Immunosuppression: evolution in practice and trends, 1994-2004

Relationships among injury, fibrosis, and time in human kidney transplants

BACKGROUND

Kidney transplant biopsies offer an opportunity to understand the pathogenesis of organ fibrosis. We studied the relationships between the time of biopsy after transplant (TxBx), histologic fibrosis, diseases, and transcript expression.

METHODS

Expression microarrays from 681 kidney transplant indication biopsies taken either early (n = 282, <1 year) or late (n = 399, >1 year) after transplant were used to analyze the molecular landscape of fibrosis in relationship to histologic fibrosis and diseases.

RESULTS

Fibrosis was absent at transplantation but was present in some early biopsies by 4 months after transplant, apparently as a self-limited response to donation implantation injury not associated with progression to failure. The molecular phenotype of early biopsies represented the time sequence of the response to wounding: immediate expression of acute kidney injury transcripts, followed by fibrillar collagen transcripts after several weeks, then by the appearance of immunoglobulin and mast cell transcripts after several months as fibrosis appeared. Fibrosis in late biopsies correlated with injury, fibrillar collagen, immunoglobulin, and mast cell transcripts, but these were independent of time. Pathway analysis revealed epithelial response-to-wounding pathways such as Wnt/β-catenin.

CONCLUSION

Fibrosis in late biopsies had different associations because many kidneys had potentially progressive diseases and subsequently failed. Molecular correlations with fibrosis in late biopsies were independent of time, probably because ongoing injury obscured the response-to-wounding time sequence. The results indicate that fibrosis in kidney transplants is driven by nephron injury and that progression to failure reflects continuing injury, not autonomous fibrogenesis.

TRIAL REGISTRATION

INTERCOM study (www.clinicalTrials.gov; NCT01299168).

FUNDING

Canada Foundation for Innovation and Genome Canada.

Protective effect of mycophenolate mofetil against nephrotoxicity and hepatotoxicity induced by tacrolimus in Wistar rats

Tacrolimus (TAC), a calcineurin inhibitor (CNI), is clinically used as an immunosuppressive agent in the transplant recipient; however, the use of TAC is greatly limited by its nephrotoxicity and hepatotoxicity. Mycophenolate mofetil (MMF), an inhibitor of the purine synthesis, has been used in combination with many immunosuppressive drugs such as TAC. The association TAC/MMF was used in organ transplantation to increase the efficiency and reduce acute rejection rates, but the effects of MMF on TAC-induced kidney and liver injuries are still not well investigated. The aims of this study are to explore whether MMF co-administration with TAC has a renoprotective and hepatoprotective effect against TAC-induced renal and hepatic injuries and to check the implication of oxidative stress in the MMF's possible protective effect. Our results showed that MMF (at 50 mg kg(-1) body weight (b.w.)) restored creatinine, in addition to increased AST and ALT levels by TAC (at 60 mg kg(-1) b.w.). Furthermore, MMF decreased DNA damage induced by TAC in the kidney and liver of rats as assessed by comet assay. This renoprotective and hepatoprotective effect of MMF was associated with an antioxidant effect. In fact, MMF co-treatment with TAC decreased oxidative damage induced by TAC. It reduced malondialdehyde (MDA) and protein carbonyl (PC) levels as well as catalase and superoxide dismutase (SOD) activities. We conclude that the co-administration MMF with TAC protect liver and kidney against TAC toxicity via an antioxidant process.

Impact of Mycophenolate Mofetil Dose Reduction on Allograft Outcomes in Kidney Transplant Recipients on Tacrolimus-Based Regimens: A Systematic Review

OBJECTIVE

To systematically evaluate the clinical consequences of mycophenolate dose reduction in renal transplant recipients on tacrolimus-based regimens.

DATA SOURCES

PubMed (1949-July 2010), EMBASE (1980-July 2010), Cochrane Database of Systematic Reviews, International Pharmaceutical Abstracts, and Web of Science were searched using the terms mycophenolate mofetil, tacrolimus, dose reduction, and kidney and/or renal transplant. References from publications identified were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Studies reporting on rejection rate, allograft survival, or renal function were included and ranked according to the US Preventive Services Task Force classification; excluded were studies that were dose-finding or used cyclosporine only, involved patients on enteric-coated mycophenolate sodium or those with multiorgan transplant, or provided no information on concomitant immunosuppressants. Data extracted were study design, sample size, immunosuppression regimen, type of transplant, and allograft outcomes.

DATA SYNTHESIS

Of 13 studies included, 1 was level I evidence, 3 were level II-2, 6 were level II-3, and 3 were level III evidence. Three focused on tacrolimus-based regimens, whereas 7 included either cyclosporine or tacrolimus. The only prospective, randomized, multicenter trial demonstrated that early taper of mycophenolate dosage to 1 g/day can be utilized without increased risk of rejection, compared with late tapering, but the rejection rate was high (30-40%). Overall, we found conflicting evidence regarding the impact of mycophenolate dose reduction on rejection rate and allograft loss and that discontinuing mycophenolate led to an increased risk of graft loss as high as 8 fold. Allograft survival was lowest in patients with gastrointestinal complications and those in whom mycophenolate was discontinued, compared with patients with neither gastrointestinal complications nor mycophenolate discontinuation.

CONCLUSIONS

Weak evidence suggests that mycophenolate dose modifications, either reduction or discontinuation, may increase rejection rate and graft loss; however, this is more apparent in cyclosporine-based regimens. Prospective, well-designed trials are necessary to definitively determine the impact of dose reduction in renal transplant recipients on tacrolimus-based regimens.

Food allergies developing after solid organ transplant

The development of food allergy is an increasingly recognized form of morbidity after solid organ transplant. It occurs more commonly in liver transplant recipients, although it has also been reported in heart, lung, kidney, and intestinal transplants. Pediatric transplant recipients are more likely to develop symptoms compared to adults, and reports of frequency vary widely from 5% to 38% in pediatric liver transplant recipients. Multiple mechanisms have been proposed in the literature, although no single mechanism can yet account for all reported observations. As food allergy can have at worst potentially fatal consequences, and at best require lifestyle adjustment through food avoidance, it is important for recipients to be aware of the donor's food allergies and particularly in pediatrics, the possibility of completely de novo allergies. This review explores the recent reports surrounding food allergy after solid organ transplant, including epidemiology, proposed mechanisms, and implications for practice.

