M.A. Gentil

The pharmacokinetics of mycophenolate mofetil in renal transplant recipients receiving standard-dose or low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus: the Symphony pharmacokinetic substudy

BACKGROUND Exposure to mycophenolic acid (MPA), the primary active metabolite of mycophenolate mofetil (MMF), is correlated with therapeutic efficacy of MMF but varies depending on the concomitantly administered immunosuppressive drugs. METHODS A 3-month pharmacokinetic substudy of the prospective, randomized, multicentre, open-label Symphony study was performed. Eighty-three adult renal transplant patients received standard-dose cyclosporine, MMF 2 g/day and corticosteroids, or daclizumab induction, MMF 2 g/day and corticosteroids plus low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus. The area under the concentration-time curve (AUC(0-12)) of MPA and its metabolites between treatment groups was compared. Pharmacokinetic sampling was performed before MMF administration and at 20, 40, 75 min; 2, 3, 6, 8, 10 and 12 h post-dose on Day 7 and Months 1 and 3. RESULTS Compared with standard-dose cyclosporine, patients receiving low-dose tacrolimus or low-dose sirolimus had significantly higher AUC(0-12) values for MPA at Day 7 and Month 1 and for free MPA at Day 7, and significantly lower AUC(0-12) values for 7-O-MPA-glucuronide (MPAG) at Month 1 and for acyl-glucuronide at Months 1 and 3 (P < 0.05). AUC(0-12) of MPA and free MPA was significantly greater with low-dose tacrolimus and low-dose sirolimus than with low-dose cyclosporine in the first month (P < 0.05). The ratio of MPA to MPAG exposure was significantly higher in the three low-dose groups than in the standard-dose cyclosporine group (P < 0.05). CONCLUSIONS Standard- and low-dose cyclosporine reduces the exposure of MPA and free MPA compared to low-dose tacrolimus or low-dose sirolimus in patients given the same dose of MMF.

Therapeutic effect of the acquisition of cytomegalovirus-specific immune response during preemptive treatment.

Background. It has been suggested that preemptive therapy against cytomegalovirus (CMV) infection after transplantation promotes a CMV-specific immune response. Our objective was to determine whether solid-organ transplant patients at high risk for CMV infection treated preemptively acquire a CMV-specific immune response and whether the acquired immune response confers immunity by controlling subsequent CMV replication episodes and by protecting from late-onset CMV disease. Methods. Patients were followed up for 18 months after transplantation. CMV viral load was determined using real-time polymerase chain reaction assays, and the T-cell immune response was characterized by intracellular cytokine staining. Results. The 21 patients studied developed CMV replication episodes at a median of 4 weeks (range 2–8 weeks) after transplantation and a CMV-specific T-cell response within a median of 12 weeks (range 10–20 weeks). The decline in the incidence of CMV replication episodes is inversely correlated with the acquisition of the CMV-specific T-cell response (linear regression r2=0.781, Pearson correlation=−0.883; P=0.001). There were no CMV replication episodes after week 47 of transplantation. In addition, after acquisition of the immune response, 42 replication episodes were cleared without treatment. The time taken for immune clearance of replication correlated with the peak viral load (P=0.01). No incidence of CMV early or late-onset disease was detected. Conclusions. Our results demonstrate that preemptive therapy is a safe and an effective strategy for the control of CMV infection in solid-organ transplant recipients at high risk for CMV infection. This is the first study that reports a therapeutic effect of the acquisition of CMV-specific immune response during preemptive treatment.

Donor-specific antibodies against HLA, MICA, and GSTT1 in patients with allograft rejection and C4d deposition in renal biopsies.

