Evaluation of pediatric patients for intestinal transplantation in the modern era.

OBJECTIVES: To review recent evaluations of pediatric patients with intestinal failure (IF) for intestinal transplantation (ITx), waiting list decisions, and outcomes of patients listed and not listed for ITx at our center. METHODS: Retrospective chart review of 97 patients evaluated for ITx from January 2014 to December 2021 including data from referring institutions and protocol laboratory testing, body imaging, endoscopy, and liver biopsy in selected cases. Survival analysis used Kaplan-Meier estimates and Cox proportional hazards regression. RESULTS: Patients were referred almost entirely from outside institutions, one-third because of intestinal failure-associated liver disease (IFALD), two-thirds because of repeated infective and non-IFALD complications under minimally successful intestinal rehabilitation, and a single patient because of lost central vein access. The majority had short bowel syndrome (SBS). Waiting list placement was offered to 67 (69%) patients, 40 of whom for IFALD. The IFALD group was generally younger and more likely to have SBS, have received more parenteral nutrition, have demonstrated more evidence of chronic inflammation and have inferior kidney function compared to those offered ITx for non-IFALD complications and those not listed. ITx was performed in 53 patients. Superior postevaluation survival was independently associated with higher serum creatinine (hazard ratio [HR] 15.410, p = 014), whereas inferior postevaluation survival was associated with ITx (HR 0.515, p = 0.035) and higher serum fibrinogen (HR 0.994, p = 0.005). CONCLUSIONS: Despite recent improvements in IF management, IFALD remains a prominent reason for ITx referral. Complications of IF inherent to ITx candidacy influence postevaluation and post-ITx survival.

Impact of the acuity circle model for liver allocation on multivisceral transplant candidates.

Liver allocation was updated on February 4, 2020, replacing a Donor Service Area (DSA) with acuity circles (AC). The impact on waitlist outcomes for patients listed for combined liver-intestine transplantation (multivisceral transplantation [MVT]) remains unknown. The Organ Procurement and Transplantation Network/United Network for Organ Sharing database was used to identify all candidates listed for both liver and intestine between January 1, 2018 and March 5, 2021. Two eras were defined: pre-AC (2018-2020) and post-AC (2020-2021). Outcomes included 90-day waitlist mortality and transplant probability. A total of 127 adult and 104 pediatric MVT listings were identified. In adults, the 90-day waitlist mortality was not statistically significantly different, but transplant probability was lower post-AC. After risk-adjustment, post-AC was associated with a higher albeit not statistically significantly different mortality hazard (sub-distribution hazard ratio[sHR]: 8.45, 95% CI: 0.96-74.05; p = .054), but a significantly lower transplant probability (sHR: 0.33, 95% CI: 0.15-0.75; p = .008). For pediatric patients, waitlist mortality and transplant probability were similar between eras. The proportion of patients who underwent transplant with exception points was lower post-AC both in adult (44% to 9%; p = .04) and pediatric recipients (65% to 15%; p = .002). A lower transplant probability observed in adults listed for MVT may ultimately result in increased waitlist mortality. Efforts should be taken to ensure equitable organ allocation in this vulnerable patient population.

Operational tolerance in intestinal transplantation.

By presenting the first case report of true operational tolerance in an intestinal transplant patient, we aim to demonstrate that tolerance is possible in a field that has been hampered by suboptimal outcomes. Although operational tolerance has been achieved in liver and kidney transplantation, and some intestinal transplant patients have been able to decrease immunosuppression, this is the first instance of true operational tolerance after complete cessation of immunosuppression. A patient received a deceased-donor small intestinal and colon allograft with standard immunosuppressive treatment, achieving excellent graft function after overcoming a graft-versus-host-disease episode 5 months posttransplant. Four years later, against medical advice, the patient discontinued all immunosuppression. During follow-up visits 2 and 3 years after cessation of immunosuppression, the patient exhibited normal graft function with full enteral autonomy and without histological or endoscopic signs of rejection. Mechanistic analysis demonstrated immune competence against third party antigen, with in vitro evidence of donor-specific hyporesponsiveness in the absence of donor macrochimerism. This proof of principle case can stimulate future mechanistic studies on diagnostic and therapeutic strategies, for example, cellular therapy trials, that can lead to minimization or elimination of immunosuppression and, it is hoped, help revitalize the field of intestinal transplantation.