Longitudinal dose and type of immunosuppression in a national cohort of Australian liver, heart, and lung transplant recipients, 1984-2006

Unconfounded comparative data on the type and dose of immunosuppressive agents among solid organ transplant recipients are sparse, as are data on longitudinal immunosuppressive therapy since transplantation. We addressed this issue in a population-based cohort of Australian liver (n = 1895), heart (n = 1220), and lung (n = 1059) transplant recipients, 1984-2006. Data on immunosuppressive therapy were retrospectively collected at discharge, three months, and one, five, 10, and 15 yr after first transplant. We computed unadjusted and adjusted estimates for the association between the type and dose of immunosuppressive therapy and organ type. After adjustment for confounders, use of induction antibody and maintenance corticosteroids was more common in heart and lung compared to liver recipients (p < 0.001), and antibody therapy for rejection more common in liver recipients (p < 0.001). Liver recipients were more likely to receive calcineurin inhibitor monotherapy, with or without corticosteroids, compared to heart and lung recipients (p < 0.001). Liver recipients consistently received lower doses of azathioprine than heart and lung recipients (p < 0.001). These differences in immunosuppression may partly explain variations in immunosuppression-related morbidity by transplanted organ, for example, malignancy risk. Longitudinal changes in the type and the dose of immunosuppressive therapy over time since transplantation also demonstrate the need for time-dependent data in observational research.

Tacrolimus trough-level variability predicts long-term allograft survival following kidney transplantation

AIMS

The purpose of this study is to investigate tacrolimus trough-level variability from 3 to 12 months following transplantation and its association with allograft survival in renal transplant recipients.

MATERIALS AND METHODS

In this observational cohort study, tacrolimus trough-level variability was used as the predictor of all-cause allograft failure (defined as return to dialysis) and patient survival (all-cause mortality).

RESULTS

In total, 394 transplants were included in the analysis. Sixty-two transplants failed during the study. Tacrolimus trough-level variability across quartile groups were: Q1 median variability 12.5 %, range 4.76-15.71 % (n = 99), Q2 median variability 18.17 %, range 15.74-21.29 % (n = 96), Q3 median variability 24.63 % range 21.42-28.88 % (n = 100), Q4 median variability 36.91 %, range 28.91-81.9 % (n = 99). Higher tacrolimus trough-level variability was associated with inferior allograft survival in univariate models [hazard ratio per quartile increase (HR), 1.46, 95 % CI 1.16-1.83, p value = 0.001] and multivariate models (HR 1.36, 95 % CI 1.05-1.78, p value = 0.019). Higher tacrolimus trough-level variability was not associated with patient survival; univariate model (HR 1.25, 95 % CI 0.90-1.74, p value = 0.17), multivariate model (HR 1.25, 95 % CI 0.86-1.83, p value = 0.23).

CONCLUSIONS

Inferior renal allograft survival was observed in recipients with higher variability in tacrolimus trough-levels.

The biosynthetic pathway of FK506 and its engineering: from past achievements to future prospects

FK506, a 23-membered macrolide produced by several Streptomyces species, is an immunosuppressant widely used to prevent the rejection of transplanted organs. In addition, FK506 and its analogs possess numerous promising therapeutic potentials including antifungal, neuroprotective, and neuroregenerative activities. Herein, we introduce the biological activities and mechanisms of action of FK506 and discuss recent progress made in understanding its biosynthetic pathway, improving production, and in the mutasynthesis of diverse analogs. Perspectives highlighting further strain improvement and structural diversification aimed at generating more analogs with improved pharmaceutical properties will be emphasized.

Progressive decline in tacrolimus clearance after renal transplantation is partially explained by decreasing CYP3A4 activity and increasing haematocrit

AIMS

The long-term disposition of tacrolimus following kidney transplantation is characterized by a gradual decrease in dose requirements and increase in dose-corrected exposure. This phenomenon has been attributed to a progressive decline in cytochrome P450 3A4 (CYP3A4) activity, although this has never been demonstrated in vivo.

METHODS

Sixty-five tacrolimus- and 10 cyclosporine-treated renal transplant recipients underwent pharmacokinetic testing at day 7 and months 1, 3, 6 and 12 after transplantation, including 8-h area under the concentration-time curve (AUC) for tacrolimus or cyclosporine and assessment of CYP3A4 activity using oral and intravenous midazolam (MDZ) drug probes.

RESULTS

Tacrolimus clearance decreased gradually throughout the entire first year but only in CYP3A5*3/*3 homozygous recipients (25.6 ± 11.1 l h(-1) at day 7; 17 ± 9.1 l h(-1) at month 12; P < 0.001). In mixed model analysis, decreasing CYP3A4 activity, measured by apparent oral MDZ clearance (924 ± 443 ml min(-1) at day 7 vs. 730 ± 344 ml min(-1) at month 1; P < 0.001), explained 55.4% of the decline in tacrolimus clearance in the first month. CYP3A4 activity decreased by 18.9 ml min(-1) for every milligram of methylprednisolone dose tapering within the first month; beyond this point it remained stable. A gradual rise in haematocrit throughout the entire first year explained 31.7% of the decrease in tacrolimus clearance in the first month and 23.6% of the decrease between months 1 and 12. Cyclosporine clearance did not change over time.

CONCLUSIONS

The maturation of tacrolimus disposition in the first year after renal transplantation observed in CYP3A5*3/*3 homozygous patients can partly be explained by a (steroid tapering-related) decline in CYP3A4 activity and a progressive increase in haematocrit.

Lymphocytes as an Indicator for Initial Kidney Function: A Single Center Analysis of Outcome after Alemtuzumab or Basiliximab Induction

Alemtuzumab, an anti-CD52 T-cell and B-cell depleting monoclonal antibody, is established for induction therapy in renal transplantation (KTx). We herein provide a comparative analysis between alemtuzumab and basiliximab induction therapy and correlate lymphocyte depletion and recovery with the clinical course after KTx. This is a single center retrospective analysis of 225 patients/consecutive kidney transplantations treated with alemtuzumab for lymphocyte depletion and 205 recipients treated with basiliximab. Mean lymphocyte counts were 22.8 ± 9.41% before Tx and 2.61 ± 3.11% between week 1 and week 3 in the alemtuzumab group and 23.77 ± 10.42% before Tx and 13.92 ± 8.20% in the basiliximab group. Delayed graft function (DGF), cytomegalovirus (CMV) status, and recipient age showed a significant correlation with lymphocyte counts in the alemtuzumab group only. The outcome was read in reference to the velocity of lymphocyte recovery and in comparison to the control group. Lymphocyte counts early after transplantation, following alemtuzumab treatment, could be identified as a predictive factor for kidney function early after transplantation. A detailed analysis of phenotype and function of lymphocytes after alemtuzumab induction together with a correlation with the clinical course is warranted.

