New directions for rabbit antithymocyte globulin (Thymoglobulin(®)) in solid organ transplants, stem cell transplants and autoimmunity

The impact of induction therapy on the risk of posttransplant lymphoproliferative disorder in adult kidney transplant recipients with donor-recipient serological Epstein-Barr virus mismatch

Posttransplant lymphoproliferative disorder (PTLD) poses a significant concern in Epstein-Barr virus (EBV)-negative patients transplanted from EBV-positive donors (EBV R-/D+). Previous studies investigating the association between different induction agents and PTLD in these patients have yielded conflicting results. Using the Organ Procurement and Transplant Network database, we identified EBV R-/D+ patients >18 years of age who underwent kidney-alone transplants between 2016 and 2022 and compared the risk of PTLD with rabbit antithymocyte globulin (ATG), basiliximab, and alemtuzumab inductions. Among the 6620 patients included, 64.0% received ATG, 23.4% received basiliximab, and 12.6% received alemtuzumab. The overall incidence of PTLD was 2.5% over a median follow-up period of 2.9 years. Multivariable analysis demonstrated that the risk of PTLD was significantly higher with ATG and alemtuzumab compared with basiliximab (adjusted subdistribution hazard ratio [aSHR] = 1.98, 95% confidence interval [CI] 1.29-3.04, P = .002 for ATG and aSHR = 1.80, 95% CI 1.04-3.11, P = .04 for alemtuzumab). However, PTLD risk was comparable between ATG and alemtuzumab inductions (aSHR = 1.13, 95% CI 0.72-1.77, P = .61). Therefore, the risk of PTLD must be taken into consideration when selecting the most appropriate induction therapy for this patient population.

Immunosuppressive Induction Therapy Using the Antithymocyteglobulin Grafalon: A Single-Center Non-Interventional Study

Background: Induction therapy with depleting antibodies in the setting of liver transplantation (LT) is discussed controversially to this day. The rabbit antithymocyteglobulin (ATG) Thymoglobulin (rATG) was introduced as early as 1984 and was frequently used as a standard regime for induction therapy after LT. There are no public reports characterizing Grafalon (ATG-F), a novel ATG, as an induction agent after LT. Objectives: The aim of this observational non-interventional study was to investigate the safety and efficacy of Grafalon induction therapy and characterize its clinical effects in the setting of LT. Methods: A cohort of 80 patients undergoing deceased donor LT at the Medical University of Vienna and receiving Grafalon as part of the clinical standard immunosuppressive regimen was prospectively included between March 2021 and November 2022. Patients were monitored closely for leukocytopenia and thrombocytopenia during the first postoperative week and followed up for incidence and severity of biopsy-proven acute rejection (BPAR), overall survival, and bacterial infections in the first year after LT. Results: The incidences of thrombocytopenia and leukocytopenia following Grafalon treatment peaked on postoperative day four, with 64% and 31%, respectively. However, there were no cases of severe leukocytopenia after the first postoperative week. Induction therapy with Grafalon resulted in a rate of localized bacterial infections and bacteremia of 28% and 21%, respectively. The rate of BPAR was 12.5% in the first year after LT; the one-year survival rate in this cohort was 90%. Conclusions: Overall, this study provides evidence of the safety and efficacy of Grafalon as an induction agent. Further studies investigating the potential long-term effects of Grafalon, as well as comparison studies with different immunosuppressive regimens, are needed in order to draw further conclusions.

European flow cytometry quality assurance guidelines for the diagnosis of primary immune deficiencies and assessment of immune reconstitution following B cell depletion therapies and transplantation

Over the last 15 years activity of diagnostic flow cytometry services have evolved from monitoring of CD4 T cell subsets in HIV-1 infection to screening for primary and secondary immune deficiencies syndromes and assessment of immune constitution following B cell depleting therapy and transplantation. Changes in laboratory activity in high income countries have been driven by initiation of anti-retroviral therapy (ART) in HIV-1 regardless of CD4 T cell counts, increasing recognition of primary immune deficiency syndromes and the wider application of B cell depleting therapy and transplantation in clinical practice. Laboratories should use their experience in standardization and quality assurance of CD4 T cell counting in HIV-1 infection to provide immune monitoring services to patients with primary and secondary immune deficiencies. Assessment of immune reconstitution post B cell depleting agents and transplantation can also draw on the expertise acquired by flow cytometry laboratories for detection of CD34 stem cell and assessment of MRD in hematological malignancies. This guideline provides recommendations for clinical laboratories on providing flow cytometry services in screening for immune deficiencies and its emerging role immune reconstitution after B cell targeting therapies and transplantation.

Lymphocyte Depleting and Modulating Therapies for Chronic Lung Allograft Dysfunction

Chronic lung rejection, also called chronic lung allograft dysfunction (CLAD), remains the major hurdle limiting long-term survival after lung transplantation, and limited therapeutic options are available to slow the progressive decline in lung function. Most interventions are only temporarily effective in stabilizing the loss of or modestly improving lung function, with disease progression resuming over time in the majority of patients. Therefore, identification of effective treatments that prevent the onset or halt progression of CLAD is urgently needed. As a key effector cell in its pathophysiology, lymphocytes have been considered a therapeutic target in CLAD. The aim of this review is to evaluate the use and efficacy of lymphocyte depleting and immunomodulating therapies in progressive CLAD beyond usual maintenance immunosuppressive strategies. Modalities used include anti-thymocyte globulin, alemtuzumab, methotrexate, cyclophosphamide, total lymphoid irradiation, and extracorporeal photopheresis, and to explore possible future strategies. When considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin and total lymphoid irradiation appear to offer the best treatment options currently available for progressive CLAD patients. SIGNIFICANCE STATEMENT: Effective treatments to prevent the onset and progression of chronic lung rejection after lung transplantation are still a major shortcoming. Based on existing data to date, considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin, and total lymphoid irradiation are currently the most viable second-line treatment options. However, it is important to note that interpretation of most results is hampered by the lack of randomized controlled trials.

Evaluating anti-thymocyte globulin induction doses for better allograft and patient survival in Asian kidney transplant recipients

Anti-thymocyte globulin (ATG) is currently the most widely prescribed induction regimen for preventing acute rejection after solid organ transplantation. However, the optimal dose of ATG induction regimen in Asian kidney recipients is unclear. Using the Korean Organ Transplantation Registry, we performed a retrospective cohort study of 4579 adult patients who received renal transplantation in South Korea and divided them into three groups according to the induction regimen: basiliximab group (n = 3655), low-dose ATG group (≤ 4.5 mg/kg; n = 467), and high-dose ATG group (> 4.5 mg/kg; n = 457). We applied the Toolkit for Weighting and Analysis of Nonequivalent Groups (TWANG) package to generate high-quality propensity score weights for intergroup comparisons. During four-year follow-ups, the high-dose ATG group had the highest biopsy-proven acute rejection rate (basiliximab 20.8% vs. low-dose ATG 22.4% vs. high-dose ATG 25.6%; P < 0.001). However, the rates of overall graft failure (4.0% vs. 5.0% vs. 2.6%; P < 0.001) and mortality (1.7% vs. 2.8% vs. 1.0%; P < 0.001) were the lowest in the high-dose ATG group. Our results show that high-dose ATG induction (> 4.5 mg/kg) was superior to basiliximab and low-dose ATG induction in terms of graft and patient survival in Asian patients undergoing kidney transplant.

