Alemtuzumab in the treatment of refractory acute rejection and bronchiolitis obliterans syndrome after human lung transplantation

Recurrent Treatment of Refractory Acute Cellular Rejection with Alemtuzumab after Lung Transplantation

We present an exceptional case of a lung transplant recipient successfully treated by multiple courses of alemtuzumab for refractory acute cellular rejection. The patient experienced multiple episodes of acute cellular rejection following the transplantation procedure. Alemtuzumab was initiated as third-line rejection treatment and was repeated six times. Each treatment course resulted in complete recovery of the pulmonary function and depletion of T- and B-lymphocytes and NK cells. The onset of rejection was consistently preceded by the recovery of NK cells, while T- and B-lymphocytes remained depleted. This suggests a rejection process mediated by NK cells. This case contributes to recent research findings suggesting that NK cells play a significant role in acute cellular rejection in lung transplant recipients and stresses the importance to further investigate the role of NK cells in rejection. Furthermore, it demonstrates that acute cellular rejection following lung transplantation can be repeatedly managed by treatment with alemtuzumab. DATA AVAILABILITY STATEMENT: The authors confirm that the data supporting the findings of this study are available within the article.

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.

Cardiac Regeneration Using Pluripotent Stem Cells and Controlling Immune Responses

Pluripotent stem cell (PSC)-derived cardiomyocytes are a promising source of cells in myocardial regeneration therapy for end-stage heart failure. Because most previous reports have focussed on xenotransplantation models using immunocompromised animals, studies on immune rejection in allogeneic transplantation models are needed for preclinical and clinical applications. Human leukocyte antigen (HLA) plays an important role in allogeneic transplantation, and cell bank projects are currently underway worldwide to stock induced pluripotent stem cells (iPSCs) generated from healthy individuals with homozygous HLA haplotypes. However, it is difficult to stock iPSCs that match the entire population in these cell banks; thus, several groups have produced hypoimmunogenic PSCs by knocking out HLA. These HLA-knockout PSCs were able to avoid rejection by T cells but still suffered rejection by natural killer (NK) cells caused by 'missing self-recognition'. Recent studies have attempted to generate hypoimmunogenic PSCs with gene editing to inhibit NK cell activation. Regenerative medicine using autologous iPSCs can be an ideal transplantation therapy, but, currently, there are major hurdles to its practical application. Hopefully, further research will resolve these issues. This review provides an overview of the current understanding and progress in this field.

Pharmacotherapy of chronic lung allograft dysfunction post lung transplantation

Chronic lung allograft dysfunction (CLAD) remains the primary cause of death in lung transplant recipients (LTRs) in spite of improvements in immunosuppression management. Despite advances in knowledge regarding the pathogenesis of CLAD, treatments that are currently available are usually ineffective and delay progression of disease at best. There are currently no evidence-based guidelines for the optimal treatment of CLAD, and management varies widely across transplant centers. Additionally, there are minimal publications available to summarize data for currently available therapies and outcomes in LTRs. We identified the major domains of the medical management of CLAD and conducted a comprehensive search of PubMed and Embase databases to identify articles published from inception to December 2021 related to CLAD in LTRs. Studies published in English pertaining to the pharmacologic prevention and treatment of CLAD were included; highest priority was given to prospective, randomized, controlled trials if available. Prospective observational and retrospective controlled trials were prioritized next, followed by retrospective uncontrolled studies, case series, and finally case reports if the information was deemed to be pertinent. Reference lists of qualified publications were also reviewed to find any other publications of interest that were not found on initial search. In the absence of literature published in the aforementioned databases, additional articles were identified by reviewing abstracts presented at the International Society for Heart and Lung Transplantation and American Transplant Congress annual meetings between 2010-2021. This document serves to provide a comprehensive review of the literature and considerations for the prevention and medical management of CLAD. This article is protected by copyright. All rights reserved.

Bronchiolitis obliterans syndrome after lung or haematopoietic stem cell transplantation: current management and future directions

Bronchiolitis obliterans syndrome (BOS) may develop after either lung or haematopoietic stem cell transplantation (HSCT), with similarities in histopathological features and clinical manifestations. However, there are differences in the contributory factors and clinical trajectories between the two conditions. BOS after HSCT occurs due to systemic graft-versus-host-disease (GVHD), whereas BOS after lung transplantation is limited to the lung allograft. BOS diagnosis after HSCT is more challenging, as the lung function decline may occur due to extrapulmonary GVHD, causing sclerosis or inflammation in the fascia or muscles of the respiratory girdle. Treatment is generally empirical with no established effective therapies. This review provides rare insights and commonalities of both conditions, that are not well elaborated elsewhere in contemporary literature, and highlights the importance of cross disciplinary learning from experts in other transplant modalities. Treatment algorithms for each condition are presented, based on the published literature and consensus clinical opinion. Immunosuppression should be optimised, and other conditions or contributory factors treated where possible. When initial treatment fails, the ultimate therapeutic option is lung transplantation (or re-transplantation in the case of BOS after lung transplantation) in carefully selected candidates. Novel therapies under investigation include aerosolised liposomal cyclosporine, Janus kinase inhibitors, antifibrotic therapies, and (in patients with BOS after lung transplantation) B-cell–directed therapies. Effective novel treatments that have a tangible impact on survival and thereby avoid the need for lung transplantation or re-transplantation are urgently required.

Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is a syndrome of progressive lung function decline, subcategorized into obstructive, restrictive, and mixed phenotypes. The trajectory of CLAD is variable depending on the phenotype, with restrictive and mixed phenotypes having more rapid progression and lower survival. The mechanisms driving CLAD development remain unclear, though allograft injury during primary graft dysfunction, acute cellular rejection, antibody-mediated rejection, and infections trigger immune responses with long-lasting effects that can lead to CLAD months or years later. Currently, retransplantation is the only effective treatment.

Modulation of tissue resident memory T cells by glucocorticoids after acute cellular rejection in lung transplantation

Acute cellular rejection is common after lung transplantation and is associated with an increased risk of early chronic rejection. We present combined single-cell RNA and TCR sequencing on recipient-derived T cells obtained from the bronchoalveolar lavage of three lung transplant recipients with rejection and compare them with T cells obtained from the same patients after treatment of rejection with high-dose systemic glucocorticoids. At the time of rejection, we found an oligoclonal expansion of cytotoxic CD8+ T cells that all persisted as tissue resident memory T cells after successful treatment. Persisting CD8+ allograft-resident T cells have reduced gene expression for cytotoxic mediators after therapy with glucocorticoids but accumulate around airways. This clonal expansion is discordant with circulating T cell clonal expansion at the time of rejection, suggesting in situ expansion. We thus highlight the accumulation of cytotoxic, recipient-derived tissue resident memory T cells within the lung allograft that persist despite the administration of high-dose systemic glucocorticoids. The long-term clinical consequences of this persistence have yet to be characterized.

Management of chronic rejection after lung transplantation

Outcomes after lung transplantation are limited by chronic lung allograft dysfunction (CLAD). The incidence of CLAD is high, and its clinical course tends to be progressive over time, culminating in graft failure and death. Indeed, CLAD is the leading cause of death beyond the first year after lung transplantation. Therapy for CLAD has been limited by a lack of high-quality studies to guide management. In this review, we will discuss the diagnosis of CLAD in light of the recent changes to definitions and will discuss the current clinical evidence available for treatment. Recently, the diagnosis of CLAD has been subdivided into bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS). The current evidence for treatment of CLAD mainly revolves around treatment of BOS with more limited data existing for RAS. The best supported treatment to date for CLAD is the macrolide antibiotic azithromycin which has been associated with a small improvement in lung function in a minority of patients. Other therapies that have more limited data include switching immunosuppression from cyclosporine to tacrolimus, fundoplication for gastroesophageal reflux, montelukast, extracorporeal photopheresis (ECP), aerosolized cyclosporine, cytolytic anti-lymphocyte therapies, total lymphoid irradiation (TLI) and the antifibrotic agent pirfenidone. Most of these treatments are supported by case series and observational studies. Finally, we will discuss the role of retransplantation for CLAD.

Induction Therapy and Therapeutic Antibodies

Prevention of allograft rejection is one of the crucial goals in solid organ transplantation to ensure durability of the graft and is chiefly mediated by cellular and humoral pathways targeting cell surface alloantigens. The risk of rejection is highest in the first post-transplant year and wanes with time albeit the risk always exists and varies with the type of organ transplanted. Induction therapies refer to the use of high-intensity immunosuppression in the immediate post-operative period to mitigate the highest risk of rejection. This term encompasses chiefly the use of antibody therapies directed against one of the key pathways in T-cell activation or abrogating effects of circulating alloantibodies. These antibodies carry more potent immunomodulatory effect than maintenance immunosuppressive therapy alone and many of them lead to durable immune cell depletion. A variety of monoclonal and polyclonal antibodies have been utilized for use not only for induction therapy, but also for treatment of allograft rejection when it occurs and as components of desensitization therapy before and after transplantation to modulate circulating alloantibodies.

Antithymocyte Globulin Treatment for Chronic Lung Allograft Dysfunction in Lung Transplant Recipients: Experience From a National Reference Transplant Center

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of mortality after the first year of transplantation and treatments can have little impact on CLAD progression in some cases. The objective of this study was to evaluate the effectiveness and safety of antithymocyte globulin (ATG) in lung transplant recipients with CLAD.

METHODS

We reviewed all patients from our center that had undergone a lung transplant between 2008 and 2019 and selected those with CLAD who were treated with ATG. The closest lung function (forced expiratory volume in the first second) to the ATG administration was recorded, as well as the values 3, 6, and 12 months before and after treatment. We followed and recorded survival during the 12 months after treatment.

RESULTS

A total of 13 patients with CLAD received ATG treatment. A favorable positive response to treatment (improvement or stabilization on lung function) was achieved in half of the patients. Most patients (71%) who responded well to ATG were in CLAD stage 1 to 2. The fall slope of forced expiratory volume in the first second is better after treatment. The median survival was 27 months, and we found a trend toward better survival in early CLAD stages 1 to 2. There were also differences in survival between rapid decliners and nonrapid decliners.

CONCLUSIONS

ATG treatment could play a role in patient with CLAD who do not respond to conventional therapies. The effect of cytolytic therapy with ATG is clearly better in those patients in early stages, with little effect in those in CLAD stage 3.

