Impacts of donor-specific anti-HLA antibodies and antibody-mediated rejection on outcomes after intestinal transplantation in children

Intestinal transplantation: Significance of immune responses

Intestinal allografts, with many resident immune cells and as a destination for circulating lymphocytes of the recipient, appear to be the most challenging solid organ transplants. The high incidence of acute rejection and frequent reports of fatal graft-versus-host disease (GvHD) after intestinal transplantation call for more research to describe the molecular mechanisms involved in the immunopathogenesis of post-transplant complications to define new therapeutic targets. In addition, according to the rapid development of immunosuppressive agents, it is time to consider novel therapeutic approaches in managing treatment-refractory patients with rejection or severe GvHD. Herein, the main immunological challenges before and after intestinal transplant including, brain-dead donor inflammation, acute rejection, antibody-mediated, and chronic rejections, as well as GvHD have been described. Besides, the new immune-based therapies used in experimental and clinical settings to improve tolerance toward intestinal allograft, and cases of operational tolerance have been reviewed.

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.

Current approaches for risk assessment of intestinal transplant patients: A view from the histocompatibility laboratory

Despite its recent decline in volumes, intestinal transplantation remains an important option for patients with irreversible intestinal failures. The long-term outcome of an intestinal transplant has stagnated. The major cause of graft loss is rejection, resulting from mismatches in human leukocyte antigens (HLA) and the presence of antibodies to mismatched donor-specific HLA antigens (DSA). Literature has reported that DSAs, either preformed before transplantation or developed de novo after transplantation, are harmful to intestinal grafts, especially for those without combined liver grafts. A comprehensive assessment of DSA by the histocompatibility laboratory is critical for successful intestinal transplantation and its long-term survival. This paper briefly reviews the history and current status of different methods for detecting DSA and their clinical applications in intestinal transplantation. The focus is on applying different antibody assays to manage immunologically challenging intestinal transplant patients before and after transplantation. A clinical case is presented to illustrate the complexity of HLA tests and the necessity of multiple assays. The review of risk assessment by the histocompatibility laboratory also highlights the need for close interaction between the laboratory and the intestinal transplant program.

Including the liver in the visceral allograft: Impact on donor-specific anti-HLA antibodies and long-term outcomes

Humoral immunity emerges as a risk factor for graft failure after visceral transplantation (VTx) and development of donor-specific anti-HLA antibodies (DSAs) has been linked with poor outcomes. In most cases, a simultaneous liver transplant can be safely performed in sensitized patients with DSA and appears protective against lymphocytotoxic antibodies. We investigated the incidence of acute (AR) and chronic rejection (CR) in 32 VTx without any B cell-depleting pre-treatment (6 isolated intestinal transplants (IT) and 26 liver-containing, multivisceral transplants (MVT) and assessed the presence of donor-specific antibodies (DSA) pre- and post-transplantation. Twenty-one patients (65 %) developed AR, 15 (57 %) of the MVT and 6 (100 %) of the IT (p = 0.05). CR occurred in 4 IT (60 %, p < 0.001). At one month, de novo DSA were present in 71 % of VTx (66 % MVT vs 100 % IT, p = 0.09). At the last available follow-up, 69 % of the MVT and 50 % of the IT patients were DSA-free. De novo DSA seemed more persistent (7/19, 37 %) than pre-Tx DSA (1/6, 17 %; p = n.s.), de novo DSA were more frequently specific for HLA class II than class I, 16/19 (84 %) vs. 7/19 (37 %; p = 0.003), and HLA-DQ was their most frequent target HLA. DQ mismatches appeared to be a risk factor for developing de novo DSA. In conclusion, liver-containing visceral allografts have superior short- and long-term outcomes compared with liver-free allografts. De novo DSA develop early and frequently after VTx performed without B cell-depleting induction therapy, but the exact role of DSA in the pathogenesis of rejection remains unclear.