The impact of induction therapy in low-immunological risk kidney transplant recipients regardless of HLA matching

BACKGROUND

Induction agents have proved to reduce the rate of acute rejection (AR) in kidney transplant recipients (KTRs) without improving long-term graft and patient survival (PS).

OBJECTIVE

This study evaluates the utility of induction therapy in low immunological risk KTRs regardless of donor-to-recipient HLA matching.

METHODS

We retrospectively reviewed the records of 218 patients undergoing kidney transplantation (KT). These patients were divided into two groups according to the usage of induction therapy: 82 did not receive any induction therapy (Group I), and 136 patients received either Anti-IL2 receptor antibodies or anti-thymocyte globulin (Group II). All patients had panel reactive antibody (PRA) < 20% and absence of donor-specific antibodies (DSA). The difference in outcomes were assessed at different intervals following KT.

RESULTS

The rate of bacterial infections at one year (p-value = 0.032) and the frequency of CMV disease (p-value = 0.044) were significantly higher in Group II (with induction therapy). The duration of hospital stay, the rate and severity of acute rejection, the occurrence of delayed graft function, the rate and type of surgical complications at one year, and the graft function and survival at one and three years were similar between the two groups (p-value = NS). In addition, the financial burden is much less in Group I (without induction therapy), reducing the total cost of the transplant procedure.

CONCLUSION

We conclude that induction therapy in low-immunological risk kidney transplant patients is not a must regardless of donor-to-recipient HLA matching. Therefore, induction therapy did not yield significant health results, but had negative financial consequences.

Characteristics of Graft-Versus-Host Disease (GvHD) After Post-Transplantation Cyclophosphamide Versus Conventional GvHD Prophylaxis

Post-transplantation cyclophosphamide (PTCy) has been shown to effectively control graft-versus-host disease (GvHD) in haploidentical (Haplo) transplantations. In this retrospective registry study, we compared GvHD organ distribution, severity, and outcomes in patients with GvHD occurring after Haplo transplantation with PTCy GvHD prophylaxis (Haplo/PTCy) versus HLA-matched unrelated donor transplantation with conventional prophylaxis (MUD/conventional). We evaluated 2 cohorts: patients with grade 2 to 4 acute GvHD (aGvHD) including 264 and 1163 recipients of Haplo and MUD transplants; and patients with any chronic GvHD (cGvHD) including 206 and 1018 recipients of Haplo and MUD transplants, respectively. In comparison with MUD/conventional transplantation ± antithymocyte globulin (ATG), grade 3-4 aGvHD (28% versus 39%, P = .001), stage 3-4 lower gastrointestinal (GI) tract aGvHD (14% versus 21%, P = .01), and chronic GI GvHD (21% versus 31%, P = .006) were less common after Haplo/PTCy transplantation. In patients with grade 2-4 aGvHD, cGvHD rate after Haplo/PTCY was also lower (hazard ratio [HR] = .4, P < .001) in comparison with MUD/conventional transplantation without ATG in the nonmyeloablative conditioning setting. Irrespective of the use of ATG, non-relapse mortality rate was lower (HR = .6, P = .01) after Haplo/PTCy transplantation, except for transplants that were from a female donor into a male recipient. In patients with cGvHD, irrespective of ATG use, Haplo/PTCy transplantation had lower non-relapse mortality rates (HR = .6, P = .04). Mortality rate was higher (HR = 1.6, P = .03) during, but not after (HR = .9, P = .6) the first 6 months after cGvHD diagnosis. Our results suggest that PTCy-based GvHD prophylaxis mitigates the development of GI GvHD and may translate into lower GvHD-related non-relapse mortality rate.

Macrophage-inducible C-type lectin activates B cells to promote T cell reconstitution in heart allograft recipients

Diminishing homeostatic proliferation of memory T cells is essential for improving the efficacy of lymphoablation in transplant recipients. Our previous studies in a mouse heart transplantation model established that B lymphocytes secreting proinflammatory cytokines are critical for T cell recovery after lymphoablation. The goal of the current study was to identify mediators of B cell activation following lymphoablation in allograft recipients. Transcriptome analysis revealed that macrophage-inducible C-type lectin (Mincle, Clec4e) expression is up-regulated in B cells from heart allograft recipients treated with murine anti-thymocyte globulin (mATG). Recipient Mincle deficiency diminishes B cell production of pro-inflammatory cytokines and impairs T lymphocyte reconstitution. Mixed bone marrow chimeras lacking Mincle only in B lymphocytes have similar defects in T cell recovery. Conversely, treatment with a synthetic Mincle ligand enhances T cell reconstitution after lymphoablation in non-transplanted mice. Treatment with agonistic CD40 mAb facilitates T cell reconstitution in CD4 T cell-depleted, but not in Mincle-deficient, recipients indicating that CD40 signaling induces T cell proliferation via a Mincle-dependent pathway. These findings are the first to identify an important function of B cell Mincle as a sensor of damage-associated molecular patterns released by the graft and demonstrate its role in clinically relevant settings of organ transplantation.

T cell depletion increases humoral response by favoring T follicular helper cells expansion

Antibody-mediated rejection is a major cause of long-term graft loss in kidney transplant patients. T follicular helper (Tfh) cells are crucial for assisting B cell differentiation and are required for an efficient antibody response. Anti-thymocyte globulin (ATG) is a widely used lymphocyte-depleting induction therapy. However, less is known about how ATG affects Tfh cell development and donor-specific antibody (DSA) formation. We observed an increase in circulating Tfh cells at 6 months after kidney transplant in patients who received ATG. Using an NP-OVA immunization model, we found that ATG-treated mice had a higher percentage of Tfh cells, germinal center B cells, and higher titers of antigen-specific antibodies compared to controls. ATG-treated animals had lower levels of IL-2, a known Bcl-6 repressor, but higher levels of IL-21, pSTAT3 and Bcl-6, favoring Tfh differentiation. In a mouse kidney transplant model, ATG-treated recipients showed an increase in Tfh cells, DSA and C4d staining in the allograft. Although ATG was effective in depleting T cells, it favored the expansion of Tfh cells following depletion. Concomitant use of IL-2, tacrolimus, or rapamycin with ATG was essential to control Tfh cell expansion. In summary, ATG depletion favors Tfh expansion, enhancing antibody-mediated response.

