Viral load kinetics and the clinical consequences of cytomegalovirus in kidney transplantation

Background

Despite advances in clinical management, cytomegalovirus (CMV) infection remains a serious complication and an important cause of morbidity and mortality following kidney transplantation. Here, we explore the importance of viral load kinetics as predictors of risk and potential guides to therapy to reduce transplant failure in a large longitudinal Genome Canada Transplant Consortium (GCTC) kidney transplant cohort.

Methods

We examined the relationship between CMV infection rates and clinical characteristics, CMV viral load kinetics, and graft and patient outcomes in 2510 sequential kidney transplant recipients in the British Columbia Transplant Program. Transplants were performed between January 1, 2008, and December 31, 2018, were managed according to a standard protocol, and were followed until December 31, 2019, representing over 3.4 million days of care.

Results

Longitudinal CMV testing was performed in 2464 patients, of whom 434 (17.6%) developed a first episode of CMV viremia at a median of 120 (range: 9-3906) days post-transplant. Of these patients, 93 (21.4%) had CMV viremia only and 341 (78.6%) had CMV viremia with clinical complications, of whom 21 (4.8%) had resulting hospitalization. A total of 279 (11.3%) patients died and 177 (7.2%) patients lost their graft during the 12 years of follow-up. Patients with CMV infection were at significantly greater risk of graft loss (p=0.0041) and death (p=0.0056) than those without. Peak viral load ranged from 2.9 to 7.0 (median: 3.5) log10 IU/mL, the duration of viremia from 2 to 100 (15) days, and the viral load area under the curve from 9.4 to 579.8 (59.7) log10 IU/mL × days. All three parameters were closely inter-related and were significantly increased in patients with more severe clinical disease or with graft loss (p=0.001). Duration of the first CMV viremic episode greater than 15 days or a peak viral load ≥4.0 log10 IU/mL offered simple predictors of clinical risk with a 3-fold risk of transplant failure.

Conclusion

Viral load kinetics are closely related to CMV severity and to graft loss following kidney transplantation and provide a simple index of risk which may be valuable in guiding trials and treatment to prevent transplant failure.

Regulatory T Cell Biomarkers Identify Patients at Risk of Developing Acute Cellular Rejection in the First Year Following Heart Transplantation

BACKGROUND

Acute cellular rejection (ACR), an alloimmune response involving CD4+ and CD8+ T cells, occurs in up to 20% of patients within the first year following heart transplantation. The balance between a conventional versus regulatory CD4+ T cell alloimmune response is believed to contribute to developing ACR. Therefore, tracking these cells may elucidate whether changes in these cell populations could signal ACR risk.

METHODS

We used a CD4+ T cell gene signature (TGS) panel that tracks CD4+ conventional T cells (Tconv) and regulatory T cells (Treg) on longitudinal samples from 94 adult heart transplant recipients. We evaluated combined diagnostic performance of the TGS panel with a previously developed biomarker panel for ACR diagnosis, HEARTBiT, while also investigating TGS' prognostic utility.

RESULTS

Compared with nonrejection samples, rejection samples showed decreased Treg- and increased Tconv-gene expression. The TGS panel was able to discriminate between ACR and nonrejection samples and, when combined with HEARTBiT, showed improved specificity compared with either model alone. Furthermore, the increased risk of ACR in the TGS model was associated with lower expression of Treg genes in patients who later developed ACR. Reduced Treg gene expression was positively associated with younger recipient age and higher intrapatient tacrolimus variability.

CONCLUSIONS

We demonstrated that expression of genes associated with CD4+ Tconv and Treg could identify patients at risk of ACR. In our post hoc analysis, complementing HEARTBiT with TGS resulted in an improved classification of ACR. Our study suggests that HEARTBiT and TGS may serve as useful tools for further research and test development.

Clinical application of immune repertoire sequencing in solid organ transplant

Background

Measurement of T cell receptor (TCR) or B cell receptor (BCR) gene utilization may be valuable in monitoring the dynamic changes in donor-reactive clonal populations following transplantation and enabling adjustment in therapy to avoid the consequences of excess immune suppression or to prevent rejection with contingent graft damage and to indicate the development of tolerance.

Objective

We performed a review of current literature to examine research in immune repertoire sequencing in organ transplantation and to assess the feasibility of this technology for clinical application in immune monitoring.

Methods

We searched MEDLINE and PubMed Central for English-language studies published between 2010 and 2021 that examined T cell/B cell repertoire dynamics upon immune activation. Manual filtering of the search results was performed based on relevancy and predefined inclusion criteria. Data were extracted based on study and methodology characteristics.

Results

Our initial search yielded 1933 articles of which 37 met the inclusion criteria; 16 of these were kidney transplant studies (43%) and 21 were other or general transplantation studies (57%). The predominant method for repertoire characterization was sequencing the CDR3 region of the TCR β chain. Repertoires of transplant recipients were found to have decreased diversity in both rejectors and non-rejectors when compared to healthy controls. Rejectors and those with opportunistic infections were more likely to have clonal expansion in T or B cell populations. Mixed lymphocyte culture followed by TCR sequencing was used in 6 studies to define an alloreactive repertoire and in specialized transplant settings to track tolerance.

Conclusion

Methodological approaches to immune repertoire sequencing are becoming established and offer considerable potential as a novel clinical tool for pre- and post-transplant immune monitoring.

Dissecting the impact of molecular T-cell HLA mismatches in kidney transplant failure: A retrospective cohort study

Introduction

Kidney transplantation is the optimal treatment in end-stage kidney disease, but de-novo donor specific antibody development continues to negatively impact patients undergoing kidney transplantation. One of the recent advances in solid organ transplantation has been the definition of molecular mismatching between donors and recipients' Human Leukocyte Antigens (HLA). While not fully integrated in standard clinical care, cumulative molecular mismatch at the level of eplets (EMM) as well as the PIRCHE-II score have shown promise in predicting transplant outcomes. In this manuscript, we sought to study whether certain T-cell molecular mismatches (TcEMM) were highly predictive of death-censored graft failure (DCGF).

Methods

We studied a retrospective cohort of kidney donor:recipient pairs from the Scientific Registry of Transplant Recipients (2000-2015). Allele level HLA-A, B, C, DRB1 and DQB1 types were imputed from serologic types using the NMDP algorithm. TcEMMs were then estimated using the PIRCHE-II algorithm. Multivariable Accelerated Failure Time (AFT) models assessed the association between each TcEMM and DCGF. To discriminate between TcEMMs most predictive of DCGF, we fit multivariable Lasso penalized regression models. We identified co-expressed TcEMMs using weighted correlation network analysis (WGCNA). Finally, we conducted sensitivity analyses to address PIRCHE and IMGT/HLA version updates.

Results

A total of 118,309 donor:recipient pairs meeting the eligibility criteria were studied. When applying the PIRCHE-II algorithm, we identified 1,935 distinct TcEMMs at the population level. A total of 218 of the observed TcEMM were independently associated with DCGF by AFT models. The Lasso penalized regression model with post selection inference identified a smaller subset of 86 TcEMMs (56 and 30 TcEMM derived from HLA Class I and II, respectively) to be highly predictive of DCGF. Of the observed TcEMM, 38.14% appeared as profiles of highly co-expressed TcEMMs. In addition, sensitivity analyses identified that the selected TcEMM were congruent across IMGT/HLA versions.

Conclusion

In this study, we identified subsets of TcEMMs highly predictive of DCGF and profiles of co-expressed mismatches. Experimental verification of these TcEMMs determining immune responses and how they may interact with EMM as predictors of transplant outcomes would justify their consideration in organ allocation schemes and for modifying immunosuppression regimens.

High-throughput sequencing defines donor and recipient HLA B-cell epitope frequencies for prospective matching in transplantation

Compatibility for human leukocyte antigen (HLA) genes between transplant donors and recipients improves graft survival but prospective matching is rarely performed due to the vast heterogeneity of this gene complex. To reduce complexity, we have combined next-generation sequencing and in silico mapping to determine transplant population frequencies and matching probabilities of 150 antibody-binding eplets across all 11 classical HLA genes in 2000 ethnically heterogeneous renal patients and donors. We show that eplets are more common and uniformly distributed between donors and recipients than the respective HLA isoforms. Simulations of targeted eplet matching shows that a high degree of overall compatibility, and perfect identity at the clinically important HLA class II loci, can be obtained within a patient waiting list of approximately 250 subjects. Internal epitope-based allocation is thus feasible for most major renal transplant programs, while regional or national sharing may be required for other solid organs.

