Shazia Shabir

Meta-Analysis of Calcineurin-Inhibitor-Sparing Regimens in Kidney Transplantation

Calcineurin-inhibitor-sparing strategies in kidney transplantation may spare patients the adverse effects of these drugs, but the efficacy of these strategies is unknown. Here, we conduct a meta-analysis to assess outcomes associated with reducing calcineurin inhibitor exposure from the time of transplantation. We search Medline, Embase, and Cochrane Register of Controlled Trials for randomized controlled trials published between 1966 and 2010 that compared de novo calcineurin-inhibitor-sparing regimens to calcineurin-inhibitor-based regimens. In this analysis, we include 56 studies comprising data from 11337 renal transplant recipients. Use of the contemporary agents belatacept or tofacitinib, in combination with mycophenolate, decreased the odds of overall graft failure (OR 0.61; 95% CI 0.39-0.96; P = 0.03). Similarly, minimization of calcineurin inhibitors in combination with various induction and adjunctive agents reduces the odds of graft failure (OR 0.73; 95% CI 0.58-0.92; P = 0.009). Conversely, the use of inhibitors of mammalian target of rapamycin (mTOR), in combination with mycophenolate, increases the odds of graft failure (OR 1.43; 95% CI 1.08-1.90; P = 0.01). Calcineurin-inhibitor-sparing strategies are associated with less delayed graft function (OR 0.89; 95% CI 0.80-0.98; P = 0.02), improved graft function, and less new-onset diabetes. The more contemporary protocols did not seem to increase rates of acute rejection. In conclusion, this meta-analysis suggests that reducing exposure to calcineurin inhibitors immediately after kidney transplantation may improve clinical outcomes.

Comparison of the Predictive Performance of eGFR Formulae for Mortality and Graft Failure in Renal Transplant Recipients

Background. To date, efforts have focused on assessing estimated glomerular filtration rate (eGFR) formulae against measured GFR. However, a more appropriate clinical gold standard is one conveying a defined clinical disadvantage. In renal transplantation, these measures are mortality and graft failure. Methods. The Long Term Efficacy and Safety Surveillance database was used to analyze 1344 renal transplant recipients. eGFR was assessed 6 months posttransplantation with the following formulae: Cockcroft-Gault; Walser; Nankivell; abbreviated modification of diet in renal disease (aMDRD); MDRD7; Rules refitted MDRD; and Mayo Clinic. The outcome measures were mortality and graft failure. Results. Although eGFR was statistically associated with subsequent mortality and graft failure in the Cox model (irrespective of which eGFR formula was used), the clinical utility of eGFR was moderate at best in predicting subsequent mortality and graft failure. No clinically relevant or statistically significant difference was discernable between formulae, with a maximum area under the receiver operating characteristic curve of 0.63 and 0.61 for 3- and 5-year mortality, respectively, and 0.66 and 0.60 for 3- and 5-year graft failure, respectively. Serum creatinine used in isolation displayed similar predictive utility, and no improvement was seen by investigating the change in creatinine or eGFR between 6 and 12 months. Conclusions. In summary, seven eGFR equations showed similar and limited utility in predicting mortality and graft failure after renal transplantation. This has important implications for the management of renal transplant recipients and the use of an eGFR as a surrogate endpoint in clinical trials.

Assessing and comparing rival definitions of delayed renal allograft function for predicting subsequent graft failure.

Background. The traditional definition of delayed graft function (DGF) rests on dialysis requirement during the first postoperative week. Subsequently, a more objective and “functional” definition of DGF (fDGF) has been proposed as an alternative to this dialysis-based definition of DGF (dDGF) and defined as a failure of the serum creatinine to decrease by at least 10% daily on 3 successive days during the first week posttransplantation, irrespective of dialysis requirement. However, an association between fDGF and long-term graft failure has not been fully established, and it is unknown whether fDGF is a better marker of subsequent outcomes than dDGF. Methods. We studied 750 adult deceased donor kidney transplant recipients (1996–2006) and analyzed the association between these two DGF definitions and long-term graft outcome. Results. Univariable associations with death-censored graft failure were seen for both dDGF and fDGF (hazard ratio [HR] 1.59; 95% confidence interval [CI] 1.16–2.18; P=0.004 and HR 1.72; 95% CI 1.26–2.36; P=0.001, respectively). On bivariable analysis (dDGF vs. fDGF), dDGF lost significance, whereas the effect of fDGF persisted (HR 1.52; 95%CI 1.03–2.25; P=0.04). This was also the case in a multivariable model, where fDGF but not dDGF was significantly associated with graft failure (HR 1.47; 95%CI 1.06–2.03; P=0.02). Results were similar for overall graft failure. Conclusions. This study confirms the utility of fDGF as an early marker of subsequent inferior allograft outcomes, suggesting superiority over the traditional (often subjective) dialysis-based definition. Wider adoption of the fDGF definition should be considered, both as a risk-stratification tool in clinical practice and a clinical trial endpoint.

Cytomegalovirus-Associated CD4(+) CD28(null) Cells in NKG2D-Dependent Glomerular Endothelial Injury and Kidney Allograft Dysfunction.

