Germinal center responses to SARS-CoV-2 mRNA vaccines in healthy and immunocompromised individuals.

Vaccine-mediated immunity often relies on the generation of protective antibodies and memory B cells, which commonly stem from germinal center (GC) reactions. An in-depth comparison of the GC responses elicited by SARS-CoV-2 mRNA vaccines in healthy and immunocompromised individuals has not yet been performed due to the challenge of directly probing human lymph nodes. Herein, through a fine-needle aspiration-based approach, we profiled the immune responses to SARS-CoV-2 mRNA vaccines in lymph nodes of healthy individuals and kidney transplant recipients (KTXs). We found that, unlike healthy subjects, KTXs presented deeply blunted SARS-CoV-2-specific GC B cell responses coupled with severely hindered T follicular helper cell, SARS-CoV-2 receptor binding domain-specific memory B cell, and neutralizing antibody responses. KTXs also displayed reduced SARS-CoV-2-specific CD4 and CD8 T cell frequencies. Broadly, these data indicate impaired GC-derived immunity in immunocompromised individuals and suggest a GC origin for certain humoral and memory B cell responses following mRNA vaccination.

Outcomes in kidney transplant recipients treated with immediate-release tacrolimus capsules versus extended-release tacrolimus capsules: A cohort study.

INTRODUCTION: Prior randomized trials and observational studies have generally reported similar outcomes in kidney transplant recipients (KTRs) treated with immediate-release tacrolimus (IR-TAC) versus extended-release tacrolimus (ER-TAC). However, many of these previous studies focused on patients with low immunological risks, had small sample sizes and brief follow-up periods, and excluded outcomes associated with graft loss, such as chronic rejection. METHODS: To address these limitations, we conducted a cohort study of 848 KTRs at a single transplantation center who had generally high immunological risks and were treated with either IR-TAC capsules (589 patients, 65.9%) or ER-TAC capsules (289 patients, 34.1%). All patients received their designated maintenance immunosuppressive regimen for at least 3 months post-transplantation. Afterwards, tacrolimus formulation was at the discretion of each patient's transplant nephrologist. For the two treatment groups, we compared the hazards of experiencing a composite outcome of acute or chronic antibody-mediated rejection (AMR), acute or chronic T-cell-mediated rejection, de novo DSA, and/or graft loss over a 3-year period starting at 3 months post-transplantation. RESULTS: In a multivariable Cox proportional hazards regression model, KTRs treated with IR-TAC capsules had an increased hazard of experiencing the composite outcome when compared to patients treated with ER-TAC capsules; however, this result was not significant (adj HR 1.24, 95% CI .92-1.68, p = .163). Similar results were obtained with inverse probability of treatment weighting (IPTW) using a propensity score (adj HR 1.25, 95% CI .93-1.68, p = .146). CONCLUSION: These findings suggest that when compared to IR-TAC capsules, ER-TAC capsules do not reduce the hazard of poor outcomes in KTRs with generally high immunological risks.

A survey of solid organ transplant recipient attitudes and concerns regarding contraception and pregnancy.

INTRODUCTION: Many women who are solid organ transplant (SOT) recipients wish to have children after transplantation. Contraception is an important component of post-transplant planning and care, given the increased risk associated with post-transplant pregnancies. We sought to understand patient attitudes and concerns about post-transplant contraception and pregnancy. METHODS: Following a comprehensive literature review, our team developed a survey that was administered to female SOT recipients of childbearing age. We used descriptive and inferential statistics to characterize participant views RESULTS: A total of 243 transplant recipients completed the survey (80.7% response rate). The mean age of respondents was 37.5 years (±8.1 years), 66.7% were kidney recipients, and 40.7% were within the first year after transplant. The most common concerns among respondents included fetal and maternal health complications. Participants generally did not agree that transplant recipients should be advised to avoid pregnancy. There was strong support for shared decision-making about pregnancy after transplantation CONCLUSION: Understanding patient perspectives can help transplant providers make better care recommendations and support patient autonomy in reproductive decisions post-transplant. Given that there are some differences in views by transplant type, individualized conversations between patients and providers are needed.

Association of donor hepatitis C virus infection status and risk of BK polyomavirus viremia after kidney transplantation.