Tran et al. combine high throughput sequencing, structural biology and computational simulation to determine the HLA allele and antibody-defined epitope frequencies in renal transplant patients and donors. These results demonstrate the feasibility of HLA epitope matching using data from a national transplantation program.

Donor-Derived Cell-Free DNA Testing in Solid Organ Transplantation: A Value Proposition

BACKGROUND

There is a need to improve personalized immunosuppression in organ transplantation to reduce premature graft loss. More efficient biomarkers are needed to better detect rejection, asymptomatic graft injury, and under-immunosuppression. Assessment of minimal necessary exposure to guide tapering and to prevent immune activation is also important. Donor-derived cell-free DNA (dd-cfDNA) has become available for comprehensive monitoring of allograft integrity. A value proposition concept was applied to assess the potential benefits of dd-cfDNA to stakeholders (patient, transplant physician, laboratory medicine specialist, hospital management, insurance companies) involved in solid organ transplantation care.

CONTENT

There is robust clinical evidence from more than 48 published studies supporting the role of dd-cfDNA for monitoring graft integrity and detection or exclusion of rejection. The value proposition framework was used to evaluate published key evidence regarding clinical validity, economic implications, and limitations of this approach. It has been shown that dd-cfDNA testing is essential for guiding earlier transplant injury intervention with potential for improved long-term outcome.

SUMMARY

Monitoring dd-cfDNA offers a rapid and reproducible method to detect graft injuries at an early actionable stage without protocol biopsies and allows for more effective personalized immunosuppression. The appropriate use of dd-cfDNA testing can provide both clinical and economic benefits to all transplantation stakeholders.

Association between transplant glomerulopathy and graft outcomes following kidney transplantation: A meta-analysis

Transplant glomerulopathy (TG), a morphological lesion associated with confluent mechanisms of endothelial injury of renal allografts, may provide a viable predictor of graft failure. This systematic literature review and meta-analysis were performed according to the PRISMA statement to examine evidence describing the association between TG and graft loss or failure and time to these events. The literature review was conducted using the Scopus, EBSCO, and Cochrane Library search engines. Hazard ratios, median survival times, and 95% confidence intervals (CIs) were estimated to evaluate graft survival in the total population and prespecified subgroups. Meta-regression analysis assessed heterogeneity. Twenty-one publications comprising 6,783 patients were eligible for data extraction and inclusion in the meta-analysis. Studies were highly heterogeneous (I² = 67.3%). The combined hazard ratio of graft loss or failure from random-effects meta-analysis was 3.11 (95% CI 2.44–3.96) in patients with TG compared with those without. Median graft survival in patients with TG was 3.25 (95% CI 0.94–11.21) years—15 years shorter than in those without TG (18.82 [95% CI 10.03–35.32] years). The effect of time from transplantation to biopsy on graft outcomes did not reach statistical significance (p = 0.116). TG was associated with a threefold increase in the risk of graft loss or failure and a 15-year loss in graft survival, indicating viability as a surrogate measure for both clinical practice and studies designed to prevent or reverse antibody-mediated rejection.

HEARTBiT: A Transcriptomic Signature for Excluding Acute Cellular Rejection in Adult Heart Allograft Patients

BACKGROUND

Nine mRNA transcripts associated with acute cellular rejection (ACR) in previous microarray studies were ported to the clinically amenable NanoString nCounter platform. Here we report the diagnostic performance of the resulting blood test to exclude ACR in heart allograft recipients: HEARTBiT.

METHODS

Blood samples for transcriptomic profiling were collected during routine post-transplantation monitoring in 8 Canadian transplant centres participating in the Biomarkers in Transplantation initiative, a large (n = 1622) prospective observational study conducted between 2009 and 2014. All adult cardiac transplant patients were invited to participate (median age = 56 [17 to 71]). The reference standard for rejection status was histopathology grading of tissue from endomyocardial biopsy (EMB). All locally graded ISHLT ≥ 2R rejection samples were selected for analysis (n = 36). ISHLT 1R (n = 38) and 0R (n = 86) samples were randomly selected to create a cohort approximately matched for site, age, sex, and days post-transplantation, with a focus on early time points (median days post-transplant = 42 [7 to 506]).

RESULTS

ISHLT ≥ 2R rejection was confirmed by EMB in 18 and excluded in 92 samples in the test set. HEARTBiT achieved 47% specificity (95% confidence interval [CI], 36%-57%) given ≥ 90% sensitivity, with a corresponding area under the receiver operating characteristic curve of 0.69 (95% CI, 0.56-0.81).

CONCLUSIONS

HEARTBiT's diagnostic performance compares favourably to the only currently approved minimally invasive diagnostic test to rule out ACR, AlloMap (CareDx, Brisbane, CA) and may be used to inform care decisions in the first 2 months post-transplantation, when AlloMap is not approved, and most ACR episodes occur.

HLA-B*58:01 Genotyping to Prevent Cases of DRESS and SJS/TEN in East Asians Treated with Allopurinol—A Canadian Missed Opportunity

Background and objective

East Asians exposed to the urate-lowering drug allopurinol have a predilection for severe cutaneous drug reactions such as drug-induced hypersensitivity syndrome or drug reaction with eosinophilia and systemic symptoms (DRESS) and Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Screening is recommended in patients of East Asian descent for the presence of HLA-B*58:01 prior to allopurinol initiation to avoid these complications. Utilization rates of the HLA-B*58:01 predictive screening test within the Greater Vancouver area, which has a population composed of 40.1% people of East Asian descent, are unknown.

Measures

We identified cases of DRESS or SJS/TEN due to allopurinol using the Vancouver General Hospital dermatology consult service database. We next compared the frequency in which the HLA-B*58:01 screening test was ordered since 2012 to the estimated frequency of new prescriptions for allopurinol prescribed for the management of gout among the East Asians.

Results

We report 5 cases of East Asian patients exposed to allopurinol for management of gout between 2012 and 2016, who developed DRESS (4 patients) or SJS/TEN (1 patient). All were of HLA-B*58:01 genotype, representing preventable cases. The HLA-B*58:01 test was ordered 6 times in 2012, whereas the estimated number of new cases of allopurinol-prescribed gout among patients of East Asian descent during that time period was 13. For 2012, testing was ordered for only 46% of at-risk patients.

Conclusion

We continue to observe cases of severe cutaneous drug reactions among high-risk individuals due to allopurinol exposure. The HLA-B*58:01 screening test for allopurinol hypersensitivity is underutilized in our geographic area.

Association of gastrointestinal events with quality of life and treatment satisfaction in osteoporosis patients: results from the Medication Use Patterns, Treatment Satisfaction, and Inadequate Control of Osteoporosis Study (MUSIC OS)

The purpose of this study was to assess the association of GI events with HRQoL and treatment satisfaction. The effect of baseline GI events persisted through 1 year of follow-up, as indicated by lower EQ-5D, OPAQ-SV, and treatment satisfaction scores among patients with vs without baseline GI events. The presence of GI events is an independent predictor of decreased HRQoL and treatment satisfaction in patients being treated for osteoporosis.

INTRODUCTION

The goal of this study was to assess the association of gastrointestinal (GI) events with health-related quality of life (HRQoL) and treatment satisfaction in patients being treated for osteoporosis.

METHODS

MUSIC OS was a multinational, prospective, observational study examining the impact of GI events on osteoporosis management in postmenopausal women. In this analysis, HRQoL and treatment satisfaction were assessed at baseline, 6, and 12 months and compared between patients with and without GI events. Covariate-adjusted scores were calculated using multivariate least-squares regression analysis, and differences between the mean scores of patients with and without baseline and post-baseline GI events were determined.

RESULTS

Among the 2959 patients in the analysis, unadjusted scores at each time point were lower (i.e., worse) for patients with GI events than patients without GI events. In adjusted analyses, the effect of baseline GI events persisted through 1 year of follow-up, as indicated by lower EQ-5D and OPAQ-SV scores at 12 months among patients with vs without baseline GI events (-0.04 for the EQ-5D utility score, -5.07 for the EQ-5D visual analog scale, -3.35 for OPAQ physical function, -4.60 for OPAQ emotional status, and -8.50 for OPAQ back pain; P ≤ 0.001 for all values). Decrements in month 12 treatment satisfaction scores were -6.46 for patients with baseline GI events and -7.88 for patients with post-baseline GI events.