Emerging data suggest that expansion of a circulating population of atypical, cytotoxic CD4+ T cells lacking costimulatory CD28 (CD4+CD28null cells) is associated with latent cytomegalovirus (CMV) infection. The purpose of the current study was to increase the understanding of the relevance of these cells in 100 unselected kidney transplant recipients followed prospectively for a median of 54 months. Multicolor flow cytometry of peripheral blood mononuclear cells before transplantation and serially posttransplantation was undertaken. CD4+CD28null cells were found predominantly in CMV‐seropositive patients and expanded in the posttransplantation period. These cells were predominantly effector‐memory phenotype and expressed markers of endothelial homing (CX3CR1) and cytotoxicity (NKG2D and perforin). Isolated CD4+CD27−CD28null cells proliferated in response to peripheral blood mononuclear cells previously exposed to CMV‐derived (but not HLA‐derived) antigens and following such priming incubation with glomerular endothelium resulted in signs of endothelial damage and apoptosis (release of fractalkine and von Willebrand factor; increased caspase 3 expression). This effect was mitigated by NKG2D‐blocking antibody. Increased CD4+CD28null cell frequencies were associated with delayed graft function and lower estimated glomerular filtration rate at end follow‐up. This study suggests an important role for this atypical cytotoxic CD4+CD28null cell subset in kidney transplantation and points to strategies that may minimize the impact on clinical outcomes.

Development and Evaluation of a Composite Risk Score to Predict Kidney Transplant Failure

BACKGROUND Although risk factors for kidney transplant failure are well described, prognostic risk scores to estimate risk in prevalent transplant recipients are limited. STUDY DESIGN Development and validation of risk-prediction instruments. SETTING & PARTICIPANTS The development data set included 2,763 prevalent patients more than 12 months posttransplant enrolled into the LOTESS (Long Term Efficacy and Safety Surveillance) Study. The validation data set included 731 patients who underwent transplant at a single UK center. PREDICTOR Estimated glomerular filtration rate (eGFR) and other risk factors were evaluated using Cox regression. OUTCOME Scores for death-censored and overall transplant failure were based on the summed hazard ratios for baseline predictor variables. Predictive performance was assessed using calibration (Hosmer-Lemeshow statistic), discrimination (C statistic), and clinical reclassification (net reclassification improvement) compared with eGFR alone. RESULTS In the development data set, 196 patients died and another 225 experienced transplant failure. eGFR, recipient age, race, serum urea and albumin levels, declining eGFR, and prior acute rejection predicted death-censored transplant failure. eGFR, recipient age, sex, serum urea and albumin levels, and declining eGFR predicted overall transplant failure. In the validation data set, 44 patients died and another 101 experienced transplant failure. The weighted scores comprising these variables showed adequate discrimination and calibration for death-censored (C statistic, 0.83; 95% CI, 0.75-0.91; Hosmer-Lemeshow χ(2)P = 0.8) and overall (C statistic, 0.70; 95% CI, 0.64-0.77; Hosmer-Lemeshow χ(2)P = 0.5) transplant failure. However, the scores failed to reclassify risk compared with eGFR alone (net reclassification improvements of 7.6% [95% CI, -0.2 to 13.4; P = 0.09] and 4.3% [95% CI, -2.7 to 11.8; P = 0.3] for death-censored and overall transplant failure, respectively). LIMITATIONS Retrospective analysis of predominantly cyclosporine-treated patients; limited study size and categorization of variables may limit power to detect effect. CONCLUSIONS Although the scores performed well regarding discrimination and calibration, clinically relevant risk reclassification over eGFR alone was not evident, emphasizing the stringent requirements for such scores. Further studies are required to develop and refine this process.

T Lymphocyte responses to nonpolymorphic HLA-derived peptides are associated with chronic renal allograft dysfunction.

Background. The routine assessment of cellular alloimmunity to guide therapy is of perennial interest because this limb of the immune system is the main target of current transplant immunosuppression. That this has not as yet been realized in clinical practice reflects the difficulty of developing a standardized assay that accounts for the high degree of polymorphism exhibited by histocompatibility antigens. Methods. We have investigated whether immune responses to peptides derived from nonpolymorphic regions of human leukocyte antigen arise after transplantation, in particular in those with chronic allograft dysfunction. Results. Peripheral blood mononuclear cell &ggr;-interferon production to peptides derived from the nonpolymorphic &agr;3 domain of class 1 human leukocyte antigen occurred more frequently in long-term renal transplant recipients than healthy controls (51/110 vs. 1/18, 46.3% vs. 5.5%; P<0.001). These responses were associated with chronic allograft dysfunction manifested by a reduced and decreasing estimated glomerular filtration rate (responders vs. nonresponders: 39.5 vs. 48.8 mL/min, P=0.015 and −4.1 vs. −1.3 mL/min/year, P=0.008). Responses occurred mostly to autologous, “cryptic self-epitopes” and arose from CD4+CD25HiCD127Hi T lymphocytes, which have been previously implicated in chronic rejection. Conclusion. These findings suggest a strategy for assessing cellular immune responses to transplantation antigens with potential for generalization.