Type 3 innate lymphoid cells are associated with a successful intestinal transplant.

Although innate lymphoid cells (ILCs) play fundamental roles in mucosal barrier functionality and tissue homeostasis, ILC-related mechanisms underlying intestinal barrier function, homeostatic regulation, and graft rejection in intestinal transplantation (ITx) patients have yet to be thoroughly defined. We found protective type 3 NKp44+ ILCs (ILC3s) to be significantly diminished in newly transplanted allografts, compared to allografts at 6 months, whereas proinflammatory type 1 NKp44- ILCs (ILC1s) were higher. Moreover, serial immunomonitoring revealed that in healthy allografts, protective ILC3s repopulate by 2-4 weeks postoperatively, but in rejecting allografts they remain diminished. Intracellular cytokine staining confirmed that NKp44+ ILC3 produced protective interleukin-22 (IL-22), whereas ILC1s produced proinflammatory interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α). Our findings about the paucity of protective ILC3s immediately following transplant and their repopulation in healthy allografts during the first month following transplant were confirmed by RNA-sequencing analyses of serial ITx biopsies. Overall, our findings show that ILCs may play a key role in regulating ITx graft homeostasis and could serve as sentinels for early recognition of allograft rejection and be targets for future therapies.

CD69+ resident memory T cells are associated with graft-versus-host disease in intestinal transplantation.

Graft-versus-host disease (GvHD) is a common, morbid complication after intestinal transplantation (ITx) with poorly understood pathophysiology. Resident memory T cells (TRM ) are a recently described CD69+ memory T cell subset localizing to peripheral tissue. We observed that T effector memory cells (TEM ) in the blood increase during GvHD and hypothesized that they derive from donor graft CD69+TRM migrating into host blood and tissue. To probe this hypothesis, graft and blood lymphocytes from 10 ITx patients with overt GvHD and 34 without were longitudinally analyzed using flow cytometry. As hypothesized, CD4+ and CD8+CD69+TRM were significantly increased in blood and grafts of GvHD patients, alongside higher cytokine and activation marker expression. The majority of CD69+TRM were donor derived as determined by multiplex immunostaining. Notably, CD8/PD-1 was significantly elevated in blood prior to transplantation in patients who later had GvHD, and percentages of HLA-DR, CD57, PD-1, and naïve T cells differed significantly between GvHD patients who died vs. those who survived. Overall, we demonstrate that (1) there were significant increases in TEM at the time of GvHD, possibly of donor derivation; (2) donor TRM in the graft are a possible source; and (3) potential biomarkers for the development and prognosis of GvHD exist.

Rejection of intestinal allotransplants is driven by memory T helper type 17 immunity and responds to infliximab.

Intestinal transplantation (ITx) can be life-saving for patients with advanced intestinal failure experiencing complications of parenteral nutrition. New surgical techniques and conventional immunosuppression have enabled some success, but outcomes post-ITx remain disappointing. Refractory cellular immune responses, immunosuppression-linked infections, and posttransplant malignancies have precluded widespread ITx application. To shed light on the dynamics of ITx allograft rejection and treatment resistance, peripheral blood samples and intestinal allograft biopsies from 51 ITx patients with severe rejection, alongside 37 stable controls, were analyzed using immunohistochemistry, polychromatic flow cytometry, and reverse transcription-PCR. Our findings inform both immunomonitoring and treatment. In terms of immunomonitoring, we found that while ITx rejection is associated with proinflammatory and activated effector memory T cells in the blood, evidence of treatment efficacy can only be found in the allograft itself, meaning that blood-based monitoring may be insufficient. In terms of treatment, we found that the prominence of intra-graft memory TNF-α and IL-17 double-positive T helper type 17 (Th17) cells is a leading feature of refractory rejection. Anti-TNF-α therapies appear to provide novel and safer treatment strategies for refractory ITx rejection; with responses in 14 of 14 patients. Clinical protocols targeting TNF-α, IL-17, and Th17 warrant further testing.

