization after a kidney graft failure: Predictors and effect on retransplantation outcomes

Patients who are candidates for a second kidney transplant (SKT) frequently have a higher level of panel reactive antibodies (PRA). We assessed the allosensitisation change after a first graft failure (GF), its predictors and impact on retransplantat outcomes. We retrospectively selected 140 adult patients who received a SKT. Recipient and donor characteristics were analyzed. We defined the delta PRA (dPRA) as the difference between peak PRA before the SKT and first one (cohort median value=+10%). Logistic regression analysis was used to determine risk factors for dPRA≥10% and acute rejection (AR) in the SKT. Univariable and multivariable Cox analysis was applied to assess independent predictors of second GF. Risk factors for dPRA≥10% at SKT were AR (OR=2.57; P=0.022), first graft survival <1 year (OR=2.47; P=0.030) and ABDR HLA mismatch (OR=1.38 per each mismatch; P=0.038). AR in the SKT was associated with dPRA≥10% (OR=2.79; P=0.047). Induction with a lymphocyte-depleting agent had a protective effect (OR=0.23; P=0.010). SKT survival was lower (P=0.008) in patients with a dPRA≥10% (75.6%, 60.5% in dPRA≥10%; 88.6%, 88.6% in dPRA<10% patients at 5 and 10 years, post-transplant respectively). Multivariable Cox regression showed that dPRA≥10% (HR=2.38, P=0.042), delayed graft function (HR=2.82, P=0.006) and AR (HR=3.30, P=0.001) in the SKT were independent predictors of retransplant failure. This study shows that an increased allosensitisation at retransplant was associated with the degree of HLA mismatch and led to poorer outcomes. De-emphasis of HLA matching in current allocation policies may be undesirable, particularly in patients with a higher chance of needing a SKT.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Derivation of a Predictive Model for Graft Loss Following Acute Kidney Injury in Kidney Transplant Recipients

Background:

Acute kidney injury (AKI) is common in the kidney transplant population.

Objective:

To derive a multivariable survival model that predicts time to graft loss following AKI.

Design:

Retrospective cohort study using health care administrative and laboratory databases.

Setting:

Southwestern Ontario (1999-2013) and Ottawa, Ontario, Canada (1996-2013).

Patients:

We included first-time kidney only transplant recipients who had a hospitalization with AKI 6 months or greater following transplant.

Measurements:

AKI was defined using the Acute Kidney Injury Network criteria (stage 1 or greater). The first episode of AKI was included in the analysis. Graft loss was defined by return to dialysis or repeat kidney transplant.

Methods:

We performed a competing risk survival regression analysis using the Fine and Gray method and modified the model into a simple point system. Graft loss with death as a competing event was the primary outcome of interest.

Results:

A total of 315 kidney transplant recipients who had a hospitalization with AKI 6 months or greater following transplant were included. The median (interquartile range) follow-up time was 6.7 (3.3-10.3) years. Graft loss occurred in 27.6% of the cohort. The final model included 6 variables associated with an increased risk of graft loss: younger age, increased severity of AKI, failure to recover from AKI, lower baseline estimated glomerular filtration rate, increased time from kidney transplant to AKI admission, and receipt of a kidney from a deceased donor. The risk score had a concordance probability of 0.75 (95% confidence interval [CI], 0.69-0.82). The predicted 5-year risk of graft loss fell within the 95% CI of the observed risk more than 95% of the time.

Limitations:

The CIs of the estimates were wide, and model overfitting is possible due to the limited sample size; the risk score requires validation to determine its clinical utility.

Conclusions:

Our prognostic risk score uses commonly available information to predict the risk of graft loss in kidney transplant patients hospitalized with AKI. If validated, this predictive model will allow clinicians to identify high-risk patients who may benefit from closer follow-up or targeted enrollment in future intervention trials designed to improve outcomes.