Effects of the CYP3A4*1B Genetic Polymorphism on the Pharmacokinetics of Tacrolimus in Adult Renal Transplant Recipients: A Meta-Analysis

BACKGROUND AND OBJECTIVE

The association between the CYP3A4*1B single nucleotide polymorphism (SNP) and tacrolimus pharmacokinetics in different studies is controversial. Therefore, a meta-analysis was employed to evaluate the correlation between the CYP3A4*1B genetic polymorphism and tacrolimus pharmacokinetics at different post-transplantation times in adult renal transplant recipients.

METHODS

Studies evaluating the CYP3A4*1B genetic polymorphism and tacrolimus pharmacokinetics were retrieved through a systematical search of Embase, PubMed, the Cochrane Library, ClinicalTrials.gov and three Chinese literature databases (up to Sept. 2014). The pharmacokinetic parameters (weight-adjusted tacrolimus daily dose and tacrolimus trough concentration/weight-adjusted tacrolimus daily dose ratio) were extracted, and the meta-analysis was performed using Stata 12.1.

RESULTS

Seven studies (involving 1182 adult renal transplant recipients) were included in this meta-analysis. For the weight-adjusted tacrolimus daily dose, in all included renal transplant recipients (European & Indian populations), CYP3A4*1/*1 recipients required a significantly lower weight-adjusted tacrolimus daily dose than did CYP3A4*1B carriers at 7 days (WMD -0.048; 95% CI -0.083 ~ -0.014), 6 months (WMD -0.058; 95% CI -0.081 ~ -0.036) and 12 months (WMD - 0.061; 95% CI -0.096 ~ -0.027) post-transplantation. In light of the heterogeneity, the analysis was repeated after removing the only study in an Indian population, and CYP3A4*1/*1 European recipients (mostly Caucasian) required a lower weight-adjusted tacrolimus daily dose within the first year post-transplantation. The tacrolimus trough concentration/weight-adjusted tacrolimus daily dose ratio (C0/Dose ratio) was significantly higher in CYP3A4*1/*1 recipients than in CYP3A4*1B carriers at 6 months (WMD 52.588; 95% CI 22.387 ~ 82.789) and 12 months (WMD 62.219; 95% CI 14.218 ~ 110.221) post-transplantation. When the only study in an Indian population was removed to examine European recipients (mostly Caucasian), the significant difference persisted at 1 month, 6 months and 12 months post-transplantation.

CONCLUSION

Based on our meta-analysis, the CYP3A4*1B genetic polymorphism affects tacrolimus dose requirements and tacrolimus trough concentration/weight-adjusted tacrolimus daily dose ratio within the first year post-transplantation in adult renal transplant recipients, especially in European recipients (mostly Caucasian).

Rabbit antithymocyte globulin induction and risk of post-transplant lymphoproliferative disease in adult and pediatric solid organ transplantation: An update

The most modifiable risk factor for post-transplant lymphoproliferative disease (PTLD) is the type and dose of induction and maintenance immunosuppressive therapy. It is challenging to identify the contribution of a single agent such as rabbit antithymocyte globulin (rATG) in the setting of multidrug therapy. Registry analyses can be helpful but are limited by methodological restrictions and inclusion of historical patient cohorts. These are typically from eras when rATG dosing was markedly higher than current dosing (e.g. total dose 14 mg/kg versus 6 mg/kg now), accompanied by higher exposure to maintenance therapies, and often an absence of antiviral prophylaxis. The largest registry analysis to assess rATG specifically found no risk of PTLD after kidney transplantation, but conflicting results have been reported, highlighting the difficulty of interpreting this type of analysis. The relative rarity of PTLD means that individually controlled trials are underpowered to assess its occurrence, but the available data do not suggest an effect of rATG. A pooled analysis of data from studies of rATG induction in kidney and heart transplantation found the incidence of PTLD to be comparable to published reports in the overall transplant population. Data on the effect of rATG dose are inconclusive, but in patients receiving antiviral prophylaxis it does not appear to be influential. Nevertheless, it would seem reasonable to employ the lowest dose of rATG compatible with effective induction, particularly in EBV-seronegative recipients and other high-risk groups such as heart-lung transplant recipients. Overall, the risk of PTLD following rATG induction therapy with modern dosing regimens and under current management conditions appears unlikely to make an important contribution to the risk:benefit balance.

Adverse Outcomes of Tacrolimus Withdrawal in Immune-Quiescent Kidney Transplant Recipients

Concerns about adverse effects of calcineurin inhibitors (CNIs) have prompted development of protocols that minimize their use. Whereas previous CNI withdrawal trials in heterogeneous cohorts showed unacceptable rates of acute rejection (AR), we hypothesized that we could identify individuals capable of tolerating CNI withdrawal by targeting immunologically quiescent kidney transplant recipients. The Clinical Trials in Organ Transplantation-09 Trial was a randomized, prospective study of nonsensitized primary recipients of living donor kidney transplants. Subjects received rabbit antithymocyte globulin, tacrolimus, mycophenolate mofetil, and prednisone. Six months post-transplantation, subjects without de novo donor-specific antibodies (DSAs), AR, or inflammation at protocol biopsy were randomized to wean off or remain on tacrolimus. The intended primary end point was the change in interstitial fibrosis/tubular atrophy score between implantation and 24-month protocol biopsies. Serially collected urine CXCL9 ELISA results were correlated with outcomes. The study was terminated prematurely because of unacceptable rates of AR (4 of 14) and/or de novo DSAs (5 of 14) in the tacrolimus withdrawal arm. Positive urinary CXCL9 predated clinical detection of AR by a median of 15 days. Analyses showed that >16 HLA-DQ epitope mismatches and pretransplant, peripheral blood, donor-reactive IFN-γ ELISPOT assay results correlated with development of DSAs and/or AR on tacrolimus withdrawal. Although data indicate that urinary CXCL9 monitoring, epitope mismatches, and ELISPOT assays are potentially informative, complete CNI withdrawal must be strongly discouraged in kidney transplant recipients who are receiving standard-of-care immunosuppression, including those who are deemed to be immunologically quiescent on the basis of current clinical and laboratory criteria.

BK virus nephropathy is not always alone

INTRODUCTION

BK virus associated allograft nephropathy (BKVAN) is an important cause of allograft lost that often occurs in the first year of transplantation. The state of over immunosuppression also predispose these patients to various opportunistic viral infection Objectives: This research aimed to study the renal transplanted patients for BK viremia and BKVAN.