Risk Factors of Rejection in Renal Transplant Recipients: A Narrative Review

Multiple factors influence graft rejection after kidney transplantation. Pre-operative factors affecting graft function and survival include donor and recipient characteristics such as age, gender, race, and immunologic compatibility. In addition, several peri- and post-operative parameters affect graft function and rejection, such as cold and warm ischemia times, and post-operative immunosuppressive treatment. Exposure to non-self-human leucocyte antigens (HLAs) prior to transplantation up-regulates the recipient’s immune system. A higher rate of acute rejection is observed in transplant recipients with a history of pregnancies or significant exposure to blood products because these patients have higher panel reactive antibody (PRA) levels. Identifying these risk factors will help physicians to reduce the risk of allograft rejection, thereby promoting graft survival. In the current review, we summarize the existing literature on donor- and recipient-related risk factors of graft rejection and graft loss following kidney transplantation.

What Therapeutic Regimen Will Be Optimal for Initial Clinical Trials of Pig Organ Transplantation?

We discuss what therapeutic regimen might be acceptable/successful in the first clinical trial of genetically engineered pig kidney or heart transplantation. As regimens based on a calcineurin inhibitor or CTLA4-Ig have proved unsuccessful, the regimen we administer to baboons is based on induction therapy with antithymocyte globulin, an anti-CD20 mAb (Rituximab), and cobra venom factor, with maintenance therapy based on blockade of the CD40/CD154 costimulation pathway (with an anti-CD40 mAb), with rapamycin, and a corticosteroid. An anti-inflammatory agent (etanercept) is administered for the first 2 wk, and adjuvant therapy includes prophylaxis against thrombotic complications, anemia, cytomegalovirus, and pneumocystis. Using this regimen, although antibody-mediated rejection certainly can occur, we have documented no definite evidence of an adaptive immune response to the pig xenograft. This regimen could also form the basis for the first clinical trial, except that cobra venom factor will be replaced by a clinically approved agent, for example, a C1-esterase inhibitor. However, none of the agents that block the CD40/CD154 pathway are yet approved for clinical use, and so this hurdle remains to be overcome. The role of anti-inflammatory agents remains unproven. The major difference between this suggested regimen and those used in allotransplantation is the replacement of a calcineurin inhibitor with a costimulation blockade agent, but this does not appear to increase the complications of the regimen.

Relationship Between Antithymocyte Globulin Concentrations and Lymphocyte Sub-Populations in Kidney Transplant Patients

BACKGROUND

Rabbit antithymocyte globulins (rATGs) are polyclonal antibodies used to prevent acute cellular rejection in kidney transplantation. Their dosing remains largely empirical and the question of an individualized dose is still unresolved.

METHODS

Data from a prospective study in 17 kidney transplant patients were used to develop a model describing the dose-concentration-response relationship of rATG with T-lymphocyte subpopulation counts over time. The model was validated using an independent cohort of kidney transplant patients treated by rATG in the same center.

RESULTS

Pharmacokinetics of rATG was described using a two-compartment model integrating a third compartment and a target-mediated elimination for active rATG. The kinetics of CD3⁺, CD4⁺, CD8⁺, and CD3^-CD56⁺ cell counts over time were described by a pharmacokinetic-pharmacodynamic model with transit compartments, integrating both CD3^-CD56⁺-independent and CD3^-CD56⁺-dependent rATG-mediated lymphocyte depletion, and a positive feedback. Elimination of rATG was influenced by age and body surface area, while its distribution was also influenced by body surface area. CD3⁺ proliferation rate decreased with age and CD3^-CD56⁺-mediated elimination was influenced by the V158F-FCGR3A polymorphism. Binary efficacy and tolerance endpoints were defined as a CD3⁺ count < 20 mm^-3 for at least 7 days and a CD4⁺ count > 200 mm^-3 at 1 year, respectively. Simulations showed that increasing or decreasing the standard 6-mg/kg dose will impact both tolerance and efficacy, while a dose decrease may be beneficial in elderly patients.

CONCLUSIONS

Our results can be used to design prospective clinical trials testing dose individualization based on patients' characteristics.

CLINICAL TRIAL REGISTRATION

Eudract No. 2009-012673-35.

Post-transplant cyclophosphamide versus anti-thymocyte globulin for graft-versus-host disease prevention in haploidentical transplantation for adult acute lymphoblastic leukemia

Graft-versus-host disease (GVHD) prophylaxis for unmanipulated haploidentical hematopoietic cell transplantation (haplo-HCT) include post-transplant cyclophosphamide (PTCy) and anti-thymocyte globulin (ATG). Utilizing EBMT registry, we compared ATG versus PTCy based GVHD prophylaxis in adult acute lymphoblastic leukemia (ALL) patients undergoing haplo-HCT. Included were 434 patients; ATG (n=98) and PTCy (n=336). Median follow-up was ~2 years. Baseline characteristics were similar between the groups except that the ATG-group was more likely to have relapsed/refractory ALL (P=0.008), non-TBI conditioning (P<0.001), peripheral blood graft source (P=<0.001) and transplanted at an earlier time-period (median year of HCT 2011 vs. 2015). The 100-day grade II-IV and III-IV acute-GVHD was similar between ATG and PTCy, as was 2-year chronic-GVHD. On multivariate analysis (MVA), leukemia-free survival (LFS) and overall survival (OS) was better with PTCy compared to ATG prophylaxis. Relapse incidence (RI) was lower in the PTCy group (P=0.03), while non-relapse mortality (NRM) was not different. Advanced disease and lower performance score were associated with poorer LFS and OS and advanced disease with inferior GVHD-free/relapse-free survival (GRFS). Peripheral grafts were associated with higher GVHD compared to bone marrow grafts. In ALL patients undergoing unmanipulated haplo-HCT, PTCy for GVHD prevention resulted in lower RI and improved LFS and OS compared to ATG.

Low-Dose Antithymocyte Globulin Has No Disadvantages to Standard Higher Dose in Pediatric Kidney Transplant Recipients: Report From the Pediatric Nephrology Research Consortium

INTRODUCTION

Rabbit antithymocyte globulin (rATG) dosing strategies for induction in pediatric kidney transplantation vary between centers. It is not known whether a lower rATG induction dose provides safe and effective immunosuppression compared with a "standard" higher dose.

METHODS

We performed a retrospective multicenter study of all isolated first-time kidney transplant recipients <21 years old who received rATG induction between 1 January 2010 and 31 December 2014 at 9 pediatric centers. An a priori cutoff of a 4.5-mg/kg cumulative rATG dose was used to identify low (≤ 4.5 mg/kg) and standard (> 4.5 mg/kg) exposure groups. Outcomes examined included 12 months posttransplant graft function (estimated glomerular filtration rate [eGFR]); the occurrence of acute rejection, donor-specific antibody (DSA), neutropenia, and viral infection (cytomegalovirus [CMV], Epstein-Barr virus [EBV], and BK virus); and 24-month outcomes of posttransplant lymphoproliferative disorder (PTLD) occurrence and patient and graft survival.