CONCLUSIONS

The presence of GI events is an independent predictor of decreased HRQoL and treatment satisfaction in patients being treated for osteoporosis.

Association of Serum MiR-142-3p and MiR-101-3p Levels with Acute Cellular Rejection after Heart Transplantation

Background

Identifying non-invasive and reliable blood-derived biomarkers for early detection of acute cellular rejection in heart transplant recipients is of great importance in clinical practice. MicroRNAs are small molecules found to be stable in serum and their expression patterns reflect both physiological and underlying pathological conditions in human.

Methods

We compared a group of heart transplant recipients with histologically-verified acute cellular rejection (ACR, n = 26) with a control group of heart transplant recipients without allograft rejection (NR, n = 37) by assessing the levels of a select set of microRNAs in serum specimens.

Results

The levels of seven microRNAs, miR-142-3p, miR-101-3p, miR-424-5p, miR-27a-3p, miR-144-3p, miR-339-3p and miR-326 were significantly higher in ACR group compared to the control group and could discriminate between patients with and without allograft rejection. MiR-142-3p and miR-101-3p had the best diagnostic test performance among the microRNAs tested. Serum levels of miR-142-3p and miR-101-3p were independent of calcineurin inhibitor levels, as measured by tacrolimus and cyclosporin; kidney function, as measured by creatinine level, and general inflammation state, as measured by CRP level.

Conclusion

This study demonstrated two microRNAs, miR-142-3p and miR-101-3p, that could be relevant as non-invasive diagnostic tools for identifying heart transplant patients with acute cellular rejection.

Rationale and design of MUSIC OS-EU: an international observational study of the treatment of postmenopausal women for osteoporosis in Europe and Canada

OBJECTIVES

The Medication Use Patterns, Treatment Satisfaction, and Inadequate Control of Osteoporosis Study (MUSIC OS-EU) was designed to better understand the rate and burden of gastrointestinal (GI) events on clinical and health care outcomes among postmenopausal women with osteoporosis.

METHODS

MUSIC OS-EU is a prospective, multinational, observational cohort study of postmenopausal women ≥50 years of age diagnosed with osteoporosis and enrolled in physician clinics in six countries: France, Italy, the Netherlands, Sweden, the United Kingdom, and Canada. The MUSIC OS-EU study has three components: (i) a physician survey to describe their management of osteoporotic patients with GI events; (ii) a retrospective chart survey to describe the receipt and type of osteoporosis medication prescribed; and (iii) a prospective cohort study including untreated and treated patients diagnosed with osteoporosis to investigate the rate of GI events and association with osteoporosis medication use patterns, health-related quality of life, treatment satisfaction and resource utilisation among postmenopausal women with osteoporosis.

RESULTS

Physicians at 97 sites completed the physician questionnaire and data for 716 patients were abstracted for the retrospective chart review. Enrolment and the baseline data collection for the prospective cohort study were conducted between March 2012 and June 2013 for 292 untreated and 2,959 treated patients, of whom 684 were new users and 2,275 were experienced users of oral osteoporosis medications.

CONCLUSIONS

The results of MUSIC OS-EU will illuminate the association of GI events with the management of osteoporosis and with patient-reported outcomes among postmenopausal women with osteoporosis in Europe and Canada.

Novel multivariate methods for integration of genomics and proteomics data: applications in a kidney transplant rejection study

Multi-omics research is a key ingredient of data-intensive life sciences research, permitting measurement of biological molecules at different functional levels in the same individual. For a complete picture at the biological systems level, appropriate statistical techniques must however be developed to integrate different 'omics' data sets (e.g., genomics and proteomics). We report here multivariate projection-based analyses approaches to genomics and proteomics data sets, using the case study of and applications to observations in kidney transplant patients who experienced an acute rejection event (n=20) versus non-rejecting controls (n=20). In this data sets, we show how these novel methodologies might serve as promising tools for dimension reduction and selection of relevant features for different analytical frameworks. Unsupervised analyses highlighted the importance of post transplant time-of-rejection, while supervised analyses identified gene and protein signatures that together predicted rejection status with little time effect. The selected genes are part of biological pathways that are representative of immune responses. Gene enrichment profiles revealed increases in innate immune responses and neutrophil activities and a depletion of T lymphocyte related processes in rejection samples as compared to controls. In all, this article offers candidate biomarkers for future detection and monitoring of acute kidney transplant rejection, as well as ways forward for methodological advances to better harness multi-omics data sets.

The Human Proteome Organization Chromosome 6 Consortium: integrating chromosome-centric and biology/disease driven strategies

The Human Proteome Project (HPP) is designed to generate a comprehensive map of the protein-based molecular architecture of the human body, to provide a resource to help elucidate biological and molecular function, and to advance diagnosis and treatment of diseases. Within this framework, the chromosome-based HPP (C-HPP) has allocated responsibility for mapping individual chromosomes by country or region, while the biology/disease HPP (B/D-HPP) coordinates these teams in cross-functional disease-based groups. Chromosome 6 (Ch6) provides an excellent model for integration of these two tasks. This metacentric chromosome has a complement of 1002-1034 genes that code for known, novel or putative proteins. Ch6 is functionally associated with more than 120 major human diseases, many with high population prevalence, devastating clinical impact and profound societal consequences. The unique combination of genomic, proteomic, metabolomic, phenomic and health services data being drawn together within the Ch6 program has enormous potential to advance personalized medicine by promoting robust biomarkers, subunit vaccines and new drug targets. The strong liaison between the clinical and laboratory teams, and the structured framework for technology transfer and health policy decisions within Canada will increase the speed and efficacy of this transition, and the value of this translational research.

BIOLOGICAL SIGNIFICANCE

Canada has been selected to play a leading role in the international Human Proteome Project, the global counterpart of the Human Genome Project designed to understand the structure and function of the human proteome in health and disease. Canada will lead an international team focusing on chromosome 6, which is functionally associated with more than 120 major human diseases, including immune and inflammatory disorders affecting the brain, skeletal system, heart and blood vessels, lungs, kidney, liver, gastrointestinal tract and endocrine system. Many of these chronic and persistent diseases have a high population prevalence, devastating clinical impact and profound societal consequences. As a result, they impose a multi-billion dollar economic burden on Canada and on all advanced societies through direct costs of patient care, the loss of health and productivity, and extensive caregiver burden. There is no definitive treatment at the present time for any of these disorders. The manuscript outlines the research which will involve a systematic assessment of all chromosome 6 genes, development of a knowledge base, and development of assays and reagents for all chromosome 6 proteins. We feel that the informatic infrastructure and MRM assays developed will place the chromosome 6 consortium in an excellent position to be a leading player in this major international research initiative. This article is part of a Special Issue: Can Proteomics Fill the Gap Between Genomics and Phenotypes?

Proteomic biomarkers of recovered heart function

AIMS

Chronic heart failure is a costly epidemic that affects up to 2% of people in developed countries. The purpose of this study was to discover novel blood proteomic biomarker signatures of recovered heart function that could lead to more effective heart failure patient management by both primary care and specialty physicians.

METHODS AND RESULTS

The discovery cohort included 41 heart transplant patients and 20 healthy individuals. Plasma levels of 138 proteins were detected in at least 75% of these subjects by iTRAQ mass spectrometry. Eighteen proteins were identified that had (i) differential levels between pre-transplant patients with end-stage heart failure and healthy individuals; and (ii) levels that returned to normal by 1 month post-transplant in patients with stable heart function after transplantation. Seventeen of the 18 markers were validated by multiple reaction monitoring mass spectrometry in a cohort of 39 heart failure patients treated with drug therapy, of which 30 had recovered heart function and 9 had not. This 17-protein biomarker panel had 93% sensitivity and 89% specificity, while the RAMP® NT-proBNP assay had the same specificity but 80% sensitivity. Performance further improved when the panel was combined with NT-proBNP, yielding a net reclassification index relative to NT-proBNP of 0.28.

CONCLUSIONS

We have identified potential blood biomarkers of recovered heart function by harnessing data from transplant patients. These biomarkers can lead to the development of an inexpensive protein-based blood test that could be used by physicians to monitor response to therapy in heart failure, resulting in more personalized, front-line heart failure patient management.

