The Living Donor Collective: A Scientific Registry for Living Donors.

In the setting of an overall decline in living organ donation and new questions about long-term safety, a better understanding of outcomes after living donation has become imperative. Adequate information on outcomes important to donors may take many years to ascertain and may be evident only by comparing large numbers of donors with suitable controls. Previous studies have been unable to fully answer critical questions, primarily due to lack of appropriate controls, inadequate sample size, and/or follow-up duration that is too short to allow detection of important risks attributable to donation. The Organ Procurement and Transplantation Network does not follow donors long term and has no prospective control group with which to compare postdonation outcomes. There is a need to establish a national living donor registry and to prospectively follow donors over their lifetimes. In addition, there is a need to better understand the reasons many potential donors who volunteer to donate do not donate and whether the reasons are justified. Therefore, the US Health Resources and Services Administration asked the Scientific Registry of Transplant Recipients to establish a national registry to address these important questions. Here, we discuss the efforts, challenges, and opportunities inherent in establishing the Living Donor Collective.

Lessons Learned: Early Termination of a Randomized Trial of Calcineurin Inhibitor and Corticosteroid Avoidance Using Belatacept.

The intent of this National Institutes of Health-sponsored study was to compare a belatacept-based immunosuppressive regimen with a maintenance regimen of tacrolimus and mycophenolate. Nineteen primary, Epstein-Barr virus-immune renal transplant recipients with a negative cross-match were randomized to one of three groups. All patient groups received perioperative steroids and maintenance mycophenolate mofetil. Patients in groups 1 and 2 were induced with alemtuzumab and maintained on tacrolimus or belatacept, respectively. Patients in group 3 were induced with basiliximab, received 3 mo of tacrolimus, and maintained on belatacept. There was one death with a functioning allograft due to endocarditis (group 1). There were three graft losses due to vascular thrombosis (all group 2) and one graft loss due to glomerular disease (group 1). Biopsy-proven acute cellular rejection was more frequent in the belatacept-treated groups, with 10 treated episodes in seven participants compared with one episode in group 1; however, estimated GFR was similar between groups at week 52. There were no episodes of posttransplant lymphoproliferative disorder or opportunistic infections in any group. Protocol enrollment was halted prematurely because of a high rate of serious adverse events. Such negative outcomes pose challenges to clinical investigators, who ultimately must weigh the risks and benefits in randomized trials.

Belatacept Combined With Transient Calcineurin Inhibitor Therapy Prevents Rejection and Promotes Improved Long-Term Renal Allograft Function.

Belatacept, a T cell costimulation blocker, demonstrated superior renal function, lower cardiovascular risk, and improved graft and patient survival in renal transplant recipients. Despite the potential benefits, adoption of belatacept has been limited in part due to concerns regarding higher rates and grades of acute rejection in clinical trials. Since July 2011, we have utilized belatacept-based immunosuppression regimens in clinical practice. In this retrospective analysis of 745 patients undergoing renal transplantation at our center, we compared patients treated with belatacept (n = 535) with a historical cohort receiving a tacrolimus-based protocol (n = 205). Patient and graft survival were equivalent for all groups. An increased rate of acute rejection was observed in an initial cohort treated with a protocol similar to the low-intensity regimen from the BENEFIT trial versus the historical tacrolimus group (50.5% vs. 20.5%). The addition of a transient course of tacrolimus reduced rejection rates to acceptable levels (16%). Treatment with belatacept was associated with superior estimated GFR (belatacept 63.8 mL/min vs. tacrolimus 46.2 mL/min at 4 years, p < 0.0001). There were no differences in serious infections including rates of cytomegalovirus or BK viremia. We describe the development of a costimulatory blockade-based strategy that ultimately allows renal transplant recipients to achieve calcineurin inhibitor-free immunosuppression.

B Cell Receptor Genes Associated With Tolerance Identify a Cohort of Immunosuppressed Patients With Improved Renal Allograft Graft Function.