Kidney transplantation (KT) from deceased donors with hepatitis C virus (HCV) into HCV-negative recipients has become more common. However, the risk of complications such as BK polyomavirus (BKPyV) remains unknown. We assembled a retrospective cohort at four centers. We matched recipients of HCV-viremic kidneys to highly similar recipients of HCV-aviremic kidneys on established risk factors for BKPyV. To limit bias, matches were within the same center. The primary outcome was BKPyV viremia ≥1000 copies/ml or biopsy-proven BKPyV nephropathy; a secondary outcome was BKPyV viremia ≥10 000 copies/ml or nephropathy. Outcomes were analyzed using weighted and stratified Cox regression. The median days to peak BKPyV viremia level was 119 (IQR 87-182). HCV-viremic KT was not associated with increased risk of the primary BKPyV outcome (HR 1.26, p = .22), but was significantly associated with the secondary outcome of BKPyV ≥10 000 copies/ml (HR 1.69, p = .03). One-year eGFR was similar between the matched groups. Only one HCV-viremic kidney recipient had primary graft loss. In summary, HCV-viremic KT was not significantly associated with the primary outcome of BKPyV viremia, but the data suggested that donor HCV might elevate the risk of more severe BKPyV viremia ≥10 000 copies/ml. Nonetheless, one-year graft function for HCV-viremic recipients was reassuring.

Tolerability of mycophenolate mofetil in elderly kidney transplant recipients: A retrospective cohort study.

BACKGROUND: Optimal immunosuppression in elderly kidney transplant recipients (KTRs) is not well defined, with mycophenolate mofetil (MMF) being poorly tolerated. Study aim was to compare MMF dose reduction incidence and reason(s) in elderly vs. nonelderly KTRs in the 1st year after transplant with a protocol dose of 1 g/day. METHODS: In this single-center retrospective study, first or repeat KTRs receiving rabbit antithymocyte globulin (rATG), MMF 1 g/day, tacrolimus, and prednisone, were stratified by age [≥60 (elderly) or <60 years (nonelderly)]. Primary outcome was MMF dose reduction incidence in the first year. Secondary outcomes included dose reduction rationale, 1-year patient and graft survival, graft function, rejection, infection, hospital presentation, and time to dose reduction. Of 335 KTRs, dose reduction incidence was significantly greater in the elderly group (66% and 54%, p = 0.04), though this did not remain significant when adjusted for sex, race, and valganciclovir use. Most common rationale was leukopenia in the elderly group and CMV in the nonelderly group. There were no significant differences in secondary outcomes. CONCLUSIONS: Mycophenolate mofetil 1 g/day was poorly tolerated in both elderly and nonelderly KTRs receiving lymphocyte-depleting induction with a high incidence of dose reductions; however, no short-term adverse graft outcomes were identified.

Kidney transplantation and donation in the transgender population: A single-institution case series.

The medical needs of the transgender population are increasingly recognized within the US health care system. Hormone therapy and gender-affirming surgery present distinct anatomic, hormonal, infectious, and psychosocial issues among transgender kidney transplant donors and recipients. We present the first reported experience with kidney transplantation and donation in transgender patients. A single-center case series (January 2014-December 2018) comprising 4 transgender kidney transplant recipients and 2 transgender living donors was constructed and analyzed. Experts in transplant surgery, transplant psychiatry, transplant infectious disease, pharmacy, and endocrinology were consulted to discuss aspects of care for these patients. Four transgender patients identified as male-to-female and 2 as female-to-male. Three of 6 had gender-affirming surgeries prior to transplant surgery, 1 of whom had further procedures posttransplant. Additionally, 4 patients were on hormone therapy. All 6 had psychiatric comorbidities. The 4 grafts have done well, with an average serum creatinine of 1.45 mg/dL at 2 years (range 1.01-1.85 mg/dL). However, patients encountered various postoperative complications, 1 of which was attributable to modified anatomy. Thus, transgender kidney transplant patients can present novel challenges in regard to surgical considerations as well as pre- and posttransplant care. Dedicated expertise is needed to optimize outcomes for this population.

Use of Dietary Supplements in Living Kidney Donors: A Critical Review.