Diagnostic Performance of Fas Ligand mRNA Expression for Acute Rejection after Kidney Transplantation: A Systematic Review and Meta-Analysis

Background

The value of Fas ligand (FASL) as a diagnostic immune marker for acute renal rejection is controversial; this meta-analysis aimed to clarify the role of FASL in acute renal rejection.

Methods

The relevant literature was included by systematic searching the MEDLINE, EMBASE, and Cochrane Library databases. Accuracy data for acute rejection (AR) and potential confounding variables (the year of publication, area, sample source, quantitative techniques, housekeeping genes, fluorescence staining, sample collection time post-renal transplantation, and clinical classification of AR) were extracted after carefully reviewing the studies. Data were analyzed by Meta-DiSc 1.4, RevMan 5.0, and the Midas module in Stata 11.0 software.

Results

Twelve relevant studies involving 496 subjects were included. The overall pooled sensitivity, specificity, positive likelihood ratio (LR), negative LR, and diagnostic odds ratio, together with the 95% CI were 0.64 (0.57–0.70), 0.90 (0.85–0.93), 5.66 (3.51–9.11), 0.30 (0.16–0.54), and 30.63 (14.67–63.92), respectively. The area under the summary receiver operating characteristic curve (AUC) was 0.9389. Fagan’s nomogram showed that the probability of AR episodes in the kidney transplant recipient increased from 15% to 69% when FASL was positive, and was reduced to 4% when FASL was negative. No threshold effect, sensitivity analyses, meta-regression, and subgroup analyses based on the potential variables had a significant statistical change for heterogeneity.

Conclusions

Current evidence suggests the diagnostic potential for FASL mRNA detection as a reliable immune marker for AR in renal allograft recipients. Further large, multicenter, prospective studies are needed to validate the power of this test marker in the non-invasive diagnosis of AR after renal transplantation.

The Polymorphism -308G/A of Tumor Necrosis Factor-α Gene Modulates the Effect of Immunosuppressive Treatment in First Kidney Transplant Subjects Who Suffer an Acute Rejection

The -308G/A SNP of tumor necrosis factor-alpha (TNF-α) gene affects TNF-α production. As its impact on transplant outcome remains open to debate, we decided to genotype it in a cohort of transplant subjects. A retrospective analysis of 439 first kidney recipients randomly divided into two subgroups (discovery and validation cohorts) was performed to identify the best predictors of acute rejection (AR). The effect on transplant outcome was analyzed by an adjusted logistic regression model. Carriers of the A allele, associated with elevated TNF-α production, presented a higher risk of AR (OR = 2.78; 95% CI = 1.40-5.51). Logistic regression analyses for AR showed an interaction between the polymorphism and treatment with thymoglobulin (p-interaction = 0.03). In recipients who did not receive thymoglobulin, carriers of A allele had higher risk of AR (OR = 4.05; 95% CI = 1.76-9.28). Moreover, carriers of A allele not treated with thymoglobulin presented higher risk of AR than those who received thymoglobulin (OR = 13.74; 95% CI = 1.59-118.7). The AUC of the model in the discovery cohort was 0.70 and in the validation cohort was 0.69. Our findings indicate that the -308G/A TNF-α polymorphism is associated with AR risk and it modulates the effectiveness of thymoglobulin treatment. This pharmacogenetic effect lets us propose this SNP as a useful predictor biomarker to tailor immunosuppressive regimens.

Pretransplant Immune- and Apoptosis-Related Gene Expression Is Associated with Kidney Allograft Function