We previously reported that two B cell receptor genes, IGKV1D-13 and IGKV4-1, were associated with tolerance following kidney transplantation. To assess the potential utility of this "signature," we conducted a prospective, multicenter study to determine the frequency of patients predicted tolerant within a cohort of patients deemed to be candidates for immunosuppressive minimization. At any single time point, 25-30% of patients were predicted to be tolerant, while 13.7% consistently displayed the tolerance "signature" over the 2-year study. We also examined the relationship of the presence of the tolerance "signature" on drug use and graft function. Contrary to expectations, the frequency of predicted tolerance was increased in patients receiving tacrolimus and reduced in those receiving corticosteroids, mycophenolate mofetil, or Thymoglobulin as induction. Surprisingly, patients consistently predicted to be tolerant displayed a statistically and clinically significant improvement in estimated glomerular filtration rate that increased over time following transplantation. These findings indicate that the frequency of patients consistently predicted to be tolerant is sufficiently high to be clinically relevant and confirm recent findings by others that immunosuppressive agents impact putative biomarkers of tolerance. The association of a B cell-based "signature" with graft function suggests that B cells may contribute to the function/survival of transplanted kidneys.

Towards Improving the Transfer of Care of Kidney Transplant Recipients.

Kidney transplant recipients require specialized medical care and may be at risk for adverse health outcomes when their care is transferred. This document provides opinion-based recommendations to facilitate safe and efficient transfers of care for kidney transplant recipients including minimizing the risk of rejection, avoidance of medication errors, ensuring patient access to immunosuppressant medications, avoidance of lapses in health insurance coverage, and communication of risks of donor disease transmission. The document summarizes information to be included in a medical transfer document and includes suggestions to help the patient establish an optimal therapeutic relationship with their new transplant care team. The document is intended as a starting point towards standardization of transfers of care involving kidney transplant recipients.

Integrating APOL1 Gene Variants Into Renal Transplantation: Considerations Arising From the American Society of Transplantation Expert Conference.

Thirteen percent of individuals of African ancestry express two variant copies of the gene encoding apolipoprotein 1 (APOL1) that has been associated with an increased risk of end-stage renal disease (ESRD) in the general population. Limited studies suggest that the survival of transplanted kidneys from donors expressing two APOL1 risk alleles is inferior to that of kidneys from donors with zero or one risk allele. In living kidney donation, two case reports describe donors expressing two APOL1 risk alleles who developed ESRD. Given the potential impact of APOL1 variants on the utility and safety of kidney transplantation and living kidney donation, the American Society of Transplantation convened a meeting with the goals of summarizing the current state of knowledge with respect to transplantation and APOL1, identifying knowledge gaps and studies to address these gaps, and considering approaches to integrating APOL1 into clinical practice. The authors recognize that current data are not sufficient to support traditional evidence-based guidelines but also recognize that it may require several years to generate the necessary data. Thus, approaches as to how APOL1 might currently be integrated into the clinical decision-making process were considered. This report summarizes the group's deliberations.

Engaging Living Kidney Donors in a New Paradigm of Postdonation Care.

Recent studies have highlighted the need for better understanding of the long-term health outcomes of living donors. Barriers to establishment of a dedicated long-term donor follow-up data system in the United States include infrastructure costs and donor retention. We propose providing all previous and future living donors with a lifelong health insurance benefit for the primary purpose of facilitating acquisition of health information after donation as an alternative to establishment of a dedicated donor follow-up data system. Donors would consent to allow collection and analysis of their medical data, and continuation of insurance coverage would require completion of regular health assessments. The extension of health insurance would be analogous to the established practice of paying people for participation in a research study and would provide a mechanism to engage donors in a new paradigm of postdonation care in which donors are actively involved in their own health maintenance. Rather than acting as an inducement for donation, providing donors with the ability to easily contribute information about their health status represents a practical strategy to acquire the long-term medical information necessary to better inform future generations of living kidney donors.

Longitudinal studies of a B cell-derived signature of tolerance in renal transplant recipients.