PATIENTS AND METHODS

This observational study was conducted between January 2013 to December 2014 to study the renal transplanted patients for BK viremia and BKVAN. In our center patients received combination of de-sensitization therapy including antithymocyte globulin (ATG), rituximab (RITU), basiliximab, therapeutic plasma exchange, and methylprednisolone (MTP), in high risks or only MTP therapy in immunologically low risk patients.

RESULTS

Of total number of 26 patients (20-52 years, M/F 17/9), seven patients received ATG and seven patient received intensive desensitizing protocols, BKVAN and BK viremia happened in three and two patients in above groups subsequently, only one patient developed BKVAN in low risk group. We also observed; cytomegalovirus (CMV) and parvovirus B19 infection and hemophagocytic syndrome (HPS), thrombotic microangiopathy (TMA) and endocarditis in our patients with BKVAN and BK viremia.

CONCLUSION

Awareness about the possibility of BK virus nephropathy and appropriate immunosuppression minimization are crucial components of management. Consideration of other opportunistic infections and specific syndromes are also very important.

Steroid withdrawal in kidney allograft recipients

This review highlights the aggregate of knowledge obtained from the temporal trend of kidney transplant immune suppression. We will discuss the burden of steroid side effects and their impact on quality of life in kidney allograft recipients, which have led to minimizing steroid exposure. Issues arising since the inception of the concept of steroid withdrawal will be discussed, along with how they have continually led to a shift in research focus on this subject matter. The usefulness of surveillance biopsies and how further elucidation of the pathophysiology of interstitial fibrosis and tubular atrophy could contribute to improving long-term allograft outcomes will also be discussed. We will elaborate on the role of calcineurin inhibitor minimization alongside steroid withdrawal in improving long-term graft survival. Future expectations of subsequent studies with a view to improving overall kidney allograft outcomes by eliminating attendant problems associated with steroids will also be covered.

Value of solid organ transplant-trained pharmacists in transplant infectious diseases

Advances in organ transplantation have led to improved graft and patient survival. Transplant pharmacist's education and training uniquely position them to contribute knowledge and skills to the management of these highly complex patients. In 2004, the United Network for Organ Sharing bylaws added requirements that all transplant programs identify one or more pharmacists with experience in transplant pharmacotherapy to be responsible for providing pharmaceutical care to solid organ transplant recipients. These bylaws also delineated the transplant pharmacist's roles and responsibilities. To further support these efforts, in 2007 the Centers for Medicare and Medicaid Services accreditation standards for transplant centers also mandated that a center have a designated, qualified expert in transplant pharmacology as a multidisciplinary team member. The transplant pharmacist is a consistent member of the transplant team that can add value to the multidisciplinary approach of prevention and treatment of transplant infectious diseases through all phases of transplant care.

Low-dose RATG with or without basiliximab in renal transplantation: a matched-cohort observational study

BACKGROUND/AIMS

In renal transplantation, peri-operative low-dose rabbit-antithymocyte-globulin (RATG) plus basiliximab induction prevented acute allograft rejection more effectively than post-operative RATG plus basiliximab induction. We investigated the specific antirejection contribution of basiliximab in this context.

METHODS

This single-center, observational, matched-cohort study evaluated allograft rejections (primary outcome), steroid exposure and side effects, GFR (iohexol plasma clearance) and treatment costs in 16 deceased-donor renal transplant recipients induced with RATG (0.5 mg/kg/day) and 32 age-, gender- and treatment-matched reference-patients given RATG plus basiliximab (20 mg on days 0 and 4).

RESULTS

Induction was well tolerated. At 18 months, 8 patients (50%) vs. 3 reference-patients (9.4%) rejected the graft [HR (95% CI): 6.53 (1.73-24.70), p = 0.006]. Difference was significant (p < 0.01) even after adjusting for recipient/donor age and gender, cold ischemia time and HLA mismatches. There were 1 antibody-mediated rejection and 2 moderate cellular rejections in patients vs. none in reference-patients (p = 0.032). The median (interquartile range) prednisone cumulative dose was remarkably higher in patients than reference-patients [4.78 (1.12-6.10) vs. 0.19 (0.18-3.81) grams, p = 0.002]. Three patients vs. 24 reference-patients were off-steroid at study end (p < 0.001). Three patients vs. no reference-patient developed new-onset diabetes (p = 0.003). Both inductions similarly depleted B-cells. Outcomes of AZA- vs. MMF-treated participants were similar. GFR was similar in all groups. Compared to MMF, AZA therapy saved ≈ EUR 2,500/year and by month 14.3 post-transplant compensated basiliximab costs.

CONCLUSION

In renal transplantation, basiliximab plus peri-operative low-dose RATG more efficiently prevented allograft rejection than RATG monotherapy, and minimized steroid exposure and toxicity. AZA- vs MMF-based maintenance immunosuppression largely compensated the extra costs of basiliximab.

Risk of merkel cell carcinoma after solid organ transplantation

BACKGROUND

Solid organ transplant recipients have elevated risks of virus-related cancers, in part because of long-term immunosuppression. Merkel cell carcinoma (MCC) is an aggressive skin cancer recently found to have a viral origin, but little is known regarding the occurrence of MCC after transplant.

METHODS

We linked the US Scientific Registry of Transplant Recipients with data from 15 population-based cancer registries to ascertain MCC occurrence among 189498 solid organ transplant recipients from 1987 to 2009. Risks for MCC following transplantation were compared with the general population using standardized incidence ratios, and Poisson regression was used to compare incidence rates according to key patient and transplant characteristics. All statistical tests were two-sided.

RESULTS

After solid organ transplantation, overall risk of MCC was increased 23.8-fold (95% confidence interval = 19.6 to 28.7, n = 110). Adjusted risks were highest among older recipients, increased with time since transplantation, and varied by organ type (all P ≤ .007). Azathioprine, cyclosporine, and mTOR inhibitors given for maintenance immunosuppression increased risk, and non-Hispanic white recipients on cyclosporine and azathioprine experienced increasing MCC risk with lower latitude of residence (ie, higher ultraviolet radiation exposure, P = .012).

CONCLUSIONS

MCC risk is sharply elevated after solid organ transplant, likely resulting from long-term immunosuppression. Immunosuppressive medications may act synergistically with ultraviolet radiation to increase risk.