RESULTS

Two hundred thirty-five patients were included. Baseline features of the low and standard rATG dose groups were similar. By 12 months, the rATG dose group had no significant impact on the occurrence of neutropenia, positive DSA, or viral polymerase chain reaction (PCR). Graft function was similar. Acute rejection rates were similar at 17% (low dose) versus 19% (standard dose) (P = 0.13). By 24 months, graft survival (96.4% vs. 94.6%) and patient survival (100% vs. 99.3%) were similar between the low- and standard-dose groups (P = 0.54 and 0.46), whereas the occurrence of PTLD trended higher in the standard-dose group (0% vs. 2.6%, P = 0.07).

CONCLUSION

A low rATG induction dose ≤ 4.5 mg/kg provided safe and effective outcomes in this multicenter low immunologic risk pediatric cohort. Prospective studies are warranted to define the optimal rATG induction dose in pediatric kidney transplantation.

Decreased incidence of acute rejection without increased incidence of cytomegalovirus (CMV) infection in kidney transplant recipients receiving rabbit anti-thymocyte globulin without CMV prophylaxis - a cohort single-center study

Induction therapy with rabbit anti-thymocyte globulin (rATG) in low-risk kidney transplant recipients (KTR) remains controversial, given the associated increased risk of cytomegalovirus (CMV) infection. This natural experiment compared 12-month clinical outcomes in low-risk KTR without CMV prophylaxis (January/3/13-September/16/15) receiving no induction or a single 3 mg/kg dose of rATG. We used logistic regression to characterize delayed graft function (DGF), negative binomial to characterize length of hospital stay (LOS), and Cox regression to characterize acute rejection (AR), CMV infection, graft loss, death, and hospital readmissions. Recipients receiving 3 mg/kg rATG had an 81% lower risk of AR (aHR 0.14 0.190.25 , P < 0.001) but no increased rate of hospital readmissions because of infections (0.68 0.911.21 , P = 0.5). There was no association between 3 mg/kg rATG and CMV infection/disease (aHR 0.86 1.101.40 , P = 0.5), even when the analysis was stratified according to recipient CMV serostatus positive (aHR 0.94 1.251.65 , P = 0.1) and negative (aHR 0.28 0.571.16 , P = 0.1). There was no association between 3 mg/kg rATG and mortality (aHR 0.51 1.253.08 , P = 0.6), and graft loss (aHR 0.34 0.731.55 , P = 0.4). Among low-risk KTR receiving no CMV pharmacological prophylaxis, 3 mg/kg rATG induction was associated with a significant reduction in the incidence of AR without an increased risk of CMV infection, regardless of recipient pretransplant CMV serostatus.

Considerations and controversies of pharmacologic management of the pediatric kidney transplant recipient

Pediatric kidney transplantation has experienced considerable growth and improvement in patient and allograft outcomes over the past 20 years, in part due to advancements in immunosuppressive regimens and management. Despite this progress, care for this unique population can be challenging due to limited pediatric transplant data and trials, intricacies related to differences in children and adolescents compared with their adult counterparts, and limitations to long-term survival facing all solid organ transplant populations. Immunosuppression and infection prevention practices vary from one pediatric transplant center to another and clinical controversies exist surrounding treatment and dosing. This review aims to summarize key aspects of pharmacologic management in this population and present pertinent data that describe the influence of practice to serve as a resource for practitioners caring for this unique specialty patient population. Additionally, this review highlights select controversies that exist within pediatric kidney transplantation.

Implications for body weight extremes in solid organ transplantation

The pharmacokinetic profiles of medications are altered in overweight and underweight patients, but few studies have described these differences in patients with body mass index extremes. As solid organ transplant programs expand their candidate selection criteria to accommodate a growing population of patients with weight extremes, it has become imperative to understand and evaluate the impact weight extremes have on the pharmacokinetics of life-sustaining immunosuppression in this population. This review will describe pharmacokinetic and dosing considerations for weight extremes in solid organ transplant recipients, including changes following bariatric surgeries, non-pharmacologic and pharmacologic management strategies for weight loss and gain, and potential drug-drug interactions with popular weight management products.

Siplizumab, an Anti-CD2 Monoclonal Antibody, Induces a Unique Set of Immune Modulatory Effects Compared to Alemtuzumab and Rabbit Anti-Thymocyte Globulin In Vitro

Antibodies are commonly used in organ transplant induction therapy and to treat autoimmune disorders. The effects of some biologics on the human immune system remain incompletely characterized and a deeper understanding of their mechanisms of action may provide useful insights for their clinical application. The goal of this study was to contrast the mechanistic properties of siplizumab with Alemtuzumab and rabbit Anti-Thymocyte Globulin (rATG). Mechanistic assay systems investigating antibody-dependent cell-mediated cytotoxicity, antibody-dependent cell phagocytosis and complement-dependent cytotoxicity were used to characterize siplizumab. Further, functional effects of siplizumab, Alemtuzumab, and rATG were investigated in allogeneic mixed lymphocyte reaction. Changes in T cell activation, T cell proliferation and frequency of naïve T cells, memory T cells and regulatory T cells induced by siplizumab, Alemtuzumab and rATG in allogeneic mixed lymphocyte reaction were assessed via flow cytometry. Siplizumab depleted T cells, decreased T cell activation, inhibited T cell proliferation and enriched naïve and bona fide regulatory T cells. Neither Alemtuzumab nor rATG induced the same combination of functional effects. The results presented in this study should be used for further in vitro and in vivo investigations that guide the clinical use of immune modulatory biologics.

B cell-derived IL-1β and IL-6 drive T cell reconstitution following lymphoablation

Understanding the mechanisms of T cell homeostatic expansion is crucial for clinical applications of lymphoablative therapies. We previously established that T cell recovery in mouse heart allograft recipients treated with anti-thymocyte globulin (mATG) critically depends on B cells and is mediated by B cell-derived soluble factors. B cell production of interleukin (IL)-1β and IL-6 is markedly upregulated after heart allotransplantation and lymphoablation. Neutralizing IL-1β or IL-6 with mAb or the use of recipients lacking mature IL-1β, IL-6, IL-1R, MyD88, or IL-6R impair CD4⁺ and CD8⁺ T cell recovery and significantly enhance the graft-prolonging efficacy of lymphoablation. Adoptive co-transfer experiments demonstrate a direct effect of IL-6 but not IL-1β on T lymphocytes. Furthermore, B cells incapable of IL-1β or IL-6 production have diminished capacity to mediate T cell reconstitution and initiate heart allograft rejection upon adoptive transfer into mATG treated B cell deficient recipients. These findings reveal the essential role of B cell-derived IL-1β and IL-6 during homeostatic T cell expansion in a clinically relevant model of lymphoablation.

Reassessing Rabbit Antithymocyte Globulin Induction in Kidney Transplantation (RETHINK): An Analysis of the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) Registry

Supplemental Digital Content is available in the text.

Background.

There is no consensus on rabbit antithymocyte globulin (rATG) dose used for induction immunosuppression in pediatric kidney transplants. We aimed to identify whether a lower rATG dose provides safe and effective immunosuppression compared with a higher dose.

