C. Gómez-Alamillo

Calcineurin inhibitors, but not rapamycin, reduce percentages of CD4+CD25+FOXP3+ regulatory T cells in renal transplant recipients.

Background. Immunosuppression in renal transplantation, although manageable in the short-term, is a major hurdle for long-term graft survival. Recently, increased frequencies of CD4+CD25high regulatory T cells (Tregs) have been described as an additional mechanism that induces alloimmune tolerance. Methods. We assessed 64 renal transplant recipients with stable renal function for at least one year. Patients were divided into two groups according to the immunosuppression they were receiving at the moment of the study: one consisted of patients receiving rapamycin (Rapa) but not calcineurin inhibitors (CNI), and the other group received CNI but not Rapa. The Rapa group was further divided into three subgroups according to their previous experience with CNI: CNI-free, CNI withdrawal, and CNI conversion. Frequencies of blood Tregs were studied by flow cytometry after staining with monoclonal antibodies specific for different markers of Tregs. Results. Frequencies of CD4+ T cells with regulatory phenotype and function were significantly decreased in peripheral blood of renal transplant patients receiving CNI compared with those receiving Rapa. This effect was independent of an early exposure to CNI because the CNI-free patients in the Rapa group showed similar frequencies of Tregs to the CNI withdrawal and CNI conversion groups. Conclusions. CNI, but not Rapa, induce a decrease of circulating Tregs in stable renal transplant recipients. Thus, Rapa might be further explored in strategies using preservation of Tregs for transplant tolerance. Furthermore, quantification of blood Tregs may be a suitable tool to identify renal transplant recipients who may be candidates for reduced immunosuppression.

Prevention of murine lupus disease in (NZB×NZW)F1 mice by sirolimus treatment

Sirolimus is a new immunosuppressive drug used to avoid allograft rejection. The immunosuppressive effect of sirolimus is due to inhibition of the mammalian target of rapamycin, necessary for the proliferation and clonal expansion of activated T-cells. Because T-cells play a central role in the pathogenesis of autoimmune disease developed in (NZB×NZW)F1 mice, we evaluated the therapeutic use of sirolimus in such mice. (NZB×NZW)F1 female mice received 1mg/kg/day of sirolimus from 12 to 37 weeks of age. The development of autoimmune disease was evaluated by measuring the serum levels of auto-antibodies (autoAbs) and their immunoglobulin isotypes, prevalence of glomerulonephritis and mortality rates. Sirolimus directly inhibited production of autoAbs, glomerular deposits of immunoglobulins and development of proteinuria; also the survival of these mice was prolonged. Our results demonstrate the beneficial effects of sirolimus in preventing the development of lupus disease in (NZB×NZW)F1 female mice. Lupus (2007) 16, 775—781.

Evolution of tacrolimus blood levels and concentration-dose ratios in patients who develop new onset diabetes mellitus after kidney transplantation

New onset diabetes mellitus (NODM) affects kidney transplantation outcome. Several risk factors, including immunosuppressive drug levels, are related with NODM development. This analysis evaluates the incidence and risk factors of NODM in kidney transplant patients receiving tacrolimus, taking into account 6‐month blood levels and concentration‐dose ratios (CDRs). Seventy‐six patients under tacrolimus therapy who received a cadaveric renal transplant in our centre and with graft survival higher than 1 year were included in the study. NODM was defined as two fasting plasma glucose values ≥126 mg/dl or symptoms of diabetes plus casual plasma glucose concentrations ≥200 mg/dl throughout the first year. We examined previously reported variables related with NODM development. The incidence of NODM at 12 months was 27.6%. Risk factors for NODM included older age, higher first tacrolimus level, higher body mass index and lower first year weight gain. In multivariate analysis, the first year occurrence of NODM was significantly determined by the first tacrolimus blood level >20 ng/ml and age older than 50 years. CDR remains significantly higher in NODM throughout the 6 months. Older age and a high first tacrolimus blood level are associated with the development of NODM during the first year after kidney transplantation. NODM patients show higher CDR during the first 6 months.

Acute renal failure associated with use of inhaled tobramycin for treatment of chronic airway colonization with Pseudomonas aeruginosa.

Aminoglycoside nephrotoxicity is a well-known clinical entity that complicates the course of infectious diseases treated under this antibiotic regime. Recently, a new administration form of tobramycin, inhaled tobramycin (TOBI), has been approved to improve the antibacterial activity and reduce nephrotoxicity. We describe the clinical case of a 73-year-old woman with chronic-obstructive pulmonary disease (COPD) who developed acute renal failure (ARF) after using TOBI. Clinical presentation and biochemical parameters were compatible with aminoglycoside-induced renal failure. Based on the clinical findings presented here, a surveillance program should be established to monitor the presence of factors predisposing to renal failure, and to measure serum levels of tobramycin.