Biomarkers of transplant tolerance would enhance the safety and feasibility of clinical tolerance trials and potentially facilitate management of patients receiving immunosuppression. To this end, we examined blood from spontaneously tolerant renal transplant recipients and patients enrolled in two interventional tolerance trials using flow cytometry and gene expression profiling. Using a previously reported tolerant cohort as well as newly identified tolerant patients, we confirmed our previous finding that tolerance was associated with increased expression of B cell-associated genes relative to immunosuppressed patients. This was not accounted for merely by an increase in total B cell numbers, but was associated with the increased frequencies of transitional and naïve B cells. Moreover, serial measurements of gene expression demonstrated that this pattern persisted over several years, although patients receiving immunosuppression also displayed an increase in the two most dominant tolerance-related B cell genes, IGKV1D-13 and IGLL-1, over time. Importantly, patients rendered tolerant via induction of transient mixed chimerism, and those weaned to minimal immunosuppression, showed similar increases in IGKV1D-13 as did spontaneously tolerant individuals. Collectively, these findings support the notion that alterations in B cells may be a common theme for tolerant kidney transplant recipients, and that it is a useful monitoring tool in prospective trials.

Interferon Gamma ELISPOT Testing as a Risk-Stratifying Biomarker for Kidney Transplant Injury: Results From the CTOT-01 Multicenter Study.

Previous studies suggest that quantifying donor-reactive memory T cells prior to kidney transplantation by interferon gamma enzyme-linked immunosorbent spot assay (IFNγELISPOT) can assist in assessing risk of posttransplant allograft injury. Herein, we report an analysis of IFNγELISPOT results from the multicenter, Clinical Trials in Organ Transplantation-01 observational study of primary kidney transplant recipients treated with heterogeneous immunosuppression. Within the subset of 176 subjects with available IFNγELISPOT results, pretransplant IFNγELISPOT positivity surprisingly did not correlate with either the incidence of acute rejection (AR) or estimated glomerular filtration rate (eGFR) at 6- or 12-month. These unanticipated results prompted us to examine potential effect modifiers, including the use of T cell-depleting, rabbit anti-thymocyte globulin (ATG). Within the no-ATG subset, IFNγELISPOT(neg) subjects had higher 6- and 12-month eGFRs than IFNγELISPOT(pos) subjects, independent of biopsy-proven AR, peak PRA, human leukocyte antigen mismatches, African-American race, donor source, and recipient age or gender. In contrast, IFNγELISPOT status did not correlate with posttransplant eGFR in subjects given ATG. Our data confirm an association between pretransplant IFNγELISPOT positivity and lower posttransplant eGFR, but only in patients who do not receive ATG induction. Controlled studies are needed to test the hypothesis that ATG induction is preferentially beneficial to transplant candidates with high frequencies of donor-reactive memory T cells.

Novel implications of Lingo-1 and its signaling partners in schizophrenia.

Myelination and neurite outgrowth both occur during brain development, and their disturbance has been previously been implicated in the pathophysiology of schizophrenia. Leucine-rich repeat and immunoglobulin domain-containing protein (Lingo-1) is a potent negative regulator of axonal myelination and neurite extension. As co-factors of Lingo-1 signaling (Nogo receptor (NgR), With No Lysine (K) (WNK1) and Myelin transcription factor 1 (Myt1)) have been implicated in the genetics of schizophrenia, we explored for the first time the role of Lingo-1 signaling pathways in this disorder. Lingo-1 protein, together with its co-receptor and co-factor proteins NgR, tumor necrosis factor (TNF) receptor orphan Y (TROY), p75, WNK1 and Myt1, have never been explored in the pathogenesis of schizophrenia. We examined protein levels of Lingo-1, NgR, TROY, p75, WNK1, Myt1 and myelin basic protein (MBP) (as a marker of myelination) within the post-mortem dorsolateral prefrontal cortex (DLPFC) (37 schizophrenia patients versus 37 matched controls) and hippocampus (Cornu Ammonis, CA1 and CA3) (20 schizophrenia patients versus 20 matched controls from the same cohort). Both of these brain regions are highly disrupted in the schizophrenia pathophysiology. There were significant increases in Lingo-1 (P<0.001) and Myt1 (P=0.023) and a reduction in NgR (P<0.001) in the DLPFC in schizophrenia subjects compared with controls. There were also increases in both TROY (P=0.001) and WNK1 (P=0.011) in the CA1 of schizophrenia subjects and, in contrast to the DLPFC, there was an increase in NgR (P=0.006) in the CA3 of schizophrenia subjects compared with controls. No significant difference was reported for MBP levels (P>0.05) between the schizophrenia and control groups in the three tested regions. This is the first time that a study has shown altered Lingo-1 signaling in the schizophrenia brain. Our novel findings may present a direct application for the use of a Lingo-1 antagonist to complement current and future schizophrenia therapies.