Methods.

We retrospectively analyzed all first-time kidney transplant recipients (aged <21 y) in the North American Pediatric Renal Trials and Collaborative Studies registry since 1998 on mycophenolate mofetil– and tacrolimus-based immunosuppression with rATG induction. An a priori cutoff of 7.5 mg/kg cumulative rATG dose was used to identify low (<7.5 mg/kg) and high (≥7.5 mg/kg) exposure groups. Primary outcome was time to first-acute rejection episode. Secondary outcomes included graft function, patient survival, hospitalizations due to infections, and time to first-posttransplant lymphoproliferative disorder episode.

Results.

Four hundred fifty-five patients met inclusion criteria (59% male, 49% whites, 26% blacks, 38% living donor source). Median cumulative rATG dose was 6.8 mg/kg with a median of 5 doses and a median 1.5 mg/kg/dose introduced at a median of postoperative 0 days. Sixty-four percent received <7.5 mg/kg total rATG. There was no difference in age at transplant, gender, race, end-stage renal disease causes, or HLA mismatch among groups. Time to first-acute rejection was similar (P = 0.07). There was no significant difference in graft or patient survival or time to posttransplant lymphoproliferative disorder. Hospitalization for infection rates was similar.

Conclusions.

These data demonstrate a wide variation in cumulative rATG induction dose. A smaller rATG dose <7.5 mg/kg may provide effective and safe immunosuppression compared with a higher dose.

Timing of Intensive Immunosuppression Impacts Risk of Transgene Antibodies after AAV Gene Therapy in Nonhuman Primates

Adeno-associated virus (AAV) vector gene therapy is a promising treatment for a variety of genetic diseases, including hemophilia. Systemic administration of AAV vectors is associated with a cytotoxic immune response triggered against AAV capsid proteins, which if untreated can result in loss of transgene expression. Immunosuppression (IS) with corticosteroids has limited transgene loss in some AAV gene therapy clinical trials, but was insufficient to prevent loss in other studies. We used a nonhuman primate model to evaluate intensive T cell-directed IS combined with AAV-mediated transfer of the human factor IX (FIX) gene. Early administration of rabbit anti-thymocyte globulin (ATG) concomitant with AAV administration resulted in the development of anti-FIX antibodies, whereas delayed ATG by 5 weeks administration did not. The anti-FIX immune response was associated with increases in inflammatory cytokines, as well as a skewed Th17/regulatory T cell (Treg) ratio. We conclude that the timing of T cell-directed IS is critical in determining transgene-product immunogenicity or tolerance. These data have implications for systemically administered AAV gene therapy being evaluated for hemophilia A and B, as well as other genetic diseases.

An Unusual Case of Morphea in the Setting of Aplastic Anemia

Cutaneous sclerosis occurs in association with a variety of systemic diseases, including hematologic malignancy, plasma cell dyscrasias, solid organ tumors, and other systemic autoimmune conditions. Herein, we present a unique case of morphea/lichen sclerosus overlap arising in association with aplastic anemia. To expand upon this rare case, we also review the literature surrounding paraneoplastic sclerosing skin disorders. A 53-year-old man presented with a 13-month history of progressive and generalized skin changes. Exam revealed irregular, hypopigmented indurated plaques with focal areas of scale on the bilateral axillae and hips, as well as hyperpigmented brown papules and plaques on the back. Laboratory evaluation revealed pancytopenia and positive anti-nuclear antibody (1:160). Bone marrow biopsy demonstrated hypocellular marrow consistent with aplastic anemia. Furthermore, skin biopsies revealed lichen sclerosus overlying superficial morphea, consistent with a paraneoplastic sclerodermoid-like eruption. While preparations for hematologic-directed therapies were made, skin-directed therapy with a combination topical steroids and topical calcineurin inhibitors was initiated. Eosinophilic fasciitis and scleroderma have been linked to aplastic anemia, and herein, we expand upon this phenomenon by presenting our case of generalized plaque morphea/lichen sclerosus overlap arising in the setting of aplastic anemia. Dermatologists must be aware of this rare association in order to identify precocious hematologic disease.

Antithymocyte Globulin: Indiscriminate Use and Complications

The safety profile of rATG is impressive, with its use in 40% of inductions in living donor transplants in the US, with a reduced incidence of acute rejection, a low incidence of CMV infections with universal prophylaxis and enabling steroid sparing regimes.

Autoimmune Myocarditis Caused by Immune Checkpoint Inhibitors Treated With Antithymocyte Globulin

The immune checkpoint inhibitors have brought about a paradigm shift in the treatment of many cancers and are being used as the first line therapy in increasing number of aggressive malignancies, including metastatic melanoma. Their adverse effects, mostly mediated by an uncontrolled overactivation of the immune system, may compromise the therapeutic benefit. Combination immune checkpoint therapies in particular, have higher therapeutic efficacy, but have also been associated with a higher incidence of severe immune-related adverse effects including autoimmune lymphocytic myocarditis. Recent clinical reports of this rare and life threatening condition indicated rapid progression of severe hemodynamic and electrical instability, with or without acute decompensated heart failure, reduced ejection fraction and shock, pointing to the need for early recognition, diagnosis and prompt management. Current guidelines for management of other immune-related adverse effects recommend high-dose glucocorticoids, with consideration of immunomodulators, such as infliximab in patients with severe colitis. However, knowledge about the treatment approaches in immune-related myocarditis remains extremely scarce. Here we report a case of severe, steroid refractory, lymphocytic myocarditis that occurred after the first cycle of combination immunotherapy with the programmed cell death protein-1 inhibitor, nivolumab, and the cytotoxic T-lymphocyte-associated protein 4 blocker, ipilimumab, for metastatic melanoma. We discuss treatment approaches including the role for transvenous pacemaker, advanced heart failure support, and interdisciplinary decision making.

Effects of immunotherapy induction on outcome and graft survival of kidney-transplanted patients with different immunological risk of rejection

BACKGROUND

In kidney transplantation, immunotherapy with thymoglobulin (rATG) has been used to down-regulate the patient immune system. rATG is a powerful immunobiologic drug used to deplete lymphocytes to prevent early acute rejection. The aim of this research was to evaluate the effects of immunotherapy by rATG on graft suvival during a 9-year period in kidney-transplanted patients with different immunological profiles.

METHODS

A sample of 469 patients were allocated into four groups (G) based on immunological risk of rejection: G1, low risk, not sensitized recipients, solid-phase immunoassay with single antigen beads (SPI-SAB) < 10%; G2, medium risk I, sensitized recipients, SPI-SAB ≥ 10 < 50%; G3, medium risk II sensitized (SPI-SAB ≥50%); and G4, high risk, sensitized recipients, SPI-SAB- donor-specific antibody positive (DSA+). Only patients from G3 and G4 received immunotherapy.