Donor-specific antibody and sensitized patients in intestinal transplantation.

PURPOSE OF REVIEW: It has been well established that antibody to donor HLA pretransplant and the development of anti-human leukocyte antigen (HLA) antibodies posttransplant contribute to inferior graft survival outcomes. This article serves to review the current status of the management of pretransplant sensitized intestinal transplant candidate as well as to review posttransplant care of patients that harbor antidonor HLA antibodies. RECENT FINDINGS: The intestinal transplant candidate oftentimes presents for transplant listing with high levels of anti-HLA antibodies that necessitate a careful preoperative strategy to avoid a donor-recipient pair that would result in a positive crossmatch. In the end, donor intestine offer acceptance is based on a balance between recipient clinical needs and allowable immunologic risk tolerance. The use of virtual crossmatching (VXM) enables the transplant center to effectively gauge the immunologic risk of each potential donor-recipient pair far in advance of allocating resources toward pursuing a donor organ. In those candidates with high levels of preformed donor anti-HLA antibodies, desensitization with a novel technique of donor splenic perfusion has been described as well as a single-center experience with a conventional desensitizing protocol. Posttransplant, with the use of a denovo donor-specific antibody (dnDSA) monitoring and treatment protocol, the well known deleterious effects of dnDSA can potentially be ameliorated, thus improving outcome. Efforts to establish a formal histologic criteria for antibody-mediated rejection (ABMR) in the intestinal graft continues to evolve with recent findings describing the relationship between DSA and histopathologic findings. SUMMARY: Techniques such as the use of VXM, novel desensitization methods and protocols, monitoring and eradicating dnDSA, along with establishing new criteria for ABMR have all contributed to improving the outcomes in transplanting the immunologically challenging intestine.

Factors Associated With 5- and 10-Year Survival After Intestinal Transplantation in Infants and Children.

OBJECTIVES: Intestinal transplantation is an option for permanent intestinal failure with parenteral nutrition intolerance. We sought to determine long-term intestinal graft survival in pediatric patients at our center and to identify factors influencing survival. METHODS: Retrospective chart review of 86 patients transplanted between 2003 and 2013, targeting potential explanatory variables related to demographics, perioperative factors, and postoperative complications. RESULTS: Intestinal graft survival was 71% and 65% after 5 and 10 years, respectively. Five-year graft survival was attained in 79% of patients with a history of anatomic intestinal failure compared with 45% with functional intestinal failure (P = 0.0055). Compared with nonsurvival, 5-year graft survival was also associated with reduced incidences of graft-versus-host disease (2% vs 16%, P = 0.0237), post-transplant lymphoproliferative disorder (3% vs 24%, P = 0.0067), and de novo donor-specific antibodies (19% vs 57%, P = 0.0451) plus a lower donor-recipient weight ratio (median 0.727 vs 0.923, P = 0.0316). Factors not associated with 5-year intestinal graft survival included graft rejection of any severity and inclusion of a liver graft. Factors associated with graft survival at 10 years were similar to those at 5 years. CONCLUSIONS: In our experience, outcomes in pediatric intestinal transplantation have improved substantially for anatomic but not functional intestinal failure. Graft survival depends on avoidance of severe infectious and immunological complications including GVHD, whereas inclusion of a liver graft provides no obvious survival benefit. Reduced success with functional intestinal failure may reflect inherently increased susceptibility to complications in this group.

Long-term survival in visceral transplant recipients in the new era: A single-center experience.