Dietary supplement use is high among US adults, with the intention by users to promote overall health and wellness. Kidney donors, who are selected based on their overall good health and wellness, can have high utilization rates of dietary supplements. We provide a framework for the evaluation of living kidney donors and use of dietary supplements. In this review, dietary supplements will include any orally administered dietary or complementary nutritional products, but excluding micronutrients (vitamins and minerals), food, and cannabis. Use of dietary supplements can influence metabolic parameters that mask future risk for chronic illness such as diabetes and hypertension. Dietary supplements can also alter bleeding risk, anesthesia and analgesic efficacy, and safety in a perioperative period. Finally, postdonation monitoring of kidney function and risk for supplement-related nephrotoxicity should be part of a kidney donor educational process. For practitioners evaluating a potential kidney donor, we provide a list of the most commonly used herbal supplements and the effects on evaluation in a predonation, perioperative donation, and postoperative donation phase. Finally, we provide recommendations for best practices for integration into a comprehensive care plan for kidney donors during all stages of evaluation. We recommend avoidance of dietary supplements in a kidney donor population, although there is a paucity of data that identifies true harm. Rather, associations, known mechanisms of action, and common sense suggest that we avoid use in this population.

Chronopharmacokinetics and Food Effects of Single-Dose LCP-Tacrolimus in Healthy Volunteers.

BACKGROUND: A modified-release version of tacrolimus, LCP-tacrolimus (LCPT; Envarsus XR, Veloxis Pharmaceuticals, Cary, NC), has been licensed in the United States for prophylaxis of organ rejection in de novo kidney transplant patients. As tacrolimus has a narrow therapeutic window, the impact of circadian patterns on LCPT drug exposure, including food and chronopharmacokinetic effects, needs to be elucidated to optimize dosing. METHODS: Two randomized, crossover, phase 1 studies were conducted in healthy volunteers. The first assessed the effect of morning versus evening dosing on the pharmacokinetic profile of LCPT 2 mg; the second assessed the effect of food on the pharmacokinetic profile of LCPT 5 mg. In both, blood samples were drawn from participants for up to 144 hours after administration of a single LCPT dose. RESULTS: No significant differences were observed between evening and morning dosing in peak blood concentration (4.4 versus 4.0 ng/mL; P = 0.27), area under the time-concentration curve (AUC) from time 0 to time of the last concentration (89.1 versus 102.6 ng/mL; P = 0.20), AUC from time 0 to infinity (99.7 versus 114.3 ng·h/mL; P = 0.18), AUC from 0 to 24 hours post-dose (AUC0-24; 49.4 versus 51.6 ng·h/mL; P = 0.56), time to reach maximum blood concentration (median, 6.0 versus 6.0 hours; P = 0.91), total clearance (arithmetic mean = 21.5 versus 19.5 L/h; P = 0.50), or terminal half-life (arithmetic mean = 26.8 versus 28.1 hours; P = 0.26). After a high-calorie meal in the morning, the AUC0-24 reduced by 54% (ratio of geometric means = 45.6%; P < 0.0001) and peak blood concentration reduced by 22% (ratio of geometric means = 78.4%; P = 0.0006). However, the terminal half-life did not differ between fasted and fed states (33.3 versus 34.8 hours; P = 0.16), implying that these differences occurred because of altered bioavailability rather than modified clearance. CONCLUSIONS: For LCPT, no chronopharmacokinetic effects were observed, whereas food significantly reduced the 24-h exposure and the peak blood concentration.

Single-center, real-world experience with granulocyte colony-stimulating factor for management of leukopenia following kidney transplantation.

BACKGROUND: Leukopenia is a frequent complication following kidney transplantation. Granulocyte colony-stimulating factor (G-CSF) has been used to accelerate white blood cell (WBC) count recovery; however, published experience in kidney transplantation is limited. METHODS: We retrospectively reviewed our kidney transplant recipients from January 2012 to September 2016 with a G-CSF order to evaluate leukopenia management (defined as WBC <3000 cells/µL). RESULTS: Thirty-six recipients were included. On average, G-CSF treatment began at 98 ± 38 days. At G-CSF initiation, mean WBC count was 1240 ± 420 cells/µL and absolute neutrophil count (ANC) was 653 ± 368 cells/µL. Mean G-CSF dose was 4.6 ± 1.2 mcg/kg/dose (total 11.8 ± 9.0 mcg/kg), 77.8% of recipients were prescribed G-CSF as outpatients, and overall, median time to WBC count recovery was 9 (IQR 4-14) days. Changes in immunosuppression and prophylaxis regimens for leukopenia were also common. Within 1 month following leukopenia onset, no patients experienced acute rejection and 5 (14%) developed infection requiring hospitalization or opportunistic infection. CONCLUSION: In kidney recipients with leukopenia, G-CSF may be helpful to achieve WBC count recovery in addition to changes in immunosuppression and prophylaxis medications. Prospective, randomized data are still needed to determine optimal G-CSF dosing in this population.