Background. Production of antibodies against donor-specific antigens is one of the central mechanisms of allograft rejection. This antibody-mediated rejection (AMR) is evidenced by the presence of circulating donor-specific antibodies and deposition of complement component C4d on renal endothelium. Although anti-human leukocyte antigen (HLA) antibodies account for a high proportion of AMR, in many cases anti-HLA antibodies cannot be demonstrated. In liver transplant, antibodies against glutathione-S-transferase T1 (GSTT1) expressed on the graft may induce an antibody response leading to a severe graft dysfunction. In addition, presence of antibodies against major-histocompatibility-complex class I chain-related gene A (MICA) has been associated with a poor graft survival in kidney transplantation. Methods. Pre- and posttransplantation sera from 19 patients fulfilling the criteria for AMR including C4d deposition in renal biopsies were included. Donor-specific antibodies against HLA-I and -II and MICA were studied using Luminex. Anti-GSTT1 antibodies were analyzed by indirect immunofluorescence and by an ELISA method. A control group of 39 patients with graft dysfunction negative for C4d was also included. Results. At the time of the biopsy, 4 (21%) patients had only anti-HLA class I antibodies; 3 (15.8%) had anti-GSTT1, 2 (10.5%) had anti-HLA-class II, and 2 (10.5%) had anti-MICA; four patients had combination of antibodies: HLA-I+MICA (n=1), HLA-I+GSTT1 (n=2), and GSTT1+MICA (n=1). No antibodies were found in 4 (21%) patients. In total, 6 (31.6%) C4d+ patients had anti-GSTT1 antibodies, whereas, among the 39 C4d-negative patients, only 3 (7.7%) had anti-GSTT1 antibodies (P=0.027). Conclusion. Besides anti-HLA antibodies, donor-specific antibodies against MICA and GSTT1 antigens could be responsible for the occurrence of antibody-mediated kidney graft rejection.

Infections in Renal Transplant Recipients Receiving Mycophenolate Versus Azathioprine-Based Immunosuppression

Differences in the incidence, etiology, type, and outcome of infections occurring during the first 6 months after transplantation were evaluated in two consecutive cohorts of kidney recipients who received immunosuppressive regimens based on either azathioprine (plus antilymphocyte globulin, cyclosporine A, and prednisone) (ATG-AZA cohort) or mycophenolate-mofetil (plus cyclosporine A and prednisone) (MMF cohort). The overall incidence of infections in the two cohorts was similar (0.99±1.06 infections/patient in the MMF cohort and 1.04±0.99 in the ATG-AZA cohort, P=0.3), as was the incidence of bacterial and fungal infections. In patients who received mycophenolate, cytomegalovirus disease occurred at a higher incidence (0.3±0.54 vs. 0.1±0.34 episodes/patient, P=0.005) and affected the upper gastrointestinal tract more frequently (0.21±0.48 vs. 0.025±0.16 episodes of cytomegalovirus ulcerative esophagitis, gastritis, or duodenitis per patient; P=0.001). A nonsignificant trend toward a higher recipient survival for patients receiving mycophenolate was noted (100% vs. 95%, P=0.07). In multivariate analysis, the following factors were independently associated with a higher risk of cytomegalovirus disease: the serostatus R–/D+ (seronegative recipients who received a kidney from a seropositive donor) (RR=35.7 [95%CI, 7.4–166.7]), treatment with mycophenolate (RR=10.4 [95%CI, 2.7–38.4]), and the development of any episodes of acute rejection (RR=10.1 [95%CI, 2.5–41.6]). These data show that kidney recipients receiving mycophenolate have a higher incidence of cytomegalovirus disease, mainly affecting the upper gastrointestinal tract, compared to those receiving azathioprine-based immunosuppression.

Mycophenolate mofetil reduces deterioration of renal function in patients with chronic allograft nephropathy. A follow-up study by the Spanish Cooperative Study Group of Chronic Allograft Nephropathy.

Background. Although studies have shown that mycophenolate mofetil (MMF) with cyclosporine (CsA) and prednisone can reduce the incidence of acute rejection and increase the half-life of the graft, the effects of MMF on established chronic allograft nephropathy (CAN) are controversial. Methods. We studied 121 patients with biopsy-proven CAN, 59 treated with CsA and prednisone and 62 treated with triple-drug therapy with azathioprine. At inclusion, each group received 2 g per day of MMF and azathioprine was stopped. Renal function was measured by the glomerular filtration rate (GFR) obtained by creatinine clearance (Cockcroft-Gault) and monitored by the slope of the GFR, adjusted using linear regression. Results. The median follow-up, after incorporation of MMF, was 36 (13–36) months, with 103 (85.1%) having a full 3-year follow-up. Before the introduction of MMF, there was progressive deterioration in renal function (GFR: 54.8±20.9 vs. 39.7±14.0 mL/min, P <0.001). After introduction of MMF, renal function remained stable (GFR: 39.7±14.0 vs. 41.3±10.8 mL/min, P =NS), with a significant change in the slope of the GFR (−0.0144 vs. +0.00045, P <0.001). In 65 patients in whom CsA blood levels remained unchanged during follow-up (148.0±65.6 vs. 154.1±58.2, P =NS), the slope of the GFR showed a reduction in loss of renal function (−0.0147 vs. −0.0001, P <0.001). Conclusions. Treatment with MMF reduced the progressive deterioration of renal function in patients with CAN, independently of the blood levels of CsA.