There is a paucity of data on long-term outcomes following visceral transplantation in the contemporary era. This is a single-center retrospective analysis of all visceral allograft recipients who underwent transplant between November 2003 and December 2013 with at least 3-year follow-up data. Clinical data from a prospectively maintained database were used to assess outcomes including patient and graft survival. Of 174 recipients, 90 were adults and 84 were pediatric patients. Types of visceral transplants were isolated intestinal transplant (56.3%), combined liver-intestinal transplant (25.3%), multivisceral transplant (16.1%), and modified multivisceral transplant (2.3%). Three-, 5-, and 10-year overall patient survival was 69.5%, 66%, and 63%, respectively, while 3-, 5-, and 10-year overall graft survival was 67%, 62%, and 61%, respectively. In multivariable analysis, significant predictors of survival included pediatric recipient (P = .001), donor/recipient weight ratio <0.9 (P = .008), no episodes of severe acute rejection (P = .021), cold ischemia time <8 hours (P = .014), and shorter hospital stay (P = .0001). In conclusion, visceral transplantation remains a good option for treatment of end-stage intestinal failure with parenteral nutritional complications. Proper graft selection, shorter cold ischemia time, and improvement of immunosuppression regimens could significantly improve the long-term survival.

Donor-specific antibody management in intestine transplantation: hope for improving the long-term durability of the intestine allograft?

PURPOSE OF REVIEW: In this review, we appraise the current status of donor-specific antibody (DSA) monitoring and treatment in the literature and highlight the current challenges in DSA management for the intestine transplant community. RECENT FINDINGS: Sensitizing events are common in patients referred for intestinal transplant, as these patients universally are repeatedly exposed to immune activation and inflammatory events. Both preformed and de novo DSA have been shown to increase rejection and graft loss in intestine recipients. Avoidance of preformed DSA with the use of virtual crossmatch (VXM) and antibody monitoring protocols to detect and treat de novo DSA may improve intestine transplant outcomes. There is no consensus on the clinical and pathologic criteria that are required to diagnose antibody-mediated rejection (AMR) in the intestine recipient. Therefore, many clinicians treat AMR based on the coincidence of DSA and acute biopsy-proven rejection. Inclusion of the liver in the intestine allograft appears to be immunologically protective in the setting of DSA with improved outcomes and a higher rate of preformed DSA clearance. Critically, DSA has been linked to chronic rejection and poor long-term outcomes in the intestine recipient. SUMMARY: On the basis of increasing evidence in the intestine transplant literature, it appears that avoidance of preformed DSA and aggressive monitoring and treatment of de novo DSA is a key to long-term survival following intestine transplantation.

Visceral transplantation in patients with intestinal-failure associated liver disease: Evolving indications, graft selection, and outcomes.

Intestinal failure (IF)-associated liver disease (IFALD) is widely recognized as a lethal complication of long-term parenteral nutrition. The pathophysiology of IFALD is poorly understood but appears to be multifactorial and related to the inflammatory state in the patient with IF. Visceral transplant for IFALD includes variants of intestine, liver, or combined liver-intestine allografts. Graft selection for an individual patient depends on the etiology of IF, abdominal and vascular anatomy, severity of IFALD, and potential for intestinal rehabilitation. The past decade has witnessed dramatic improvement in the management of IFALD, principally due to improved lipid emulsion formulations and the multidisciplinary care of the patient with IF. As the recognition and treatment of IFALD continue to improve, the requirement of liver-inclusive visceral grafts appears to be decreasing, representing a paradigm shift in the care of the patient with IF. This review highlights the current indications, graft selection, and outcomes of visceral transplantation for IFALD.

Impact of early reoperation on graft survival after liver transplantation: Univariate and multivariate analysis.