β Cell Glucotoxic-Associated Single Nucleotide Polymorphisms in Impaired Glucose Tolerance and New-Onset Diabetes After Transplantation

Emerging paradigms of new-onset diabetes after transplantation (NODAT) have focused on pathways and risk factors (e.g., posttransplant hyperglycemia and immunosuppressive agents) to its pathogenesis with the aim of identifying those at risk and developing preventative strategies (1). Identification of potential NODATassociated single nucleotide polymorphisms (SNPs) has increased our knowledge base of these pathways (2, 3). In particular, a recent genome-wide association study of 26 NODAT patients (and 230 controls), with subsequent de novo SNP genotyping in 57 NODAT patients (and 383 controls), discovered eight SNPs associated with pancreatic A-cell apoptosis (4). This Belfast cohort was limited to white, nondiabetic adult recipients who had received a cadaveric renal transplant between 1986 and 2005. New-onset diabetes after transplantation was defined as a new requirement for oral hypoglycemics or insulin after transplantation until August 2012. However, evidence is now emerging to identify abnormal glucose metabolism post transplantation by means of biochemical analyses including the oral glucose tolerance test (OGTT) (5, 6). We sought to examine the association of the identified eight SNPs in an independent cohort using biochemical diagnoses of impairedglucosetolerance(IGT)andNODAT. From 2009 to 2012, 112 patients were prospectively followed up over a 12-month period in a single-center adult tertiary center. To exclude preexisting diabetes, patients underwent glucose testing (minimum 8 hr fasting) immediately before transplantation and excluded if 6.1 mmol/L or higher or HbA1c of 6.5% or higher. In addition, live donor recipients underwent OGTTs within a week of transplantation. Oral glucose tolerance tests were then performed at 7 days, and then 3 months and 12 months for all renal transplants if fasting glucose was less than 7.0 mmol/L, to confirm the presence or persistence of posttransplant hyperglycemia. Impaired glucose tolerance was diagnosed if 2-hr OGTT glucose was 7.8 to 11 mmol/L. New-onset diabetes after transplantation was diagnosed if fasting glucose was 7 mmol/L or higher or 2-hr OGTT was 11.1 mmol/L or higher from day 7 onward, or HbA1c was 6.5% or higher from 3 months onward. Exclusion criteria of pretransplant diabetes and non-white ethnicity resulted in 68 patients being tested for the eight candidate SNPs (rs10484821, rs11580170, rs1836882, rs198372, rs2020902, rs2861484, rs4394754, rs7533125); genotyping was performed using Sequenom iPLEX and Taqman technologies. Event analyses using binary logistic regression was used adjusting for age, sex, baseline body mass index (BMI), and change in BMI over 12 months from transplantation. All patients had a homogenous immunosuppression regimen over the 12 months consisting of CD25 monoclonal antibody induction and maintenance tacrolimus, mycophenolic acid, and prednisolone. The cohort was aged 45 years (T15), 2.81 (T1.41) human leukocyte antigen mismatch, were 59% men, and 73% live donor recipients. Either IGT or NODAT occurred in over half the study population, with median time of onset 7 days and 18 days, respectively, after transplantation (IGT, 18/68 patients; NODAT, 18/68 patients). Significant differences were seen in the BMI change over 12 months for those who developed IGT (P=0.007) and NODAT (P=0.002) compared to those who did not. The NODAT group were also significantly older compared to those without NODAT (54 vs. 41 years; P=0.002). One candidate SNP that was found to be associated with posttransplant hyperglycemia in both cohorts was rs198372 for gene NPPA. Rs198372 genotype GG (vs. non-GG) was protective for IGT-onset on univariate (P=0.015) and multivariate analysis (OR, 0.21 [0.05Y 0.88]; P=0.033) in the adjusted model. No other SNPs demonstrated statistical significance for association with NODAT or IGT, although the power to detect an effect size of 1.5 was on average 10.2% across the tested SNPs and therefore (as expected) the possibility of a type II error certainly exists. NPPA encodes natriuretic peptides that inhibit cytokine and leptin production that are associated with inflammation and insulin resistance in human adipose tissue. Indeed, the Birmingham cohort who developed IGT exhibited an average increase in BMI of 2.3 kg/m at 1 year after transplantation, consistent with leptin level or weight gain known association (7). Elevated leptin levels increase interleukin-1A promoting Acell apoptosis in pancreatic islets and free fatty acids inducing apoptosis by caspase activation (4). McCaughan et al. (4) reported a 9.6% NODAT incidence over 12 years follow-up (57 patients with a median onset of 100 months), whereas in Birmingham at only 12 months, over 25% (18 patients) developed IGT and the same number had NODAT. This may reflect differences between the cohorts (for instance, all patients in Birmingham received maintenance CNI therapy compared with 75% in Belfast). However, it also highlights the importance of the use of detailed OGTT data in unmasking posttransplant glucose abnormalities. Also, this in turn may influence the genotype-phenotype relationship. This study supports further replication of the initial Belfast findings in regard to rs198372 as a candidate SNP for identifying patients at risk for developing posttransplant hyperglycemia and a potential biochemical pathway for manipulation.