Native kidney BK virus nephropathy, a systematic review.

BACKGROUND: There is a growing base of literature describing BK nephropathy (BKVN) in patients outside of the setting of kidney transplant. Previous systematic reviews of the literature have been limited by methodology or by the scope of patients included. STUDY DESIGN AND METHODS: Systematic Review (Prospero # CRD42018088524). SETTING & POPULATION: Patients without kidney transplant who had biopsy-proven BKVN. SELECTION CRITERIA FOR STUDIES: Full-text articles that describe native BKVN patient cases. ANALYTICAL APPROACH: Descriptive synthesis. RESULTS: The search identified 630 unique articles of which 51 were included in the final review. Sixty-five cases (including two new cases presented in this review) were identified, all but one occurred in the setting of known immunosuppression. LIMITATIONS: The primary limitation was the exclusion of studies that did not fulfill the stringent review criteria. We excluded reports with only a clinical diagnosis of BKVN, such as those with viruria and/or viremia without biopsy. CONCLUSIONS: As of May 2018, there are 65 reported cases of BKVN in native kidneys. This represents the most comprehensive description of biopsy-proven BKVN in native kidneys to date. Evaluation for BK nephropathy should be considered in immunocompromised patients who exhibit unexplained renal failure.

Twelve-Month Outcomes After Transplant of Hepatitis C-Infected Kidneys Into Uninfected Recipients: A Single-Group Trial.

Background: Organs from hepatitis C virus (HCV)-infected deceased donors are often discarded. Preliminary data from 2 small trials, including THINKER-1 (Transplanting Hepatitis C kidneys Into Negative KidnEy Recipients), suggested that HCV-infected kidneys could be safely transplanted into HCV-negative patients. However, intermediate-term data on quality of life and renal function are needed to counsel patients about risk. Objective: To describe 12-month HCV treatment outcomes, estimated glomerular filtration rate (eGFR), and quality of life for the 10 kidney recipients in THINKER-1 and 6-month data on 10 additional recipients. Design: Open-label, nonrandomized trial. (ClinicalTrials.gov: NCT02743897). Setting: Single center. Participants: 20 HCV-negative transplant candidates. Intervention: Participants underwent transplant with kidneys infected with genotype 1 HCV and received elbasvir-grazoprevir on posttransplant day 3. Measurements: The primary outcome was HCV cure. Exploratory outcomes included 1) RAND-36 Physical Component Summary (PCS) and Mental Component Summary (MCS) quality-of-life scores at enrollment and after transplant, and 2) posttransplant renal function, which was compared in a 1:5 matched sample with recipients of HCV-negative kidneys. Results: The mean age of THINKER participants was 56.3 years (SD, 6.7), 70% were male, and 40% were black. All 20 participants achieved HCV cure. Hepatic and renal complications were transient or were successfully managed. Mean PCS and MCS quality-of-life scores decreased at 4 weeks; PCS scores then increased above pretransplant values, whereas MCS scores returned to baseline values. Estimated GFRs were similar between THINKER participants and matched recipients of HCV-negative kidneys at 6 months (median, 67.5 vs. 66.2 mL/min/1.73 m2; 95% CI for between-group difference, -4.2 to 7.5 mL/min/1.73 m2) and 12 months (median, 72.8 vs. 67.2 mL/min/1.73 m2; CI for between-group difference, -7.2 to 9.8 mL/min/1.73 m2). Limitation: Small trial. Conclusion: Twenty HCV-negative recipients of HCV-infected kidneys experienced HCV cure, good quality of life, and excellent renal function. Kidneys from HCV-infected donors may be a valuable transplant resource. Primary Funding Source: Merck.

Results of ASERTAA, a Randomized Prospective Crossover Pharmacogenetic Study of Immediate-Release Versus Extended-Release Tacrolimus in African American Kidney Transplant Recipients.