Renal transplant candidates present immune dysregulation, caused by chronic uremia. The aim of the study was to investigate whether pretransplant peripheral blood gene expression of immune factors affects clinical outcome of renal allograft recipients. Methods. In a prospective study, we analyzed pretransplant peripheral blood gene expression in87 renal transplant candidates with real-time PCR on custom-designed low density arrays (TaqMan). Results. Immediate posttransplant graft function (14-day GFR) was influenced negatively by TGFB1 (P = 0.039) and positively by IL-2 gene expression (P = 0.040). Pretransplant blood mRNA expression of apoptosis-related genes (CASP3, FAS, and IL-18) and Th1-derived cytokine gene IFNG correlated positively with short- (6-month GFR CASP3: P = 0.027, FAS: P = 0.021, and IFNG: P = 0.029) and long-term graft function (24-month GFR CASP3: P = 0.003, FAS: P = 0.033, IL-18: P = 0.044, and IFNG: P = 0.04). Conclusion. Lowered pretransplant Th1-derived cytokine and apoptosis-related gene expressions were a hallmark of subsequent worse kidney function but not of acute rejection rate. The pretransplant IFNG and CASP3 and FAS and IL-18 genes' expression in the recipients' peripheral blood is the possible candidate for novel biomarker of short- and long-term allograft function.

Acute Antibody-Mediated Rejection in Kidney Transplant Based on the 2013 Banff Criteria: Single-Center Experience in Uruguay

BACKGROUND

Acute antibody-mediated rejection (AMR) diagnosis criteria have changed in recent consensus of Banff, with current evidence of C4d-negative AMR. Our objective was to evaluate incidence of AMR in renal transplantation according to Banff 2013 criteria and to examine the histological features and outcome.

METHODS

This retrospective study involved all kidney transplants with histological diagnosis of acute rejection (AR) at our center between 2000 and 2014. All the biopsies with AR were re-assessed by a nephro-pathologist and classified by use of the Banff 2013 criteria.

RESULTS

Of 205 kidney transplants, biopsy-proven AR was diagnosed in 25 cases (12%). Re-assessing them according to Banff 2013 criteria, AMR was diagnosed in 17 (8.3%) and represented 68% of the confirmed rejections. AMR diagnosis was performed on day 23 ± 26, with median of 11 days. From the 17 cases, 7 had concomitant T-cell-mediated rejection. All cases presented endothelial edema and acute tubular necrosis. Glomerulitis was found in 12 cases and capillaritis in 14. In 3, associated thrombotic micro-angiopathy (TMA) was found. Intimal and transmural arteritis was evidenced in 5 and 1 patient. In 2, transplant glomerulopathy was present. Seven of the 10 biopsies with C4d staining in the peri-tubular capillaries were positive. Twelve cases received plasmapheresis, 6 received gamma-globulin, and 6 received rituximab. After administration of anti-AMR therapy, 16 cases recovered renal function, reaching a serum creatinine level of 1.5 ± 0.6 mg %. Graft survival at 1 year was lower in the AMR group versus patients without AMR (81.9% vs 98.9%, log-rank test, P < .001). Risk factors for AMR were re-transplant (30% vs 7%, P = .02), HLA-DR mismatch (1.06 ± 0.65 vs 0.7 ± 0.6, P = .03), panel-reactive antibody (28% ± 33 vs 6.2 ± 13, P = .00), and delayed graft function (82% vs 30%, P = .00).

CONCLUSIONS

Adapting the new Banff 2013 criteria increased the sensitivity of the diagnosis of ARM. Regarding our data, despite an adequate response to the therapy, it resulted in a worse graft survival by the first year of renal transplant.

De Novo Donor-Specific HLA Antibodies Are Associated With Rapid Loss of Graft Function Following Islet Transplantation in Type 1 Diabetes

Outcomes after islet transplantation continue to improve but etiology of graft failure remains unclear. De novo donor-specific human leukocyte antigen (HLA) antibodies (DSA) posttransplant are increasingly recognized as a negative prognostic marker. Specific temporal associations between DSA and graft function remain undefined particularly in programs undertaking multiple sequential transplants. Impact of de novo DSA on graft function over 12 months following first islet transplant was determined prospectively in consecutive recipients taking tacrolimus/mycophenolate immunosuppression at a single center. Mixed-meal tolerance test was undertaken in parallel with HLA antibody assessment pretransplant and 1-3 months posttransplant. Sixteen participants received a total of 26 islet transplants. Five (19%) grafts were associated with de novo DSA. Five (31%) recipients were affected: three post-first transplant; two post-second transplant. DSA developed within 4 weeks of all sensitizing grafts and were associated with decreased stimulated C-peptide (median [interquartile range]) at 3 months posttransplant (DSA negative: 613(300-1090); DSA positive 106(34-235) pmol/L [p = 0.004]). De novo DSA directed against most recent islet transplant were absolutely associated with loss of graft function despite maintained immunosuppression at 12 months in the absence of a rescue nonsensitizing transplant. Alemtuzumab induction immunosuppression was associated with reduced incidence of de novo DSA formation (p = 0.03).

