Calprotectin: a novel noninvasive marker for intestinal allograft monitoring

Intestinal Transplant Immunology and Intestinal Graft Rejection: From Basic Mechanisms to Potential Biomarkers

Intestinal transplantation (ITx) remains a lifesaving option for patients suffering from irreversible intestinal failure and complications from total parenteral nutrition. Since its inception, it became obvious that intestinal grafts are highly immunogenic, due to their high lymphoid load, the abundance in epithelial cells and constant exposure to external antigens and microbiota. This combination of factors and several redundant effector pathways makes ITx immunobiology unique. To this complex immunologic situation, which leads to the highest rate of rejection among solid organs (>40%), there is added the lack of reliable non-invasive biomarkers, which would allow for frequent, convenient and reliable rejection surveillance. Numerous assays, of which several were previously used in inflammatory bowel disease, have been tested after ITx, but none have shown sufficient sensibility and/or specificity to be used alone for diagnosing acute rejection. Herein, we review and integrate the mechanistic aspects of graft rejection with the current knowledge of ITx immunobiology and summarize the quest for a noninvasive biomarker of rejection.

REG3α is a novel biomarker that potentially correlates with acute allograft rejection after intestinal transplantation

Monitoring of intestinal allograft function remains a challenge. While frequent endoscopies and biopsies are the gold standard, no single biomarker exists to screen for intestinal transplant rejection. The novel REG3α, an antimicrobial peptide secreted by intestinal enterocytes and Paneth cells, has been associated with inflammatory bowel disease as well as intestinal graft versus host disease. Our aim was to identify and describe a role of REG3α in monitoring or predicting acute allograft rejection after intestinal transplantation (ITx). Since 2019, we have incorporated REG3α into the standard monitoring of patients after ITx. We conducted a retrospective analysis of a prospectively maintained IRB-approved database and present, herein, the results of 2 adults with irreversible intestinal failure who underwent isolated ITx under this monitoring protocol. Increases in REG3α corresponded with acute allograft rejection in both cases and preceded acute allograft rejection by 1 week in one of the cases. We describe REG3α as a non-invasive marker of acute allograft rejection after adult isolated ITx which not only corresponded with acute allograft rejection but also preceded histopathological changes by 1 week.

Grant monitoring after intestinal transplantation

PURPOSE OF REVIEW

The current review aims to describe in detail the most common practices utilized to monitor graft function in intestinal transplant (ITx) recipients. In addition, to discussing the role of endoscopy and stool studies it will examine the use of other potential biomarkers which have been utilized. Data will be discussed from contemporary publications in the field, the Intestinal Transplant Registry as well as detailed data from a large, ITx single-center.

RECENT FINDINGS

Significant improvements have been made in early outcomes following ITx, yet long-term survival remains challenged by infection and rejection, both of which can present with diarrhea. While endoscopy and stool studies are the gold-standard for graft monitoring, calprotectin, citrulline, measurements of immunoreactivity and donor-specific antibodies have been investigated in the field and are herein reviewed.

SUMMARY

Despite a number of tests which are currently available for monitoring ITx recipients, a strong need exists for improved noninvasive, timely and accurate biomarkers to help improve ITx graft and patient survival.

Graft assessment for acute rejection after intestinal transplantation: current status and future perspective

Intestinal transplantation has since its inception evolved as a lifesaving treatment option for patients with irreversible intestinal failure who can no longer be sustained on parenteral nutrition. Improvement in short-term survival after transplantation has also justified the expansion of treatment indications. Unfortunately, success is somewhat limited by a plateau observed in long-term survival. The reason for this sub-optimal long-term result experienced in this cohort may in part be attributed to the intestinal graft with the lymphoid content it carries inflicting the host with multiple complications where acute cellular rejection is one of the most common causes for graft loss. Graft monitoring is for this reason of paramount importance and detection of rejection at an early stage essential to enable early instigation of treatment and successful reversal of the pathology. Due to the challenges in diagnosing acute rejection with a noninvasive marker we are still limited to a surveillance protocol using endoscopy and biopsies for the diagnosis of rejection. The purpose of our paper is to review the adequacy of different methods in monitoring the graft for acute rejection using biomarkers, endoscopy and imaging. In conclusion, the evidence base continues to support the use of histology for the diagnosis of acute rejection. The role of biomarkers are still debatable, although markers such as calprotectin might be beneficial in excluding an ongoing process.

Faecal Calprotectin

Calprotectin is a calcium- and zinc-binding protein of the S-100 protein family which is mainly found within neutrophils and throughout the human body. The presence of calprotectin in faeces is a consequence of neutrophil migration into the gastrointestinal tissue due to an inflammatory process. Faecal calprotectin concentrations demonstrate good correlation with intestinal inflammation and faecal calprotectin is used as a biomarker in gastrointestinal disorders. Faecal calprotectin is a very sensitive marker for inflammation in the gastrointestinal tract, and useful for the differentiation of inflammatory bowel disease (IBD) from irritable bowel syndrome (IBS). Faecal calprotectin is used for the diagnosis, monitoring disease activity, treatment guidance and prediction of disease relapse and post-operative recurrence in IBD. There may also potentially be a role for faecal calprotectin in the management of infectious gastroenteritis, acute appendicitis, peptic ulcer disease, cystic fibrosis, coeliac disease, transplant rejection and graft versus host disease. Further studies are needed to confirm its utility in these conditions. Analysis of faecal calprotectin consists of an extraction step followed by quantification by immunoassay. Over the past few decades, several assays and extraction devices including point-of-care methods have been introduced by manufacturers. The manufacturer-quoted cut-off values for different faecal calprotectin assays are generally similar. However, the sensitivities and specificities at a given cut-off, and therefore the optimum cut-off values, are different between assays. A reference standard for calprotectin is lacking. Therefore, assay standardisation is required for more accurate and traceable test results for faecal calprotectin.