Acute Rejection in the Modern Lung Transplant Era

Acute cellular rejection (ACR) remains a common complication after lung transplantation. Mortality directly related to ACR is low and most patients respond to first-line immunosuppressive treatment. However, a subset of patients may develop refractory or recurrent ACR leading to an accelerated lung function decline and ultimately chronic lung allograft dysfunction. Infectious complications associated with the intensification of immunosuppression can also negatively impact long-term survival. In this review, we summarize the most recent evidence on the mechanisms, risk factors, diagnosis, treatment, and prognosis of ACR. We specifically focus on novel, promising biomarkers which are under investigation for their potential to improve the diagnostic performance of transbronchial biopsies. Finally, for each topic, we highlight current gaps in knowledge and areas for future research.

Desensitization and management of allograft rejection

PURPOSE OF REVIEW

Chronic lung allograft dysfunction (CLAD) limits the success of lung transplantation. Among the risk factors associated with CLAD, we recognize pretransplant circulating antibodies against the human leukocyte antigens (HLA), acute cellular rejection (ACR) and antibody-mediated rejection (AMR). This review will summarize current data surrounding management of desensitization, ACR, AMR, and CLAD.

RECENT FINDINGS

Strategies in managing in highly sensitized patients waiting for lung transplant include avoidance of specific HLA antigens and reduction of circulating anti-HLA antibodies at time of transplant. Several multimodal approaches have been studied in the treatment of AMR with a goal to clear circulating donor-specific antibodies (DSAs) and to halt the production of new antibodies. Different immunosuppressive strategies focus on influence of the host immune system, particularly T-cell responses, in order to prevent ACR and the progression of CLAD.

SUMMARY

The lack of significant evidence and consensus limits to draw conclusion regarding the impact of specific immunosuppressive regimens in the management of HLA antibodies, ACR, and CLAD. Development of novel therapeutic agents and use of multicenter randomized clinical trials will allow to better define patient-specific treatments and improve the length and quality of life of lung transplant recipients.

Developments in lung transplantation over the past decade

With an improved median survival of 6.2 years, lung transplantation has become an increasingly acceptable treatment option for end-stage lung disease. Besides survival benefit, improvement of quality of life is achieved in the vast majority of patients. Many developments have taken place in the field of lung transplantation over the past decade. Broadened indication criteria and bridging techniques for patients awaiting lung transplantation have led to increased waiting lists and changes in allocation schemes worldwide. Moreover, the use of previously unacceptable donor lungs for lung transplantation has increased, with donations from donors after cardiac death, donors with increasing age and donors with positive smoking status extending the donor pool substantially. Use of ex vivo lung perfusion further increased the number of lungs suitable for lung transplantation. Nonetheless, the use of these previously unacceptable lungs did not have detrimental effects on survival and long-term graft outcomes, and has decreased waiting list mortality. To further improve long-term outcomes, strategies have been proposed to modify chronic lung allograft dysfunction progression and minimise toxic immunosuppressive effects. This review summarises the developments in clinical lung transplantation over the past decade.

Many developments have taken place in lung transplantation over the last decade: indications have broadened, donor criteria expanded, allocations systems changed, and novel therapeutic interventions implemented, leading to improved long-term survivalhttp://bit.ly/2vnpwc1

Alemtuzumab as a Therapy for Chronic Lung Allograft Dysfunction in Lung Transplant Recipients With Short Telomeres

Alemtuzumab, a monoclonal antibody targeting CD52 that causes lymphocyte apoptosis, is a form of advanced immunosuppression that is currently used as a therapy for refractory acute cellular rejection and chronic lung allograft dysfunction in lung transplant recipients (1–3). Side effects of alemtuzumab include bone marrow suppression, infection, and malignancy. Whether alemtuzumab can be safely used in allograft recipients that have an increased propensity for bone marrow suppression due to telomeropathies is unknown. In a retrospective case series, we report outcomes associated with alemtuzumab in three lung allograft recipients with short telomere lengths, comparing endpoints such as leukopenia, transfusion needs, infection, hospitalization and survival to those of 17 patients without known telomeropathies that received alemtuzumab. We show that the use of alemtuzumab in lung transplant recipients with short telomeres is safe, though is associated with an increased incidence of neutropenia, thrombocytopenia and anemia requiring packed red blood cell transfusions. Alemtuzumab appears to be an acceptable advanced immunosuppressive therapy in patients with telomeropathies, though given the design and scope of this study, the actual clinical effect needs further evaluation in larger trials.

Surveillance for acute cellular rejection after lung transplantation

Acute cellular rejection (ACR) is a common complication following lung transplantation (LTx), affecting almost a third of recipients in the first year. Established, comprehensive diagnostic criteria exist but they necessitate allograft biopsies which in turn increases clinical risk and can pose certain logistical and economic problems in service delivery. Undermining these challenges further, are known problems with inter-observer interpretation of biopsies and uncertainty as to the long-term implications of milder or indeed asymptomatic episodes. Increased risk of chronic lung allograft dysfunction (CLAD) has long been considered the most significant consequence of ACR. Consensus is lacking as to whether this applies to mild ACR, with contradictory evidence available. Given these issues, research into alternative, minimal or non-invasive biomarkers represents the main focus of research in ACR. A number of potential markers have been proposed, but none to date have demonstrated adequate sensitivity and specificity to allow translation from bench to bedside.

Rabbit antithymocyte globulin for the treatment of chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of death beyond the first year after lung transplantation. Several treatments have been used to prevent the progression or reverse the effects of CLAD. Cytolytic therapy with rabbit antithymocyte globulin (rATG) has previously shown to be a potential option. However, the effect on patients with restrictive allograft syndrome (RAS) versus bronchiolitis obliterans syndrome (BOS) and the effect of cumulative dosing are unknown.