BACKGROUND: Differences in tacrolimus dosing across ancestries is partly attributable to polymorphisms in CYP3A5 genes that encode tacrolimus-metabolizing cytochrome P450 3A5 enzymes. The CYP3A5*1 allele, preponderant in African Americans, is associated with rapid metabolism, subtherapeutic concentrations, and higher dose requirements for tacrolimus, all contributing to worse outcomes. Little is known about the relationship between CYP3A5 genotype and the tacrolimus pharmacokinetic area under the curve (AUC) profile in African Americans or whether pharmacogenetic differences exist between conventional twice-daily, rapidly absorbed, immediate-release tacrolimus (IR-Tac) and once-daily extended-release tacrolimus (LifeCycle Pharma Tac [LCPT]) with a delayed absorption profile. STUDY DESIGN: Randomized prospective crossover study. SETTING & PARTICIPANTS: 50 African American maintenance kidney recipients on stable IR-Tac dosing. INTERVENTION: Recipients were randomly assigned to continue IR-Tac on days 1 to 7 and then switch to LCPT on day 8 or receive LCPT on days 1 to 7 and then switch to IR-Tac on day 8. The LCPT dose was 85% of the IR-Tac total daily dose. OUTCOMES: Tacrolimus 24-hour AUC (AUC0-24), peak and trough concentrations (Cmax and Cmin), time to peak concentration, and bioavailability of LCPT versus IR-Tac, according to CYP3A5 genotype. MEASUREMENTS: CYP3A5 genotype, 24-hour tacrolimus pharmacokinetic profiles. RESULTS: ∼80% of participants carried the CYP3A5*1 allele (CYP3A5 expressers). There were no significant differences in AUC0-24 or Cmin between CYP3A5 expressers and nonexpressers during administration of either IR-Tac or LCPT. With IR-Tac, tacrolimus Cmax was 33% higher in CYP3A5 expressers compared with nonexpressers (P=0.04): With LCPT, this difference was 11% (P=0.4). LIMITATIONS: This was primarily a pharmacogenetic study rather than an efficacy study; the follow-up period was too short to capture clinical outcomes. CONCLUSIONS: Achieving therapeutic tacrolimus trough concentrations with IR-Tac in most African Americans results in significantly higher peak concentrations, potentially magnifying the risk for toxicity and adverse outcomes. This pharmacogenetic effect is attenuated by delayed tacrolimus absorption with LCPT. TRIAL REGISTRATION: Registered at ClinicalTrials.gov, with study number NCT01962922.

Comparing Outcomes between Antibody Induction Therapies in Kidney Transplantation.

Kidney transplant recipients often receive antibody induction. Previous studies of induction therapy were often limited by short follow-up and/or absence of information about complications. After linking Organ Procurement and Transplantation Network data with Medicare claims, we compared outcomes between three induction therapies for kidney recipients. Using novel matching techniques developed on the basis of 15 clinical and demographic characteristics, we generated 1:1 pairs of alemtuzumab-rabbit antithymocyte globulin (rATG) (5330 pairs) and basiliximab-rATG (9378 pairs) recipients. We used paired Cox regression to analyze the primary outcomes of death and death or allograft failure. Secondary outcomes included death or sepsis, death or lymphoma, death or melanoma, and healthcare resource utilization within 1 year. Compared with rATG recipients, alemtuzumab recipients had higher risk of death (hazard ratio [HR], 1.14; 95% confidence interval [95% CI], 1.03 to 1.26; P<0.01) and death or allograft failure (HR, 1.18; 95% CI, 1.09 to 1.28; P<0.001). Results for death as well as death or allograft failure were generally consistent among elderly and nonelderly subgroups and among pairs receiving oral prednisone. Compared with rATG recipients, basiliximab recipients had higher risk of death (HR, 1.08; 95% CI, 1.01 to 1.16; P=0.03) and death or lymphoma (HR, 1.12; 95% CI, 1.01 to 1.23; P=0.03), although these differences were not confirmed in subgroup analyses. One-year resource utilization was slightly lower among alemtuzumab recipients than among rATG recipients, but did not differ between basiliximab and rATG recipients. This observational evidence indicates that, compared with alemtuzumab and basiliximab, rATG associates with lower risk of adverse outcomes, including mortality.

Automated Reminders and Physician Notification to Promote Immunosuppression Adherence Among Kidney Transplant Recipients: A Randomized Trial.