What immunosuppression should be used for old-to-old recipients?

Elderly patients receiving a kidney from old donors (old-to-old) are a growing population of transplant recipients. This population cumulates risks of complications due to the co-morbidities and the immunodeficiency state and the frailty of the recipients together with the kidney senescence of the donors. In this context, the choice of immunosuppression is complicated and must take into account some contradictory principles explaining why no consensus exists today.

A 3'-UTR Polymorphism in Soluble Epoxide Hydrolase Gene Is Associated with Acute Rejection in Renal Transplant Recipients

Background and Purpose

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites that play a protective role against damaging processes that may occur after re-oxygenation of the graft. We aimed to investigate whether the presence of functional polymorphisms in the gene encoding soluble epoxy hydrolase (EPHX2), which metabolizes EETs to less active compounds, may play a role in the outcome of renal transplantation.

Methods

In a group of 259 Caucasian renal transplant recipients and 183 deceased donors, we determined the presence of three common EPHX2 SNPs, namely rs41507953 (K55R), rs751141 (R287Q) and rs1042032 A/G. Associations with parameters of graft function and the incidence of acute rejection were retrospectively investigated throughout the first year after grafting by logistic regression adjusting for clinical and demographic variables.

Results

Carriers of the rs1042032 GG genotype displayed significantly lower estimated glomerular filtration rate (eGFR) (38.15 ± 15.57 vs. 45.99 ± 16.05; p = 0.04) and higher serum creatinine values (1.57 ± 0.58 vs. 1.30 ± 0.47 g/dL; p=0.02) one year after grafting, compared to patients carrying the wildtype A-allele. The same GG genotype was also associated to increased risk of acute rejection. Interestingly, this association was observed for the genotype of both recipients [OR =6.34 (1.35-29.90); p = 0.015] and donors [OR = 5.53 (1.10-27.80); p=0.042]. A statistical model including both genotypes along with other meaningful demographic and clinical variables resulted in an increased significance for the association with the recipients’ genotype [OR=8.28 (1.21-74.27); p=0.031].

Conclusions

Our results suggest that genetic variability in the EETs-metabolizing gene, EPHX2, may have a significant impact on the outcome of deceased-donor renal transplantation.

The impact of early and late acute rejection on graft survival in renal transplantation

Background

Advances in immunosuppression after kidney transplantation have decreased the influence of early acute rejection (EAR) on graft survival. Several studies have suggested that late acute rejection (LAR) has a poorer effect on long-term graft survival than EAR. We investigated whether the timing of acute rejection (AR) influences graft survival, and analyzed the risk factors for EAR and LAR.

Methods

We performed a retrospective cohort study involving 709 patients who underwent kidney transplantation between 2000 and 2009 at the Samsung Medical Center, Seoul, Korea. Patients were divided into three groups: no AR, EAR, and LAR. EAR and LAR were defined as rejection before 1 year and after 1 year, respectively. Differences in graft survival between the three groups and risk factors of graft failure were analyzed.