Longitudinal Analysis of Whole Blood Transcriptomes to Explore Molecular Signatures Associated with Acute Renal Allograft Rejection

In this study, we explored a time course of peripheral whole blood transcriptomes from kidney transplantation patients who either experienced an acute rejection episode or did not in order to better delineate the immunological and biological processes measureable in blood leukocytes that are associated with acute renal allograft rejection. Using microarrays, we generated gene expression data from 24 acute rejectors and 24 nonrejectors. We filtered the data to obtain the most unambiguous and robustly expressing probe sets and selected a subset of patients with the clearest phenotype. We then performed a data-driven exploratory analysis using data reduction and differential gene expression analysis tools in order to reveal gene expression signatures associated with acute allograft rejection. Using a template-matching algorithm, we then expanded our analysis to include time course data, identifying genes whose expression is modulated leading up to acute rejection. We have identified molecular phenotypes associated with acute renal allograft rejection, including a significantly upregulated signature of neutrophil activation and accumulation following transplant surgery that is common to both acute rejectors and nonrejectors. Our analysis shows that this expression signature appears to stabilize over time in nonrejectors but persists in patients who go on to reject the transplanted organ. In addition, we describe an expression signature characteristic of lymphocyte activity and proliferation. This lymphocyte signature is significantly downregulated in both acute rejectors and nonrejectors following surgery; however, patients who go on to reject the organ show a persistent downregulation of this signature relative to the neutrophil signature.

Longitudinal analysis of whole blood transcriptomes to explore molecular signatures associated with acute renal allograft rejection

In this study, we explored a time course of peripheral whole blood transcriptomes from kidney transplantation patients who either experienced an acute rejection episode or did not in order to better delineate the immunological and biological processes measureable in blood leukocytes that are associated with acute renal allograft rejection. Using microarrays, we generated gene expression data from 24 acute rejectors and 24 nonrejectors. We filtered the data to obtain the most unambiguous and robustly expressing probe sets and selected a subset of patients with the clearest phenotype. We then performed a data-driven exploratory analysis using data reduction and differential gene expression analysis tools in order to reveal gene expression signatures associated with acute allograft rejection. Using a template-matching algorithm, we then expanded our analysis to include time course data, identifying genes whose expression is modulated leading up to acute rejection. We have identified molecular phenotypes associated with acute renal allograft rejection, including a significantly upregulated signature of neutrophil activation and accumulation following transplant surgery that is common to both acute rejectors and nonrejectors. Our analysis shows that this expression signature appears to stabilize over time in nonrejectors but persists in patients who go on to reject the transplanted organ. In addition, we describe an expression signature characteristic of lymphocyte activity and proliferation. This lymphocyte signature is significantly downregulated in both acute rejectors and nonrejectors following surgery; however, patients who go on to reject the organ show a persistent downregulation of this signature relative to the neutrophil signature.

Alteration of human blood cell transcriptome in uremia

Background

End-stage renal failure is associated with profound changes in physiology and health, but the molecular causation of these pleomorphic effects termed “uremia” is poorly understood. The genomic changes of uremia were explored in a whole genome microarray case-control comparison of 95 subjects with end-stage renal failure (n = 75) or healthy controls (n = 20).

Methods

RNA was separated from blood drawn in PAXgene tubes and gene expression analyzed using Affymetrix Human Genome U133 Plus 2.0 arrays. Quality control and normalization was performed, and statistical significance determined with multiple test corrections (qFDR). Biological interpretation was aided by knowledge mining using NIH DAVID, MetaCore and PubGene

Results

Over 9,000 genes were differentially expressed in uremic subjects compared to normal controls (fold change: -5.3 to +6.8), and more than 65% were lower in uremia. Changes appeared to be regulated through key gene networks involving cMYC, SP1, P53, AP1, NFkB, HNF4 alpha, HIF1A, c-Jun, STAT1, STAT3 and CREB1. Gene set enrichment analysis showed that mRNA processing and transport, protein transport, chaperone functions, the unfolded protein response and genes involved in tumor genesis were prominently lower in uremia, while insulin-like growth factor activity, neuroactive receptor interaction, the complement system, lipoprotein metabolism and lipid transport were higher in uremia. Pathways involving cytoskeletal remodeling, the clathrin-coated endosomal pathway, T-cell receptor signaling and CD28 pathways, and many immune and biological mechanisms were significantly down-regulated, while the ubiquitin pathway and certain others were up-regulated.

Conclusions

End-stage renal failure is associated with profound changes in human gene expression which appears to be mediated through key transcription factors. Dialysis and primary kidney disease had minor effects on gene regulation, but uremia was the dominant influence in the changes observed. This data provides important insight into the changes in cellular biology and function, opportunities for biomarkers of disease progression and therapy, and potential targets for intervention in uremia.

Computational biomarker pipeline from discovery to clinical implementation: plasma proteomic biomarkers for cardiac transplantation

Recent technical advances in the field of quantitative proteomics have stimulated a large number of biomarker discovery studies of various diseases, providing avenues for new treatments and diagnostics. However, inherent challenges have limited the successful translation of candidate biomarkers into clinical use, thus highlighting the need for a robust analytical methodology to transition from biomarker discovery to clinical implementation. We have developed an end-to-end computational proteomic pipeline for biomarkers studies. At the discovery stage, the pipeline emphasizes different aspects of experimental design, appropriate statistical methodologies, and quality assessment of results. At the validation stage, the pipeline focuses on the migration of the results to a platform appropriate for external validation, and the development of a classifier score based on corroborated protein biomarkers. At the last stage towards clinical implementation, the main aims are to develop and validate an assay suitable for clinical deployment, and to calibrate the biomarker classifier using the developed assay. The proposed pipeline was applied to a biomarker study in cardiac transplantation aimed at developing a minimally invasive clinical test to monitor acute rejection. Starting with an untargeted screening of the human plasma proteome, five candidate biomarker proteins were identified. Rejection-regulated proteins reflect cellular and humoral immune responses, acute phase inflammatory pathways, and lipid metabolism biological processes. A multiplex multiple reaction monitoring mass-spectrometry (MRM-MS) assay was developed for the five candidate biomarkers and validated by enzyme-linked immune-sorbent (ELISA) and immunonephelometric assays (INA). A classifier score based on corroborated proteins demonstrated that the developed MRM-MS assay provides an appropriate methodology for an external validation, which is still in progress. Plasma proteomic biomarkers of acute cardiac rejection may offer a relevant post-transplant monitoring tool to effectively guide clinical care. The proposed computational pipeline is highly applicable to a wide range of biomarker proteomic studies.

A computational pipeline for the development of multi-marker bio-signature panels and ensemble classifiers

Background

Biomarker panels derived separately from genomic and proteomic data and with a variety of computational methods have demonstrated promising classification performance in various diseases. An open question is how to create effective proteo-genomic panels. The framework of ensemble classifiers has been applied successfully in various analytical domains to combine classifiers so that the performance of the ensemble exceeds the performance of individual classifiers. Using blood-based diagnosis of acute renal allograft rejection as a case study, we address the following question in this paper: Can acute rejection classification performance be improved by combining individual genomic and proteomic classifiers in an ensemble?

Results

The first part of the paper presents a computational biomarker development pipeline for genomic and proteomic data. The pipeline begins with data acquisition (e.g., from bio-samples to microarray data), quality control, statistical analysis and mining of the data, and finally various forms of validation. The pipeline ensures that the various classifiers to be combined later in an ensemble are diverse and adequate for clinical use. Five mRNA genomic and five proteomic classifiers were developed independently using single time-point blood samples from 11 acute-rejection and 22 non-rejection renal transplant patients. The second part of the paper examines five ensembles ranging in size from two to 10 individual classifiers. Performance of ensembles is characterized by area under the curve (AUC), sensitivity, and specificity, as derived from the probability of acute rejection for individual classifiers in the ensemble in combination with one of two aggregation methods: (1) Average Probability or (2) Vote Threshold. One ensemble demonstrated superior performance and was able to improve sensitivity and AUC beyond the best values observed for any of the individual classifiers in the ensemble, while staying within the range of observed specificity. The Vote Threshold aggregation method achieved improved sensitivity for all 5 ensembles, but typically at the cost of decreased specificity.

Conclusion

Proteo-genomic biomarker ensemble classifiers show promise in the diagnosis of acute renal allograft rejection and can improve classification performance beyond that of individual genomic or proteomic classifiers alone. Validation of our results in an international multicenter study is currently underway.