Gut microbiota and its implications in small bowel transplantation

The gut microbiota is mainly composed of a diverse population of commensal bacterial species and plays a pivotal role in the maintenance of intestinal homeostasis, immune modulation and metabolism. The influence of the gut microbiota on solid organ transplantation has recently been recognized. In fact, several studies indicated that acute and chronic allograft rejection in small bowel transplantation (SBT) is closely associated with the alterations in microbial patterns in the gut. In this review, we focused on the recent findings regarding alterations in the microbiota following SBTand the potential roles of these alterations in the development of acute and chronic allograft rejection. We also reviewed important advances with respect to the interplays between the microbiota and host immune systems in SBT. Furthermore, we explored the potential of the gut microbiota as a microbial marker and/or therapeutic target for the predication and intervention of allograft rejection and chronic dysfunction. Given that current research on the gut microbiota has become increasingly sophisticated and comprehensive, large cohort studies employing metagenomic analysis and multivariate linkage should be designed for the characterization of host-microbe interaction and causality between microbiota alterations and clinical outcomes in SBT. The findings are expected to provide valuable insights into the role of gut microbiota in the development of allograft rejection and other transplant-related complications and introduce novel therapeutic targets and treatment approaches in clinical practice.

The endoscopic surveillance of the transplanted small intestine: a single center experience and a proposal for a grading score

OBJECTIVE

Microscopic examination of endoscopic biopsies forms the basis of acute cellular rejection (ACR) monitoring after intestinal transplantation (ITx). The endoscopy findings during acute rejection (AR) are known but a grading system for its severity is lacking. We designed and implemented a five-stage grading score based on acknowledged endoscopic features of AR, to allow a faster preliminary diagnosis of AR and intra- and interpatient comparisons.

METHODS

Two investigators reviewed and graded the endoscopy reports after 28 ITx using a novel score and correlated the results with pathology findings.

RESULTS

We reviewed 512 ileoscopies: 370 examinations (74%) were normal (G0), 59 had mild alterations (erythema, edematous villi-G1) and 36 showed moderate changes (erosions, blunted villi-G2); 17 ileoscopies revealed advanced changes (ulcerations, villus loss-G3). In 18 endoscopies the changes were severe (mucosal loss-G4). Inter-reviewer agreement was very good (kappa = 0.81). Biopsies from 86 endoscopy sessions (17%) indicated ACR with 63 cases having moderate or severe ACR. For mild ACR the sensitivity of the score was 29% and the specificity was 86% whereas the positive (PPV) and negative predictive values (NPVs) were 14% and 93% respectively. During advanced ACR the sensitivity and specificity were 92% and 86%, respectively whereas the PPV and NPV were 49% and 98% respectively.

CONCLUSIONS

Endoscopy alone has a limited ability to reliably diagnose intestinal ACR. We suggest a novel grading score summarizing ACR findings and allowing comparisons between intestinal graft endoscopies.

Advances in small bowel transplantation

Small bowel transplantation is a life-saving surgery for patients with intestinal failure. The biggest problem in intestinal transplantation is graft rejection. Graft rejection is the main reason for morbidity and mortality. Rejection has a negative effect on the survival of the graft. While 50%-75% of small bowel transplantation patients experience acute rejection, chronic rejection occurs in approximately 15% of patients. Immune monitoring is crucial after small bowel transplantation. Unlike other types of transplantation, there are no non-invasive or reliable markers to predict rejection in small bowel transplantation. The diagnosis of AR is confirmed by clinical symptoms, endoscopic appearance, and pathological specimens taken by endoscopy. Thus, histopathological examinations obtained by protocol biopsies remain as the gold standard for intestinal graft monitoring; however, biopsies have some complications, especially in small grafts. In addition to the high complication rate, biopsies are non-diagnostic; thus, multiple biopsies should be performed to exclude rejection. Therefore, auxiliary assays, such as measurements of citrulline and calprotectin in the blood, cytofluorographic examination of peripheral blood immune cells, cytokine profiling, and distinct gene-set-change measurements, are increasingly being used in small bowel transplantation. Developments in the understanding of genes seem to be promising that limited gene sets, taken from blood or from intestinal biopsies, will enhance pathological diagnosis. Bone marrow mesenchymal stem cell transplantation with SBT and tissue engineering are also promising procedures.