Results

Of the 709 patients, 198 (30%) had biopsy-proven AR [EAR=152 patients (77%); LAR=46 patients (23%)]. A total of 65 transplants were lost. The 5-year graft survival rates were 97%, 89%, and 85% for patients with no AR, EAR, and LAR, respectively. These differences were significant (P<0.001 for both by log-rank test). In time-dependent Cox regression analysis, EAR (hazards ratio, 3.37; 95% confidence interval, 1.90–5.99) and LAR (hazards ratio, 5.32; 95% confidence interval, 2.65–10.69) were significantly related to graft failure. When we set LAR as standard and compared it with EAR, there was no statistical difference between EAR and LAR (P=0.21).

Conclusion

AR, regardless of its timing, significantly worsened graft survival. Treatments to reduce the incidence of AR and improve prognosis are needed.

New directions for rabbit antithymocyte globulin (Thymoglobulin(®)) in solid organ transplants, stem cell transplants and autoimmunity

In the 30 years since the rabbit antithymocyte globulin (rATG) Thymoglobulin^® was first licensed, its use in solid organ transplantation and hematology has expanded progressively. Although the evidence base is incomplete, specific roles for rATG in organ transplant recipients using contemporary dosing strategies are now relatively well-identified. The addition of rATG induction to a standard triple or dual regimen reduces acute cellular rejection, and possibly humoral rejection. It is an appropriate first choice in patients with moderate or high immunological risk, and may be used in low-risk patients receiving a calcineurin inhibitor (CNI)-sparing regimen from time of transplant, or if early steroid withdrawal is planned. Kidney transplant patients at risk of delayed graft function may also benefit from the use of rATG to facilitate delayed CNI introduction. In hematopoietic stem cell transplantation, rATG has become an important component of conventional myeloablative conditioning regimens, following demonstration of reduced acute and chronic graft-versus-host disease. More recently, a role for rATG has also been established in reduced-intensity conditioning regimens. In autoimmunity, rATG contributes to the treatment of severe aplastic anemia, and has been incorporated in autograft projects for the management of conditions such as multiple sclerosis, Crohn’s disease, and systemic sclerosis. Finally, research is underway for the induction of tolerance exploiting the ability of rATG to induce immunosuppresive cells such as regulatory T-cells. Despite its long history, rATG remains a key component of the immunosuppressive armamentarium, and its complex immunological properties indicate that its use will expand to a wider range of disease conditions in the future.

A 12-month single arm pilot study to evaluate the efficacy and safety of sirolimus in combination with tacrolimus in kidney transplant recipients at high immunologic risk

The optimal immunosuppressive strategy for renal transplant recipients at high immunologic risk remains a topic of investigation. This prospective single arm pilot study was undertaken to evaluate the safety and efficacy of a combined tacrolimus and sirolimus regimen in recipients at immunological high risk and to compare outcomes with a contemporaneous control group received tacrolimus and mycophenolate mofetil. Patients that received a renal allograft between 2010 and 2011 at high risk (defined as panel reactive antibodies > 50%, 4 or more human leukocyte antigen mismatches, or retransplantation) were enrolled. All patients received basiliximab induction and corticosteroids. A total of 28 recipients treated with tacrolimus and sirolimus were enrolled in this study and 69 recipients were retrospectively reviewed as a control group. The sirolimus group showed a higher, but not statistically significant, incidence of biopsy proven acute rejection and a lower glomerular filtration rate than the control group. Furthermore, sirolimus group was associated with significant increases in BKV infection (P = 0.031), dyslipidemia (P = 0.004), and lymphocele (P = 0.020). The study was terminated prematurely due to a high incidence of adverse events. A de novo tacrolimus/sirolimus combination regimen may not be an ideal choice for recipients at high immunological risk.

Antibody-mediated rejection in young kidney transplant recipients: the dilemma of noncompliance and insufficient immunosuppression

BACKGROUND

Antibody-mediated rejection (ABMR) is a recognized cause of late kidney allograft loss. Although ABMR may occur despite appropriate chronic immunosuppressive therapy, non-adherence both facilitates and accelerates the activation of the effector phase of the humoral immune response against the donor tissue, leading in turn to progressive kidney allograft rejection. Given the poor efficacy of rescue therapies for both acute and chronic late ABMR, establishing appropriate preventive strategies at different times before and after transplantation is a critical management goal.