Number of peripheral blood regulatory T cells and lymphocyte activation at 3 months after conversion to mTOR inhibitor therapy.

BACKGROUND Mammalian target of rapamycin (mTOR) inhibitors are effective for induction and maintenance of regulatory T cells (Tregs). OBJECTIVE To assess the effects of conversion from calcineurin inhibitors (CNIs) to mTOR on the number of circulating Tregs and lymphocyte activation. PATIENTS AND METHODS In 18 renal transplant recipients receiving CNI therapy (cyclosporine in 9, and tacrolimus in 9), treatment was converted to mTOR inhibitors (everolimus in 14, and rapamycin in 4). Peripheral blood samples were obtained before and 3 months after conversion. The number of circulating Tregs was measured using flow cytometry, and defined as CD4+/CD25high/CD127low/CD27+/CD62L+/CD45RO+/Foxp3+. Lymphocyte activation was assessed indirectly according to production of intracellular adenosine triphosphate (iATP) on polyclonal activation using a phytohemaglutinin assay (Immuknow; Cylex, Inc, Columbia, Maryland). RESULTS In 15 patients (83.3%), the absolute number of Tregs increased significantly (P=.001) after conversion (median, 16.35 cells/mm3; 95% confidence interval [CI], 13.97-21.94) vs 3 months after conversion (32.03 cells/mm3; 95% CI, 26.25-41.66). The iATP production decreased from 326 ng/mL (95% CI, 302-419) to 248 ng/mL (95% CI, 196-318; P=.02), and increased in 4 patients (22.22%). No significant correlation was demonstrated between Treg concentration and change in iATP production. No rejection episodes were reported during follow-up. CONCLUSIONS Despite the small number of patients in whom therapy was converted from CNI inhibitors to mTOR inhibitors, the data suggest an increase in the absolute number of Tregs after conversion. In addition, the concentration of activated peripheral CD4+ T cells decreased to nearly that associated with risk of infection due to overimmunosuppression.

Correlation of C0 and C2 Levels With Cyclosporine Side Effects in Kidney Transplantation

Cyclosporine has a narrow therapeutic window requiring close monitoring to ensure adequate immunosuppression while avoiding nephrotoxicity and other side effects. Pharmacokinetic studies have suggested that cyclosporine levels at 2 hours postdose (C2) is the best single time point to predict area under the concentration curve (AUC) in kidney transplant recipients. C2 also predicted acute rejection episodes and nephrotoxicity better than trough levels (C0). Targeting cyclosporine levels to minimize side effects while maintaining adequate immunosuppressive effects is of clinical interest. There are conflicting evidence and few reports about whether cyclosporine-related side effects are a dose-dependent phenomenon. The aim of this single center study was to ascertain whether cyclosporine side effects were dose-dependent and which single time point level (C0 or C2) was more closely related to them. We analyzed 225 patients on Neoral-based immunosuppression with C0 and C2 levels measured on the same day of 2 different visits. Serum creatinine, glucose, uric acid, potassium, total cholesterol, triglycerides, and 24-hour urinary sodium elimination were measured by routine biochemical analyses. Blood pressure was measured at each visit. A significant positive correlation was observed between C2 and C0 concentrations and levels of potassium (P < .001), total cholesterol (P < .001), systolic blood pressure (P < .001), and pulse pressure (P < .01). There was a significant negative correlation between C2 and uric acid (P < .001). AUCs of receiver operating characteristic (ROC) curves for both C2 and C0 levels were significant as predictors of hyperkalemia (P < .001), hyperuricemia (P = .001), hypercholesterolemia (P < .05), and high systolic blood pressure (P < .05). There were no significant differences between the capacities of C2 or C0 to predict these variables. In conclusion, potassium, total cholesterol, uric acid, and systolic hypertension were influenced by cyclosporine in a dose-dependent manner. Both C2 and C0 were useful to predict cyclosporine side effects.

Prediction of Delayed Graft Function by Means of a Novel Web‐Based Calculator: A Single‐Center Experience

Renal failure persisting after renal transplant is known as delayed graft function (DGF). DGF predisposes the graft to acute rejection and increases the risk of graft loss. In 2010, Irish et al. developed a new model designed to predict DGF risk. This model was used to program a web‐based DGF risk calculator, which can be accessed via http://www.transplantcalculator.com . The predictive performance of this score has not been tested in a different population. We analyzed 342 deceased‐donor adult renal transplants performed in our hospital. Individual and population DGF risk was assessed using the web‐based calculator. The area under the ROC curve to predict DGF was 0.710 (95% CI 0.653–0.767, p < 0.001). The “goodness‐of‐fit” test demonstrates that the DGF risk was well calibrated (p = 0.309). Graft survival was significantly better for patients with a lower DGF risk (5‐year survival 71.1% vs. 60.1%, log rank p = 0.036). The model performed well with good discrimination ability and good calibration to predict DGF in a single transplant center. Using the web‐based DGF calculator, we can predict the risk of developing DGF with a moderate to high degree of certainty only by using information available at the time of transplantation.