Current status of intestinal and multivisceral transplantation

Clinical-nutritional autonomy is the ultimate goal of patients with intestinal failure (IF). Traditionally, patients with IF have been relegated to lifelong parenteral nutrition (PN) once surgical and medical rehabilitation attempts at intestinal adaptation have failed. Over the past two decades, however, outcome improvements in intestinal transplantation have added another dimension to the therapeutic armamentarium in the field of gut rehabilitation. This has become possible through relentless efforts in the standardization of surgical techniques, advancements in immunosuppressive therapies and induction protocols and improvement in postoperative patient care. Four types of intestinal transplants include isolated small bowel transplant, liver-small bowel transplant, multivisceral transplant and modified multivisceral transplant. Current guidelines restrict intestinal transplantation to patients who have had significant complications from PN including liver failure and repeated infections. From an experimental stage to the currently established therapeutic modality for patients with advanced IF, outcome improvements have also been possible due to the introduction of tacrolimus in the early 1990s. Studies have shown that intestinal transplant is cost-effective within 1-3 years of graft survival compared with PN. Improved survival and quality of life as well as resumption of an oral diet should enable intestinal transplantation to be an important option for patients with IF in addition to continued rehabilitation. Future research should focus on detecting biomarkers of early rejection, enhanced immunosuppression protocols, improved postoperative care and early referral to transplant centers.

Intestinal transplantation

Intestinal transplantation has now emerged as a lifesaving therapeutic option and standard of care for patients with irreversible intestinal failure. Improvement in survival over the years has justified expansion of the indications for intestinal transplantation beyond the original indications approved by Center for Medicare and Medicaid services. Management of patients with intestinal failure is complex and requires a multidisciplinary approach to accurately select candidates who would benefit from rehabilitation versus transplantation. Significant strides have been made in patient and graft survival with several advancements in the perioperative management through timely referral, improved patient selection, refinement in the surgical techniques and better understanding of the immunopathology of intestinal transplantation. The therapeutic efficacy of the procedure is well evident from continuous improvements in functional status, quality of life and cost-effectiveness of the procedure. This current review summarizes various aspects including current practices and evidence based recommendations of intestinal transplantation.

The Place of Calprotectin, Lactoferrin, and High-Mobility Group Box 1 Protein on Diagnosis of Acute Appendicitis with Children

The purpose of this study is to investigate the role of serum calprotectin (CP), lactoferrin (LF), and high-mobility group protein B1 (HMGB-1) levels and fecal CP and LF levels in differential diagnosis of acute uncomplicated appendicitis from other causes of abdominal pain and further from complicated appendicitis. Totally, 120 children were included grouped into 4 as: healthy controls, patients with right lower quadrant pain with other than surgical causes, patients with uncomplicated appendicitis, and patients with complicated appendicitis. Serum CP, LF, HMGB-1, C-reactive protein (CRP) levels, and white blood cell (WBC) count were studied as well as the fecal CP and LF levels. There was a statistically significant difference between control group and both uncomplicated and complicated acute appendicitis groups, regarding all parameters. In diagnosis of complicated acute appendicitis, area under curve (AUC) for fecal LF, serum CP, and serum HMGB-1 were determined as 1.00 and the cutoff level was determined as 25 μg/g feces, 670 ng/mL, and 30 ng/mL, respectively. In differential diagnosis of uncomplicated and complicated AA, the most accurate parameter was fecal LF with an AUC of 0.977. At a 60 μg/g cutoff value for this variable, sensitivity, specificity, and accuracy were 96.7, 93.3, and 95.0 %, respectively. In conclusion, HMGB-1, calprotectin, and lactoferrin constitute novel markers in diagnosis of AA. Moreover, their levels may be helpful for the clinicians to judge about the severity of the condition. Larger studies are warranted to determine the diagnostic potential of HMGB-1, LF, and CP in AA diagnosis.

The concept of gut rehabilitation and the future of visceral transplantation

In the 1990s, the introduction of visceral transplantation fuelled interest in other innovative therapeutic modalities for gut rehabilitation. Ethanol lock and omega-3 lipid formulations were introduced to reduce the risks associated with total parenteral nutrition (TPN). Autologous surgical reconstruction and bowel lengthening have been increasingly utilized for patients with complex abdominal pathology and short-bowel syndrome. Glucagon-like peptide 2 analogue, along with growth hormone, are available to enhance gut adaptation and achieve nutritional autonomy. Intestinal transplantation continues to be limited to a rescue therapy for patients with TPN failure. Nonetheless, survival outcomes have substantially improved with advances in surgical techniques, immunosuppressive strategies and postoperative management. Furthermore, both nutritional autonomy and quality of life can be restored for more than two decades in most survivors, with social support and inclusion of the liver being favourable predictors of long-term outcome. One of the current challenges is the discovery of biomarkers to diagnose early rejection and further improve liver-free allograft survival. Currently, chronic rejection with persistence of preformed and development of de novo donor-specific antibodies is a major barrier to long-term graft function; this issue might be overcome with innovative immunological and tolerogenic strategies. This Review discusses advances in the field of gut rehabilitation, including intestinal transplantation, and highlights future challenges. With the growing interest in individualized medicine and the value of health care, a novel management algorithm is proposed to optimize patient care through an integrated multidisciplinary team approach.

The current state of intestine transplantation: indications, techniques, outcomes and challenges

Intestine transplantation is the least common form of organ transplantation in the United States and often deemed one of the most difficult. Patient and graft survival have historically trailed well behind other organ transplants. Over the past 5-10 years registry reports and single center series have demonstrated improvements to patient survival after intestinal transplantation that now match patient survival for those without life-threatening complications on parenteral nutrition. For various reasons including improvements in medical care of patients with intestinal failure and difficulty accessing transplant care, the actual number of intestine transplants has declined by 25% over the past 6 years. In light of the small numbers of intestine transplants, many physicians and the lay public are often unaware that this is a therapeutic option. The aim of this review is to describe the current indications, outcomes and advances in the field of intestine transplantation and to explore concerns over future access to this important and life-saving therapy.