CASE-DIAGNOSIS/TREATMENT

In this report, we discuss the differential diagnoses and management of ABMR based on the clinical case report of a young kidney transplant recipient with progressive ABMR due to poor immunosuppressive adherence. In the absence of sensitive and specific non-invasive monitoring tools for alloimmune activation, the clinical dilemma in the management of the adolescent patient lies in differentiating between suboptimal prescribed immunosuppression and deliberate non-adherence to adequate immunosuppression dosing. Despite the advent of therapies to reduce ABMR injury, the graft is destined for untimely functional loss.

CONCLUSIONS

New biomarkers and tools for the accurate characterization of alloimmune risk before and after transplantation, and serial testing for de novo changes in circulating donor-specific alloantibodies, are urgently needed to support the delivery of optimized immunosuppression exposure.

Pre-transplant immune state defined by serum markers and alloreactivity predicts acute rejection after living donor kidney transplantation

Acute rejection (AR) remains a major cause for long-term kidney allograft failure. Reliable immunological parameters suitable to define the pre-transplant immune state and hence the individual risk of graft rejection are highly desired to preferably adapt the immunosuppressive regimen in advance. Donor and third party alloreactivities were determined by mixed lymphocyte cultures. Soluble forms of CD25, CD30, and CD44 were detected in patients' serum by ELISA. Various lymphocyte subpopulations were measured using flow cytometry. All patients received triple immunosuppression (tacrolimus/mycophenolate mofetil/steroids) and were grouped according to biopsy results within the first year: rejection-free (RF, n = 13), borderline (BL, n = 5), or acute rejection (AR, n = 7). Patients with AR showed the highest pre-transplant alloreactivities and serum levels (sCD25/sCD30/sCD44) according to the pattern RF < BL < AR. Relying on serum analysis only, multivariate logistic regression (logit link function) yielded a prognostic score for prediction of rejection with 75.0% sensitivity and 69.2% specificity. Patients with rejection showed markedly higher pre-transplant frequencies of CD4(+) /CD8(+) T cells lacking CD28, but lower numbers of CD8(+) CD161(bright) T cells and NK cells than RF individuals. Pre-transplant immune state defined by alloreactivity, serum markers, and particular lymphocyte subsets seems to correlate with occurrence of graft rejection after kidney transplantation. A prognostic score based on pre-transplant serum levels has shown great potential for prediction of rejection episodes and should be further evaluated.

How to improve the survival of the kidney transplant - is it only the pharmaceutical management?

Kidney transplantation is the best treatment option in chronic kidney disease patients. Despite the new potent immunosuppressants, the long-term graft survival has not significantly improved. This is a rather complex issue with interrelationship between pretransplant donor-recipient variables, recipient post-transplant perioperative non/immunological factors, the combination/dose of maintenance immunosuppression and the general noncompliance of the patient. The recipients with an increased immunological risk should be maintained on triple therapy with steroids, preferably tacrolimus (Tac) or cyclosporine (CsA) plus mycophenolate mofetil (MMF). Eventual calcineurin inhibitor (CNI) minimization should be coupled with either protocol biopsies or frequent biochemistry monitoring including periodical assessment of anti-human leukocyte antigen and donor-specific antibodies. Recipients with standard immunological risks may be considered for as low as possible triple immunosuppression (steroids, Tac/CsA, MMF) after a period of 6 - 12 months. In cases of CNI minimization, a modification with a higher dose of the other two drugs in the triple therapy combination might be considered. The nonadherence to the prescribed maintenance therapy should be regularly checked-up. In conclusion, antibody induction, MMF, steroids and low-dose Tac/CsA should be the mainstream therapy in majority of patients. The short- and mid-term encouraging results for CNI minimization/withdrawal seem to correspond to recent findings of chronic antibody-mediated rejection, and long-term results need further evaluation.