RESULTS

Of 255 patients who received a kidney from a living donor (LD), 42 (16.47%) from all groups (G) had T-cell-mediated rejection (TCMR) and four (G1) lost their grafts, 8 (3.14%) had antibody-mediated rejection (AMR), and two lost their graft in G1 and G4. Of 214 patients who received a kidney from deceased donors (DD), 37 (17.29%) had TCMR with one lost graft in G1. AMR was shown in 13 (6.07%) patients, with three losses observed in G2. Statistical differences between the groups in the 9-year graft survival rate were found only in the comparison of G1 versus G2 (P = 0.005) and G2 versus G4 (P = 0.047) for DD. For LD, no statistical differences were found.

CONCLUSION

This clinical retrospective study shows that immunotherapy induction was associated with improvement of outcomes, graft function, and survival in patients treated with immunotherapy in comparison with patients who did not received induction therapy. These findings strongly suggest that immunotherapy should be used for all patients transplanted with kidneys from deceased donors.

Interleukin-27 promotes CD8+ T cell reconstitution following antibody-mediated lymphoablation

Antibody-mediated lymphoablation is used in solid organ and stem cell transplantation and autoimmunity. Using murine anti-thymocyte globulin (mATG) in a mouse model of heart transplantation, we previously reported that the homeostatic recovery of CD8+ T cells requires help from depletion-resistant memory CD4+ T cells delivered through CD40-expressing B cells. This study investigated the mechanisms by which B cells mediate CD8+ T cell proliferation in lymphopenic hosts. While CD8+ T cell recovery required MHC class I expression in the host, the reconstitution occurred independently of MHC class I, MHC class II, or CD80/CD86 expression on B cells. mATG lymphoablation upregulated the B cell expression of several cytokine genes, including IL-15 and IL-27, in a CD4-dependent manner. Neither treatment with anti-CD122 mAb nor the use of IL-15Rα-/- recipients altered CD8+ T cell recovery after mATG treatment, indicating that IL-15 may be dispensable for T cell proliferation in our model. Instead, IL-27 neutralization or the use of IL-27Rα-/- CD8+ T cells inhibited CD8+ T cell proliferation and altered the phenotype and cytokine profile of reconstituted CD8+ T cells. Our findings uncover what we believe is a novel role of IL-27 in lymphopenia-induced CD8+ T cell proliferation and suggest that targeting B cell-derived cytokines may increase the efficacy of lymphoablation and improve transplant outcomes.

Acute cellular rejection treatment outcomes stratified by Banff grade in pediatric kidney transplant

INTRODUCTION

There are limited data to guide optimal treatment strategies for acute cellular rejection (ACR) based on Banff grade for pediatric kidney transplant recipients. This report reviews a large pediatric transplant center's experience with ACR.

MATERIALS AND METHODS

A retrospective analysis of pediatric kidney transplant recipients at our center from 2007 to 2014 was performed. Primary outcomes were incidence of graft failure and graft function one year following ACR based on Banff grade and treatment received.

RESULTS

A total of 204 patients were reviewed, of which 65 received rejection treatment with either an oral steroid cycle (n = 16), intravenous steroid pulse (n = 28), or anti-thymocyte globulin (rATG, n = 21). Overall, patients received rATG for treatment of more severe rejection associated with impaired graft function and as a group experienced statistically significant improvements in eGFR over the year following treatment, though most did not regain baseline graft function.

DISCUSSION

Our data suggest that rATG is partially effective in treating ACR, but our study was underpowered to determine the effect of different treatments based on Banff grade. Since there is limited literature to guide clinical treatment of ACR in children, large transplant centers should collaborate to evaluate outcomes and establish evidence-based practice.

The Efficacy of Rabbit Anti-Thymocyte Globulin for Acute Kidney Transplant Rejection in Patients Using Calcineurin Inhibitor and Mycophenolate Mofetil-Based Immunosuppressive Therapy

Background

T cell depleting antibody therapy with rabbit anti-thymocyte globulin (rATG) is the treatment of choice for glucocorticoid-resistant acute kidney allograft rejection (AR) and is used as first-line therapy in severe AR. Almost all studies investigating the effectiveness of rATG for this indication were conducted at the time when cyclosporine A and azathioprine were the standard of care. Here, the long-term outcome of rATG for AR in patients using the current standard immunosuppressive therapy (i.e., tacrolimus and mycophenolate mofetil) is described.

Material/Methods

Between 2002 to 2012, 108 patients were treated with rATG for AR. Data on kidney function in the year following rATG and long-term outcomes were collected.

Results

Overall survival after rATG was comparable to overall survival of all kidney transplantation patients (P=0.10). Serum creatinine 1 year after rATG was 179 μmol/L (interquartile range (IQR) 136–234 μmol/L) and was comparable to baseline serum creatinine (P=0.22). Early AR showed better allograft survival than late AR (P=0.0007). In addition, 1 year after AR, serum creatinine was lower in early AR (157 mol/L; IQR 131–203) compared to late AR (216 mol/L; IQR 165–269; P<0.05). The Banff grade of rejection, kidney function at the moment of rejection, and reason for rATG (severe or glucocorticoid resistant AR) did not influence the allograft survival.

Conclusions

Treatment of AR with rATG is effective in patients using current standard immunosuppressive therapy, even in patients with poor allograft function. Early identification of AR followed by T cell depleting treatment leads to better allograft outcomes.

Does Rabbit Antithymocyte Globulin (Thymoglobuline®) Have a Role in Avoiding Delayed Graft Function in the Modern Era of Kidney Transplantation?

Delayed graft function (DGF) increases the risk of graft loss by up to 40%, and recent developments in kidney donation have increased the risk of its occurrence. Lowering the risk of DGF, however, is challenging due to a complicated etiology in which ischemia-reperfusion injury (IRI) leads to acute tubular necrosis. Among various strategies explored, the choice of induction therapy is one consideration. Rabbit antithymocyte globulin (rATG [Thymoglobuline]) has complex immunomodulatory effects that are relevant to DGF. In addition to a rapid and profound T-cell depletion, rATG inhibits leukocyte migration and adhesion. Experimental studies of rATG have demonstrated attenuated IRI-related tissue damage in reperfused tissues, consistent with histological evidence from transplant recipients. Starting rATG intraoperatively instead of postoperatively can improve kidney graft function and reduce the incidence of DGF. rATG is effective in preventing acute rejection in kidney transplant recipients at high immunological risk, supporting delayed calcineurin inhibitor (CNI) introduction which protects the graft from early insults. A reduced rate of DGF has been reported with rATG (started intraoperatively) and delayed CNI therapy compared to IL-2RA induction with immediate CNI in patients at high immunological risk, but not in lower-risk patients. Overall, induction with rATG induction is the preferred choice for supporting delayed introduction of CNI therapy to avoid DGF in high-risk patients but shows no benefit versus IL-2RA in lower-risk individuals. Evidence is growing that intraoperative rATG ameliorates IRI, and it seems reasonable to routinely start rATG before reperfusion.