Evaluation of serial monitoring of donor-specific antibodies in pediatric and adult intestinal/multivisceral transplant recipients

BACKGROUND

The study purpose was to add to limited literature assessing anti-HLA donor-specific antibody (DSA) appearance, clearance, specificity, and impact in intestinal/multivisceral (MV) transplant as well as the value of serial monitoring following an institutional protocol shift implementing serial monitoring.

METHODS

This single-center retrospective review included intestinal/MV recipients transplanted 1/1/15-9/31/17 with completed DSA testing. Patients were divided into groups based on DSA presence post-transplant. The primary outcome was biopsy-proven acute rejection (BPAR). Secondary outcomes included graft loss and death. Descriptive analysis of DSA was completed.

RESULTS

Of the 35 intestinal/MV recipients (60% pediatric) with DSA testing, 24 patients had post-transplant DSA. Fifteen patients in the DSA(+) group had T-cell-mediated BPAR versus five in the DSA(-) group (63% vs 45%, p = .47). Days to BPAR were 25 [IQR 19-165] (DSA(+) group) versus 232 [IQR 25.5-632.5] (DSA(-) group) (p = .066). There were no differences between groups for graft loss or death. One hundred and five DSA were identified in the DSA(+) group with 63% being class II, and 54% cleared during follow-up. DSA were directed against 50 different HLA alleles, with the most common being directed against HLA- DQ (35%). Time to first DSA and to clearance did not differ between class I and II.

CONCLUSION

Findings confirm previous data that suggest post-transplant DSA in this population may lead to increased BPAR or shorter time to BPAR, although not statistically significant. Most DSA were identified within the first month after transplant, and ahead of rejection identification on biopsy. DSA therefore may have utility as an early rejection biomarker and use may be considered in place of early protocol biopsies, particularly in pediatric patients. We identified novel findings of DSA directed against a large breadth of HLA in intestinal/MV patients.

Current Anesthetic Management in a 20-Month-Old Pediatric Patient With Intestinal Transplantation Due to Microvillous Inclusion Disease

Intestinal transplantation is a complex procedure both in terms of anesthesia and surgery. In particular, pediatric anesthesia management during intestinal transplant surgery can become even more complicated. It has been stated that propofol, remifentanil, and sevoflurane reduce patient mortality by reducing the incidence of intestinal ischemiareperfusion injury. Although studies of these agents continue to be conducted in vivo or in vitro, these anesthetics are currently used for specific procedures that have a high risk of incurring ischemia-reperfusion injury. Herein, we present the case of a male child, aged 20 months, who was dependent on total parenteral nutrition and was found to have intestinal failure associated with liver disease type 1. Hematologic tests showed findings of anemia and metabolic acidosis. Propofol was administered for induction of anesthesia. Anesthesia maintenance was achieved using sevoflurane with remifentanil infusion. We ensured safe and adequate vascular access in the patient and performed hematologic and biochemical tests with detailed system controls. Before the procedure, we prepared a leukocyte-poor erythrocyte suspension, leukocyte-poor random or apheresis platelets, and ABO- and Rh-compatible fresh frozen plasma. We monitored for signs of acidosis, hypotension, coagulation disorders, and hyperkalemia during the reperfusion period.We maintained patient normothermia. In this case report on the anesthetic management of a pediatric patient aged 20 months who received a small bowel transplant due to microvillous inclusion disease, we found that the selection of anesthetic agents may affect the prognosis of future surgical procedures.

Liver Inclusion Appears to Be Protective Against Graft Loss-Due-to Chronic But Not Acute Rejection Following Intestinal Transplantation