BACKGROUND: Data on rate, risk factors, and consequences of early reoperation after liver transplantation are still limited. STUDY DESIGN: Single-center retrospective analysis of data of 428 patients, who underwent liver transplantation in period between January 2009 and December 2014. Univariate and multivariate analysis were used to study the risk factors of early reoperation and its impact on graft survival. RESULTS: Of 428 patients, 74 (17.3%) underwent early reoperation. Of them, 46 (62.2%) underwent reoperation within the first week and 28 (37.8%) underwent reoperation later than 1 week after transplantation. With multivariate analysis, significant risk factors of early reoperation included pretransplant ICU admission, previous abdominal surgery and diabetes. Early reoperation itself was not found to be an independent predictor of graft loss. However, early reoperation later than 7 days from transplant was found to be independent predictor of graft loss (odds ratio [OR] = 5.125; 95% CI, 1.358-19.552; P = .016). In our series, other independent predictors of graft loss were MELD score (P = .010) and operative time (P = .048). CONCLUSIONS: This analysis demonstrates that early reoperations later than a week appear to negatively impact the graft survival. The timing of early reoperation should be a focus of additional studies.

World's smallest combined en bloc liver-pancreas transplantation.

We present a case of a 2-year-old child who underwent a combined en bloc liver and pancreas transplant following complications of WRS. WRS is characterized clinically through infantile insulin-dependent diabetes mellitus, neutropenia, recurrent infections, propensity for liver failure following viral infections, bone dysplasia, and developmental delay. Usually, death occurs from fulminant liver and concomitant kidney failure. Few cases with WRS are reported in the literature, mostly from consanguineous parents. To the best of our knowledge, combined en bloc liver and pancreas transplant has not been performed in small children.

Fecal pancreatic elastase-1 in the evaluation of pancreatic function after pediatric intestinal transplantation.

Fat malabsorption is common after SBT. To identify whether anatomic variant transplants differ in occurrence of exocrine pancreatic insufficiency that could contribute to fat malabsorption, we measured FPE repeatedly in 54 recipients of a SBT, ages 6.2 to 320 months. FPE determination most distant from SBT was 6.1 years. Of the 54, 39% received an isolated intestinal graft (native pancreas only), 48% received an en bloc liver-intestinal-pancreas graft (native and graft pancreas), and 13% received a multivisceral graft (graft pancreas only). Initial FPE was normal (>200 µg/g) in 15 of the 54 at a median of 22 (11-61) days after SBT. Recipients of a liver-intestine-pancreas transplant were more likely to have normal FPE within 30 days after SBT than were isolated intestinal or multivisceral transplant recipients (47%, 19%, and 0%, respectively, P = .049). Of the remaining 39 patients, 34 eventually demonstrated a normal FPE at a median of 168 (31-943) days after SBT. Type of SBT did not influence the likelihood of achieving a normal FPE level or time when it occurred. Five (9%) patients failed to achieve normal FPE, including 3 who died within 2 years after SBT. In conclusion, possessing both graft and native pancreas as in transplantation of an en bloc liver-intestinal-pancreas graft facilitates early normalization of FPE that eventually occurs in most patients irrespective of transplant type. Failure to recover normal pancreatic function may be associated with severe post-transplant complications.

The use of vascular homografts in pediatric small bowel transplantation: Single-center experience over a decade.

Intestinal transplantation in children has evolved with more isolated small intestine transplants being performed compared to combined liver-intestine transplants. Consequently, surgical techniques have changed, frequently requiring the use of vascular homografts of small caliber to revascularize the isolated small intestine, the impact of which on outcomes is unknown. Among 106 pediatric intestine and multivisceral transplants performed at our center since 2003, 33 recipients of an isolated small intestine graft were included in this study. Outcome parameters were thrombotic complications, graft, and patient survival. A total of 29 of 33 (87.9%) patients required arterial and/or venous homografts from the same donor, mainly iliac or carotid artery and iliac or innominate vein, respectively (donor's median age 1.1 years [2 months to 23 years], median weight 10 kg [14.7-48.5]). Post-transplant, there were three acute arterial homograft thromboses and one venous thrombosis resulting in two peri-operative graft salvages and two graft losses. Three of four thromboses occurred in patients with primary hypercoagulable state, including the two graft losses. Overall, at a median of 4.1 years (1-10.2) from transplant, 29 of 33 (88%) patients are alive with 26 of 33 (79%) functioning grafts. The procurement of intact, size-matched donor vessels and the management of effective post-transplant anticoagulation are critical.