The Calcineurin Inhibitor-Sparing (CIS) Trial - individualised calcineurin-inhibitor treatment by immunomonitoring in renal allograft recipients: protocol for a randomised controlled trial

Background

Adequate monitoring tools are required to optimise the immunosuppressive therapy of an individual patient. Particularly, in calcineurin inhibitors, as critical dose drugs with a narrow therapeutic range, the optimal monitoring strategies are discussed in terms of safety and efficacy. Nevertheless, no pharmacokinetic monitoring markers reflect the biological activity of the drug. A new quantitative analysis of gene expression was employed to directly measure the functional effects of calcineurin inhibition: the transcriptional activities of the nuclear factor of activated T-cell (NFAT)-regulated genes in the peripheral blood.

Methods/Design

The CIS study is a randomised prospective controlled trial, comparing a ciclosporin A (CsA)-based immunosuppressive regimen monitored by CsA trough levels to a CsA-based immunosuppressive regimen monitored by residual NFAT-regulated gene expression. Pulse wave velocity as an accepted surrogate marker of the cardiovascular risk is assessed in both study groups. Our hypothesis is that an individualised CsA therapy monitored by residual NFAT-regulated gene expression results in a significantly lower cardiovascular risk compared to CsA therapy monitored by CsA trough levels.

Discussion

There is a lack of evidence in individualising standard immunosuppression in renal allograft recipients. The CIS study will consider the feasibility of individualised ciclosporin A immunosuppression by pharmacodynamic monitoring and evaluate the opportunity to reduce cardiovascular risk while maintaining sufficient immunosuppression.

Trial registration

EudraCT identifier 2011-003547-21, registration date 18 July 2011

https://www.clinicaltrialsregister.eu

The transplant patient and transplant medicine in family practice

Over the last two decades in particular there has been a remarkable increase in the number of solid organ transplants being performed worldwide alongside improvements in long-term survival rates. However, the infrastructure at transplant centres has been unable to keep pace with the current volume of the transplant patient work load. These pressures on transplant specialist centres has led to calls for an increased role of the general practitioner (GP) managing particular aspects of transplant patients' medical care. Indeed, many aspects of follow-up care such as screening for malignancies, preventing infection through immunisation programmes, and managing cardiovascular risk factors are already important aspects of family practice medicine. This paper aims to review some of the aspects of transplant patient care that is important for healthcare workers in family practice to manage.

Immunophenotyping and efficacy of low dose ATG in non-sensitized kidney recipients undergoing early steroid withdrawal: a randomized pilot study

Rabbit antithymocyte globulin (ATG) is commonly used as an induction therapy in renal transplant recipients, but the ideal dosage in tacrolimus-based early steroid withdrawal protocols has not been established. The purpose of this pilot study was to determine the immunophenotyping and efficacy of lower dose ATG in low immunological-risk kidney transplant recipients. In this prospective study, 45 patients were randomized (1∶1) to our standard dose ATG (total dose 3.75 mg/kg)(sATG) vs. lower dose 2.25 mg/kg (lowATG). All patients underwent early steroid withdrawal within 7 days. The primary end point was biopsy-proven acute rejection at 12 months. Prospective immunophenotyping of freshly isolated PBMCs was performed at baseline, 3, 6, 12 months post-transplant. The rate of acute rejection was 17% and 10% in the sATG and lowATG, respectively. Effector memory T cells, Tregs and recent thymic emigrants T cells had similar kinetics post-transplant in both groups. No statistically significant differences were found in graft survival, patient survival or infections between the two groups, though there was a non-significant increase in leukopenia (43%v s. 30%), CMV (8% vs. 0) and BK (4% vs. 0) infections in sATG group vs. lowATG. In sum, in low immunological risk kidney recipients undergoing steroid withdrawal, low dose ATG seems to be efficacious in preventing acute rejection and depleting T cells with potentially lower infectious complications. A larger study is warranted to confirm these findings.

Trial Registration

ClinicalTrials.gov NCT00548405

Anti-TCR mAb induces peripheral tolerance to alloantigens and delays islet allograft rejection in autoimmune diabetic NOD mice

BACKGROUND

Clinical application of islet transplantation to treat type 1 diabetes has been limited by islet allograft destruction by both allogeneic and autoimmune diabetogenic T-cell responses. The current study aims at determining whether an anti-T-cell receptor (TCR) monoclonal antibody (mAb) has potential as a novel and potent induction immunotherapy for islet transplantation.

METHODS

We have investigated the therapeutic efficacy and mechanisms of action of anti-TCR therapy in four different murine models, which comprise either allo- or autoimmune responses alone or both together.

RESULTS

T-cell response to islet allografts was potently abrogated by a brief treatment with an anti-TCRβ mAb (clone H57-597), resulting in long-term survival of BALB/c islet allografts in streptozotocin-induced diabetic B6 mice. Moreover, transient anti-TCR treatment permanently prevented BALB/c skin allograft rejection on Rag1 B6 recipients that were reconstituted with Foxp3 cell-depleted B6 splenocytes, but did not impair the reconstituted cells' ability to reject the later transplanted C3H skin allografts (transplanted at 120 days after BALB/c skin grafting). Transient anti-TCR treatment was also able to completely prevent diabetes onset in NOD.SCID.γc mice that were transferred with lymphocytes from diabetic NOD mice. Next, transient anti-TCR treatment significantly prolonged the survival of transplanted BALB/c islets in overtly diabetic NOD mice, which comprise both allogeneic and autoimmune diabetogenic T-cell responses to the transplanted islets.

CONCLUSIONS

Overall, anti-TCR mAb induced peripheral tolerance to specific alloantigens even in the absence of Foxp3-expressing natural regulatory T cells. These findings reveal the potential for using TCR-targeting mAbs as induction immunotherapy for islet transplantation.

Discovery of structurally simplified analogs of colchicine as an immunosuppressant

We have discovered a new class of colchicine-derived therapeutic agents for immune diseases including rejection of organ-transplantation and autoimmune disease. Compound 2, which had been developed to overcome poor pharmacokinetic properties of compound 1, a first-generation colchicine analog, turned out to show toxicity such as intestinal toxicity and loss of weight during in vivo tests. The deletion of 7-carboxamide group and middle ring-truncation in colchicine allowed us to have structurally simplified analogs with strong immunosuppressive activity. Herein, we report non-alkaloid tricyclic compound 7 and 12 as immunosuppressants which exhibited a strong immunosuppressive in vivo efficacy on the T-dependent antibody response, the Zymosan A-induced arthritis model and the Carrageenan-induced edema model. Compound 7 and 12 revealed less toxicity than the previous lead compound 2, and their minimum lethal doses (MLD) were proved to exceed 100 mg/kg.