In intestinal transplantation, while other centers have shown that liver-including allografts have significantly more favorable graft survival and graft loss-due-to chronic rejection (CHR) rates, our center has consistently shown that modified multivisceral (MMV) and full multivisceral (MV) allografts have significantly more favorable acute cellular rejection (ACR) and severe ACR rates compared with isolated intestine (I) and liver-intestine (LI) allografts. In the attempt to resolve this apparent discrepancy, we performed stepwise Cox multivariable analyses of the hazard rates of developing graft loss-due-to acute rejection (AR) vs. CHR among 350 consecutive intestinal transplants at our center with long-term follow-up (median: 13.5 years post-transplant). Observed percentages developing graft loss-due-to AR and CHR were 14.3% (50/350) and 6.6% (23/350), respectively. Only one baseline variable was selected into the Cox model indicating a significantly lower hazard rate of developing graft loss-due-to AR: Transplant Type MMV or MV (p < 0.000001). Conversely, two baseline variables were selected into the Cox model indicating a significantly lower hazard rate of developing graft loss-due-to CHR: Received Donor Liver (LI or MV) (p = 0.002) and Received Induction (p = 0.007). In summary, while MMV/MV transplants (who receive extensive native lymphoid tissue removal) offered protection against graft loss-due-to AR, liver-containing grafts appeared to offer protection against graft loss-due-to CHR, supporting the results of other studies.

The Importance Of Avoiding Time-Dependent Bias When Testing The Prognostic Value Of An Intervening Event - Two Acute Cellular Rejection Examples In Intestinal Transplantation

In testing the prognostic value of the occurrence of an intervening event (clinical event that occurs post-transplant), 3 proper statistical methodologies for testing its prognostic value exist (time dependent covariate, landmark, and semi-Markov modelling methods). However, time-dependent bias has appeared in many clinical reports, whereby the intervening event is statistically treated as a baseline variable (as if it occurred at transplant). Using a single-center cohort of 445 intestinal transplant cases to test the prognostic value of 1^st acute cellular rejection (ACR) and severe (grade of) ACR on the hazard rate of developing graft loss, we demonstrate how the inclusion of such time-dependent bias can lead to severe underestimation of the true hazard ratio (HR). The (statistically more powerful) time dependent covariate method in Cox's multivariable model yielded significantly unfavorable effects of 1^st ACR (P<.0001; HR=2.492) and severe ACR (P<.0001; HR=4.531). In contrast, when using the time-dependent biased approach, multivariable analysis yielded an incorrect conclusion for the prognostic value of 1^st ACR (P=.31, HR=0.877, 35.2% of 2.492) and a much smaller estimated effect of severe ACR (P=.0008; HR=1.589; 35.1% of 4.531). In conclusion, this study demonstrates the importance of avoiding time-dependent bias when testing the prognostic value of an intervening event.

Antibody-removal therapies for de novo DSA in pediatric intestinal recipients: Why, when, and how? A single-center experience

BACKGROUND

Donor-specific anti-HLA antibodies (DSA) impact negatively on the outcome of intestinal grafts. Although the use of antibody-removal therapies (ART) is becoming more frequent in the last few years, issues regarding their timing and effectiveness remain under discussion.

METHODS

In the present study, we report our experience with eight ART procedures (based on plasmapheresis, intravenous immunoglobulin, and rituximab) in eight pediatric intestinal and multivisceral transplants with de novo DSA (dnDSA).

RESULTS

ART were performed when dnDSA appeared in two contexts: (1) concomitant with rejection (acute or chronic) or (2) without rejection or any other clinical symptom. Complete DSA removal was observed in seven out of eight patients, showing an effectiveness of 88%. In the group treated for dnDSA without clinical symptoms, the success rate was 100%, with complete DSA removal and without rejection afterward. A shorter time between DSA detection and ART performance appeared as a significant factor for the success of the therapy (p = 0.0002). DSA against HLA-A and DQ alleles were the most resistant to ART, whereas anti-DR DSA were the most sensitive. In addition, the 8-year allograft survival rate in recipients undergoing ART was similar to that in those without DSA, being significantly lower in non-treated DSA-positive recipients (p = 0.013).

CONCLUSION

The results confirm the effectiveness of ART in terms of DSA removal and allograft survival and encourage its early use even in the absence of clinical symptoms.

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.

Beyond 10 years, with or without an intestinal graft: Present and future?