Multicenter validation of urinary CXCL9 as a risk-stratifying biomarker for kidney transplant injury.

Noninvasive biomarkers are needed to assess immune risk and ultimately guide therapeutic decision-making following kidney transplantation. A requisite step toward these goals is validation of markers that diagnose and/or predict relevant transplant endpoints. The Clinical Trials in Organ Transplantation-01 protocol is a multicenter observational study of biomarkers in 280 adult and pediatric first kidney transplant recipients. We compared and validated urinary mRNAs and proteins as biomarkers to diagnose biopsy-proven acute rejection (AR) and stratify patients into groups based on risk for developing AR or progressive renal dysfunction. Among markers tested for diagnosing AR, urinary CXCL9 mRNA (odds ratio [OR] 2.77, positive predictive value [PPV] 61.5%, negative predictive value [NPV] 83%) and CXCL9 protein (OR 3.40, PPV 67.6%, NPV 92%) were the most robust. Low urinary CXCL9 protein in 6-month posttransplant urines obtained from stable allograft recipients classified individuals least likely to develop future AR or a decrement in estimated glomerular filtration rate between 6 and 24 months (92.5-99.3% NPV). Our results support using urinary CXCL9 for clinical decision-making following kidney transplantation. In the context of acute dysfunction, low values can rule out infectious/immunological causes of injury. Absent urinary CXCL9 at 6 months posttransplant defines a subgroup at low risk for incipient immune injury.

A neuregulin 1 transmembrane domain mutation causes imbalanced glutamatergic and dopaminergic receptor expression in mice.

The neuregulin 1 gene has repeatedly been identified as a susceptibility gene for schizophrenia, thus mice with genetic mutations in this gene offer a valuable tool for studying the role of neuregulin 1 in schizophrenia-related neurotransmission. In this study, slide-based receptor autoradiography was used to quantify glutamatergic N-methyl-d-aspartate (NMDA), dopaminergic D2, cannabinoid CB1 and acetylcholine M1/4 receptor levels in the brains of male heterozygous transmembrane domain neuregulin 1 mutant (Nrg1(+/-)) mice at two ages. Mutant mice expressed small but significant increases in NMDA receptor levels in the cingulate cortex (7%, p=0.044), sensory cortex (8%, p=0.024), and motor cortex (8%, p=0.047), effects that were independent of age. In the nucleus accumbens and thalamus Nrg1(+/-) mice exhibited age-dependent alterations in NMDA receptors. Nrg1(+/-) mice showed a statistically significant increase in NMDA receptor levels in the nucleus accumbens of 14-week-old Nrg1(+/-) mice compared to control littermates of the same age (12%, p=0.026), an effect that was not seen in 20-week-old mice. In contrast, NMDA receptor levels in the thalamus, while initially unchanged in 14-week-old mice, were then decreased in the 20-week-old Nrg1(+/-) mice compared to control littermates of the same age (14%, p=0.011). Nrg1(+/-) mutant mice expressed a significant reduction in D2 receptor levels (13-16%) in the striatum compared to controls, independent of age. While there was a borderline significant increase (6%, p=0.058) in cannabinoid CB1 receptor levels in the substantia nigra of Nrg1(+/-) mice compared to controls, CB1 as well as acetylcholine M1/4 receptors showed no change in Nrg1(+/-) mice in any other brain region examined. These data indicate that a Nrg1 transmembrane mutation produces selective imbalances in glutamatergic and dopaminergic neurotransmission, which are two key systems believed to contribute to schizophrenia pathogenesis. While the effects on these systems are subtle, they may underlie the susceptibility of these mutants to further impacts.

Molecular evidence of N-methyl-D-aspartate receptor hypofunction in schizophrenia.