Risk of diffuse large B-cell lymphoma after solid organ transplantation in the United States

Non-Hodgkin lymphoma arising in the context of immunosuppression is an important adverse outcome after solid organ transplantation. Diffuse large B-cell lymphoma (DLBCL) is the most commonly diagnosed subtype of post-transplantation non-Hodgkin lymphoma, but few studies of transplant recipients have examined subtype-specific risks. Therefore, we examined DLBCL risk in the Transplant Cancer Match Study, including registry-based cancer ascertainment among 96,615 solid organ transplants performed from 2000 to 2008. We determined standardized incidence ratios (SIRs) and 95% confidence intervals comparing DLBCL risk in transplant recipients with that in the general population, and used multivariable Poisson regression models to assess the impact of potential risk factors. We identified 321 incident cases of DLBCL, over 12 times more than expected based on general population rates (SIR = 12.6, 95% confidence interval = 11.2-14.0). SIRs were highest in young recipients and those receiving a lung or pancreas/kidney-pancreas transplant, and were greatly elevated for extranodal DLBCLs at the site of the transplantation compared with other sites. DLBCL risk was highest in the first year following transplantation, and SIRs for early-onset DLBCL risk were elevated in association with Epstein-Barr virus-negative serostatus and use of polyclonal antibody induction therapy. In conclusion, associations between recipient and transplant factors and post-transplantation DLBCL risk suggest a complicated interrelationship among multiple risk factors and timing of disease.

Long-term outcomes after organ transplantation in diabetic end-stage renal disease

Patients with type 1 diabetic end-stage renal disease (ESRD) may be offered single kidney transplantation from a live donor (LDK) or a deceased donor (DDK) to replace the lost kidney function. In the latter setting the patient may also receive a simultaneous pancreas together with a kidney from the same donor (SPK). Also in some cases a pancreas after kidney may be offered to those who have previously received a kidney alone (PAK). The obvious benefit of a successful SPK transplantation is that the patients not only recover from uremia but also obtain normal blood glucose control without use of insulin or other hypoglycemic agents. Accordingly, this combined procedure has become an established treatment for type 1 diabetic patients with ESRD. Adequate long-term blood glucose control may theoretically lead to reduced progression or even reversal of microvascular complications. Another potential beneficial effect may be improvement of patient and kidney graft survival. Development of diabetic complications usually takes a decade to develop and accordingly any potential benefits of a pancreas transplant will not easily be disclosed during the first decade after transplantation. The purpose of the review is to assess the present literature of outcomes after kidney transplantation in patients with diabetic ESRD, with our without a concomitant pancreas transplantation. The points of interest given in this review are microvascular complications, graft outcomes, cardiovascular outcomes and mortality.

Tuberculosis in solid-organ transplant recipients: disease characteristics and outcomes in the current era

We determined the characteristics of posttransplant tuberculosis and the impact of rifampin-based antituberculosis regimens on outcomes in the current era. Patients comprised 64 transplant recipients with tuberculosis, divided into 2 consecutive cohorts: an earlier cohort (cases occurring from 2003 to 2007) and a later cohort (cases from 2008 to 2011). Patients from the later versus earlier era had tuberculosis develop later after transplant (odds ratio, 1.01; 95% CI, 1.00-1.02; P= .05), were more likely to be liver transplant recipients (odds ratio, 4.52; 95% CI, 1.32-15.53; P= .02), and were more likely to receive tacrolimus-based immunosuppression (odds ratio, 3.24; 95% CI, 1.14-9.19; P= .03). Mortality rate was 10% in the later cohort and 21% in the earlier cohort (P= .20). Rifampin-based treatment was less likely to be used in patients with prior rejection (P= .04). However, neither rejection rate (P= .71) nor mortality (P= .93) after tuberculosis differed between recipients who received rifampin and recipients who did not. Thus, notable changes have occurred in the epidemiological characteristics of tuberculosis in transplant recipients. Overall mortality rate has improved, with about 90% of the patients now surviving after tuberculosis.

Risk of serious opportunistic infections after solid organ transplantation: interleukin-2 receptor antagonists versus polyclonal antibodies. A meta-analysis

BACKGROUND

We aimed to evaluate and quantify the risk of serious opportunistic infections after induction with polyclonal antibodies versus IL-2 receptor antagonists (IL-2RAs) in randomized clinical trials.

METHODS

PRISMA guidelines were followed and random-effects models were performed.

RESULTS

70 randomized clinical trials (10,106 patients) were selected: 36 polyclonal antibodies (n = 3377), and 34 IL-2RAs (n = 6729). Compared to controls, polyclonal antibodies showed higher risk of serious opportunistic infections (OR: 1.93, 95% CI: 1.34-2.80; p < 0.0001); IL-2RAs were associated with lower risk of serious opportunistic infections (OR: 0.80, 95% CI: 0.68-0.94; p = 0.009). Polyclonal antibodies were associated with higher risk of bacterial (OR: 1.58, 95% CI: 1.00-2.50; p = 0.049) and viral infections (OR: 2.37, 95% CI: 1.60-3.49; p < 0.0001), while IL-2RAs were associated with lower risk of cytomegalovirus (CMV) disease (OR: 0.73, 95% CI: 0.56-0.97; p = 0.032). Adjusted indirect comparison: compared to polyclonal antibodies, IL-2RAs were associated with lower risk of serious opportunistic infections (OR: 0.41, 95% CI: 0.34-0.49; p < 0.0001), bacterial infections (OR: 0.51, 95% CI: 0.39-0.67; p < 0.0001) and CMV disease (OR: 0.58, 95% CI: 0.34-0.98; p = 0.043). Results remained consistent across allografts.

CONCLUSION

The risk of serious opportunistic infections, bacterial infections and CMV disease were all significantly decreased with IL-2RAs compared to polyclonal antibodies.

Olmesartan attenuates tacrolimus-induced biochemical and ultrastructural changes in rat kidney tissue

Tacrolimus, a calcineurin inhibitor, is clinically used as an immunosuppressive agent in organ transplantation, but its use is limited due to its marked nephrotoxicity. The present study investigated the effect of olmesartan (angiotensin receptor blocker) on tacrolimus-induced nephrotoxicity in rats. A total of 24 rats were divided into four groups, which included control, tacrolimus, tacrolimus + olmesartan, and olmesartan groups. Tacrolimus-induced nephrotoxicity was assessed biochemically and histopathologically. Tacrolimus significantly increased BUN and creatinine level. Treatment with olmesartan reversed tacrolimus-induced changes in the biochemical markers (BUN and creatinine) of nephrotoxicity. Tacrolimus significantly decreased GSH level and catalase activity while increasing MDA level. Olmesartan also attenuated the effects of tacrolimus on MDA, GSH, and catalase. In tacrolimus group histological examination showed marked changes in renal tubule, mitochondria, and podocyte processes. Histopathological and ultrastructural studies showed that treatment with olmesartan prevented tacrolimus-induced renal damage. These results suggest that olmesartan has protective effects on tacrolimus-induced nephrotoxicity, implying that RAS might be playing role in tacrolimus-induced nephrotoxicity.