White blood cell differentials enrich whole blood expression data in the context of acute cardiac allograft rejection

Acute cardiac allograft rejection is a serious complication of heart transplantation. Investigating molecular processes in whole blood via microarrays is a promising avenue of research in transplantation, particularly due to the non-invasive nature of blood sampling. However, whole blood is a complex tissue and the consequent heterogeneity in composition amongst samples is ignored in traditional microarray analysis. This complicates the biological interpretation of microarray data. Here we have applied a statistical deconvolution approach, cell-specific significance analysis of microarrays (csSAM), to whole blood samples from subjects either undergoing acute heart allograft rejection (AR) or not (NR). We identified eight differentially expressed probe-sets significantly correlated to monocytes (mapping to 6 genes, all down-regulated in ARs versus NRs) at a false discovery rate (FDR) ≤ 15%. None of the genes identified are present in a biomarker panel of acute heart rejection previously published by our group and discovered in the same data***.

Dialysis patients treated with Epoetin α show improved exercise tolerance and physical function: A new analysis of the Canadian Erythropoietin Study Group trial

The risks/benefits of anemia treatment in dialysis patients have been redefined in the US Epoetin α label. This analysis was carried out to determine if increasing hemoglobin (Hb) levels improve exercise tolerance and physical function in anemic dialysis patients. This is a new analysis of the Canadian Erythropoietin Study Group trial, a double-blind, randomized, placebo-controlled trial in dialysis patients. Subjects were 18 to 75 years old, on hemodialysis for >3 months, and had a baseline Hb <9.0 g/dL. Patients with a history of diabetes mellitus, ischemic heart disease, or severe/uncontrolled hypertension were excluded. Patients were randomized to receive Epoetin α to a target Hb of 9.5 to 11.0 g/dL (n=40) or a target of 11.5 to 13.0 g/dL (n=38), or receive placebo (n=40). Results from patients in the Epoetin-α-treated arms were combined for this analysis. Hb level, exercise tolerance (Treadmill Stress Test and 6-Minute Walk Test) and patient-reported physical function measures (Physical Summary domain from the Kidney Disease Questionnaire, and 4 domains from the Sickness Impact Profile) were reported at baseline and months 2, 4, and 6. Differences in measures were statistically significant for exercise tolerance (Treadmill Stress, P=0.0001) and patient-reported physical function (Kidney Disease Questionnaire Physical, P=0.0001; Sickness Impact Profile Physical, P=0.0015) across all time points for Epoetin-α-treated patients compared with placebo. Improvements were seen at 2 months and were maintained through months 4 and 6. Dialysis patients receiving Epoetin α showed improved exercise tolerance and physical function. These findings should be considered as physicians weigh the risks and benefits of treatment.

Proteomic signatures in plasma during early acute renal allograft rejection

Acute graft rejection is an important clinical problem in renal transplantation and an adverse predictor for long term graft survival. Plasma biomarkers may offer an important option for post-transplant monitoring and permit timely and effective therapeutic intervention to minimize graft damage. This case-control discovery study (n = 32) used isobaric tagging for relative and absolute protein quantification (iTRAQ) technology to quantitate plasma protein relative concentrations in precise cohorts of patients with and without biopsy-confirmed acute rejection (BCAR). Plasma samples were depleted of the 14 most abundant plasma proteins to enhance detection sensitivity. A total of 18 plasma proteins that encompassed processes related to inflammation, complement activation, blood coagulation, and wound repair exhibited significantly different relative concentrations between patient cohorts with and without BCAR (p value <0.05). Twelve proteins with a fold-change >or=1.15 were selected for diagnostic purposes: seven were increased (titin, lipopolysaccharide-binding protein, peptidase inhibitor 16, complement factor D, mannose-binding lectin, protein Z-dependent protease and beta(2)-microglobulin) and five were decreased (kininogen-1, afamin, serine protease inhibitor, phosphatidylcholine-sterol acyltransferase, and sex hormone-binding globulin) in patients with BCAR. The first three principal components of these proteins showed clear separation of cohorts with and without BCAR. Performance improved with the inclusion of sequential proteins, reaching a primary asymptote after the first three (titin, kininogen-1, and lipopolysaccharide-binding protein). Longitudinal monitoring over the first 3 months post-transplant based on ratios of these three proteins showed clear discrimination between the two patient cohorts at time of rejection. The score then declined to baseline following treatment and resolution of the rejection episode and remained comparable between cases and controls throughout the period of quiescent follow-up. Results were validated using ELISA where possible, and initial cross-validation estimated a sensitivity of 80% and specificity of 90% for classification of BCAR based on a four-protein ELISA classifier. This study provides evidence that protein concentrations in plasma may provide a relevant measure for the occurrence of BCAR and offers a potential tool for immunologic monitoring.

The CLEAR study: a 5-day, 3-g loading dose of mycophenolate mofetil versus standard 2-g dosing in renal transplantation

BACKGROUND AND OBJECTIVES

Adequate early mycophenolic acid (MPA) exposure is associated with lower rates of acute rejection in renal transplantation. The aim of this randomized controlled trial was to determine if higher initial mycophenolate mofetil (MMF) doses increased the proportion of patients reaching therapeutic MPA levels (30 to 60 mg.h/L) by day 5.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

De novo renal transplant patients were randomized to receive intensified dosing of MMF (1.5 g twice daily on days 1 to 5, then 1.0 g twice daily) or standard dosing (1.0 g twice daily). All recipients received tacrolimus and prednisone. Full MPA areas under the curve (AUCs) were completed on days 3 and 5, whereas a limited sampling strategy was utilized at four subsequent time points.

RESULTS

At day 5, 47.5% of the MMF 3-g arm achieved the MPA therapeutic window versus 54.4% of the MMF 2-g arm. However, MPA AUC levels were significantly higher in the 3-g arm at day 3 and 5. This resulted in a trend for fewer treated acute rejections at 6 months. Significantly more acute rejections (treated, biopsy-proven including and excluding borderline) occurred in patients with MPA AUC levels<30 mg.h/L compared with those >or=30 mg.h/L at day 5. No significant differences were seen in common adverse events.

CONCLUSIONS

A limited intensified dose of MMF increased early MPA exposure and was well tolerated. Further studies are required to determine whether limited intensified MMF dosing can reduce acute rejection.

The costs of change: direct medical costs of solid organ transplantation in British Columbia, Canada, 1995-2003

OBJECTIVES

Solid organ transplantations are among the most expensive treatments yet relatively few investigators have reported well-characterized and reliable information on costs. The objective here was to compare the direct medical costs of kidney, liver, heart, and lung transplantations in British Columbia (BC), Canada.

METHODS

Using data from a province-wide population-based registry, resource utilization data were collated for 1333 patients who underwent solid organ transplantation between 1995 and 2003. Resource categories included hospital stays, physician fees, laboratory and diagnostic testing, and immunosuppressants. Mean costs (2003 $CDN) were derived for the index hospitalization and each of the 2 years after hospital discharge. To enable valid comparisons, the same costing methodology was applied to all four programs.

RESULTS

The mean costs of transplantation varied from $27,695 for kidney recipients to $89,942 for lung recipients, with inpatient hospital stays comprising the largest component. Mean costs for the first and second follow-up years ranged from $27,592 and $11,424 for lung recipients to $21,144 and $8086 for liver recipients. Immunosuppressants accounted for between two-thirds and three-fourths of costs by the second year. Within each program, variations in costs could not be accounted for by demographic factors.

CONCLUSIONS

We observed in BC a threefold variation in mean costs of organ transplantation procedures, with the variations between programs diminishing during follow-up. Policymakers and decision-makers seeking to better understand the deployment of resources for transplantation may focus on clinical factors at the time of hospitalization and factors that influence use and costs of immunosuppressants during the induction and maintenance phases.

Probability, predictors, and prognosis of posttransplantation glomerulonephritis

Glomerulonephritis (GN) is the leading cause of chronic kidney disease among recipients of renal transplants. Because modern immunosuppressive regimens have reduced the incidence of rejection-related graft loss, the probability and clinical significance of posttransplantation GN (PTGN) requires reevaluation. In this Canadian epidemiologic study, we monitored 2026 sequential renal transplant recipients whose original renal disease resulted from biopsy-proven GN (36%), from presumed GN (7.8%), or from disorders other than GN (56%) for 15 yr without loss to follow-up. Kaplan-Meier estimates of PTGN in the whole population were 5.5% at 5 yr, 10.1% at 10 yr, and 15.7% at 15 yr. PTGN was diagnosed in 24.3% of patients whose original renal disease resulted from biopsy-proven GN, compared with 11.8% of those with presumed GN and 10.5% of those with disorders other than GN. Biopsy-proven GN in the native kidney, male gender, younger age, and nonwhite ethnicity predicted PTGN. Current immunosuppressive regimens did not associate with a reduced frequency of PTGN. Patients who developed PTGN had significantly reduced graft survival (10.2 versus 69.7%; P < 0.0001). In summary, in the Canadian population, PTGN is a common and serious complication that causes accelerated graft failure, despite the use of modern immunosuppressive regimens.

