THE ROLE OF CYP3A5 GENOTYPE AND TACROLIMUS MONITORING IN STABLE KIDNEY TRANSPLANTATIONS

INTRODUCTION AND AIMS: Despite Tacrolimus (TAC) dosing is routinely directed by Therapeutic Drug Monitoring (TDM), some patients reach the concentrations target (CT) quickly, while others achieve the same CT slower, increasing the risk of graft-rejection caused by TAC under-exposure. METHODS: We studied the CYP3A5 genotype in patients receiving very high doses of TAC, to confirm them as extensive metabolizers (EM) [1]. We focused on CYP3A5 6986A > G, the most important polymorphism related to TAC metabolism in which the wild-type genotype is CYP3A5*1 and its variant is CYP3A5*3 [2]. We performed TAC TDM among kidney transplant (KTx) recipients who were clinically stable for over a year. The immunosuppressive regimens included TAC, mycophenolate mofetil and corticosteroids for all patients. All patients had stable liver and kidney functions and concomitant TAC inducing or inhibiting drugs. One year after transplantation, the target blood concentration of TAC (CT) was 5-8 ng/ml. We use an immunoassay method to measure TAC levels (ACMIA on a Siemens Dimension\uae Integrated Chemistry Systems Tacrolimus). The patients were divided in two groups based on the TAC doses at the moment of TDM: Group 1, patients with TAC daily doses 6 mg / 24 hours. The doses were uniformed to 1 mg/Kg. All patients underwent Sanger sequencing of CYP3A5 gene to characterize CYP3A5 polymorphisms. Patients with CYP3A5*1 and *1/*3 were considered extensive metabolizer (EM), while the ones with CYP3A5*3 were poor metabolizer (PM) [3]. Statistical analysis was performed using Sigma Stat and results were considered significant when p <0.05. RESULTS: A total of 22 KTx recipients were included in the study. Mean age was 51\ub114 years. Mean weight was 64.9 \ub114.3 Kg. All patients had reached CT with mean daily dose of TAC after at least one year from transplantation of 11.8 \ub111.2 mg. Group 1 and 2 mean doses (dose/Kg) at the moment of TDM were 2.9\ub1 1.4 (0.05\ub10.03 mg/Kg) and 12.5 \ub1 3.5 (0.2\ub10.05), respectively (p <0,001). Analysing the CYP3A5 genotype, we demonstrated that Group 1 presents the PM genotype, while Group 2 could arbour both PM and EM polymorphisms. The clinical use of TAC is complicated by its high pharmacokinetic variability among patients as well as its narrow therapeutic index. This can lead to under-exposure, which potentially increases the risk of rejection, or over-exposure with the risk of toxicity such as nephrotoxicity, hypertension, hyperglycaemia, and neurotoxicity. TAC blood concentrations variabilities were partially dependent on variations in the CYP3A5 gene. In KTx, individuals with genotype CYP3A5 *1/*1 or *1/*3 require minor adjustments of significantly lower doses compared with the genotype CYP3A5 *3/*3, with the expression 1, which requires 1.5 to 2 times the required dose to reach target concentrations [4]. CYP3A5 genotype guided dosing allows to achieve initial target TAC concentrations promptly after transplantation, thus potentially reducing the risk of graft-rejection due to under-exposure. CONCLUSIONS: This study shows that cooperation between nephrology, clinical pharmacology and genetics may optimize the therapy with TAC to achieve faster CT and reduce the risk of rejection and welfare cost

Serological and T Cell Responses After Varicella Zoster Virus Vaccination in HIV-Positive Patients Undergoing Renal Dialysis

Limited data on varicella zoster virus (VZV) vaccine responses are available in HIV-positive adults, especially among those with end-stage renal disease on dialysis or undergoing kidney transplantation (KT). Serological and T cell responses were analyzed using anti-VZV IgG titers, enzyme-linked immunosorbent assay and flow cytometric intracellular cytokine staining (ICS) in two HIV-positive kidney transplant candidates undergoing dialysis and receiving VZV immunization. The results were compared with two HIV-positive and two HIV-negative VZV-seropositive patients (two kidney transplant candidates and two kidney transplant recipients), and with one HIV-negative vaccinee. HIV-positive VZV-susceptible patients received two doses of VZV vaccine 12 weeks apart. No adverse events were reported. Serological data were indicative of immunological response in one patient and corresponded to T cell responses. The second patient showed only a transient increase in anti-VZV IgG titers, but reported positive CD4+ T cell responses that were maintained after KT. Positive T cell and serological responses were detected in both HIV-positive and HIV-negative controls. VZV vaccination appeared safe and effective in HIV-positive KT candidates. VZV-specific T cell immunity was detected among transplant candidates and after KT. The assessment of VZV-specific T cell immunity using flow cytometric ICS may be more reliable compared to serology in assessing responses to VZV vaccine in this group