BACKGROUND: Immunosuppression nonadherence increases the risk for kidney transplant loss after transplantation. Wireless-enabled pill bottles have created the opportunity to monitor medication adherence in real time. Reminders may help patients with poor memory or organization. Provision of adherence data to providers may motivate patients to improve adherence and help providers identify adherence barriers. STUDY DESIGN: Randomized controlled trial. SETTING & PARTICIPANTS: Kidney transplant recipients (n=120) at a single center. INTERVENTION: Participants were provided wireless pill bottles to store tacrolimus and record bottle openings. Participants were randomly assigned 1:1:1 to adherence monitoring with customized reminders (including alarms, texts, telephone calls, and/or e-mails), monitoring with customized reminders plus provider notification (every 2 weeks, providers received notification if adherence decreased to <90% during that period), or wireless pill bottle use alone (control). OUTCOMES: The main outcome was bottle-measured tacrolimus adherence during the last 90 days of the 180-day trial. A secondary outcome was tacrolimus whole-blood concentrations at routine clinical visits. MEASUREMENTS: Adherence for the primary outcome was assessed via wireless pill bottle openings. RESULTS: Mean participant age was 50 years; 60% were men, and 40% were black. Mean adherence was 78%, 88%, and 55% in the reminders, reminders-plus-notification, and control arms (P<0.001 for comparison of each intervention to control). Mean tacrolimus levels were not significantly different between groups. LIMITATIONS: The study did not assess clinical end points. Participants and study coordinators were not blinded to intervention arm. CONCLUSIONS: Provider notification and customized reminders appear promising in helping patients achieve better medication adherence, but these strategies require evaluation in trials powered to detect differences in clinical outcomes.

Barriers to vaccination in renal transplant recipients.

Vaccine-preventable diseases remain at the forefront of challenges in the long-term care of renal transplant recipients (RTR). Although global vaccination campaigns targeting patients with end-stage renal disease or RTR are standard, rates of vaccination among renal transplant candidates and RTRs remain suboptimal. We highlight the multifactorial barriers leading to low vaccination rates in this vulnerable population.

Persistent BK viremia does not increase intermediate-term graft loss but is associated with de novo donor-specific antibodies.

There are limited data regarding intermediate-term outcomes in patients with persistent BK viremia. Other viral infections have been implicated in the development of allosensitization through heterologous immunity, but the relationship between BK viremia and donor-specific antibodies (DSAs) is unexplored. In 2008, we initiated routine post-transplant BK viremia and DSA screening at our center; 785 kidney or kidney-pancreas transplant recipients were included in our study. Of these recipients, 132 (17%) recipients developed BK viremia during the study period. The median duration of BK viremia was 140 days (interquartile range=40-393 days), and persistent BK viremia was defined as lasting ≥140 days. Kaplan-Meier curves were generated to assess differences in patient and allograft survival on the basis of BK viremia status; survival was modeled using Cox proportional hazard regression. After a median follow-up of 3 years, there was no significant difference in terms of patient (hazard ratio [HR], 0.83; 95% confidence interval [95% CI], 0.28 to 2.49) or allograft survival (HR, 0.80; 95% CI, 0.37 to 1.73) between patients with and without BK viremia, which was confirmed in a time-varying analysis. In our logistic regression model, persistent BK viremia was strongly associated with the development of class II (HR, 2.55; 95% CI, 1.30 to 4.98) but not class I (HR, 1.13; 95% CI, 0.46 to 2.77) DSAs. These data suggest that persistent BK viremia does not negatively affect intermediate-term patient or allograft survival but is associated with increased risk for de novo DSA, although the exact mechanism is unclear.

Assessing the Utility of a Genotype-Guided Tacrolimus Equation in African American Kidney Transplant Recipients: A Single Institution Retrospective Study.

Tacrolimus metabolism is heavily influenced by the CYP3A5 genotype, which varies widely among African Americans (AA). We aimed to assess the performance of a published genotype-informed tacrolimus dosing model in an independent set of adult AA kidney transplant (KTx) recipients. CYP3A5 genotypes were obtained for all AA KTx recipients (n = 232) from 2010 to 2019 who met inclusion criteria at a single transplant center in Philadelphia, Pennsylvania, USA. Medical record data were used to calculate predicted tacrolimus clearance using the published AA KTx dosing equation and two modified iterations. Observed and model-predicted trough levels were compared at 3 days, 3 months, and 6 months post-transplant. The mean prediction error at day 3 post-transplant was 3.05 ng/mL, indicating that the model tended to overpredict the tacrolimus trough. This bias improved over time to 1.36 and 0.78 ng/mL at 3 and 6 months post-transplant, respectively. Mean absolute prediction error-a marker of model precision-improved with time to 2.33 ng/mL at 6 months. Limiting genotype data in the model decreased bias and improved precision. The bias and precision of the published model improved over time and were comparable to studies in previous cohorts. The overprediction observed by the published model may represent overfitting to the initial cohort, possibly limiting generalizability.

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation.

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.