The use of consensus guidelines for management of cytomegalovirus infection in renal transplantation

Cytomegalovirus (CMV) infection imposes a significant economic burden on susceptible patients after renal transplantation. Our study was conducted to determine the prediction, probability, consequences, and treatment costs of CMV infection under Canadian consensus guidelines in 270 sequential transplant patients. Transplant patients from donors positive (D(+)) for CMV into recipients negative (R(-)) for CMV received antiviral prophylaxis for 14 weeks and all but donor negative (D(-))/R(-) patients were monitored weekly for the CMVpp65 marker expression. Marker-positive patients and patients with CMV infection or disease received antiviral treatment. Within the first 6 months, 27% of the 270 patients tested had incidences of asymptomatic CMV infection, while 9% had CMV syndrome or disease. Only 1% of patients had infection after 6 months. The CMVpp65 marker levels were significantly greater in patients with syndrome or disease; but post-test probabilities and predictive value of the marker assay were low. Mean direct costs for care were $2256 and ranged from $927 for D(-)/R(-) patients to $7069 in the D(+)/R(-) patients. Extension of antiviral prophylaxis to D(+) or D(+)/R(+) patients significantly increased the estimated mean costs for an absolute reduction to 4% in CMV syndrome or disease. Our studies show that current guidelines for treatment enable effective control of CMV infection; however, alternative strategies have different economic impact.

Biomarkers in transplantation: Prospective, blinded measurement of predictive value for the flow cytometry crossmatch after negative antiglobulin crossmatch in kidney transplantation

This prospective, blinded observational study was conducted to measure the predictive value the of flow cytometric crossmatch for biopsy-proven acute rejection, graft loss, or death following kidney transplantation. Patients were selected for renal transplantation on the basis of a conventional antihuman globulin cytotoxic T-cell crossmatch. Flow crossmatch was performed simultaneously, but the results were not disclosed to the transplant team. A total of 257 kidney transplant recipients were enrolled in the study; 78 patients experienced biopsy-proven rejection in the first post-transplant year, and 41 patients lost their graft or died during the period of follow-up (mean: 2046 days). Kaplan-Meier estimates of rejection, graft loss, or patient death did not differ between subjects with a positive or negative flow crossmatch. Cox analyses showed no influence of the flow crossmatch on the risk of biopsy-proven acute rejection (P = 0.987). The sensitivity and specificity of the flow crossmatch for prediction of biopsy-proven rejection were 0.128 and 0.883, and the positive and negative post-test probabilities were 0.323 and 0.301, respectively. The magnitude of the channel shift did not influence the multivariate Cox regression model. The area under the receiver operating characteristic curve of the flow crossmatch was 0.483 (P = 0.71) and 0.572 (P = 0.38), respectively for the living and cadaver transplant recipients, indicating no discriminative value in this study population. Flow crossmatch appears to have no significant incremental value in predicting biopsy-proven acute rejection, graft loss, or death following kidney transplantation in patients who have a negative antihuman globulin cytotoxic T-cell crossmatch against their donor.

Immune Response Gene Polymorphisms in Renal Transplant Recipients

BACKGROUND

T-cell activation and regulation are under genetic control and vary between individuals. However, the influence of functional immune response gene polymorphisms on transplant outcomes remains controversial.

METHODS

A case-control design compared 100 white renal transplant recipients with or without acute graft rejection during the first year posttransplant and 50 normal controls. The polymorphic frequencies of the T-cell signaling genes CD45, CD40L and CTLA-4, and the cytokine genes TNF-alpha, IFN-gamma, IL-10 and TGF-beta1 were studied. The primary analysis examined rejection risk, and subsidiary analyses graft failure and patient death.

RESULTS

Multivariate analysis showed no significant association between acute rejection and single nucleotide polymorphisms in CTLA-4, TGF-beta1, IL-10 or TNF-alpha genes or dinucleotide repeat polymorphisms in IFN-gamma and CD40L genes. Allele CD40L-147 was associated with reduced graft failure (P=0.004), and TGFb-25pro with increased graft failure (P=0.0007), although the latter showed a bidirectional dose effect. There was no significant association between patient death and any polymorphisms in the genes examined. The variant (G) allele of the CD45 gene was not detected in the study population. Minor differences in carriage rates observed by univariate analysis did not predict graft or patient outcome in multivariate analysis.

CONCLUSION

The primary analysis demonstrated no significant association between the immune response gene polymorphisms examined and acute renal graft rejection in Caucasian patients receiving triple immunosuppression. Subsidiary analyses suggesting an influence of CD40L and TGFbeta1 genes on graft survival require independent confirmation.

Two-Hour Post-Dose Cyclosporine Levels in Renal Transplantation in Argentina: A Cost-Effective Strategy for Reducing Acute Rejection

Monitoring of cyclosporine (microemulsion CsA) at 2 hours post-dose (C2), a measure of absorption and exposure, appears superior to trough (C0) monitoring for prediction of rejection risk. The purpose of this study was to determine whether C2 was cost-effective compared to C0 in Argentina.

METHODS

A predictive decision model was adapted to Argentina to predict costs associated with C0 and C2 measurements in the first year after transplantation. Patients were treated with microemulsion CsA, steroids and azathioprine or MMF. Parameter estimates for the C0 strategy were based on event rates observed in published clinical trials. The model was adapted to Argentinean health system through local protocols and expert opinions; costs were valued in Argentinean pesos and converted to US dollars (1 USD = 2.85 ARS).

RESULTS

Incidence of acute rejection was predicted to be 25.0% at 1-year among patients monitored by C0 and 18.0% by C2. Graft survival was predicted to be 1.4% lower in the C0 group. No important differences were identified in co-morbidity, C0 and C2 monitoring costs, and in ambulatory-based adverse events between C0 and C2 cohorts. The model predicted an average cost per patient of $16,269 for C0 and $16,343 for C2 testing (year 1). Sensitivity analyses indicated that the average daily dose of microemulsion CsA was the most important parameter leading to the incremental cost per patient.

CONCLUSIONS

C2 is expected to provide a potentially important reduction in the risk of acute rejection without increasing the estimated cost of care in the first year post-transplant.

An economic model of 2-hour post-dose ciclosporin monitoring in renal transplantation

BACKGROUND

Monitoring of microemulsion ciclosporin (cyclosporine; Neoral) by 2-hour post-dose drug concentrations (C2) is an accurate measure of ciclosporin absorption efficiency and exposure, and appears superior to trough (C0) monitoring for prediction of rejection risk. A predictive decision model was used to determine if this approach also reduces total treatment costs in the first 12 months after renal transplantation.

METHODS

Parameter estimates for key clinical events were derived from the literature and from prospective pharmacokinetic studies comprising 234 adult HLA-non-identical renal graft recipients at seven Canadian centres. Patients were treated with microemulsion ciclosporin (Neoral), corticosteroids and azathioprine or mycophenolate mofetil. Using the perspective of the Canadian healthcare provider, total treatment costs for the C2 versus the C0 strategy were modelled over 12 months, and then remodelled using conservative estimates to extend the timeframe to 5 years. Health resources were valued in 1999 Canadian dollars.

RESULTS

The incidence of acute rejection was estimated to be 25% at 1 year in patients monitored by C0 and 18% in those monitored by C2. Patient survival was considered to be independent of monitoring strategy, and graft loss was predicted to be 1.4% lower in the C2 group. The studies suggested no important differences in comorbidity and the costs of C0 and C2 monitoring and ambulatory-based adverse events were held equivalent. Using these inputs, the average cost per patient for the first year post-transplant was Can dollars 46,857 for C0 monitoring and Can dollars 45,306 for C2 monitoring, rising to Can dollars 146,879 and Can dollars 142,569 after 5 years. The predicted cost for initial hospitalisation was Can dollars 11,280 for C0 and Can dollars 10,806 for C2 monitoring. The cost of maintenance immunosuppressive drug use, graft loss and dialysis was Can dollars 19,098 in the C0 group and Can dollars 18,612 in the C2 group, while acute rejection treatment costs were Can dollars 2169 and Can dollars 1577, respectively. An additional Can dollars 14,310 was consumed by other events, including repeat hospitalisation, for each group. Sensitivity analysis indicated that the most influential parameters affecting savings due to C2 monitoring were a reduction in the duration of initial and follow-up hospitalisations and reduced risks of acute rejection and subsequent graft loss.