Impact of kidney transplant morbidity on elderly recipients' outcomes

Background and aims Nowadays, advanced age does not represent an absolute contraindication to kidney transplantation (KT). However, aging is frequently associated with multiple comorbidities and lower performance status, making KT candidates less surgically fit. Limited data are available on the impact of KT morbidity on elderly recipients' outcomes. Methods Retrospective study on a single center cohort of 130 KT recipients over 65 years old, representing 16.2% of KT clinical series, during the period 2000-2018. Number and severity of comorbidities were evaluated with the Charlson Comorbidity index (CCI). Results The median age at transplantation was 67 [IQR66-71] years and median CCI was 5 [IQR4-6]. The prevalence of postoperative complications with a Clavien-Dindo (C-D) severity score > 2 was 29%. Increasing age did not predict KT morbidity in terms of C-D score > 2, infectious, respiratory, cardiologic, urologic or vascular complications, delayed graft function, symptomatic lymphocele, bleeding, acute or chronic rejection. Conversely, CCI score was a predictor of overall complications with C-D score > 2, cardiologic, respiratory and vascular complications, and bleeding. Among others, CCI score, post-KT cardiologic complications, C-D score > 2 were identified as significant predictors of both early mortality and graft loss in univariate analysis. Increasing recipient age did not correlate with graft loss risk and graft loss did not impact patient survival. C-D score > 2 was a predictor of poor survival even in multivariate analysis. Conclusions Elderly recipients showed a significant vulnerability to KT morbidity which correlates with CCI. While graft loss did not impact recipient survival, severe postoperative complications (C-D > 2) were independently associated increased mortality

Hypothermic machine perfusion can safely prolong cold ischemia time in deceased donor kidney transplantation. A retrospective analysis on postoperative morbidity and graft function

In deceased donor kidney transplantation (KT), a prolonged cold ischemia time (CIT) is a negative prognostic factor for KT outcome, and the efficacy of hypothermic machine perfusion (HMP) in prolonging CIT without any additional hazard is highly debated. We conducted a retrospective study on a cohort of 154 single graft deceased donor KTs, in which a delayed HMP, after a preliminary period of static cold storage (SCS), was used to prolong CIT for logistic reasons. Primary outcomes were postoperative complications as well as 1\ua0year graft survival and function. 73 cases (47.4%) were managed with HMP and planned KT, while 81 (52.6%) with SCS and urgent KT. The median CIT in HMP group and SCS group was 29\ua0hour:57\ua0minutes [27-31\ua0hour:45\ua0minutes] and 11\ua0hour:25\ua0minutes [9-14\ua0hour:30\ua0minutes], respectively (P\ua0<.001). The period of SCS in the HMP group was significantly shorter than in the SCS group (10 vs. 11\ua0hour:25\ua0minutes, P\ua0=.02) as well as the prevalence of expanded criteria donors was significantly higher (43.8% vs. 18.5%, P\ua0<.01). After propensity score matching for these two baseline characteristics, the HMP and SCS groups showed comparable outcomes in terms of delayed graft function, vascular, and urologic complications, infections, and episodes of graft rejection. At 1 year follow-up, serum creatinine levels were comparable between the groups. Therefore, the use of HMP to prolong the CIT and convert KT into a planned procedure seemed to have an adequate safety profile, with outcomes comparable to KT managed as an urgent procedure and a CIT nearly three time shorter

Detection of transplant renal artery stenosis with contrast-enhanced ultrasound

Transplant renal artery stenosis (TRAS) is a vascular complication occurring during the first 2 years after kidney transplantation, with an incidence and a prevalence ranging from 1% to 23%, and from 1.5% to 4%, respectively. Detection of TRAS is the key, since most stenoses may progress to renal graft loss, however it may be difficult to detect due to its nonspecific clinical manifestations. Although Doppler ultrasound has become a primary imaging technique, digital subtraction angiography (DSA) remains the gold standard for diagnosing TRAS. We present a case of delayed graft function following kidney transplantation complicated by a lateral by-pass with prosthesis upstream and downstream of renal anastomosis, TRAS criteria were unclear using Doppler ultrasound, contrast-enhanced computed tomography-scan, and DSA. Only contrast-enhanced ultrasound (CE-US), observing a delayed and pulsating contest impregnation of renal parenchyma, supported the hypothesis of TRAS that was confirmed by the measurement of trans-anastomosis pressure gradient during DSA. Keywords: Transplant renal artery stenosis (TRAS), Kidney transplantation (KT), Doppler ultrasound (DUS), Digital subtraction angiography (DSA), Contrast-enhanced ultrasound (CE-US

Acute rejection in kidney transplantation and the evaluation of associated polymorphisms (SNPs): the importance of sample size

Background: Acute rejection (AR) is one of the most frequent complications after kidney transplantation (KT). Scientific evidence reports that some single-nucleotide polymorphisms (SNPs) located in genes involved in the immune response and in the pharmacokinetics and pharmacodynamics of immunosuppressive drugs are associated with rejection in renal transplant patients. The aim of this study was to evaluate some SNPs located in six genes: interleukin-10 (IL-10), tumor necrosis factor (TNF), adenosine triphosphate-binding cassette sub-family B member 1 (ABCB1), uridine diphosphate glucuronosyltransferase family 1 member A9 (UGT1A9), inosine monophosphate dehydrogenase 1 (IMPDH1) and IMPDH2.Methods: We enrolled cases with at least one AR after KT and two groups of controls: patients without any AR after KT and healthy blood donors. Genetic analysis on DNA was performed. The heterozygosity (HET) was determined and the Hardy-Weinberg equilibrium (HWE) test was performed for each SNP. The sample size was calculated using the QUANTO program and the genetic associations were calculated using the SAS program (SAS Institute Inc., Cary, NC, USA).Results: In our previous preliminary study (sample size was not reached for cases), the results showed that patients with the C allele in the SNP rs1045642 and the A allele in the SNP rs2032582 of the ABCB1 gene had more frequent AR. In contrast, with the achievement of sample size, the trend of the previous data was not confirmed.Conclusions: Our study highlights a fundamental aspect of scientific research that is generally presumed, i.e. the sample size of groups enrolled for a scientific study. We believe that our study will make a significant contribution to the scientific community in the discussion of the importance of the analysis and the achievement of sample size to evaluate the associations between SNPs and the studied event