Severe acute cellular rejection after intestinal transplantation is associated with poor patient and graft survival

Biologicals in the prevention and treatment of intestinal graft rejection: The state of the art Biologicals in Intestinal Transplantation

Intestinal transplantation is the standard treatment for patients with intestinal failure with severe complications due to parenteral nutrition; however, rejection leads to graft failure in approximately half of both adult and pediatric recipients within 5 years of transplantation. Although intensive immunosuppressive therapy is used in an attempt to reduce this risk, commonly used treatment strategies are generally practice- and/or expert-based, as head-to-head comparisons are lacking. In this ever-developing field, biologicals designed to prevent or treat rejection are used increasingly, with both infliximab and vedolizumab showing potential in the treatment of acute cellular rejection in individual cases and in relatively small patient cohorts. To help advance progress in clinical care, we review the current use of biologicals in intestinal transplantation, and we provide future perspectives to guide this progress.

Endoscopic Surveillance of the Intestinal Allograft: Recommendations From the Intestinal Rehabilitation and Transplant Association Working Group

Intestinal transplant (ITx) rejection lacks a reliable noninvasive biomarker and rejection surveillance relies on serial endoscopies and mucosal biopsies followed by histologic assessment. Endoscopic biopsies are also essential for identifying other ITx-related complications such as infectious, allergic, and inflammatory graft enteritis as well as post-transplant lymphoproliferative disease or graft versus host disease. In spite of its central role in ITx, published guidelines on endoscopy and biopsy are lacking and significant variability between centers in terms of timing and technical performance exists. Therefore, an international expert group convened and discussed several aspects related to the surveillance endoscopy after ITx with the aim to summarize and standardize its practice. This article summarizes these considerations on endoscopic ITx monitoring and highlights practices of surveillance and for-cause endoscopy, biopsy techniques, pathologic evaluation, potential risks and complications, outsourcing, and less-invasive monitoring techniques.

Risk factors for renal dysfunction after isolated intestinal transplantation

INTRODUCTION

Kidney dysfunction is a known complication of intestinal transplantation; however, the rate of development and risk factors for chronic kidney disease (CKD) remain poorly defined.

METHODS

This was a single-center retrospective review of isolated adult intestinal allograft recipients from 2011 to 2019. Patients who died or experienced graft loss within 1-year or had a prior transplant were excluded. Estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI equation at 0-, 6- and 12-months post-transplant, and multivariable linear regression was performed to identify variables associated with adjusted eGFR at 1-year. Independent variables included age, ethnicity, BMI, history of diabetes/hypertension, vasopressor use, TPN and stoma days, urinary or bloodstream infections, intravenous contrast exposure, rejection, concomitant immunosuppression, and time above the therapeutic range of tacrolimus. Variables with a p < .1 in univariate analysis were considered for multivariable modeling.

RESULTS

Thirty-three patients were included with a mean age of 43.9 ± 13.0. A mean 42.3% decline in eGFR was observed at 1-year post-transplant, with 15.2% of patients developing new stage 4/5 CKD. Factors associated with a greater decline in adjusted eGFR in the univariate model included increasing age, decreased BMI, stoma days, and vasopressor use. In the adjusted multivariable model patient age (β = -.77, p < .01) and stoma days (β = -.06, p < .01) remained significant. Tacrolimus and sirolimus exposure were not associated with decline in eGFR at 1 year.

CONCLUSIONS

Renal dysfunction is common following intestinal transplantation. The need for stoma creation should be carefully considered, and reversal should be performed when feasible for renal protection.

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.

Small bowel transplant - novel indications and recent progress

INTRODUCTION

Advances in the management of intestinal failure have led to a reduction in the number of intestinal transplants. The number of bowel transplants has been mainly stable even though a slight increase has been observed in the last 5 years.

AREAS COVERED

Standard indication includes patients with a reasonable life expectancy. Recent progress can be deduced by the increased number of intestine transplants in adults: this is due to the continuous improvement of 1-year graft survival worldwide (without differences in 3- and 5-year) associated with better abdominal wall closure techniques. This review aims to provide an update on new indications and changes in trends of pediatric and adult intestine transplantation. This analysis, which stretches through the past 5 years, is based on a collection of related manuscripts from PubMed.

EXPERT COMMENTARY

Intestinal transplants should be solely intended for a group of individuals for whom indications for transplantation are clear and both medical and surgical rehabilitations have failed. Nevertheless, many protocols developed over the years have not yet solved the key question represented by the over-immunosuppression. Novel indications and recent progress in the bowel transplant field, minimal yet consistent, represent a pathway to be followed.