METHODS

The charts of lung transplant patients treated with rATG at Barnes-Jewish Hospital from 2009 to 2016 were retrospectively reviewed. The primary outcome was response to rATG; patients were deemed responders if their FEV₁ improved in the 6 months after rATG treatment. Safety endpoints included incidence of serum sickness, cytokine release syndrome, malignancy, and infectious complications.

RESULTS

108 patients were included in this study; 43 (40%) patients were responders who experienced an increase in FEV₁ after rATG therapy. No predictors of response to rATG therapy were identified. Serum sickness occurred in 22% of patients, 15% experienced cytokine release syndrome, and 19% developed an infection after therapy.

CONCLUSION

40% of patients with CLAD have an improvement in lung function after treatment with rATG although the improvement was typically minimal.

Detection, classification, and management of rejection after lung transplantation

Rejection is a major complication following lung transplantation. Acute cellular rejection, lymphocytic bronchiolitis, and antibody-mediated rejection (AMR) are all risk factors for the subsequent development of chronic lung allograft dysfunction (CLAD). Acute cellular rejection and lymphocytic bronchiolitis have well defined histopathologic diagnostic criteria and grading. Diagnosis of AMR requires a multidisciplinary approach. CLAD is the major barrier to long-term survival following lung transplantation. The most common phenotype of CLAD is bronchiolitis obliterans syndrome (BOS) which is defined by a persistent obstructive decline in lung function. Restrictive allograft dysfunction (RAS) is a second phenotype of CLAD and is associated with a worse prognosis. This article will review the diagnosis, staging, clinical presentation, and treatment of acute rejection, AMR, and CLAD following lung transplantation.

The role of the immune system in lung transplantation: towards improved long-term results

Over the past 35 years, lung transplantation has evolved from an experimental treatment to the treatment of choice for patients with end-stage lung disease. Beyond the immediate period after lung transplantation, rejection and infection are the leading causes of death. The risk of rejection after lung transplantation is generally higher than after other solid organ transplants, and this necessitates more intensive immunosuppression. However, this more intensive treatment does not reduce the risk of rejection sufficiently, and rejection is one of the most common complications after transplantation. There are multiple forms of rejection including acute cellular rejection, antibody-mediated rejection, and chronic lung allograft dysfunction. These have posed a vexing problem for clinicians, patients, and the field of lung transplantation. Confounding matters is the inherent effect of more intensive immunosuppression on the risk of infections. Indeed, infections pose a direct problem resulting in morbidity and mortality and increase the risk of chronic lung allograft dysfunction in the ensuing weeks and months. There are complex interactions between microbes and the immune response that are the subject of ongoing studies. This review focuses on the role of the immune system in lung transplantation and highlights different forms of rejection and the impact of infections on outcomes.

Diagnosis, Pathophysiology and Experimental Models of Chronic Lung Allograft Rejection

Chronic rejection is the Achilles heel of modern lung transplantation, characterized by a slow, progressive decline in allograft function. Clinically, this manifests as obstructive disease, restrictive disease, or a mixture of the 2 depending on the underlying pathology. The 2 major phenotypes of chronic rejection include bronchiolitis obliterans syndrome and restrictive allograft syndrome. The last decade of research has revealed that each of these phenotypes has a unique underlying pathophysiology which may require a distinct treatment regimen for optimal control. Insights into the intricate alloimmune pathways contributing to chronic rejection have been gained from both large and small animal models, suggesting directions for future research. In this review, we explore the pathological hallmarks of chronic rejection, recent insights gained from both clinical and basic science research, and the current state of animal models of chronic lung rejection.

Drug-Induced Hematological Cytopenia in Kidney Transplantation and the Challenges It Poses for Kidney Transplant Physicians

Drug-induced hematological cytopenia is common in kidney transplantation. Various cytopenia including leucopenia (neutropenia), thrombocytopenia, and anemia can occur in kidney transplant recipients. Persistent severe leucopenia or neutropenia can lead to opportunistic infections of various etiologies. On the contrary, reducing or stopping immunosuppressive medications in these events can provoke a rejection. Transplant clinicians are often faced with the delicate dilemma of balancing cytopenia and rejection from adjustments of immunosuppressive regimen. Differentials of drug-induced cytopenia are wide. Identification of culprit medication and subsequent modification is also challenging. In this review, we will discuss individual drug implicated in causing cytopenia and correlate it with corresponding literature evidence.

Cyclophosphamide for Refractory Acute Cellular Rejection After Lung Transplantation

Background

Acute cellular rejection (ACR) is a major risk factor for chronic lung allograft dysfunction after lung transplantation. Acute cellular rejection can persist or recur despite augmentation of immunosuppression by conventional methods. There are limited therapeutic options in treating these recurrent and refractory ACRs. We describe our experience with cyclophosphamide therapy for recurrent and refractory ACR in lung transplant recipients.

Methods

Six consecutive patients who were treated with cyclophosphamide for recurrent or refractory ACR were included in the series. The primary outcome measures were improvement in ACR score and forced expiratory volume at 1 second. Secondary outcome measures included adverse drug events including bone marrow suppression, gastrointestinal side effects, and infections.