CONCLUSIONS

Compared with traditional trough concentration monitoring, ciclosporin monitoring at 2 hours post-dose produced a predicted saving of Can dollars 1551 during the first year after renal transplant. Although modelling assumptions become more restrictive over time, this projection allows a preliminary assessment of the long-term economic impact of the routine use of C2 monitoring.

New concepts in cyclosporine monitoring

PURPOSE OF REVIEW

Inadequate cyclosporine exposure is a key risk factor for acute rejection, and may contribute to the development of chronic rejection and graft failure. Pre-dose monitoring does not accurately measure drug exposure because of extensive inter- and intra-patient variability in cyclosporine absorption and metabolism. Limited sampling, using individual timed specimens, offers a new, simple and accurate alternative for clinical monitoring of cyclosporine.

RECENT FINDINGS

The area under the first 4 h of the concentration-time curve (AUC ) and the single-point concentration at 2 h post-dose (C2) are key measures of cyclosporine exposure. De novo studies show that achieving an AUC value of more than 4400 microg.h/l or a C2 level of 1500-2000 microg/l during the first 5 days post-transplant minimizes the risk of rejection and improves graft function. Maintenance studies suggest that reducing the C2 level to approximately 800 microg/l after 3-6 months may improve the serum creatinine level, blood pressure, general well-being and reduce adverse effects.

SUMMARY

Single-point C2 monitoring can be implemented quickly and simply with appropriate site and patient training. The timing of phlebotomy is more critical, but immunoassay bias is lower with 2 h post-dose than with trough level measures. Single-point C2 monitoring may be effective in liver and heart replacement, but initial target levels for liver transplantation are lower because cyclosporine is transported directly to the liver via the portal system. C2 monitoring is now being widely adopted as an accurate and practical measure of drug exposure, and can be combined with pharmacodynamic methods to optimize immunosuppression.

Expression of QK/QR/RRRAA or DERAA motifs at the third hypervariable region of HLA-DRB1 and disease severity in rheumatoid arthritis

OBJECTIVE

To examine the relationship between disease severity in patients with confirmed rheumatoid arthritis (RA) and the carriage of alleles expressing the high risk epitope (HRE) QK/QR/RRRAA or the low risk epitope (LRE) DERAA at positions 70-74 of the third hypervariable region of HLA-DRB1.

METHODS

A case-control design to compare allele carriage rates in 204 Caucasian subjects with severe RA and mild RA and healthy controls. Patients had a mean disease duration of 12-18 years and severity of RA was defined using clinical and therapeutic criteria. Molecular typing at the HLA-DRB1 locus was performed using a polymerase chain reaction method.

RESULTS

Eighty-seven percent of patients (52/60) with severe RA had one or more of the alleles bearing the QK/QR/RRRAA motif or HRE, compared with 54% (21/39) with mild RA (OR 5.57, p = 0.0007) and 39% (41/105) of controls (OR 10.15, p < 0.0001). Twenty-five percent of patients (15/60) with severe disease expressed 2 disease associated HRE DRB1 alleles, compared with 13% of patients (5/39) with mild disease (OR 2.3, p = NS) and 5% (5/105) of controls (OR 6.67, p = 0.0003). In contrast, only 5% of patients (3/60) with severe RA expressed one of the LRE alleles that carry the DERAA motif at positions 70-74, compared with 31% of patients (12/39) with mild RA (OR 0.12, p = 0.0013) and 22% of controls (23/105) (OR 0.19, p = 0.0082). No patient or control was homozygous for LRE alleles. Eighty-three percent (50/60) of patients with severe RA expressed the HRE without the LRE, compared with 44% (17/39) of those with mild disease (OR 6.47, p < 0.0001) and 35% (37/105) of controls (OR 9.19, p < 0.0001). In contrast, only one patient (2%) with severe disease expressed the LRE without the HRE, compared with 20% (8/39) of those with mild disease (OR 0.07, p = 0.0047) and 16% (17/105) of controls (OR 0.09, p = 0.009). There was no significant difference between the 3 groups in the frequency of patients who expressed both or neither epitope. Logistic regression showed that age at disease onset (p = 0.0009), duration of disease (p = 0.007), positive rheumatoid factor status (p = 0.003), and presence of the HRE or LRE (p = 0.00005) were significantly associated with the presence of severe disease.

CONCLUSION

HLA-DRB1 alleles appear to confer an important bidirectional influence on the risk of disease severity in RA, with 20-fold difference in OR between those associated with the highest (HLA-DRB1*0401) and lowest (HLA-DRB1*1301/02) risk. The HRE and LRE exhibit diametrically opposed effects, which may be mutually antagonistic. These data support a multistep pathogenesis in which MHC class II genes are one component of a coordinate genetic and environmental interaction leading to immunological injury and joint destruction.

Economic analysis of basiliximab in renal transplantation

BACKGROUND

Basiliximab is a chimeric monoclonal directed against the alpha-chain of the interleukin-2 receptor. International studies have shown that it is highly effective in preventing acute rejection in patients receiving Neoral, and causes no measurable incremental toxicity, but its economic value remains unknown.

METHODS

This study employed an economic model to examine the potential economic benefit of basiliximab. Parameter estimates were derived from a randomized, prospective, double-blind study conducted in 21 renal transplant centers in seven countries in which 380 adult primary allograft recipients were randomized within center to receive basiliximab (20 mg i.v.) on days 0 and 4 or placebo in addition to dual immunosuppression with Neoral and steroids. Key clinical events included primary hospitalization, immunosuppressive drug use, patient and graft survival, graft rejection, treatment of rejection, dialysis, and repeat hospitalization. Health resources were valued via a comprehensive electronic cost dictionary, based upon a detailed economic evaluation of renal transplantation in Canada. Medication costs were calculated from hospital pharmacy acquisition costs; basiliximab was assessed a zero cost.

RESULTS

The average estimated cost per patient for the first year after transplant was $55,393 (Canadian dollars) for placebo and $50,839 for basiliximab, rising to $141,690 and $130,592, respectively, after 5 years. A principal component of the cost in both groups was accrued during the initial transplant hospitalization ($14,663 for standard therapy and $14,099 for basiliximab). An additional $15,852 and $14,130 was attributable to continued care, graft loss, and dialysis in the two groups, whereas follow-up hospitalization consumed an additional $15,538 for placebo and $13,916 for basiliximab. The mean incremental cost of dialysis was $5,397 for placebo compared with $3,821 for basiliximab, whereas incremental costs of graft loss were $2,548 compared with $2,295 in the two treatment groups. The principal costs associated with repeat admission to the transplant ward and the general ward were marginally higher for placebo ($7,395 vs. $6,300 and $5,986 vs. $4,625). Treatment of acute rejection and maintenance immunosuppressive drug use were associated with only limited savings as a result of basiliximab (savings <$200 each). Sensitivity analysis indicated that the most influential parameters affecting the savings as a result of using basiliximab were a reduction in the duration of initial and repeat hospitalization followed by the reduced risks of acute rejection and graft loss.

CONCLUSIONS

Before accounting for the cost of the therapy itself, basiliximab produces an estimated economic saving of $4,554 during the first year after transplant, of which $3,344 is attributable to the reduced costs of graft dysfunction, including graft loss and dialysis ($1,722) and follow-up hospitalizations ($1,622). When marketed, basiliximab is expected to cost approximately $3,000 per course (two doses of 20 mg), resulting in a net first-year saving of $1,554. Under these circumstances, basiliximab can be considered a dominant therapy in renal transplantation.

Association between dinucleotide repeat in non-coding region of interferon-gamma gene and susceptibility to, and severity of, rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis ranges from a mild, non-deforming arthropathy with little long-term disability to severe, incapacitating, deforming arthritis which may be refractory to conventional disease-modifying agents. Epidemiological studies show an important genetic influence in rheumatoid arthritis, and MHC region genes and cytokine genes within and outside this region have been considered as candidates. We did a case-control study to test whether polymorphisms in the interferon-gamma gene are associated with severity of rheumatoid arthritis.