Blockade of N-methyl-D-aspartate receptors (NMDARs) produces behavior in healthy people that is similar to the psychotic symptoms and cognitive deficits of schizophrenia and can exacerbate symptoms in people with schizophrenia. However, an endogenous brain disruption of NMDARs has not been clearly established in schizophrenia. We measured mRNA transcripts for five NMDAR subunit mRNAs and protein for the NR1 subunit in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia and control (n=74) brains. Five NMDAR single-nucleotide polymorphisms (SNPs) previously associated with schizophrenia were tested for association with NMDAR mRNAs in postmortem brain and for association with cognitive ability in an antemortem cohort of 101 healthy controls and 48 people with schizophrenia. The NR1 subunit (mRNA and protein) and NR2C mRNA were decreased in postmortem brain from people with schizophrenia (P=0.004, P=0.01 and P=0.01, respectively). In the antemortem cohort, the minor allele of NR2B rs1805502 (T5988C) was associated with significantly lower reasoning ability in schizophrenia. In the postmortem brain, the NR2B rs1805502 (T5988C) C allele was associated with reduced expression of NR1 mRNA and protein in schizophrenia. Reduction in NR1 and NR2C in the DLPFC of people with schizophrenia may lead to altered NMDAR stoichiometry and provides compelling evidence for an endogenous NMDAR deficit in schizophrenia. Genetic variation in the NR2B gene predicts reduced levels of the obligatory NR1 subunit, suggesting a novel mechanism by which the NR2B SNP may negatively influence other NMDAR subunit expression and reasoning ability in schizophrenia.

Adaptive immunity rather than viral cytopathology mediates polyomavirus-associated nephropathy in mice.

Nephropathy associated with BK polyomavirus causes kidney allograft dysfunction and failure. Understanding the pathogenesis of polyomavirus-associated allograft nephropathy (PVAN) is hampered by the species specificity of Polyomaviridae family members. Using a mouse polyomavirus (MPyV) kidney transplant model, we investigated clinically relevant variables that may contribute to PVAN. We found that the timing and source (i.e. donor vs. recipient) of MPyV infection and the titer of the viral inoculum have significant effects on the extent of allograft injury, with acute infection of the recipient by high-titer MPyV inoculums producing the most profound PVAN. In contrast, altering the degree of MHC matching or increasing ischemia/reperfusion injury by prolonging the cold ischemic time of the allograft did not affect the severity of PVAN. Survival correlated positively with serum creatinine levels, but not with viral loads in the kidney allograft. Using splenectomized alymphoplasia mice, which are unable to mount primary adaptive immune responses, we further demonstrate that persistent high viral loads in the kidney are not sufficient to cause advanced PVAN. These findings suggest that the mechanism of PVAN in mice is not a direct consequence of viral cytopathology, but rather involves interplay between viral infection and the recipient antidonor immune response.

Donor-specific indirect pathway analysis reveals a B-cell-independent signature which reflects outcomes in kidney transplant recipients.

To investigate the role of donor-specific indirect pathway T cells in renal transplant tolerance, we analyzed responses in peripheral blood of 45 patients using the trans-vivo delayed-type hypersensitivity assay. Subjects were enrolled into five groups-identical twin, clinically tolerant (TOL), steroid monotherapy (MONO), standard immunosuppression (SI) and chronic rejection (CR)-based on transplant type, posttransplant immunosuppression and graft function. The indirect pathway was active in all groups except twins but distinct intergroup differences were evident, corresponding to clinical status. The antidonor indirect pathway T effector response increased across patient groups (TOL < MONO < SI < CR; p < 0.0001) whereas antidonor indirect pathway T regulatory response decreased (TOL > MONO = SI > CR; p < 0.005). This pattern differed from that seen in circulating naïve B-cell numbers and in a cross-platform biomarker analysis, where patients on monotherapy were not ranked closest to TOL patients, but rather were indistinguishable from chronically rejecting patients. Cross-sectional analysis of the indirect pathway revealed a spectrum in T-regulatory:T-effector balance, ranging from TOL patients having predominantly regulatory responses to CR patients having predominantly effector responses. Therefore, the indirect pathway measurements reflect a distinct aspect of tolerance from the recently reported elevation of circulating naïve B cells, which was apparent only in recipients off immunosuppression.