Results

Five of the 6 patients treated demonstrated complete resolution of ACR on follow-up biopsies. Acute cellular rejection score improved after cyclophosphamide treatment (P = 0.03). None of the patients had high grade (≥A3) ACR in the 3 months after cyclophosphamide administration. Cyclophosphamide had no effect on forced expiratory volume at 1 second trend or bronchiolitis obliterans score. All patients tolerated cyclophosphamide with minor gastrointestinal side effects, mild bone marrow suppression, and nonfatal infections that were amenable to treatment.

Conclusions

Cyclophosphamide therapy is an option in treating recurrent and refractory ACR in patients who have failed conventional treatments. Cyclophosphamide is tolerated well without serious adverse drug events (ADE).

Pathology of Lung Rejection: Cellular and Humoral Mediated

Acute rejection is an important risk factor for bronchiolitis obliterans syndrome, the clinical manifestation of chronic airway rejection in lung allograft recipients. Patients with acute rejection might be asymptomatic or present with symptoms that are not specific and can be also seen in other conditions. Clinical tests such as pulmonary function tests and imaging studies among others usually are abnormal; however, their results are also not specific for acute rejection. Histopathologic features of acute rejection in adequate samples of transbronchial lung biopsy of the lung allograft are currently the gold standard to assess for acute rejection in lung transplant recipients. Acute alloreactive injury can affect both the vasculature and the airways. Currently, the guidelines of the 2007 International Society of Heart and Lung Transplantation consensus conference are recommended for the histopathologic assessment of rejection. There are no specific morphologic features recognized to diagnose antibody-mediated rejection (AMR) in lung allografts. Therefore, the diagnosis of AMR currently requires a “triple test” including clinical features, serologic evidence of donor-specific antibodies, and pathologic findings supportive of AMR. Complement 4d deposition is used to support a diagnosis of AMR in many solid organ transplants; however, its significance for the diagnosis of AMR in lung allografts is not entirely clear. This chapter discusses the currently recommended guidelines for the assessment of cellular rejection of lung allografts and summarizes our knowledge about morphologic features and immunophenotypic tests that might help in the diagnosis of AMR.

Acute rejection

Despite induction immunosuppression and the use of aggressive maintenance immunosuppressive regimens, acute allograft rejection following lung transplantation is still a problem with important diagnostic and therapeutic challenges. As well as causing early graft loss and mortality, acute rejection also initiates the chronic alloimmune responses and airway-centred inflammation that predispose to bronchiolitis obliterans syndrome (BOS), also known as chronic lung allograft dysfunction (CLAD), which is a major source of morbidity and mortality after lung transplantation. Cellular responses to human leukocyte antigens (HLAs) on the allograft have traditionally been considered the main mechanism of acute rejection, but the influence of humoral immunity is increasingly recognised. As with other several other solid organ transplants, antibody-mediated rejection (AMR) is now a well-accepted and distinct clinical entity in lung transplantation. While acute cellular rejection (ACR) has defined histopathological criteria, transbronchial biopsy is less useful in AMR and its diagnosis is complicated by challenges in the measurement of antibodies directed against donor HLA, and a determination of their significance. Increasing awareness of the importance of non-HLA antigens further clouds this issue. Here, we review the pathophysiology, diagnosis, clinical presentation and treatment of ACR and AMR in lung transplantation, and discuss future potential biomarkers of both processes that may forward our understanding of these conditions.

Chronic lung allograft dysfunction phenotypes and treatment

Chronic lung allograft dysfunction (CLAD) remains a major hurdle limiting long-term survival post lung transplantation. Given the clinical heterogeneity of CLAD, recently two phenotypes of CLAD have been defined [bronchiolitis obliterans syndrome (BOS) vs. restrictive allograft syndrome (RAS) or restrictive CLAD (rCLAD)]. BOS is characterized by an obstructive pulmonary function, air trapping on CT and obliterative bronchiolitis (OB) on histopathology, while RAS/rCLAD patients show a restrictive pulmonary function, persistent pleuro-parenchymal infiltrates on CT and pleuroparenchymal fibro-elastosis on biopsies. Importantly, the patients with RAS/rCLAD have a severely limited survival post diagnosis of 6-18 months compared to 3-5 years after BOS diagnosis. In this review, we will review historical evidence for this heterogeneity and we will highlight the clinical, radiological, histopathological characteristics of both phenotypes, as well as their risk factors. Treatment of CLAD remains troublesome, nevertheless, we will give an overview of different treatment strategies that have been tried with some success. Adequate phenotyping remains difficult but is clearly needed for both clinical and scientific purposes.

Comparison of extracorporeal photopheresis and alemtuzumab for the treatment of chronic lung allograft dysfunction

BACKGROUND

Survival after lung transplantation is limited by chronic lung allograft dysfunction (CLAD). Immunomodulatory therapies such as extracorporeal photopheresis (ECP) and alemtuzumab (AL) have been described for refractory CLAD, but comparative outcomes are not well defined.

METHODS

We retrospectively reviewed spirometric values and clinical outcomes after therapy with ECP, AL, or no treatment (NT) in patients with CLAD who underwent transplant between January 2005 and December 2014. We used inverse probability-weighted regression adjustment (IPWRA) to adjust for potential confounders affecting treatment choice.