Risk factors associated with post-kidney transplant malignancies: an article from the Cancer-Kidney International Network

In kidney transplant recipients, cancer is one of the leading causes of death with a functioning graft beyond the first year of kidney transplantation, and malignancies account for 8-10% of all deaths in the USA (2.6 deaths/1000 patient-years) and exceed 30% of deaths in Australia (5/1000 patient-years) in kidney transplant recipients. Patient-, transplant- and medication-related factors contribute to the increased cancer risk following kidney transplantation. While it is well established that the overall immunosuppressive dose is associated with an increased risk for cancer following transplantation, the contributive effect of different immunosuppressive agents is not well established. In this review we will discuss the different risk factors for malignancies after kidney transplantation.

A Review of Induction with Rabbit Antithymocyte Globulin in Pediatric Heart Transplant Recipients

Pediatric heart transplantation (pHTx) represents only a small proportion of cardiac transplants. Due to these low numbers, clinical data relating to induction therapy in this special population are far less extensive than for adults. Induction is used more widely in pHTx than in adults, mainly because of early steroid withdrawal or complete steroid avoidance. Antithymocyte globulin (ATG) is the most frequent choice for induction in pHTx, and rabbit antithymocyte globulin (rATG, Thymoglobulin^®) (Sanofi Genzyme) is the most widely-used ATG preparation. In the absence of large, prospective, blinded trials, we aimed to review the current literature and databases for evidence regarding the use, complications, and dosages of rATG. Analyses from registry databases suggest that, overall, ATG preparations are associated with improved graft survival compared to interleukin-2 receptor antagonists. Advantages for the use of rATG have been shown in low-risk patients given tacrolimus and mycophenolate mofetil in a steroid-free regimen, in sensitized patients with pre-formed alloantibodies and/or a positive donor-specific crossmatch, and in ABO-incompatible pHTx. Registry and clinical data have indicated no increased risk of infection or post-transplant lymphoproliferative disorder in children given rATG after pHTx. A total rATG dose in the range 3.5–7.5 mg/kg is advisable.

Kinetic of the CMV-specific T-cell immune response and CMV infection in CMV-seropositive kidney transplant recipients receiving rabbit anti-thymocyte globulin induction therapy: A pilot study

BACKGROUND

Some studies have suggested that rATG treatment may be associated with an increased incidence of CMV infection and delayed CMV immune response. However, the evidences supporting this matter are scarce. This study aims to characterize the kinetic of the CMV-specific T-cell immune response before and after rATG induction therapy and the relationship with the development of CMV infection in CMV-seropositive kidney transplant recipients.

METHODS

An observational prospective study of CMV-seropositive kidney transplant patients that received rATG induction therapy was performed. A pretransplant sample was obtained before the surgery to determine the CMV-specific immunity. CMV viral load (by PCR) and CMV-specific T-cell immune response (by flow cytometry) were determined during the follow-up at 0.5, 1, 2, 3, 6, and 12 months post transplantation.

RESULTS

A total of 23 patients were included in the study. CMV prophylaxis was administrated for a media of 90 days after transplantation. At the end of follow-up, 18 (78.3%) patients had CMV-specific immunity with a median value of 0.31% CD8⁺ CD69⁺ INF-γ⁺ T cells at a median of 16 weeks post transplantation. Five patients never acquired CMV-specific immunity. No statistically significant association between CMV infection and CMV-specific T-cell immune response (P = .086) was observed. However, patients with positive pretransplant CMV-specific immunity developed earlier immunity and achieved higher levels of CD8⁺ CD69⁺ INF-γ+ T-cell post-transplantation than patients with negative pretransplant immunity.

CONCLUSIONS

CMV-specific immune monitoring in addition to CMV-serology may be useful to stratify patient's risk of CMV infection before transplantation.

Overview of Immunosuppressive Therapy in Solid Organ Transplantation

Mechanisms of rejection, new pharmacologic approaches, and genomic medicine are major foci for current research in transplantation. It is hoped that these new agents and personalized immunosuppression will provide for less toxic regimens that are effective in preventing both acute and chronic allograft rejection. Until new agents are available, practitioners must use various combinations of currently approved agents to find the best regimens for improved long-term outcomes.

Rabbit anti-human thymocyte immunoglobulin for the rescue treatment of chronic antibody-mediated rejection after pediatric kidney transplantation

BACKGROUND

Chronic antibody-mediated rejection (cAMR) is the leading cause of late kidney graft loss, but current therapies are often ineffective. Rabbit anti-human thymocyte immunoglobulin (rATG) may be helpful, but its use is virtually undocumented.

METHODS

Data were analyzed retrospectively from nine pediatric kidney transplant patients with cAMR were treated with rATG (1.5 mg/kg × 5 days) at our center after non-response to pulsed prednisolone, intravenous immunoglobulin, rituximab, and increased immunosuppressive intensity (including switching to belatacept in some cases), with or without bortezomib.

RESULTS

The median time from diagnosis to cAMR was 179 days. rATG was started 5-741 days after diagnosis. Median estimated glomerular filtration rate (eGFR) increased from 40 mL/min/1.73 m² when rATG was started to 62 mL/min/1.73 m² 9 months later (p = 0.039). Four patients showed substantially higher eGFR after 9 months and 2 patients showed a small improvement; eGFR continued to decline in 3 patients after starting rATG. No grafts were lost during follow-up. At last follow-up, donor-specific antibodies (DSAs) were no longer detectable in 4 out of 8 patients for whom data were available, median fluorescence intensity had decreased substantially in 1 out of 8 patients; anti-HLA DQ DSAs persisted in 2 out of 8 patients. No adverse events with a suspected relation to rATG, including allergic reactions, leukocytopenia or infections, were observed in any of the patients.

CONCLUSIONS

In this small series of patients, rATG appears a promising treatment for unresponsive cAMR. Further evaluation, including earlier introduction of rATG, is warranted.

Application of Natural Language Processing and Network Analysis Techniques to Post-market Reports for the Evaluation of Dose-related Anti-Thymocyte Globulin Safety Patterns

OBJECTIVE

To evaluate the feasibility of automated dose and adverse event information retrieval in supporting the identification of safety patterns.

METHODS

We extracted all rabbit Anti-Thymocyte Globulin (rATG) reports submitted to the United States Food and Drug Administration Adverse Event Reporting System (FAERS) from the product's initial licensure in April 16, 1984 through February 8, 2016. We processed the narratives using the Medication Extraction (MedEx) and the Event-based Text-mining of Health Electronic Records (ETHER) systems and retrieved the appropriate medication, clinical, and temporal information. When necessary, the extracted information was manually curated. This process resulted in a high quality dataset that was analyzed with the Pattern-based and Advanced Network Analyzer for Clinical Evaluation and Assessment (PANACEA) to explore the association of rATG dosing with post-transplant lymphoproliferative disorder (PTLD).

RESULTS

Although manual curation was necessary to improve the data quality, MedEx and ETHER supported the extraction of the appropriate information. We created a final dataset of 1,380 cases with complete information for rATG dosing and date of administration. Analysis in PANACEA found that PTLD was associated with cumulative doses of rATG >8 mg/kg, even in periods where most of the submissions to FAERS reported low doses of rATG.