Multivisceral transplantation: where do we stand?

Intestinal transplantation is the definitive therapy for patients with irreversible intestinal failure and can be combined with transplantation of other abdominal organs, such as stomach, spleen, and pancreas with or without liver. There is an increasing trend in the volume of intestinal and multivisceral transplantation in the past few decades and there is also increasing trend in patient and graft survival primarily due to improved patient selection, advances in immunosuppression, and improved perioperative management. This review summarizes the various key elements in patient selection, types of grafts, and updates in the perioperative management involved in multivisceral transplantation.

Frequency of abnormal fecal biomarkers in irritable bowel syndrome

PRIMARY STUDY OBJECTIVE

Determine the frequency of abnormal fecal biomarker test results in patients with 13 irritable bowel syndrome (IBS)-related ICD-9 (International Statistical Classification of Diseases and Related Health Problems) codes.

STUDY DESIGN

Quantitative review of de-identified records from patients in whom IBS was a possible diagnosis.

METHODS

Records were selected for analysis if they included any of 13 IBS-related diagnostic codes and laboratory test results of fecal testing for all biomarkers of interest. Data collection was restricted to one 12-month period. Frequency distributions were calculated to identify rates of abnormal results for each biomarker within the total number of tests conducted in the eligible population.

RESULTS

Two thousand, two hundred fifty-six records were included in the study, of which 1867 (82.8%) included at least one abnormal value. Quantitative stool culture for beneficial bacteria (Lactobacillus and Bifidobacterium) indicated low growth suggestive of intestinal dysbiosis in 73.1% of records, followed by abnormally elevated eosinophil protein X (suggestive of food allergy) in 14.3%, elevated calprotectin (suggestive of inflammation) in 12.1%, detection of parasites in 7.5%, and low pancreatic elastase (suggestive of exocrine pancreatic insufficiency) in 7.1%.

CONCLUSIONS

Abnormal fecal biomarkers are prevalent in patients with diagnoses suggestive of IBS. Abnormal fecal biomarker testing, if confirmed in additional independent clinical trials, could substantially reduce the economic costs associated with diagnosis and management of IBS.

The use of fecal calprotectin as a biomarker in gastrointestinal disease

Abdominal discomfort including pain, bloating and diarrhea is common. It often arises from functional gastrointestinal disorders but may indicate inflammatory bowel disease (IBD). Calprotectin is an abundant neutrophil protein that is released during inflammation. When measured in feces, it can be used to differentiate between non-organic and inflammatory intestinal disorders, especially to identify IBD. Fecal calprotectin might also be useful to monitor patients with IBD under treatment and to predict the risk of recurrence of active disease prior to clinical relapse. The use of fecal calprotectin has been investigated in a number of gastrointestinal disorders other than IBD, for example, as screening test for colorectal cancer but the available data are limited. This article summarizes the current literature on the use of fecal calprotectin in clinical practice.

Utility of an immune cell function assay to differentiate rejection from infectious enteritis in pediatric intestinal transplant recipients

The Cylex Immune Cell Function Assay measures cell-mediated immunity based on ATP production by stimulated CD4 + cells. We hypothesized that this test would discriminate acute cellular rejection (ACR) from infectious enteritis (IE) in pediatric intestinal transplant (ITx) recipients with allograft dysfunction. We retrospectively analyzed 224 Cylex assays drawn in 47 children who received 53 ITx. Samples were classified as stable, ACR, or IE based on clinical status. ATP values were analyzed using Kruskal-Wallis and t-tests. Overall, there was a statistically significant difference in ATP values based on clinical status (p = 0.03); however, overlap was observed between groups. The median ATP value during ACR was significantly greater than during stable periods (p = 0.02). No difference was seen in IE vs. stability (p = 0.8). The difference in median ATP value in ACR vs. IE approached significance (p = 0.1). Relative to previous levels, ACR episodes were associated with a median ATP increase of 101 ng/mL and IE episodes with a decrease of 3 ng/mL (p = 0.3). These data indicate that the Cylex assay has limited utility in differentiating ACR from IE, largely due to interpatient variability. Following longitudinal intrapatient trends may be an adjunctive tool in discriminating IE from ACR and guiding immunosuppression adjustments in select patients.

Clinical practice guidelines--Nursing management for pediatric patients with small bowel or multivisceral transplant

PURPOSE

Small bowel or multivisceral transplant is a relatively new treatment for irreversible intestinal damage, and no published practice guidelines exist. The purpose of this article is to report evidence regarding the best plan of care to achieve adequate nutrition and appropriate development for children.

DESIGN AND METHODS

An integrative review was conducted with 54 articles related to management of this transplant population. A nine-member nursing team integrated the findings.

PRACTICE IMPLICATIONS

This resulting guideline represents the best research and best practices on which to base staff education and competency validations to manage this medically fragile patient population.