METHODS

Interferon gamma dinucleotide repeat polymorphisms were examined with quantitative genescan technology, and HLA-DR alleles were identified by PCR and restriction-fragment-length polymorphism analysis. We studied 60 patients with severe rheumatoid arthritis, 39 with mild disease, and 65 normal controls.

FINDINGS

Susceptibility to, and severity of, rheumatoid arthritis were related to a microsatellite polymorphism within the first intron of the interferon-gamma gene. A 126 bp allele was seen in 44 (73%) of 60 patients with severe rheumatoid arthritis, compared with eight (21%) of 39 with mild disease (odds ratio 10.66 [95% CI 4.1-24.9]), and with eight (12%) of 65 normal controls (19.59 [7.7-49.9]). Conversely, a 122 bp allele at the same locus was found in four (7%) patients with severe disease compared with 25 (64%) of those with mild disease (0.04 [0.01-0.1]) and with 52 (80%) of controls (0.018 [0.005-0.06]).

INTERPRETATION

This association may be valuable for understanding the mechanism of disease progression, for predicting the course of the disease, and for guiding therapy.

Development of a biologically distinct EBV-related lymphoproliferative disorder following autologous bone marrow transplantation for an EBV-negative post-renal allograft Burkitt's lymphoma

Post-transplant lymphoproliferative disorder (PTLD) is a known complication of both solid organ transplantation and allogeneic bone marrow transplantation (BMT) but is rarely seen following autologous BMT. We report the case of a 45 year-old female who developed Burkitt's lymphoma eight years after a renal allograft. This PTLD was found to have lambda light chain restriction, contained del(8)(q24) and add(14)(q32), and was negative for EBV on immunohistochemical and DNA-based PCR analyses. Immunoglobulin heavy chain (IgH) PCR studies revealed a prominent clonal rearrangement. She responded to intravenous cyclophosphamide and proceeded to high-dose chemoradiotherapy and mafosfamide-purged autologous BMT. Thirty-nine days post-BMT she presented with cough and fever and developed hepatic dysfunction; abnormal lymphoplasmacytoid cells were noted in the peripheral blood. Investigations revealed kappa light chain restriction, an oligoclonal IgH rearrangement, a normal karyotype and PCR studies for EBV were positive, consistent with a clinically and biologically distinct PTLD. She initially improved following discontinuation of immunosuppression, but then deteriorated abruptly and died 58 days post-BMT. It is likely that the two separate episodes of PTLD in this patient, one of which was atypical, arose as a result of both the chronic use of cyclosporine and the impairment of cell-mediated immunity associated with autologous BMT. The sequence of events in this patient should contribute to a better understanding of late-onset, EBV-negative PTLD.

Effect of gastrointestinal inflammation and age on the pharmacokinetics of oral microemulsion cyclosporin A in the first month after bone marrow transplantation

Cyclosporin A (CsA) absorption is highly variable in BMT patients. Neoral, a new microemulsion formulation of CsA, permits increased absorption with less variable pharmacokinetic parameters in non-BMT patients. We evaluated the pharmacokinetics of CsA after BMT in patients received microemulsion CsA. Two oral doses of 3mg/kg were given 48 h apart between 14 and 28 days after allogeneic BMT in 20 adults, and one dose in seven children, while subjects were receiving a continuous i.v. infusion of CsA. Whole blood samples were taken throughout the dosing interval to calculate the incremental CsA exposure using maximum concentration (Cmax), time to Cmax (tmax), concentration at 12 h after the dose (C12), the area under the concentration-time curve (AUC), and to establish inter- and intra-patient pharmacokinetic variability. Drug exposure was substantially lower in children than adults, with an AUC of 861+/-805 vs 2629+/-1487 micromg x h/l (P = 0.001), respectively, and absorption was delayed and diminished in both groups by comparison with solid organ recipients. Intra-patient variability in adults for AUC was high at 0.59+/-0.34, while inter-patient variability, measured as the coefficient of variation (c.v.), was 0.55 for the first and 0.54 for the second dose. In adults, gastrointestinal (GI) inflammation due to either mucositis or GVHD resulted in a higher AUC of 3077+/-1551 microg x h/l compared to 1795+/-973 microg x h/l (P = 0.02), and a similar trend was observed in children. AUC seemed little affected by the CsA formulation (liquid or capsule), or co-administration with liquids or food. Trough (12 h) CsA levels correlated poorly with incremental AUC. Sparse sample modeling of the AUC using two-point predictors taken at 2.5 and 5 h after dosing accurately approximated AUC in adults (r2 = 0.94), while 1.5 and 5 h was superior in children (r2 = 0.98). These data suggest that 12 h postdose trough measurements of CsA may not be the most appropriate way to evaluate CsA blood concentrations in order to establish therapeutic efficacy in BMT patients. Based on this study, the dose of microemulsion CsA should be adjusted based on recipient age, and the presence of GI inflammation secondary to mucositis or GVHD. These data would suggest that sparse sampling at time points earlier than the trough more accurately reflects the AUC and may correlate more closely with therapeutic efficacy early post-BMT.

Distribution of DRB1 and DQB1 HLA class II alleles in occupational asthma due to western red cedar

Occupational asthma caused by western red cedar is a common problem in sawmill industries. The objective of this study was to examine a possible association of human leukocyte antigen (HLA) class II genetic markers with susceptibility or resistance to western red cedar induced asthma. The distribution of DRB1 and DQB1 HLA class II alleles and DRB1-DQB1 haplotypes was studied in 56 Caucasian patients with proven red cedar asthma and 63 healthy Caucasian control subjects exposed to red cedar dust. DRB1 and DQB1 high resolution typing was performed by the polymerase chain reaction-based method. Patients with red cedar asthma had a higher frequency of HLA DQB1*0603 and DQB1*0302 alleles compared to a group of healthy exposed control subjects and a reduced frequency of DQB1*0501 allele. The frequency of the DRB1*0401-DQB1* 0302 haplotype was increased and the DRB1*0101-DQB1*0501 haplotype was reduced. These findings suggest that genetic factors such as human leukocyte antigen class II antigens may be associated with susceptibility or resistance to development of red cedar asthma.

The role of inflammatory mediators in the mechanism of the host immune response induced by ischemia-reperfusion injury

Our previous study suggested that inflammatory mediators released due to IRI lead to host's immune response by upregulating MHC II in the host's peripheral T lymphocytes. This study hypothesized the role of platelet-activating factor (PAF) in the mechanism of induced MHC II upregulation due to IRI on peripheral T lymphocytes. The objectives of this study were to investigate the role of PAF in the induction of host immune reactivity and the protective effect of PAF-antagonist TCV-309 in combination with prostaglandin E1 (PGE1) against the host's immune response caused by IRI. Thirty female domestic swine were divided into three groups. Group A (6 donors, 6 recipients) had no pharmacological intervention. Group B (6 donors, 6 recipients) was the experimental group treated with TCV-309 + PGE1. Group C underwent sham operation. The ex vivo preservation time for groups A and B was 4 hr at 4 degrees C. To detect the changes in MHC II expression on T cells due to IRI, blood samples were collected before reperfusion (baseline level), 1, 2, and 3 days post-reperfusion. Two-colour flow cytometry analysis (FACS) was used to study MHC II-DR-beta expression in peripheral T lymphocytes. Swine anti-MHC II and anti-CD3 antibodies were used for this purpose. The FACS analyses demonstrated that in group A, there was a significant increase (p < 0.05) in MHC II intensity on peripheral T lymphocytes on day 2 post-reperfusion. By the third day post-reperfusion, MHC intensity had a tendency to decrease but did not reached the baseline level. In group B and C, however, there was no significant change in the level of MHC II in T lymphocytes at any of the post-reperfusion times. In group A, the number of CD3+MHC+ T lymphocytes significantly decreased (p < 0.05) by one day post-reperfusion and remained at this level until the third day post-reperfusion. In groups B and C, no significant change in the number of CD3+MHC+ T cells was observed. The results of this study suggested that the release of inflammatory mediators (e.g. PAF) due to IRI played a role in the mechanism of IRI-induced host's immune response. The results also suggested that the combination of TCV-309 + PGE1 could reduce this immune response.