High Regulatory T-Cell Levels at 1 Year Posttransplantation Predict Long-Term Graft Survival Among Kidney Transplant Recipients

INTRODUCTION Regulatory T cells (Tregs) have gained an important role in mechanisms of tolerance and protection against the transplant rejection. However, only limited retrospective data have shown a relationship between peripheral blood Tregs and better long-term graft survival. The purpose of the present study was to investigate prospectively circulating Treg levels and their association with long-term graft survival. METHODS Ninety kidney transplant recipients underwent measurement of Treg levels in peripheral blood before as well as at 6 months and 1 year posttransplantation. Receiver operating characteristic curves were applied to test the sensitivity and specificity of Treg levels to predict prognosis. RESULTS Treg levels before transplantation correlated with those at 6 months and 12 months posttransplantation (P < .001 and P = .002, respectively). Patients who maintained high Treg levels (above 70th percentile) at both 6 and 12 months displayed better long-term graft survival at 4 and 5 years follow-up (P = .04 and P = .043 respectively). There was no effect on patient survival. CONCLUSION Detection of high levels of peripheral blood Tregs was associated with better graft survival possibly using as a potential marker of prognosis.

Predictive factors of allosensitization in renal transplant patients switched from calcineurin to mTOR inhibitors

Conversion of kidney‐transplant recipients from calcineurin inhibitors to mTOR inhibitors has been suggested to be a risk factor for increased alloimmune response. We have analyzed the development of new HLA‐antibodies (HLA‐Abs) early after conversion in 184 patients converted in stable phase at our hospital and compared with a control group of nonconverted comparable 63 transplants. Using single‐antigen solid‐phase immunoassay analysis, a preconversion and a 3–6 months postconversion sera were prospectively analyzed in every patient for the appearance of new HLA‐Abs. Renal function at 2 years postconversion and cumulative graft survival were compared between groups. In 16 patients, new HLA‐Abs (3‐DSA and 13‐NonDSA), not present at the moment of conversion, were detected (8.7% vs. 3.1% in the control group). The type of mTORi used, type of CNI preconversion, the presence of steroids, time of conversion, or indication for conversion did not have influence on this effect but the presence of HLA‐Abs before conversion highly correlated with the appearance of new specificities. Patients with de novo HLA‐Abs showed a trend to worst graft function and survival. In conclusion, conversion to mTORi can be followed by early appearance of de novo HLA‐Abs, especially in patients with HLA‐Abs preconversion, and this complication should be screened early after conversion.

New-onset Diabetes After Transplantation: Drug-Related Risk Factors

INTRODUCTION New-onset diabetes after transplantation (NODAT), an important complication of renal transplantation leads to reduced graft function and increased patient morbidity and mortality. Because of its high incidence and immense impact on clinical outcomes, prevention of NODAT is highly desirable. Several modifiable and nonmodifiable risk factors for NODAT have been described. The aim of this study was to analyze the influence of various drugs on the development of NODAT during the first year. METHODS A retrospective analysis was performed on 303 adult kidney transplant recipients free of previously known diabetes. NODAT was defined as a fasting plasma glucose level ≥ 126 mg/dL confirmed by repeat testing on a different day. We excluded patients with transiently elevated fasting plasma glucose during the first 3 months. RESULTS NODAT was diagnosed in 37 recipients (12.2%). Univariate analysis identified several variables related to NODAT: recipient age (P < .001), body mass index (P < .001), donor age (P = .005), family history of diabetes (P < .001), statin use (P = .005), diuretic use (P = .040) and tacrolimus therapy (P = .029). After multivariate analysis, recipient age (relative risk [RR] = 1.060, 95% confidence interval [CI] 1.019- 1.102, P = .004), family history of diabetes (RR = 3.562, 95% CI 1.574-8.058, P = .002), smoking habit (RR 2.514, 95% CI 1.118-5.655, P = .026) and diuretic use (RR = 2.496, 95% CI 1.087-5.733, P = .031) were independently associated with NODAT development. CONCLUSIONS In our population of kidney transplant recipients, the main nonmodifiable risk factors for NODAT were recipient age and a family history of diabetes. Diuretic use was a modifiable risk factor associated with the development of NODAT. To reduce NODAT incidence, it is necessary to consider not only immunosuppressive therapy, but also concomitant drugs such as diuretics.