Diagnostics and prognostics of inflammatory bowel disease with fecal neutrophil-derived biomarkers calprotectin and lactoferrin

Crohn's disease (CD), ulcerative colitis (UC), and colitis unclassified, collectively defined as inflammatory bowel disease (IBD), are the consequence of chronic inflammatory reactions in the gastrointestinal tissue. Endoscopy with biopsies is the mainstay in the diagnosis of this inflammation and is also important in the assessment of disease activity and monitoring of treatment. Furthermore, mucosal healing is increasingly becoming a therapeutic target for treatment of IBD and the golden standard of assessing it is endoscopy. However, due to the costs, invasiveness, and to limited endoscopic capacity, the need is strong for reliable surrogate markers of intestinal inflammation. Bowel contents, being in close contact with intestinal mucosa, can take up molecules that are measurable from stool samples and thus can serve as markers of inflammation. The fecal neutrophil-derived biomarkers, especially calprotectin and lactoferrin, have several features of an ideal test for detecting intestinal inflammation: they are noninvasive, simple, and low in cost. The utility of these biomarkers in distinguishing IBD from noninflammatory conditions such as irritable bowel syndrome is well documented. They correlate closely with endoscopic activity both in CD and UC. They allow serial monitoring of disease activity and of treatment success, and can even serve in predicting clinical relapse in unsymptomatic patients or sustained remission after induction with TNF-α-blocking agents. In this review an overview will be given to the role of fecal neutrophil-derived biomarkers calprotectin and lactoferrin in diagnostics and prognostics of IBD.

Citrulline level is a potent indicator of acute rejection in the long term following pediatric intestinal/multivisceral transplantation

Citrulline has been advocated as a marker for acute cellular rejection (ACR) in intestinal transplantation; however, its significance as a forewarning in the long-term follow-up remains unknown. This study aimed to investigate the association between citrulline levels and the grading of ACR to establish a cutoff point that accurately predicts ACR beyond 3 months posttransplant in the pediatric patient population. During a 16-year period (1995-2011), a total of 13 499 citrulline samples were prospectively collected from 111 consecutive pediatric intestinal/multivisceral transplant recipients: 2155 were obtained concurrently with intestinal biopsies. There were 185 ACR episodes observed among 74/111 (67%) patients (median follow-up: 4.4 years). Citrulline levels were inversely proportional to the severity of ACR. Negative predictive values for any type of ACR (cutoff, 20 μmol/L) and moderate/severe ACR (cutoff, 10 μmol/L) were 95% and 99%, respectively. When patients were divided according to graft size, diagnostic accuracy using the same cutoff was identical. Similarly, subgroup analysis by the timing of citrulline measurement prior to biopsy varying from 1 to 7 days demonstrated comparable results. Citrulline is a potent indicator as a danger signal for ACR, being an exclusionary, noninvasive biomarker with excellent negative predictive values in the long term after pediatric intestinal/multivisceral transplant.

Increased monocyte expression of sialoadhesin during acute cellular rejection and other enteritides after intestine transplantation in children

BACKGROUND

Sialoadhesin (CD169) facilitates T-cell priming when overexpressed on inflammatory monocytes. Monocyte-derived macrophages prime acute cellular rejection after intestine transplantation (ITx).The purpose of this study was to evaluate whether CD169-expressing activated monocytes associate with or predict ITx rejection.

METHODS

After informed consent (ClinicalTrials.gov NCT No. 01163578), activated CD169+CD14+monocytes were measured by flow cytometry in five normal healthy adult volunteers (group A), and 56 children with ITx sampled cross-sectionally (group B, 26), longitudinally (group C, 18), or during infection/inflammation without rejection (group D: acute enteritis, 9; Helicobacter pylori, 1; Streptococcal pharyngitis 1; and posttransplant lymphoma, 1). Activated monocytes were tested for correlations with donor-specific alloreactivity in simultaneous mixed lymphocyte co-cultures.

RESULTS

Median age was 3 years (range 0.5-21 yr), and distribution of ITx-alone:combined liver-ITx was 25:31. Higher frequencies (%) of activated monocytes were seen during rejection in group B and infection/inflammation without rejection in group D (58 ± 28 and 73 ± 26), compared with nonrejectors or normal controls (10.6 ± 7.9 or 10.7 ± 6.5, P=0.001). In longitudinal monitoring, rejectors also showed higher activated monocyte frequencies (%) before ITx (64 ± 26 vs. 13.4 ± 8.6, P=0.0007) and during acute cellular rejection (55 ± 28 vs. 22.4 ± 15, P=0.006) when compared with nonrejectors. Activated monocytes correlated significantly with allospecific CD154+T-cytotoxic memory cells (Spearman r=0.688, P=7.1E-05) and CD154+B cells (r=0.518, P=0.005) in ITx recipients without inflammation/infection but not in group D.

CONCLUSIONS

Monocytes overexpress sialoadhesin nonspecifically during ITx rejection and systemic or enteritic inflammatory states. When combined with allospecific T and B cells, this information may differentiate between rejection and other enteritides.

Characterization of the ileal microbiota in rejecting and nonrejecting recipients of small bowel transplants

Small bowel transplantation can be a life-preserving procedure for patients with irreversible intestinal failure. Allograft rejection remains a major source of morbidity and mortality and its accurate diagnosis and treatment are critical. In this study, we used pyrosequencing of 16S ribosomal RNA gene tags to compare the composition of the ileal microbiota present during nonrejection, prerejection and active rejection states in small bowel transplant patients. During episodes of rejection, the proportions of phylum Firmicutes (p < 0.001) and the order Lactobacillales (p < 0.01) were significantly decreased, while those of the phylum Proteobacteria, especially the family Enterobacteriaceae, were significantly increased (p < 0.005). Receiver-operating characteristic analysis revealed that relative proportions of several bacterial taxa in ileal effluents and especially Firmicutes, could be used to discriminate between nonrejection and active rejection. In conclusion, the findings obtained during this study suggest that small bowel transplant rejection is associated with changes in the microbial populations in ileal effluents and support microbiota profiling as a potential diagnostic biomarker of rejection. Future studies should investigate if the dysbiosis that we observed is a cause or a consequence of the rejection process.