Outcome of kidney transplant in chronic hepatitis C virus patients: effect of pretransplantation Interferon-Alpha2b monotherapy

Hepatitis C virus (HCV) infection represents an important problem for hemodialysis patients especially following renal transplantation. We assessed the outcome of HCV-positive patients undergoing renal transplantation after treatment during the pretransplant period with alpha-interferon 2b (alpha-IFN2b). Data from all HCV-infected patients (n=38) undergoing renal transplantation from a cadaveric donor between January 1997 and June 2002 were retrospectively reviewed. Viral clearance was achieved in 7 of 13 patients receiving alpha-IFN2b monotherapy during the pretransplant period. Controls were HCV-negative renal transplantation recipients operated during the same period (n=273). HCV-positive compared to HCV-negative patients showed no differences in age, gender, underlying disease, donor type, or immunosuppressive regimen, but there were significant differences (P<.001) in the mean (+/-SD) time on dialysis (155+/-70 versus 43+/-47 months), retransplant incidence (26% versus 5%), immunization rate as assessed by panel reactive antibodies (PRA) peak >50% (55% versus 18%), or 1-year survival of recipients (88% versus 97%) and of grafts (76% versus 89%). In contrast, all seven HCV RNA-negative patients who were before transplantation survived to the end of follow up with functioning grafts in six subjects and remained with normal liver function and clearance of HCV RNA. We conclude that kidney transplantation in HCV-positive compared with HCV-negative patients shows lower recipient and graft survival rates, possibly due to the higher incidence of risk factors, such as duration of hemodialysis, higher retransplantation rate, or hyperimmunization. Responders to pretransplantation IFN therapy show an excellent prognosis of liver function and overall outcome close to HCV-negative renal transplant recipients.

Anti-glutathione S-transferase T1 antibody-mediated rejection in C4d-positive renal allograft recipients

BACKGROUND Chronic humoral rejection is a progressive form of graft injury, with defined diagnostic criteria, the crucial one being the evidence of circulating anti-donor antibodies. These antibodies are mainly directed against human leucocyte antigens (HLA), but other targets have also been described. We previously reported that antibodies against the Glutathione S-transferase T1 (GSTT1) enzyme appear in recipients without the GSTT1 gene who receive a graft from a GSTT1-positive donor. The primary aim of this study was to analyse the role of GSTT1 in cases of antibody-mediated rejection (AMR) in the absence of anti-HLA antibodies. A second objective was to describe the distribution of the GSTT1 enzyme in the human kidney. METHODS Four renal biopsies from four renal transplanted patients with declined renal function and circulating anti-donor GSTT1 antibodies were studied for C4d deposits in sections of paraffin-embedded tissue samples. Anti-donor-specific HLA and MICA antibody detection was done with the Luminex platform and anti-GSTT1 antibodies were tested by indirect immunofluorescence on rat tissues and ELISA assay. DNA of the patients was extracted for GSTT1 genotyping. RESULTS Four patients with the GSTT1 donor/recipient mismatch developed anti-GSTT1 antibodies 32, 42, 48 and 60 months after the transplant. One patient also had donor-specific anti-HLA antibodies. Their biopsies showed pathologic lesions compatible with chronic antibody-mediated rejection (CAMR), along with positive C4d deposition in peritubular capillaries in three of them, being no valuable in the other case. CONCLUSION This is the first study reporting an association between the appearance of chronic antibody-mediated renal allograft rejection and the occurrence of de novo production of anti-GSTT1 antibodies, in the absence of anti-HLA donor-specific antibodies. This fact suggests a potential role of the GSTT1 system in anti-graft immune response.

Influence of MRP2 on MPA pharmacokinetics in renal transplant recipients–results of the Pharmacogenomic Substudy within the Symphony Study