RESULTS

Of 267 patients, 31 received immunomodulatory therapies for CLAD, and 78 received NT. The slope of forced expiratory volume in 1 second (FEV₁) decline significantly improved after treatment with AL and with ECP compared with pre-treatment FEV₁ slope; however, there was no significant change in slope of forced vital capacity (FVC). Comparison with NT was limited because of clinical differences in treatment groups. After IPWRA, we found no significant difference in mean difference of FEV₁ slope (ml/month) when comparing treatment with NT, suggesting stabilization of lung function in the treatment group. We found no difference between the 2 immunomodulatory therapies 1, 3, and 6 months post-treatment (-49.9 [95% CI -581.8, +482.0], p = 0.85; +27.7 [95% CI -167.6, +223.0], p = 0.78; -9.6 [95% CI -167.5, +148.2], p = 0.91). We found no difference in mean FVC slope or differences between ECP and AL in infection rates or survival after treatment.

CONCLUSIONS

Immunomodulatory therapy for CLAD with ECP or AL was associated with a significant change in FEV₁ slope post-treatment compared with pre-treatment slope, with minimal effect on FVC. There was no difference between the 2 therapies in their effect on pulmonary function.

Rescue alemtuzumab for refractory acute cellular rejection and bronchiolitis obliterans syndrome after lung transplantation

Refractory acute cellular rejection (rACR) is associated with death and bronchiolitis obliterans syndrome (BOS) post-lung transplantation. We report the largest cohort of lung transplant recipients (LTRs) treated with rescue alemtuzumab for rACR or BOS. RACR outcomes included burden of ACR 30 days before and 180 days after rescue assessed by a novel composite rejection standardized score (CRSS, range 0-6) and freedom from ≥A2 ACR. BOS outcomes included freedom from BOS progression and FEV1 decline >10%. Univariate parametric and nonparametric statistical approaches were used to assess treatment response. Kaplan-Meier method with log rank conversion was used to assess freedom from events. Fifty-seven alemtuzumab doses (ACR 40 and BOS 17) given to 51 patients were included. Median time to rescue was 722 (IQR 42-1403) days. CRSS declined significantly (3 vs 0.67, P<0.001) after rescue. Freedom from ≥A2 was 62.5% in rACR. Freedom from BOS progression was 52.9% at 180 days in the BOS cohort. Freedom from FEV1 decline >10% was 70% in BOS grade 1 and 14.3% in advanced BOS grades 2-3. Infections developed in 72.5% and 76.5% of rACR and BOS groups. Rescue alemtuzumab appears useful for rACR. Patients with BOS 1 may have transient benefit, and patients with advanced BOS seem not to respond to alemtuzumab.

Diagnosis of Acute Cellular Rejection and Antibody-Mediated Rejection on Lung Transplant Biopsies: A Perspective From Members of the Pulmonary Pathology Society

Context.—

The diagnosis and grading of acute cellular and antibody-mediated rejection (AMR) in lung allograft biopsies is important because rejection can lead to acute graft dysfunction and/or failure and may contribute to chronic graft failure. While acute cellular rejection is well defined histologically, no reproducible specific features of AMR are currently identified. Therefore, a combination of clinical features, serology, histopathology, and immunologic findings is suggested for the diagnosis of AMR.

Objective.—

To describe the perspective of members of the Pulmonary Pathology Society (PPS) on the workup of lung allograft transbronchial biopsy and the diagnosis of acute cellular rejection and AMR in lung transplant.

Data Sources.—

Reports by the International Society for Heart and Lung Transplantation (ISHLT), experience of members of PPS who routinely review lung allograft biopsies, and search of literature database (PubMed).

Conclusions.—

Acute cellular rejection should be assessed and graded according to the 2007 working formulation of the ISHLT. As currently no specific features are known for AMR in lung allografts, the triple test (clinical allograft dysfunction, donor-specific antibodies, pathologic findings) should be used for its diagnosis. C4d staining might be performed when morphologic, clinical, and/or serologic features suggestive of AMR are identified.

Advances in Understanding Bronchiolitis Obliterans After Lung Transplantation

Bronchiolitis obliterans syndrome (BOS) remains a major complication after lung transplantation, causing significant morbidity and mortality in a majority of recipients. BOS is believed to be the clinical correlate of chronic allograft dysfunction, and is defined as an obstructive pulmonary function defect in the absence of other identifiable causes, mostly not amenable to treatment. Recently, it has become clear that BOS is not the only form of chronic allograft dysfunction and that other clinical phenotypes exist; however, we focus exclusively on BOS. Radiologic findings typically demonstrate air trapping, mosaic attenuation, and hyperinflation. Pathologic examination reveals obliterative bronchiolitis lesions and a pure obliteration of the small airways (< 2 mm), with a relatively normal surrounding parenchyma. In this review, we highlight recent advances in diagnosis, pathologic examination, and risk factors, such as microbes, viruses, and antibodies. Although the pathophysiological mechanisms remain largely unknown, we review the role of the airway epithelium and inflammation and the various experimental animal models. We also clarify the clinical and therapeutic implications of these findings. Although significant progress has been made, the exact pathophysiological mechanisms and adequate therapy for posttransplantation BOS remain unknown, highlighting the need for further research to improve long-term posttransplantation BOS-free and overall survival.

Future direction of immunosuppression in lung transplantation

PURPOSE OF REVIEW

Immunosuppression regimens have helped improve rejection episodes following lung transplantation, but long-term outcomes are still not comparable with cardiac, hepatic, or renal transplantation. This review summarizes the immunobiology that contributes to rejection events and future opportunities in outcomes on the basis of providing optimized delivery of the immunosuppression based on immune-monitoring techniques, taking into account individual patient pharmacokinetics and phenotypic variance.