Association between donor-specific antibodies and acute rejection and resolution in small bowel and multivisceral transplantation

BACKGROUND

Donor-specific antibodies (DSA) are associated with acute kidney graft rejection, but their role in small bowel/multivisceral allograft remains unclear. We carried out a prospective study to understand the impact of DSA in the setting of intestinal allograft rejection.

METHODS

Thirteen patients (15 grafts) were serially evaluated for DSA levels pre- and posttransplant. DSA was determined by Luminex and the results were interpreted as fluorescence intensity (FI), with FI more than 3000 considered positive.

RESULTS

The clinical rejection episodes in allografts were significantly associated with the presence of DSA (P=0.041).We obtained 291 biopsy samples from graft ileum and date-matched DSA assay reports. Sixty-three (21.65%) of the biopsies showed acute rejection. The appearance of DSA were preformed (n=5, anti-human leukocyte antigen class II=3, anti-class I and II=2), de novo (n=4, 15.25±4.72 days after transplantation, anti-class II=1, and anti-class I and II=3) and never (n=6). Among the 63 biopsies, 30(47.6%) had significant correlations with positive DSA (kappa=0.30, P<0.001) and manifested severe rejection grade (P=0.009).

CONCLUSIONS

In this cohort of small bowel/multivisceral transplantation patients, there was a high incidence of DSA. The presence of DSA should alert the clinical team of a higher risk of rejection, and reduction of the FI is clinically associated with resolution. Serial endoscopy guided biopsies combined with simultaneous DSA measurement in postintestinal transplantation follow-up is an effective means of screening for cellular and humoral-based forms of acute rejection.

Proteomic analysis reveals innate immune activity in intestinal transplant dysfunction

BACKGROUND

Many patients with intestinal failure require intestinal transplantation (ITx) to survive. Acute cellular rejection poses a challenge in ITx because its biologic components are incompletely understood. New methodologies for its integrative and longitudinal analysis are needed.

METHODS

In this study, we characterized episodes of acute cellular rejection in ITx recipients using a noninvasive proteomic analysis. Ostomy effluent was obtained from all patients undergoing ITx at University of California, Los Angeles from July 2008 to September 2009 during surveillance endoscopies in the first 8 weeks post-ITx. Effluent was analyzed using 17-plex Luminex technology and matrix-assisted laser desorption/ionization proteomics.

RESULTS

Of 56 ostomy effluent samples from 17 ITx recipients, 14% developed biopsy-proven rejection at a median of 25 days post-ITx. Six had mild rejection, two were indeterminate for rejection, and no graft loss was seen in the first 3 months posttransplantation. Effluent levels of five innate immune cytokines were elevated in the posttransplantation phase: granulocyte colony-stimulating factor, interleukin-8, tissue necrosis factor-α, interleukin-1β, and interferon-γ. Proteomic analysis revealed 17 protein features differentially seen in rejection, two identified as human neutrophil peptide 1 and 2. This was confirmed by the presence of human neutrophil peptide-positive lamina propria neutrophils in biopsy tissue samples.

CONCLUSIONS

Proteomic and cytokine analysis of ostomy effluents suggests an early and unappreciated role of innate immune activation during rejection.

Increased expression of peripheral blood leukocyte genes implicate CD14+ tissue macrophages in cellular intestine allograft rejection

Recurrent rejection shortens graft survival after intestinal transplantation (ITx) in children, most of whom also experience early acute cellular rejection (rejectors). To elucidate mechanisms common to early and recurrent rejection, we used a test cohort of 20 recipients to test the hypothesis that candidate peripheral blood leukocyte genes that trigger rejection episodes would be evident late after ITx during quiescent periods in genome-wide gene expression analysis and would achieve quantitative real-time PCR replication pre-ITx (another quiescent period) and in the early post-ITx period during first rejection episodes. Eight genes were significantly up-regulated among rejectors in the late post-ITx and pre-ITx periods, compared with nonrejectors: TBX21, CCL5, GNLY, SLAMF7, TGFBR3, NKG7, SYNE1, and GK5. Only CCL5 was also up-regulated in the early post-ITx period. Among resting peripheral blood leukocyte subsets in randomly sampled nonrejectors, CD14(+) monocytes expressed the CCL5 protein maximally. Compared with nonrejectors, rejectors demonstrated higher counts of both circulating CCL5(+)CD14(+) monocytes and intragraft CD14(+) monocyte-derived macrophages in immunohistochemistry of postperfusion and early post-ITx biopsies from the test and an independent replication cohort. Donor-specific alloreactivity measured with CD154(+) T-cytotoxic memory cells correlated with the CCL5 gene and intragraft CD14(+) monocyte-derived macrophages at graft reperfusion and early post-ITx. CCL5 gene up-regulation and CD14(+) macrophages likely prime cellular ITx rejection. Infiltration of reperfused intestine allografts with CD14(+) macrophages may predict rejection events.