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.

Update on immunosuppressive strategies in intestinal transplantation

PURPOSE OF REVIEW

The intestine is the most immunologically complex solid organ allograft with the greatest risk of both rejection and graft-versus-host disease (GVHD). High levels of immunosuppression are required, further increasing morbidity. Due to low volume of transplants and few centers with experience, there is paucity of evidence-based, standardized, and effective therapeutic regimens. We herein review the most recent data about immunosuppression, focusing on novel and emerging therapies.

RECENT FINDINGS

Recent data are moving the field toward increasing use of basilixumab and consideration of alemtuzumab for induction and inclusion of mammalian target of rapamycin inhibitors and antimetabolites for maintenance. For rejection, we highlight novel roles for tumor necrosis factor-α inhibition, α4β7 integrin inhibition, microbiome modulation, desensitization protocols, and tolerance induction strategies. We also highlight emerging novel therapies for GVHD, especially the promising role of Janus kinase inhibition.

SUMMARY

New insights into immune pathways associated with rejection and GVHD in intestinal allografts have led to an evolution of therapies from broad-based immunosuppression to more targeted strategies that hold promise for reducing morbidity from infection, rejection, and GVHD. These should be the focus of further study to facilitate their widespread use.

"Stoma or no stoma": First report of intestinal transplantation without stoma

Recent data suggest that frequent endoscopy and biopsy without evidence of graft dysfunction does not appear to confer survival advantage after intestinal transplantation. After abandoning protocol surveillance, endoscopic examination was decreased significantly at our center. These observations led us to question the need for stoma creation in intestinal transplantation. Herein, we report clinical outcomes of intestinal transplantation without stoma, compared to conventional transplant with stoma. Data analysis was limited to adult intestinal transplantation without liver allograft between 2015 and 2018. We compared patient and graft survival, frequency of endoscopic evaluation, episodes of acute rejection, nutritional therapy, and renal function between "Control group (with stoma)," n = 18 grafts in 16 patients and "Study group (without stoma)," n = 16 grafts in 15 patients. Overall outcome was similar between the 2 groups with respect to graft and patient survival, episodes of acute rejection, and its response to treatment. Nutritional outcomes were similar in both groups. Fewer antidiarrheal medications were required in the study group, but this did not translate into demonstrable gains in preservation of renal function, despite an apparent trend to improvement. Intestinal transplantation without stoma appears to be an acceptable practice model without obvious adverse impact on outcome.

Donor helper innate lymphoid cells are replaced earlier than lineage positive cells and persist long-term in human intestinal grafts - a descriptive study

Intestinal grafts carry large donor lymphoid load that is replaced by recipient cells. The dynamics of this process may influence the tolerance, rejection or graft-versus-host disease. We analysed distribution and turnover of T and B (Lin+) lymphocytes, natural killer (NK) and helper innate lymphoid cells (hILC) in intestinal epithelium (IEp) and lamina propia (LP) from a long-term cohort of eight intestinal recipients and from a single patient monitored deeply during the first 8 months post-transplant (posTx). Long-term intestinal grafts showed significantly higher %hILC than native bowels in IEp and LP until 10 years posTx and recovery to normal levels was observed afterwards. We also observed an imbalance between hILC subsets in IEp [increase of type 1 (ILC1) and decrease in type 3 (ILC3) innate lymphoid cells] that persisted along posTx time even when %hILC was similar to native bowels. Regarding hILC origin, we still detected the presence of donor cells at 13 years posTx. However, this chimerism was significantly lower than in Lin+ and NK populations. According to these findings, observation from the patient monitored in early posTx period showed that recipient hILC repopulate earlier and faster than Lin+ cells, with increase in ILC1 related to rejection and infection episodes.

Current outcomes after pediatric and adult intestinal transplantation

PURPOSE OF REVIEW

In this article, we will review the outcomes of patients with intestinal transplant (ITx) with a focus on factors affecting long-term graft and patient survival.

RECENT FINDINGS

The most recent International Intestinal Transplant Registry reports a 1-, 5-, and 10-year graft survival of 71%, 50%, and 41% respectively, for ITx grafts transplanted since 2000. Over the past decades, significant improvements have been achieved in short-term graft and patient outcomes for ITx recipients. The improvement in short-term outcomes may be related to the focused treatment of antihuman leukocyte antigen antibodies, the use of induction immunotherapy protocols, refinements in surgical techniques, establishment of dedicated ITx units, and improved postoperative management.However, long-term graft and patient outcomes for ITx recipients remain stagnant. Issues impairing long-term outcomes of ITx include the challenges in the diagnosis and treatment of chronic rejection and antibody-mediated rejection, progressive decline in renal function, and long-term infectious and malignancy risks especially related to cytomegalovirus, Epstein-Barr virus and posttransplant lymphoproliferative disorder after ITx.