Long-term outcomes in children undergoing intestinal transplantation remain unclear. Seventy-one children underwent intestinal transplantation in our center from 1989 to 2007. We report on 10-year posttransplant outcomes with (group 1, n = 26) and without (group 2, n = 9) a functional graft. Ten-year patient and graft survival rates were 53% and 36%, respectively. Most patients were studying or working, one third having psychiatric disorders. All patients in group 1 were weaned off parenteral nutrition with mostly normal physical growth and subnormal energy absorption. Graft histology from 15 late biopsies showed minimal abnormality. However, micronutrient deficiencies and fat malabsorption were frequent; biliary complications occurred in 4 patients among the 17 who underwent liver transplantation; median renal clearance was 87 mL/min/1.73 m² . Four patients in group 1 experienced late acute rejection. Among the 9 patients in group 2, 4 died after 10 years and 2 developed significant liver fibrosis. Liver transplantation and the use of a 3-drug regimen including sirolimus or mycophenolate mofetil were associated with improved graft survival. Therefore, intestinal transplantation may enable a satisfactory digestive function in the long term. The prognosis of graft removal without retransplantation is better than expected. Regular monitoring of micronutrients, early psychological assessment, and use of sirolimus are recommended.

Microsimulation Model to Compare Enteral and Parenteral Iron Supplementation in Children With Intestinal Failure

BACKGROUND

Children with chronic intestinal failure have a high prevalence of anemia, commonly from iron deficiency, leading to frequent blood transfusions. No current guideline exists for iron supplementation in these children. In this analysis, we evaluate the effectiveness and the cost-effectiveness of using parenteral, enteral, and no iron supplementation to reduce blood transfusions.

METHODS

We created a microsimulation model of pediatric intestinal failure over a 1-year time horizon. Model outcomes included cost (US dollars), blood transfusions received, and hemoglobin trend. Strategies tested included no supplementation, daily enteral supplementation, and monthly parenteral supplementation. We estimated parameters for the model using an institutional cohort of 55 patients. Model parameters updated each 1-month cycle using 2 regressions. A multivariate mixed-effects linear regression estimated hemoglobin values at the next month based on data from the prior month. A mixed-effects logistic regression on hemoglobin predicted the probability of receiving a blood transfusion in a given month.

RESULTS

Compared with no supplementation, both enteral and parenteral iron supplementation reduced blood transfusions required per patient by 0.3 and 0.5 transfusions per year, respectively. Enteral iron cost $34 per avoided blood transfusion. Parenteral iron cost an additional $6600 per avoided blood transfusion compared with enteral iron.

CONCLUSIONS

We found both parenteral and enteral iron to be effective at reducing blood transfusions. The cost of enteral iron makes it the desired choice in patients who can tolerate it. Future work should aim to identify which subpopulations of patients may benefit most from one strategy over the other.

Donor-Specific Antibodies in Pediatric Intestinal and Multivisceral Transplantation: The Role of Liver and Human Leukocyte Antigen Mismatching

Rejection is one of the most important drawbacks for graft and patient survival in intestinal and multivisceral transplantation. However, there is no consensus on the diagnostic criteria for humoral rejection, and the literature about the role of donor-specific antibodies (DSA) on allograft outcome and the risk factors that contribute to their development is scant with contradictory results. The present study analyzes the role of DSA exclusively in a pediatric cohort of 43 transplants. Among our patients, 11.6% showed preformed DSA, but they did not correlate with more rejection or less allograft survival. Having previous transplants was the main sensitization factor with an odds ratio (OR) = 44.85 (P = 0.001). In total, 16.3% of recipients developed de novo donor-specific antibodies (dnDSA), mostly directed against human leukocyte antigen (HLA) class II, polyspecific and complement fixing. Additionally, the presence of dnDSA had a deleterious effect on graft rejection (hazard ratio [HR] = 11.00; P = 0.01) and survival (HR = 66.52; P < 0.001) in an observational period of 5 years after transplantation. The inclusion of the liver emerged as the main protective factor against dnDSA development with an OR = 0.07 (P = 0.007). The analysis of HLA compatibility at the serological and epitope level with the computational tools HLAMatchmaker and PIRCHE revealed no association between HLA mismatching and dnDSA. In conclusion, this study performed in pediatric recipients shows the deleterious effect of dnDSA on intestinal transplantation supported by the complement-fixing activity observed. Additionally, the liver inclusion in the allografts showed to be a protective factor against dnDSA generation.