RECENT FINDINGS

Drug toxicities, narrow therapeutic drug monitoring windows, and current immunoassays currently do not assist in detecting the global degree of immunosuppression. The currently available randomized control trials for induction therapy or maintenance therapies do not provide additional benefits compared with previously reported retrospective trials. To push beyond the current barriers, transplant teams are focusing on the role of pharmacokinetics, assessing phenotypic variable to potentially modify to quadruple therapy and using extracorporeal photopheresis.

SUMMARY

Conventional practice for the choices of immunosuppression is being evaluated on the basis of randomized control trials as opposed to retrospective studies or single-center trials. The future direction of immunosuppression will be continued by dynamic processes taking into consideration measures to improve tolerance, reducing treatment burden, and providing the best level of evidence while accounting for rejection, infections, renal function, and other comorbidities.

Lymphocyte depletion after alemtuzumab induction disrupts intestinal fungal microbiota in cynomolgus monkeys

BACKGROUND

The interactions of specific fungal phylotypes with immune cells have been recently documented; however, little is known whether gut fungal microbiota is influenced by aberrant immune response in immunosuppressive state. This study aimed to define the biologic impact of lymphocyte depletion on gut fungal microbiota and their relationship.

METHODS

Fifteen male cynomolgus monkeys with CD52 antigen negative on erythrocytes were administered intravenously with a single dose (3.0 mg kg body weight) of alemtuzumab. Depletion and repopulation of circulating and mucosal lymphocytes were determined. The dynamic variations of intestinal fungal microbiota were characterized using 18S ribosomal DNA-based molecular techniques.

RESULTS

The fungal microbiota in colonal mucosa was perturbed during lymphocyte depletion, characterized by increased diversity and colonization of Candida albicans, Aspergillus clavatus, and Saccharomyces cerevisiae. The diversity of the fecal fungal population decreased markedly after mucosal lymphocyte depletion, and specific fungal phylotypes, especially Candida albicans, Saccharomyces cerevisiae, and Botryotinia fuckeliana, were expanded (P<0.05). After reconstitution of mucosal lymphocytes, the composition and diversity of the gut fungal microbiota were both recovered. A close association of the community diversity and Candida albicans colonization with T lymphocyte subsets was also identified.

CONCLUSION

Our findings demonstrate that mucosal lymphocyte depletion leads to the dysbiosis of gut fungal microbiota, suggesting its role in maintaining host-fungus homeostasis. The pathophysiologic consequences of this altered fungal colonization might provide novel clues to uncover the underlying mechanism of enteric fungal infection in immunosuppressive therapies.

An international ISHLT/ATS/ERS clinical practice guideline: diagnosis and management of bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major complication of lung transplantation that is associated with poor survival. The International Society for Heart and Lung Transplantation, American Thoracic Society, and European Respiratory Society convened a committee of international experts to describe and/or provide recommendations for 1) the definition of BOS, 2) the risk factors for developing BOS, 3) the diagnosis of BOS, and 4) the management and prevention of BOS. A pragmatic evidence synthesis was performed to identify all unique citations related to BOS published from 1980 through to March, 2013. The expert committee discussed the available research evidence upon which the updated definition of BOS, identified risk factors and recommendations are based. The committee followed the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) approach to develop specific clinical recommendations. The term BOS should be used to describe a delayed allograft dysfunction with persistent decline in forced expiratory volume in 1 s that is not caused by other known and potentially reversible causes of post-transplant loss of lung function. The committee formulated specific recommendations about the use of systemic corticosteroids, cyclosporine, tacrolimus, azithromycin and about re-transplantation in patients with suspected and confirmed BOS. The diagnosis of BOS requires the careful exclusion of other post-transplant complications that can cause delayed lung allograft dysfunction, and several risk factors have been identified that have a significant association with the onset of BOS. Currently available therapies have not been proven to result in significant benefit in the prevention or treatment of BOS. Adequately designed and executed randomised controlled trials that properly measure and report all patient-important outcomes are needed to identify optimal therapies for established BOS and effective strategies for its prevention.

Immunosuppression and allograft rejection following lung transplantation: evidence to date

The enduring success of lung transplantation is built on the use of immunosuppressive drugs to stop the immune system from rejecting the newly transplanted lung allograft. Most patients receive a triple-drug maintenance immunosuppressive regimen consisting of a calcineurin inhibitor, an antiproliferative and corticosteroids. Induction therapy with either an antilymphocyte monoclonal or an interleukin-2 receptor antagonist are prescribed by many centres aiming to achieve rapid inhibition of recently activated and potentially alloreactive T lymphocytes. Despite this generic approach acute rejection episodes remain common, mandating further fine-tuning and augmentation of the immunosuppressive regimen. While there has been a trend away from cyclosporine and azathioprine towards a preference for tacrolimus and mycophenolate mofetil, this has not translated into significant protection from the development of chronic lung allograft dysfunction, the main barrier to the long-term success of lung transplantation. This article reviews the problem of lung allograft rejection and the evidence for immunosuppressive regimens used both in the short- and long-term in patients undergoing lung transplantation.