Intestinal transplantation: current status and future directions

Three decades after the first intestinal transplant was performed in humans, this life-saving procedure has come of age and now offers hope of long-term survival in a small group of patients with life-threatening complications of intestinal failure and parenteral nutrition. Success rates have greatly improved, largely through advances in immunosuppression protocols, improved surgical technique and postoperative care, and accumulated experience. Management of the intestinal transplant recipient entails careful surveillance, prevention, and treatment of rejection and infection, as well as optimization of feeding and nutrition. With this approach, survival and quality of life are demonstrably improved, such that intestinal transplantation is now an established and accepted procedure for this very select group of highly-complex patients.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.

Intestine transplantation in children: update 2010

This article reviews the current status of pediatric intestinal transplantation, focusing on referral and listing criteria, surgical techniques, patient management, monitoring, complications after transplant, and short- and long-term patient outcome. Intestine transplantation has become the standard of care for children who develop life-threatening complications associated with intestinal failure. The results of intestinal failure treatment have significantly improved in the last decade following the establishment of gut rehabilitation programs and advances in transplant immunosuppressive protocols, surgical techniques, and posttransplant monitoring. The 1-year patient survival is now 80% and more than 80% of the children who survive the transplant are weaned off parenteral nutrition. Early referral for pretransplant assessment and careful follow-up after transplant with prompt recognition and treatment of transplant-related complications are key factors contributing to superior patient outcomes and survival. The best results are being obtained at high-volume centers with survival rates of up to 75% at 5 years.

Intestinal transplantation: current outcomes and opportunities

PURPOSE OF REVIEW

This review highlights current outcomes in intestinal transplantation and summarizes advances that have recently occurred in five interrelated areas: progress in intestinal rehabilitation, immunologic and technical modifications, awareness of opportunities for improved allograft monitoring, and better assessment of long-term complications and morbidities.

RECENT FINDINGS

Improved long-term management of patients with intestinal failure as well as improved outcomes with intestine transplant are changing the previously established paradigms of timing for referral. For those requiring transplant, use of monoclonal and polyclonal antibody induction protocols have been associated with improved outcomes. Experience at centers of excellence demonstrates 1 and 5 year patient survival rates of 93 and 78%, respectively with ongoing investigations focusing on lowering long-term causes of graft loss such as chronic rejection or morbidities such as renal dysfunction. Descriptions of tissue, proteomic and genomic technologies to complement traditional methodologies to monitor graft function are emerging.

SUMMARY

Optimal timing for referral of children with intestinal failure and improved medical and surgical therapies increase the opportunity for intestinal adaptation without the need for transplant. For those undergoing transplant, technical and immunologic modifications, developments in graft monitoring, and reduction of long-term morbidities are leading to improved outcomes.

Clinical management of motility disorders in children

We review the current clinical evaluation and management of the most common esophageal and gastrointestinal motility disorders in children based on the literature and our experience in a pediatric motility center in the United States. The disorders discussed include esophageal achalasia, pre- and post-fundoplication motility disorders, gastroparesis, motility disorders occurring after repair of congenital atresias, motility disorders associated with gastroschisis, chronic intestinal pseudo-obstruction, motility after intestinal transplantation, motility disorders after colonic resection for Hirschsprung's disease, chronic functional constipation, and motility disorders associated with imperforate anus.

Human gut microbiome adopts an alternative state following small bowel transplantation

Small bowel transplants provide an exceptional opportunity for long-term study of the microbial ecology of the human small bowel. The ileostomy created at time of transplant for ongoing monitoring of the allograft provides access to samples of ileal effluent and mucosal biopsies. In this study, we used qPCR to assay the bacterial population of the small bowel lumen of 17 small bowel transplant patients over time. Surprisingly, the posttransplant microbial community was found to be dominated by Lactobacilli and Enterobacteria, both typically facultative anaerobes. This represents an inversion of the normal community that is dominated instead by the strictly anaerobic Bacteroides and Clostridia. We found this inverted community also in patients with ileostomies who did not receive a transplant, suggesting that the ileostomy itself is the primary ecological determinant shaping the microbiota. After surgical closure of the ileostomy, the community reverted to the normal structure. Therefore, we hypothesized that the ileostomy allows oxygen into the otherwise anaerobic distal ileum, thus driving the transition from one microbial community structure to another. Supporting this hypothesis, metabolomic profiling of both communities demonstrated an enrichment for metabolites associated with aerobic respiration in samples from patients with open ileostomies. Viewed from an ecological perspective, the two communities constitute alternative stable states of the human ileum. That the small bowel appears to function normally despite these dramatic shifts suggests that its ecological resilience is greater than previously realized.

Update on intestinal rehabilitation after intestinal transplantation

PURPOSE OF REVIEW

The past decade has seen improvements in patient selection and a greater range of surgical procedures available to patients with intestinal failure, and this, combined with more effective immunosuppressive regimens, has transformed survival after intestinal transplantation (ITx). Much more is known about optimizing rehabilitation of the engrafted intestine in the first 12 months after transplant, but it is also becoming apparent that there are some long-term health issues to consider.

RECENT FINDINGS

The key issues in rehabilitation of ITx are the immunogenic nature of the intestinal graft, which means a higher risk of rejection and necessitates relatively high levels of immune suppression that promotes infections, including Epstein-Barr virus-driven lymphoma, viral gastroenteritis and renal impairment; and those related to the specifics of an intestinal allograft (nutritional support, chylous ascites, growth, food allergy, fat soluble vitamin deficiencies, metabolic bone disease). In this article, recent publications about approaches for establishing nutrition and methods for monitoring the health of the ITx patient are reviewed.