BACKGROUND The aim of this study was to determine the relationship between single-nucleotide polymorphisms (SNPs) in MRP2 genes and mycophenolic acid (MPA) pharmacokinetics in renal transplant recipients of the Symphony Pharmacogenomic substudy. METHODS Sixty-six renal transplant recipients of eight Spanish centres were randomized into four branches of immunosuppressive regimen: low dose of cyclosporine, standard dose of cyclosporine, tacrolimus and sirolimus, all in addition to mycophenolate mofetil and steroids. Fifty-five patients were genotyped for SNPs in MRP2, C24T and C3972T. Pharmacokinetic sampling was done before MPA administration and up to 12 h post-dose at Day 7, 1 month and 3 months post-transplant. Relationships of area under the curve (AUC) of MPA and MPAG plasma sampling with the presence of MRP2 SNPs and with the immunosuppressive regimens were studied. RESULTS At steady-state conditions, MPA-reduced exposure was observed in C24T variant allele in MRP2 (CC: 68.73 ± 6.78; *T: 48.12 ± 4.90, P = 0.023); no significant differences linked to C3972T SNP were observed. Taking into account groups of treatment, lower MPA AUC in variant allele of C24T was only found under macrolides treatment with statistically significant differences at Month 3 (Tac and SRL, CC: 86.52 ± 10.98 versus *T: 41.99 ± 4.82, P = 0.001; CsA, CC: 52.31 ± 5.30 versus *T: 54.24 ± 8.30, P = 0.772); for C3972T, the same tendency was found but differences at steady state did not reach statistical significance. CONCLUSIONS Renal transplant recipients T carriers of C24T MRP2 with macrolides treatment were associated with reduced MPA AUC in steady-state conditions. Patients treated with cyclosporine lost the effect of this polymorphism.

Renal transplantation in patients with hepatitis C virus antibody. A long national experience

Background. Renal transplantation is the best therapy for patients with hepatitis C virus (HCV) infection with end-stage renal disease. Patient and graft survival are lower in the long term compared with HCV-negative patients. The current study evaluated the results of renal transplantation in Spain in a long period (1990–2002), focusing on graft failure. Methods. Data on the Spanish Chronic Allograft Nephropathy Study Group including 4304 renal transplant recipients, 587 of them with HCV antibody, were used to estimate graft and patient survival at 4 years with multivariate Cox models. Results. Among recipients alive with graft function 1 year post-transplant, the 4-year graft survival was 92.8% in the whole group; this was significantly better in HCV-negative vs HCV-positive patients (94.4% vs 89.5%, P < 0.005). Notably, HCV patients showed more acute rejection, a higher degree of proteinuria accompanied by a diminution of renal function, more graft biopsies and lesions of de novo glomerulonephritis and transplant glomerulopathy. Serum creatinine and proteinuria at 1 year, acute rejection, HCV positivity and systolic blood pressure were independent risk factors for graft loss. Patient survival was 96.3% in the whole group, showing a significant difference between HCV-negative vs HCV-positive patients (96.6% vs 94.5%, P < 0.05). Serum creatinine and diastolic blood pressure at 1 year, HCV positivity and recipient age were independent risk factors for patient death. Conclusions. Renal transplantation is an effective therapy for HCV-positive patients with good survival but inferior than results obtained in HCV-negative patients in the short term. Notably, HCV-associated renal damage appears early with proteinuria, elevated serum creatinine showing chronic allograft nephropathy, transplant glomerulopathy and, less frequently, HCV-associated de novo glomerulonephritis. We suggest that HCV infection should be recognized as a true risk factor for graft failure, and preventive measures could include pre-transplant therapy with interferon.

Deficient long-term response to pandemic vaccine results in an insufficient antibody response to seasonal influenza vaccination in solid organ transplant recipients.

Background. Little is known about the long-term antibody response to the 2009-H1N1 vaccine in solid organ transplant recipients (SOTR) and its clinical repercussion on the efficacy of following 2010–2011 influenza vaccine. Methods. We performed a multicenter prospective study in SOTR receiving one dose of the nonadjuvant 2010–2011 seasonal influenza vaccine and determined the immunological response at 5 weeks after vaccination. Results. One hundred SOTR were included. Long-term antibody titers to the previous vaccine were only detected in one third of the patients. Patients with baseline titers had significantly higher seroprotection for the 2009-H1N1 strain (100% vs. 73%, relative risks [RR] 1.37, 95% confidence intervals [CI] 1.19–1.57; P=0.006), for H3N2 strain (100% vs. 62.2%, RR 1.61, 95% CI 1.36–1.90; P=0.005), and for B strain (100% vs. 69%; P=0.02). The seroconversion rate in patients with baseline titers was 90.9% vs. 73% (RR 2.97, 95% CI 0.75–11.74; P=0.07) for the 2009-H1N1 strain, 92.2% vs. 62.2% (RR 5.29, 95% CI 0.8–35.7; P=0.02) for the H3N2 strain, and 58.3% vs. 69% (P=0.45) for the B strain. Conclusions. SOTR response to the 2010–2011 influenza vaccine was not optimal. The response was related to baseline titers; however, most of the patients did not exhibit detectable antibodies at vaccination lacking long-term response. New strategies are necessary to improve vaccination efficacy.