The impact of intercenter sharing on the outcomes of pediatric split liver transplantation.

BACKGROUND: Split liver transplantation allows for expansion of the pool of organs available for pediatric liver transplantation. The impact of sharing segments of the same liver between centers has not been studied. STUDY DESIGN: Retrospective analysis of 24 pediatric split liver transplant cases in a recent cohort. We evaluated the outcomes of pediatric recipients who shared organs with adult patients in our own center (group A) compared to recipients who shared organs with adult patients in other centers. (group B). RESULTS: One-, 3-, and 5-year graft survival for group A was 100%, 100%, and 100% vs 83%, 71%, and 57% for group B (P = .039). Postoperative complications included biliary complications (41.7% in group A vs 50% in group B, P = .682), vascular complications (8.3% in group A vs 41.7% in group B, P = .059), and postoperative bleeding (16.7% in group A vs 25% in group B, P = .615). High-grade Clavien-Dindo complications were 0% in group A vs 33.3% in group B, P = .028. CONCLUSIONS: Organ sharing between centers appears to be associated with significantly poorer graft survival. Possible explanations include greater procurement-related injury or suboptimal vessel distribution. Future larger studies focused on this area may be helpful to formulate policy considerations.

Intestinal Transplant Inflammation: the Third Inflammatory Bowel Disease.

Intestinal transplantation is the most immunologically complex of all abdominal organ transplants. Understanding the role both humoral and innate and adaptive cellular immunity play in intestinal transplantation is critical to improving outcomes and increasing indications for patients suffering from intestinal failure. Recent findings highlighting the impact of donor-specific antibodies on intestinal allografts, the role of NOD2 as a key regulator of intestinal immunity, the protective effects of innate lymphoid cells, and the role of Th17 in acute cellular rejection are reviewed here.

Advances in allograft monitoring after intestinal transplantation.

PURPOSE OF REVIEW: The intestinal allograft, with an enormous lymphoid load, is a highly immunogenic organ which elicits a strong alloimmune response. In the early posttransplant period, a robust graft biopsy protocol via a temporary ileostomy is utilized for surveillance to detect rejection. In the later posttransplant period, after enteral continuity is reestablished, graft biopsies via a colonoscopy become more cumbersome. Alternative methods for intestinal allograft monitoring other than graft biopsy are of particular interest. RECENT FINDINGS: Biomarkers and diagnostic tools, such as granzyme B, perforin, fecal calprotectin, citrulline, donor-specific antibody, and zoom video endoscopy have all been studied for application as reliable methods of performing intestinal allograft surveillance. Each modality has the capability to monitor a separate and unique process in the host-allograft immune response. SUMMARY: The goal to find a reliable, reproducible, and noninvasive method for intestinal graft monitoring remains an elusive one. Many of the current modalities available only serve to act as complementary tests in conjunction with astute clinical observations. Graft biopsy remains the gold standard for monitoring the intestinal allograft.

The microbiome and its implications in intestinal transplantation.

PURPOSE OF REVIEW: This article summarizes the complex interplay between the microbiota and host immune responses, and its impact on intestinal transplantation and allograft rejection. RECENT FINDINGS: Recent findings highlight the importance of Paneth cells as crucial producers of antimicrobial peptides that control the intestinal host-microbial interface as well as the essential role of NOD2 as a master regulator of antimicrobial host defenses. Moreover, complex interactions between innate and adaptive immune responses have been shown to critically shape host antimicrobial Th17 responses, which may be key for the pathogenesis of inflammatory bowel diseases and intestinal allograft rejection. SUMMARY: A growing body of evidence indicates that crosstalk between the microbiome and innate and adaptive host immunity determines alloimmune responses and outcomes in intestinal transplantation. Elaboration of this emerging field might lead to novel mechanistic insight into these complex interactions and allow for new therapeutic approaches.