SUMMARY

Addressing and preventing early and late complications is the key to improving short-term and long-term outcomes after ITx.

Intestinal Preservation Injury: A Comparison Between Rat, Porcine and Human Intestines

Advanced preservation injury (PI) after intestinal transplantation has deleterious short- and long-term effects and constitutes a major research topic. Logistics and costs favor rodent studies, whereas clinical translation mandates studies in larger animals or using human material. Despite diverging reports, no direct comparison between the development of intestinal PI in rats, pigs, and humans is available. We compared the development of PI in rat, porcine, and human intestines. Intestinal procurement and cold storage (CS) using histidine-tryptophan-ketoglutarate solution was performed in rats, pigs, and humans. Tissue samples were obtained after 8, 14, and 24 h of CS), and PI was assessed morphologically and at the molecular level (cleaved caspase-3, zonula occludens, claudin-3 and 4, tricellulin, occludin, cytokeratin-8) using immunohistochemistry and Western blot. Intestinal PI developed slower in pigs compared to rats and humans. Tissue injury and apoptosis were significantly higher in rats. Tight junction proteins showed quantitative and qualitative changes differing between species. Significant interspecies differences exist between rats, pigs, and humans regarding intestinal PI progression at tissue and molecular levels. These differences should be taken into account both with regards to study design and the interpretation of findings when relating them to the clinical setting.

The parallel paradigm between intestinal transplant inflammation and inflammatory bowel disease

PURPOSE OF REVIEW

A significant shift in our understanding of the molecular and cellular basis for inflammatory bowel disease (IBD) mirrors research that has been ongoing in intestinal transplantation. The blurring of lines between these two disease states creates an avenue into potential therapeutic interventions which take advantage of these molecular similarities.

RECENT FINDINGS

Traditional knowledge of T-cell involvement in IBD has expanded to highlight the role of T helper 17 (Th17) cells as key effector cells. A similar role has been demonstrated in cellular rejection of intestinal allografts. Genetic polymorphism related to the propagation and function of Th17 cells has been found to confer significant risk of developing autoimmune conditions. Interleukin-23, a cytokine identified as crucial to the expansion of Th17 cells, has become a validated molecular target in psoriatic arthritis and IBD, and could become a target for intestinal transplant therapies.

SUMMARY

Intestinal transplant rejection and IBD share a similar phenotype, especially as it relates to key effector cells and gene polymorphisms. Improvements in our understanding of the immune-pathogenesis of IBD, as well as molecular targeting exploiting that knowledge, provide a potential route to improve outcomes for intestinal transplant patients.

Small-for-size Syndrome Does Not Occur in Intestinal Transplantation Without Liver Containing Grafts

BACKGROUND

The ideal donor in intestinal transplantation (ITX) is generally considered to be 50% to 70% of recipient body weight. This may be due to concerns for "small for size" syndrome as seen in liver transplantation. We report our experience using smaller donors (donor-recipient weight ratio [DRWR], < 50%) in ITX recipients.

METHODS

We studied a group of ITX recipients with DRWR of 50% or less to unmatched controls who received intestinal allografts with DRWR greater than 50%. We examined patient and graft survival and enteral autonomy from parenteral nutrition as surrogate markers for safety of using smaller donors and ease of abdominal wall closure between groups to determine the value.

RESULTS

There was no difference in overall patient and graft survival, time to enteral autonomy from parenteral nutrition, and weight gain after ITX over time between groups. The need for complicated abdominal closure techniques was significantly more frequent in the control group than in the study group (34.6% vs 6.9%, P = 0.01). Secondary abdominal closure occurred more frequently in the control group (15.4% vs 0%, P = 0.014). Wound revisions also occurred more frequently in the control group (15.4% vs 0%, P = 0.028).

CONCLUSIONS

Our data suggest that ITX using smaller donors (DRWR ≤ 50%) seems to be an acceptable practice without adverse impact on surgical complications, nutritional autonomy, and patient and graft survival. Abdominal wall closure seems easier in recipients of smaller donors and "small for size" syndrome as described in liver transplantation does not occur with intestinal allografts.