How immunosuppressive therapy affects T cells from kidney transplanted patients of different age: the role of latent cytomegalovirus infection

The average age of patients receiving renal transplantation is increasing as programmes have been established which support the donation of organs from elderly donors to older recipients. Little is known about the effect of immunosuppressive therapy on the immune system of older patients. In this study, T cell function and the composition of the T cell repertoire were analysed in immunosuppressed renal transplant recipients of different age and cytomegalovirus (CMV) status in comparison to age- and CMV-matched controls. Independent of age and CMV status, the production of interleukin (IL)-2 and interferon (IFN)-γ by T cells was decreased in the patient groups and autologous serum from patients was capable of inhibiting the proliferation of CD3⁺ T cells. CXCR5 expression on T cells was increased in patients versus controls reflecting reduced endogenous IL-2 signalling under immunosuppressive therapy. In CMV-seronegative patients kidney transplantation and immunosuppressive therapy did not induce changes in the CD8⁺ T cell pool, but there was a moderate increase in CD4⁺CD28⁻ effector T cells when compared to age-matched controls. In contrast, latent CMV infection triggered a shift from early to late differentiated CD4⁺ and CD8⁺ T cells in patients and controls. This shift was most pronounced in elderly transplant patients under immunosuppressive therapy. In conclusion, our results demonstrate that immunosuppressive therapy following kidney transplantation is effective in patients older than 65 years. Latent CMV infection, however, accelerates age-related changes in the T cell repertoire in elderly people under immunosuppressive therapy. These patients should therefore be monitored with special care.

Care of the liver transplant patient

OBJECTIVE

To provide an approach to the care of liver transplant (LT) patients, a growing patient population with unique needs.

METHODS

A literature search of PubMed for guidelines and review articles using the keywords "liver transplantation", "long term complications" and "medical management" was conducted, resulting in 77 articles.

RESULTS

As a result of being on immunosuppression, LT recipients are at increased risk of infections and must be screened regularly for metabolic complications and malignancies.

DISCUSSION

Although immunosuppression is key to maintaining allograft health after transplantation, it comes with its own set of medical issues to follow. Physicians following LT recipients must be aware of the greater risk for hypertension, diabetes, dyslipidemia, renal failure, metabolic bone disease and malignancies in these patients, all of whom require regular monitoring and screening. Vaccination, quality of life, sexual function and pregnancy must be specifically addressed in transplant patients.

Everolimus: a guide to its use in liver transplantation

The mammalian target of rapamycin inhibitor everolimus (Zortress®, Certican®) was recently approved in the USA and a number of EU countries for use in combination with a reduced dosage of tacrolimus and corticosteroids for the prophylaxis of organ rejection in adult liver transplant recipients. Compared with standard-exposure tacrolimus, early use of everolimus plus a reduced dosage of tacrolimus did not compromise efficacy in liver transplant recipients. In addition, significantly better renal function with everolimus plus reduced-exposure tacrolimus than with standard-exposure tacrolimus was seen from 6 weeks post-transplant onwards. Everolimus plus reduced-exposure tacrolimus has an acceptable tolerability profile in liver transplant recipients.

Mycophenolate mofetil enhances the negative effects of sirolimus and tacrolimus on rat kidney cell metabolism

Background and Purpose

Mycophenolate mofetil (MMF) per se is not known to have negative effects on the kidney. MMF alone or in combination with sirolimus, can be the basis of calcineurin inhibitor (CNI)-free, kidney sparing drug protocols. However, long-term outcomes in patients on MMF/SRL seem to be inferior to those treated with regimens that include the CNI tacrolimus (TAC) due to an increased risk of allo-immune reactions. Interestingly, potential enhancement of the negative effects of SRL and TAC on the kidney by MMF has never been considered.

Experimental Approach

It was our aim to study the effects of TAC, SRL and MMF alone and evaluate their interactions when combined on the rat kidney. For this purpose we used a comprehensive molecular marker approach including measurements of urinary 8-isoprostane concentrations (oxidative stress marker) and changes of urinary metabolite patterns (¹H-NMR spectroscopy) and comparing these markers to renal function (glomerular filtration rate (GFR)) and morphologic alterations (histology).

Key Results

While MMF alone did not impact GFR, its interaction with SRL and TAC led to a significant decrease of rats’ renal function. The decline went in parallel with a significant increase in urinary isoprostane concentrations and an enhancement of negative effects on urinary metabolite patterns.

Conclusions

In broad summary, the present study showed that MMF may enhance the negative effects of TAC on kidney function and may even display nephrotoxic properties when combined with SRL.

Effect of different immunosuppressive drugs on immune cells from young and old healthy persons

BACKGROUND

Life expectancy, as well as the average age of patients undergoing solid organ transplantation, increases constantly. Consequently, immunosuppressive therapy is no longer limited to young organ recipients.

OBJECTIVE

Here, we investigate how different types of immunosuppressive therapy, namely the calcineurin inhibitors cyclosporin A and tacrolimus, as well as the mTOR inhibitor rapamycin, affect the function of immune cells in young and elderly persons.

METHODS

Proliferation, cell viability, cytokine production (IL-2, IFN-γ), H2O2 production and telomere length of phytohemagglutinin (PHA)-stimulated human peripheral blood mononuclear cells (PBMCs) of young (n = 13; median age 27 years) and old (n = 19; median age 71 years) healthy donors were analyzed.

RESULTS

The inhibition of proliferation was dampened in PBMCs from elderly donors, especially after incubation with rapamycin. All three immunosuppressive drugs inhibited the production of IL-2 equally well, whereas the production of IFN-γ was less well inhibited by rapamycin. Both calcineurin inhibitors increased H2O2 concentrations after stimulation with PHA and led to a shortening of telomeres in PBMCs from young and old individuals. Rapamycin had only minor effects on H2O2 production and telomere length.