Bronchiolitis obliterans syndrome: the Achilles' heel of lung transplantation

Lung transplantation is a therapeutic option for patients with end-stage pulmonary disorders. Unfortunately, chronic lung allograft dysfunction (CLAD), most commonly manifest as bronchiolitis obliterans syndrome (BOS), continues to be highly prevalent and is the major limitation to long-term survival. The pathogenesis of BOS is complex and involves alloimmune and nonalloimmune pathways. Clinically, BOS manifests as airway obstruction and dyspnea that are classically progressive and ultimately fatal; however, the course is highly variable, and distinguishable phenotypes may exist. There are few controlled studies assessing treatment efficacy, but only a minority of patients respond to current treatment modalities. Ultimately, preventive strategies may prove more effective at prolonging survival after lung transplantation, but their remains considerable debate and little data regarding the best strategies to prevent BOS. A better understanding of the risk factors and their relationship to the pathological mechanisms of chronic lung allograft rejection should lead to better pharmacological targets to prevent or treat this syndrome.

Monitoring of nonsteroidal immunosuppressive drugs in patients with lung disease and lung transplant recipients: American College of Chest Physicians evidence-based clinical practice guidelines

OBJECTIVES

Immunosuppressive pharmacologic agents prescribed to patients with diffuse interstitial and inflammatory lung disease and lung transplant recipients are associated with potential risks for adverse reactions. Strategies for minimizing such risks include administering these drugs according to established, safe protocols; monitoring to detect manifestations of toxicity; and patient education. Hence, an evidence-based guideline for physicians can improve safety and optimize the likelihood of a successful outcome. To maximize the likelihood that these agents will be used safely, the American College of Chest Physicians established a committee to examine the clinical evidence for the administration and monitoring of immunosuppressive drugs (with the exception of corticosteroids) to identify associated toxicities associated with each drug and appropriate protocols for monitoring these agents.

METHODS

Committee members developed and refined a series of questions about toxicities of immunosuppressives and current approaches to administration and monitoring. A systematic review was carried out by the American College of Chest Physicians. Committee members were supplied with this information and created this evidence-based guideline.

CONCLUSIONS

It is hoped that these guidelines will improve patient safety when immunosuppressive drugs are given to lung transplant recipients and to patients with diffuse interstitial lung disease.

Managing complications following lung transplantation

Lung transplantation has become a proven therapeutic option for patients with end-stage lung disease, extending life and providing improved quality of life to those who otherwise would continue to be breathless and oxygen-dependent. Over the past 20 years, considerable experience has been gained in understanding the multitude of medical and surgical issues that impact upon patient survival. Today, clinicians have an armamentarium of tools to manage diverse problems such as primary graft dysfunction, acute and chronic allograft rejection, airway anastomotic issues, infectious complications, renal dysfunction, diabetes and osteoporosis, hematological and gastrointestinal problems, malignancy, and other unique issues that confront immunosuppressed solid organ transplant recipients.

Bronchiolitis obliterans syndrome: the final frontier for lung transplantation

Bronchiolitis obliterans syndrome (BOS) is a form of chronic lung allograft dysfunction that affects a majority of lung transplant recipients and is the principal factor limiting long-term transplant survival. BOS is characterized by progressive airflow obstruction unexplained by acute rejection, infection, or other coexistent condition. Although BOS is a proven useful clinical syndrome that identifies patients at increased risk for death, its clinical course and underlying causative factors are now recognized to be increasingly heterogeneous. Regardless of the clinical history, the primary pathologic correlate of BOS is bronchiolitis obliterans, a condition of intraluminal airway fibrosis. This article highlights the body of developing research illustrating the mechanisms by which BOS is mediated, including alloimmune reactivity, the emerging roles of humoral and autoimmunity, activation of innate immune cells, and response to nonimmune-related allograft insults, such as infection and aspiration. In addition, we underscore emerging clinical implications and promising future translational research directions that have the potential to advance our knowledge and improve patient outcomes.

Antibody immunosuppressive therapy in solid-organ transplant: Part I

Currently, a wide variety of both polyclonal and monoclonal antibodies are being routinely utilized to prevent and treat solid organ rejection. More commonly, these agents are also administered in order to delay introduction of calcineurin inhibitors, especially in patients with already compromised renal function. While these antibody therapies dramatically reduced the incidence of acute rejection episodes and improved both short and long-term graft survival, they are also associated with an increased incidence of opportunistic infections and neoplastic complications. Therefore, effective patient management must necessarily balance these risks against the potential benefits of the therapy.

A review of bronchiolitis obliterans syndrome and therapeutic strategies

Lung transplantation is an important treatment option for patients with advanced lung disease. Survival rates for lung transplant recipients have improved; however, the major obstacle limiting better survival is bronchiolitis obliterans syndrome (BOS). In the last decade, survival after lung retransplantation has improved for transplant recipients with BOS. This manuscript reviews BOS along with the current therapeutic strategies, including recent outcomes for lung retransplantation.

Alemtuzumab in solid organ transplantation and in composite tissue allotransplantation

Alemtuzumab (Campath®, Genzyme Corporation, MA, USA) is a potent monoclonal antilymphocyte, anti-CD52 antibody. Since the 1980s, alemtuzumab has been used extensively in organ transplantation as an induction agent – also with the aim of avoiding or reducing maintenance immunosuppression. We herein review the literature on alemtuzumab in solid organ and composite tissue allotransplantation with an emphasis on clinical and mechanistic aspects of alemtuzumab. In summary, the use of alemtuzumab in solid organ and composite tissue allotransplantation shows excellent early results and holds potential for wider use in conjunction with immunosuppression minimization protocols.