SUMMARY

ITx appears to be cost-effective compared with parenteral nutrition, but ITx recipients continue to be vulnerable to infections, nutritional deficiencies and rejection over the long-term and, therefore, require support from and involvement of a multidisciplinary team for patients to become safely integrated with their local community.

Current perspectives on pediatric intestinal transplantation

Irreversible intestinal failure in children is predominantly caused by surgical conditions such as volvulus, necrotizing enterocolitis, and gastroschisis. Functional intestinal failure from motility disorders such as intestinal pseudo-obstruction or enterocyte dysfunction with microvillus inclusion disease also may require intestine replacement. Approved indications for intestinal transplantation include liver dysfunction, loss of major venous access, frequent central line-related sepsis, and recurrent episodes of severe dehydration despite intravenous fluid management. Surgical options include transplantation of the isolated intestine, combined liver-intestine transplantation, or multivisceral transplantation of the stomach, duodenum, pancreas, and small bowel (with or without the liver). Immunosuppression for intestinal transplantation is based on tacrolimus therapy, often with induction immunosuppression using antilymphocyte antibodies (eg, antithymocyte antibody and alemtuzumab). Experience at centers of excellence demonstrates 1- and 5-year patient survival rates of 95% and 77%, respectively, with ongoing investigations focusing on lowering long-term causes of graft loss such as chronic rejection.

Present prospects and future perspectives of intestinal and multivisceral transplantation

PURPOSE OF REVIEW

This article reviews the most current indications, technical aspects and results of intestinal and multivisceral transplantation.

RECENT FINDINGS

The introduction of induction therapy in the past 8 years, combined with advancements on surgical technique and clinical management, was vital for the improvement in patient and graft survival.

SUMMARY

Intestinal transplantation is now a viable option for patients with intestinal failure who have failed parenteral nutrition. The improvement in the survival of intestinal and multivisceral transplant recipients has extended its use to selected patients with neoplastic disease, extensive splanchnic thrombosis and abdominal catastrophes.

Significance of serum bile acids in small bowel allograft rejection in pigs

OBJECTIVES

To examine changes in individual bile acids in serum in a pig model of allogenic small bowel transplantation.

METHODS

Seventeen pigs were divided into two groups: group 1 (n=10), controls; group 2 (n=7), allotransplantation, nonimmunosuppressed recipients. Both groups received a segmental intestine. Intestinal specimens for histologic studies were obtained at the end of cold flushing (T0) and on postoperative day 8 (T1). Total and individual bile acid concentrations were measured in serum samples taken at T0 and T1.

RESULTS

All animals survived until the end of the study. In group 1, intestinal histology revealed no significant changes between T0 and T1 specimens. In contrast, in group 2, graft histology revealed moderate to severe rejection at T1 in all specimens. In contrast to group 1, serum levels of total bile acids increased significantly in group 2 at T1 compared with baseline (P=0.001). The increase was due to secondary bile acids which were significantly higher at T1 compared with baseline (P=0.0003). In contrast, secondary bile acids increased but not significantly at T1 in group 1 compared with baseline (P=0.056).

CONCLUSION

Our study suggests that total and secondary serum bile acids may be a useful diagnostic tool for the diagnosis of acute intestinal rejection.

Current status of small bowel and multivisceral transplantation

Intestinal transplantation has shown exceptional growth over the past 20 years with remarkable progress. As with other solid organ transplants, intestinal transplantation has moved out of the experimental realm to become the stan dard of care for many patients with intestinal failure. Intestinal transplantation may soon be extended routinely to patients who, although not strictly meeting the criteria for intestinal failure, may benefit from intestinal transplantation, such as patients who have nonresectable indolent tumors or diffuse thrombosis of the portomesenteric system. As clinical experience has increased with intestinal transplantation, outcomes have improved. The currently reported 1-year graft and patient survival rate is 80%, which approaches that for other solid abdominal organs. Unfortunately, most of the gains in survival are seen in the first postoperative year, with long-term survival remaining basically unchanged since the early 1990s. With improved outcomes, more centers have entered into the intestinal transplant arena. In the United States alone, 20 centers performed at least one intestinal transplant in 2007. Increase in access to intestinal transplantation and more widespread awareness of this option likely will result in a consistent increase in the number of yearly transplants for the foreseeable future. Immunosuppressive regimens continue to evolve, with induction therapy being the major change in the past 5 years. Although rejection rates in the first year after transplant have been reduced by induction therapy, long-term side effects of heavy immunosuppression continue to weigh negatively on transplant outcomes. The future for immunosuppression lies in two areas: (1) individual monitoring of the immunosuppression level for each individual patient and (2) development of serum and tissue markers for the early identification of rejection. It is likely that a combination of technologies will allow immunosuppression to be tailored to each recipient. Development of these approaches to immunosuppression is necessary to predict graft dysfunction ahead of irreversible graft injury and allows adjustments in immunosuppression before the onset of rejection. Intestinal transplantation continues to be performed only in situations in which all other therapeutic modalities have failed. No randomized trials compare intestinal transplantation to long-term PN to establish guidelines for a timely referral for this treatment option. Late referral remains a crippling problem in the field of intestinal transplantation, with a great number of patients in need of simultaneous liver transplantation at the time of listing for intestinal transplantation. Early referral for isolated intestinal transplant will reduce the need for simultaneous multiorgan transplants and increase the residual organs available for patients in need of (primarily) liver transplantation.