Evaluation of Calprotectin Level in Intestinal Content as an Early Marker for Graft Rejection

Application of Intestinal Barrier Molecules in the Diagnosis of Acute Cellular Rejection After Intestinal Transplantation

Diagnosing acute rejection after intestinal transplantation currently heavily relies on histopathological analysis of graft biopsies. However, the invasive risks associated with ileoscopic examination and the inaccessibility for biopsy after ileostomy closure hinder real-time detection of rejection responses. Molecules comprising the intestinal barrier have been identified as physiological and molecular biomarkers for various bowel conditions and systemic diseases. To investigate the potential of barrier function-related molecules in diagnosing rejection after intestinal transplantation, plasma samples were collected longitudinally from transplant recipients. The samples were categorized into "indeterminate for rejection (IND)" and "acute rejection (AR)" groups based on clinical diagnoses at each time point. The longitudinal association between plasma levels of these barrier function-related molecules and acute rejection was analyzed using the generalized estimating equations (GEE) method. Logistic GEE models revealed that plasma levels of claudin-3, occludin, sIgA, and zonulin were independent variables correlated with the clinical diagnosis of acute rejection. The subsequent prediction model demonstrated moderate ability in discriminating between IND and AR samples, with a sensitivity of 76.0%, specificity of 89.2%, and accuracy of 84.6%. In conclusion, monitoring plasma levels of claudin-3, occludin, sIgA, and zonulin shows great potential in aiding the diagnosis of acute rejection after intestinal transplantation.

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.

Immunosuppression Regimens for Intestinal Transplantation in Children

Pediatric intestinal transplant serves as the only definitive treatment for children with irreversible intestinal failure. Successful intestinal transplant hinges upon appropriate management of immunosuppression. The indications for intestinal transplant have changed over time. Immunosuppression regimens can be divided into induction and maintenance phases along with treatment of acute rejection. Intestinal transplant induction now often includes antithymocyte globulin or basiliximab in addition to corticosteroids. Maintenance regimens continue to be dominated by tacrolimus, with additional agents used to either decrease goal tacrolimus levels to limit toxicity or as an adjunct in sensitized patients. Careful monitoring can help to limit serious complications, such as rejection, infection, and malignancy. Future work will aim to decrease variation in practice and identify methods to determine optimal immunosuppression for a particular patient. Furthermore, there is a need for non-invasive monitoring of the intestinal graft and functional assessments of immunosuppression.

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.

Post-transplant colitis after kidney transplantation: clinical, endoscopic and histological features

Chronic immunosuppression may increase the risk of post-transplant infection and medication-related injury and may also be responsible for the increased risk of gastrointestinal complications in kidney transplant recipients. Differentiating the various forms of post-transplant colitis is challenging, since most have similar clinical and histological features. This study evaluated the incidence of post-transplant gastrointestinal complications during screening colonoscopy. Kidney transplant recipients undergoing a colonoscopy for any reasons in the period 2014-2018 were included. Among the 134 patients completing the colonoscopy, 74 patients (56%) had an abnormal finding: an adenoma was found in 25 patients (18.6%), while 19 patients (14.1%) had colitis. Mycophenolic acid/related colitis was the most common colitis (6%), while 7 patients (5.2%) developed a de novo inflammatory bowel disease. Patients with post-transplant colitis were younger and with shorter time from transplant compared to patients without colitis. In conclusions, immunosuppression may predispose kidney transplant recipients to an increased risk of post-transplant colitis. Diagnostic colonoscopy should be encouraged in all transplant patients with refractory diarrhea and gastrointestinal symptoms to allow a prompt diagnosis and a timely treatment, finally improving the quality of life and long-term outcomes of affected patients.

Diagnostic Lessons from a Complex Case of Postintestinal Transplantation Enteropathy

Recent advances in the field of intestinal transplantation have been mitigated by the incidence of allograft rejection. In such events, early identification and appropriate timing of antirejection therapy are crucial in retaining graft function. We present the case of a patient who suffered severe postintestinal transplantation allograft enteropathy, primarily characterized by extensive mucosal ulcerations, and was refractory to all conventional therapy. This progressed as chronic rejection; however crucially this was not definitively diagnosed until allograft function had irreversibly diminished. We argue that the difficulties encountered in this case can be attributed to the inability of our current array of investigative studies and diagnostic guidelines to provide adequate clinical guidance. This case illustrates the importance of developing reliable and specific markers for guiding the diagnosis of rejection and the use of antirejection therapeutics in this rapidly evolving field of transplant surgery.

Small bowel transplantation

BACKGROUND

Small bowel transplantation evolution, because of its complexity, was slower than other solid organs. Several advances have enabled its clinical application.

AIM

To review intestinal transplantation evolution and its current status.

METHOD

Search in MEDLINE and ScIELO literature. The terms used as descriptors were: intestinal failure, intestinal transplantation, small bowel transplantation, multivisceral transplantation. Were analyzed data on historical evolution, centers experience, indications, types of grafts, selection and organ procurement, postoperative management, complications and results.

CONCLUSION

Despite a slower evolution, intestinal transplantation is currently the standard therapy for patients with intestinal failure and life-threatening parenteral nutrition complications. It involves some modalities: small bowel transplantation, liver-intestinal transplantation, multivisceral transplantation and modified multivisceral transplantation. Currently, survival rate is similar to other solid organs. Most of the patients become free of parenteral nutrition.

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.

[Plasma citrulline concentration as a biomarker of intestinal function in short bowel syndrome and in intestinal transplant]

INTRODUCTION

Citrulline is a non-essential amino acid produced solely in the enterocyte. The aim of this study was to analyse the role of serum citrulline as a biomarker of enterocyte load in children with intestinal failure due to short bowel syndrome (SBS) and its relationship to enteral adaptation.

MATERIAL AND METHODS

Plasma citrulline concentration was determined by chromatography (normal value>15 μmol/L) in 57 patients (age 0.5-18 years) admitted to our Intestinal Rehabilitation Unit with intestinal failure. Those who were dehydrated, with renal insufficiency, or other conditions able to modify the results were excluded. Patients were divided into 4 groups: group i: SBS totally dependent on parenteral nutrition (PN); group ii: SBS under mixed enteral-parenteral nutrition; group iii: IF weaned from PN after a rehabilitation period; group iv: small bowel transplanted patients weaned from PN and taking a normal diet.

RESULTS

The mean ± SD plasma citrulline values were: group i (n=15): 7.1 ± 4.1; group ii (n=11): 15.8 ± 8.9; group iii (n=13): 20.6 ± 7.5; group iv (n=25): 28.8 ± 10.1. Values were significantly lower in group i in comparison with groups ii-iii-iv (P<.001), and in group ii in comparison with groups iii-iv (P<.001). A low citrulline was associated with remnant small bowel length (P<.001, r=0.85). In group iv citrulline levels decreased >50% in 3 patients who developed moderate-severe rejection, and in one patient who developed viral enteritis.

CONCLUSIONS

1. Plasma citrulline could be a sensitive and specific biomarker of the residual functional enterocyte load. 2. It is related to enteral feeding tolerance. 3. Its prognostic value in the process of intestinal adaptation and as a rejection marker in small bowel transplanted patients needs to be confirmed.

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.

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.