CONCLUSION

We demonstrated the feasibility of investigating a dose-related safety pattern for a particular product in FAERS using a set of automated tools.

Differential depletion of total T cells and regulatory T cells and prolonged allotransplant survival in CD3Ɛ humanized mice treated with polyclonal anti human thymocyte globulin

Thymoglobulin (ATG) is a polyclonal rabbit antibody against human thymocytes used as a T cell-depleting agent to prevent or treat allotransplant rejection. The aim of the present study was to investigate the effect of low dose ATG treatment exclusively on T cells using a humanized BALB/c human CD3Ɛ transgenic mouse model expressing both human and murine T cell receptors (TCR). Mice received a single intravenous (i.v.) injection of ATG. Blood and peripheral lymphoid organs were obtained after different time points. We found a significant T cell depletion in this mouse model. In addition, regulatory T cells (Tregs) proved to be less sensitive to depletion than the rest of T cells and the Treg:non-Treg ratio was therefore increased. Finally, we also investigated the effect of ATG in a heterotopic allogenic murine model of heart transplantation. Survival and transplant function were significantly prolonged in ATG-treated mice. In conclusion, we showed (a) an immunosuppressive effect of ATG in this humanized mouse model which is exclusively mediated by reactivity against human CD3Ɛ; (b) provided evidence for a relative resistance of Tregs against this regimen; and

Post-transplant cyclophosphamide versus anti-thymocyte globulin as graft- versus-host disease prophylaxis in haploidentical transplant

Severe graft-versus-host disease is a major barrier for non-T-cell-depleted haploidentical stem cell transplantation. There is no consensus on the optimal graft-versus-host disease prophylaxis. This study compared the two most commonly used graft-versus-host disease prophylaxis regimens (post-transplant cyclophosphamide-based vs. the anti-thymocyte globulin-based) in adults with acute myeloid leukemia reported to the European Society for Blood and Bone Marrow Transplantation. A total of 308 patients were analyzed; 193 received post-transplant cyclophosphamide-based regimen and 115 anti-thymocyte globulin-based regimen as anti-graft-versus-host disease prophylaxis. The post-transplant cyclophosphamide-based regimen was more likely to be associated to bone marrow as graft source (60% vs. 40%; P=0.01). Patients in the post-transplant cyclophosphamide-based regimen group had significantly less grade 3-4 acute graft-versus-host disease than those in the anti-thymocyte globulin-based group (5% vs. 12%, respectively; P=0.01), comparable to chronic graft-versus-host disease. Multivariate analysis showed that non-relapse mortality was lower in the post-transplant cyclophosphamide-based regimen group [22% vs. 30%, Hazard ratio (HR) 1.77(95%CI: 1.09-2.86); P=0.02] with no difference in relapse incidence. Patients receiving post-transplant cyclophosphamide-based regimen had better graft-versus-host disease-free, relapse-free survival [HR 1.45 (95%CI: 1.04-2.02); P=0.03] and leukemia-free survival [HR 1.48 (95%CI: 1.03-2.12); P=0.03] than those in the anti-thymocyte globulin-based group. In the multivariate analysis, there was also a trend for a higher overall survival [HR 1.43 (95%CI: 0.98-2.09); P=0.06] for post-transplant cyclophosphamide-based regimen versus the anti-thymocyte globulin-based group. Notably, center experience was also associated with non-relapse mortality and graft-versus-host disease-free, relapse-free survival. Haplo-SCT using a post-transplant cyclophosphamide-based regimen can achieve better leukemia-free survival and graft-versus-host disease-free, relapse-free survival, lower incidence of graft-versus-host disease and non-relapse mortality as compared to anti-thymocyte globulin-based graft-versus-host disease prophylaxis in patients with acute myeloid leukemia.

Prediction, prevention, and management of delayed graft function: where are we now?

Delayed graft function (DGF) remains a major barrier to improved outcomes after kidney transplantation. High-risk transplant recipients can be identified, but no definitive prediction model exists. Novel biomarkers to predict DGF in the first hours post-transplant, such as neutrophil gelatinase-associated lipocalin (NGAL), are under investigation. Donor management to minimize the profound physiological consequences of brain death is highly complex. A hormonal resuscitation package to manage the catecholamine "storm" that follows brain death is recommended. Donor pretreatment with dopamine prior to procurement lowers the rate of DGF. Hypothermic machine perfusion may offer a significant reduction in the rate of DGF vs simple cold storage, but costs need to be evaluated. Surgically, reducing warm ischemia time may be advantageous. Research into recipient preconditioning options has so far not generated clinically helpful interventions. Diagnostic criteria for DGF vary, but requirement for dialysis and/or persistent high serum creatinine is likely to remain key to diagnosis until current work on early biomarkers has progressed further. Management centers on close monitoring of graft (non)function and physiological parameters. With so many unanswered questions, substantial reductions in the toll of DGF in the near future seem unlikely but concentrated research on many levels offers long-term promise.

Efficacy of rabbit anti-thymocyte globulin for steroid-resistant acute rejection after liver transplantation

Acute cellular rejection after liver transplantation (LT) can be treated with steroid pulse therapy, but there is no ideal treatment for steroid-resistant acute rejection (SRAR). We aimed to determine the feasibility and potential complications of rabbit anti-thymocyte globulin (rATG) application to treat SRAR in liver transplant recipients. We retrospectively reviewed medical records of 429 recipients who underwent LT at Severance Hospital between January 2010 and March 2015. We compared clinical features and graft survival between patients with steroid-sensitive acute rejection (SSAR; n = 23) and SRAR (n = 11). We also analyzed complications and changes in laboratory findings after 2.5 mg/kg rATG treatment in patients with SRAR for 6 to 10 days. There were no significant differences in gender, age, model for end-stage liver disease score, Child-Turcotte-Pugh score, or original liver diseases between patients with SSAR and SRAR, although deceased donors were more frequently associated with the SRAR group (P = 0.004). All SRAR patients responded positively to rATG treatment; after treatment, the patients' median AST levels decreased from 138 to 63 IU/L, and their median ALT levels dropped from 327 to 70 IU/L 1 day after rATG treatment (P = 0.022 and 0.017, respectively). Median aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin levels significantly decreased 1 month post-treatment (P = 0.038, 0.004, and 0.041, respectively). Median survival after LT was 23 months, and median survival after rATG was 22 months in patients with SRAR. Adverse effects included hepatitis C virus (HCV) reactivation, fungemia, and cytomegalovirus (CMV) infection. Nine SRAR patients survived with healthy liver function, 1 died from a traffic accident during follow-up, and 1 died from graft-versus-host disease and fungemia. Administration of rATG is an effective therapeutic option for SRAR with acceptable complications in liver transplant recipients. However, the occurrence of HCV reactivation and CMV infection in LT patients should be monitored after rATG treatment in these patients.