Antibody-mediated rejection in pediatric small bowel transplantation: Capillaritis is a major determinant of C4d positivity in intestinal transplant biopsies

The diagnostic criteria for antibody-mediated rejection (ABMR) after small bowel transplantation (SBT) are not clearly defined, although the presence of donor-specific antibodies (DSAs) has been reported to be deleterious for graft survival. We aimed to determine the incidence and prognostic value of DSAs and C4d in pediatric SBT and to identify the histopathologic features associated with C4d positivity. We studied all intestinal biopsies (IBx) obtained in the first year posttransplantation (N = 345) in a prospective cohort of 23 children. DSAs and their capacity to fix C1q were identified by using Luminex technology. Eighteen patients (78%) had DSAs, and 9 had the capacity to fix C1q. Seventy-eight IBx (22.6%) were C4d positive. The independent determinants of C4d positivity were capillaritis grades 2 and 3 (odds ratio [OR] 4.02, P = .047 and OR 5.17, P = .003, respectively), mucosal erosion/ulceration (OR 2.8, P = .019), lamina propria inflammation grades 1 and 2/3 (OR 1.95, P = .043 and OR 3.1, P = .016, respectively), and chorion edema (OR 2.16, P = .028). Complement-fixing DSAs and repeated C4d-positive IBx were associated with poor outcome (P = .021 and P = .001, respectively). Our results support that capillaritis should be considered as a feature of ABMR in SBT and identify C1q-fixing DSAs and repeated C4d positivity as potential markers of poor outcome.

Chronic Rejection After Intestinal Transplant: Where Are We in Order to Avert It?

Chronic rejection affects the long-term survival of all solid organ transplants and, among intestinal allografts, occurs in up to 10% of the recipients. The insidious clinical evolution of the chronic allograft enteropathy, the absence of noninvasive biomarkers, and the late endoscopic findings delay its diagnosis. No pharmacological approach has been proven effective, and allograft removal nowadays still represents the only available therapy. The inclusion of the liver in the visceral allograft appears to be the only intervention affecting the development of chronic rejection, as revealed by large-center studies and registry reports. A significant body of evidence emerged from the experimental setting and provided essential knowledge on the complex mechanisms behind the development of chronic allograft enteropathy. More recently, donor-specific antibodies have been suggested as an early, key element in the natural history of chronic allograft enteropathy and several novel approaches, tackling the antibody-mediated graft injury, have gained acceptance in clinical settings and are believed to impact on chronic rejection. The inclusion of a liver allograft is advocated when re-transplanting a sensitized recipient, due to its protective effect against humoral immunity. Multicenter trials are required to understand and tackle chronic rejection, and find the therapeutic answer to this clinical dilemma.

Intestinal transplantation: a review

PURPOSE OF REVIEW

The purpose of this article is to review the existing literature on the current indications, surgical techniques, immunosuppressive therapy and outcomes following intestinal transplantation (ITx).

RECENT FINDINGS

Over recent years, ITx has become a more common operation with approximately 2500 procedures carried out worldwide by 2014. It is reserved for patients with intestinal failure and who have developed complications of home parenteral nutrition or who have a high risk of dying from their underlying disease. Recent advances such as the improvement in survival rates, not only for isolated small bowel transplants but also following inclusion of a liver graft in combined liver-small bowel transplant, and the utility of citrulline as a noninvasive biomarker to appreciate acute rejection herald an exciting shift in the field of ITx.

SUMMARY

With advancements in immunosuppressive drugs, induction regimens, standardization of surgical techniques and improved postoperative care, survival is increasing. In due course, it will most likely become as good as remaining on home parenteral nutrition and as such could become a viable first-line option.