CONCLUSION

Our results demonstrate that the effects of immunosuppressive drugs on PBMCs differ between young and elderly persons. Calcineurin inhibitors compared to rapamycin have a more pronounced prosenescence effect. These data indicate that specific treatment regimens for the elderly might therefore be considered.

Neurologic complications of pancreas and small bowel transplantation

In the past decade, substantial improvements in patient and graft survival for pancreas and small bowel transplants have been achieved. Despite this progress, many patients still develop neurologic complications in the course of their illness. Small bowel transplants produce more neurologic complications because of the complex metabolic environment in which the procedure is performed and because of the intense immune suppression necessitated by the greater immunogenicity of the intestinal mucosa. Pancreas transplants stabilize and/or improve the signs and symptoms of diabetic neuropathy over time. Because transplantation of the pancreas is often coupled with a kidney transplant and small intestine with liver, neurologic complications in these patients sometimes reflect problems involving the organ partner or both organs. The spectrum of neurologic complications for pancreas and small bowel transplant recipients is similar to other organ transplants but their frequency varies depending on the type of transplant performed.

HPV-related cancers after solid organ transplantation in the United States

Transplant recipients have elevated cancer risk including risk of human papillomavirus (HPV)-associated cancers of the cervix, anus, penis, vagina, vulva and oropharynx. We examined the incidence of HPV-related cancers in 187 649 US recipients in the Transplant Cancer Match Study. Standardized incidence ratios (SIRs) compared incidence rates to the general population, and incidence rate ratios (IRRs) compared rates across transplant subgroups. We observed elevated incidence of HPV-related cancers (SIRs: in situ 3.3-20.3, invasive 2.2-7.3), except for invasive cervical cancer (SIR 1.0). Incidence increased with time since transplant for vulvar, anal and penile cancers (IRRs 2.1-4.6 for 5+ vs. <2 years). Immunophenotype, characterized by decreased incidence with HLA DRB1:13 and increased incidence with B:44, contributed to susceptibility at several sites. Use of specific immunosuppressive medications was variably associated with incidence; for example, tacrolimus, was associated with reduced incidence for some anogenital cancers (IRRs 0.4-0.7) but increased incidence of oropharyngeal cancer (IRR 2.1). Thus, specific features associated with recipient characteristics, transplanted organs and medications are associated with incidence of HPV-related cancers after transplant. The absence of increased incidence of invasive cervical cancer highlights the success of cervical screening in this population and suggests a need for screening for other HPV-related cancers.

Population PKPD of voclosporin in renal allograft patients

The aims of this population-pharmacokinetic/pharmacodynamic (POP-PKPD) analysis of voclosporin in renal allograft patients were to build a POP-PKPD model for voclosporin and calcineurin activity (CNa) and identify clinically relevant covariates that could assist dosing of the drug. POP-PKPD modeling was performed using a stochastic approximation of the standard expectation maximization (SAEM) algorithm for nonlinear mixed-effects as implemented in Monolix™ 3.2. Voclosporin whole blood concentrations were obtained from de novo renal allograft patients and assayed using a validated LC/MS/MS assay. CNa was measured using a (32)P-radiolabeled assay. A two-compartment model with simultaneous sigmoid inhibitory Emax model was used to describe the PKPD relationship between voclosporin concentration and CNa. The POP-PKPD model was then utilized to simulate an optimal initial dosing strategy. Eighty-seven patients were included in the POP-PKPD study. Population mean estimates (relative standard error, rse) for oral clearance (CL/F) and first compartment volume of distribution (V1), were 717 mL min(-1) (35%) and 2010 mL (17%), respectively. Maximum CNa Inhibition (Imax), effective concentration (C50), and baseline immunosuppression (S0) were 0.87 pmol/min/mg (8.0%), 123 ng/mL (10%), and 1.15 pmol/min/mg (4.0%), respectively. Covariate analyses demonstrated that age and body surface area significantly influenced CL/F: CLi=717(Agei/48.8)-0.57(BSAi/1.99)1.1, while serum triglycerides significantly altered S0: S0i=1.15(TRIGi/1.97)0.15.

Comparison of several functional methods to evaluate the immune response on stable kidney transplant patients

The introduction of new immunosuppressive drugs in the last two decades has been associated with a significant decline in the prevalence of acute rejection and a huge improvement of graft survival. Monitoring blood levels of immunosuppressive drugs is the most common way to control drug doses in renal transplant patients. This approach is useful and widely used but doesn't give accurate information about the immune status of the patient. For this goal, there are many "in house" protocols which give more information, but cannot be standardized, limiting their applicability to compare results between different laboratories. In this study we compare three classical functional methods to evaluate the immune response: Mixed lymphocyte reaction (MLR), phytohemagglutinin stimulated peripheral blood lymphocytes (PBLs), and anti-CD3 monoclonal antibodies (mAbs) against PBL with the only FDA-labeled assay to measure the patient immune status: Cylex ImmuKnow® that measures the intracelullar ATP in CD4+ lymphocytes. We used n=111 stable renal transplant patients, all the patients with more than one year functioning grafts. We referred the results to a control population of healthy blood donors (n=125).

RESULTS

Measurement of intracellular ATP in CD4+ lymphocytes is able to differentiate immunosuppressed populations in renal transplant patients from health controls (242.30±21.62 vs. 386.43±25.12, p 0.0001). By contrary, there were no differences between controls and renal recipients when functional response was measured by MLR, PHA and anti-CD3 mAbs (2.48±0.45 vs. 2.37±0.41; 2.84±0.76 vs. 2.37±0.32; 2.32±0.34 vs. 1.89±0.38 respectively). In summary, our results show that the measurement of ATP in CD4+ lymphocytes gives more accurate information in comparison to the classical methods.

Trends in the biosynthesis and production of the immunosuppressant tacrolimus (FK506)

The current off-patent state of tacrolimus (FK506) has opened the hunting season for new generic pharmaceutical formulations of this immunosuppressant. This fact has boosted the scientific and industrial research on tacrolimus for the last 5 years in order to improve its production. The fast discovery of tacrolimus producer strains has generated a huge number of producers, which presents the biosynthetic cluster of FK506 as a high promiscuous genetic region. For the first time, the current state-of-the-art on the tacrolimus biosynthesis, production improvements and drug purification is reviewed. On one hand, all the genes involved in the tacrolimus biosynthesis, in addition to the traditional PKS/NRPS, as well as their regulation are analysed. On the other hand, tacrolimus direct and indirect precursors are reviewed as a straight manner to improve the final yield, which is a current trend in the field. Twenty years of industrial and scientific improvements on tacrolimus production are summarised, whereas future trends are also drafted.