Long-term outcome of lung transplantation is predicted by the number of HLA-DR mismatches

Comparison of human leukocyte antigen immunologic risk stratification methods in lung transplantation

Outcomes after lung transplantation (LTx) remain poor, despite advances in sequencing technology and development of algorithms defining immunologic compatibility. Presently, there is no consensus regarding the best approach to define human leukocyte antigen (HLA) compatibility in LTx. In this study, we compared 5 different HLA compatibility tools in a high-resolution HLA-typed, clinically characterized cohort, to determine which approach predicts outcomes after LTx. In this retrospective single-center study, 277 donor-recipient transplant pairs were HLA-typed using next generation sequencing. HLA compatibility was defined using HLAMatchmaker, HLA epitope mismatch algorithm (HLA-EMMA), predicted indirectly recognizable HLA epitopes (PIRCHE), electrostatic mismatch score (EMS), and amino acid mismatches (AAMMs). Associations with HLA mismatching and survival, chronic lung allograft dysfunction (CLAD), and anti-HLA donor-specific antibody (DSA) were calculated using adjusted Cox proportional modeling. Lower HLA class II mismatching was associated with improved survival as defined by HLAMatchmaker (P < .01), HLA-EMMA (P < .05), PIRCHE (P < .05), EMS (P < .001), and AAMM (P < .01). All approaches demonstrated that HLA-DRB1345 matching was associated with freedom from restrictive allograft syndrome and HLA-DQ matching with reduced DSA development. Reducing the level of HLA mismatching, in T cell or B cell epitopes, electrostatic differences, or amino acid, can improve outcomes after LTx and potentially guide immunosuppression strategies.

Development and validation of primary graft dysfunction predictive algorithm for lung transplant candidates

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Accurate prediction of PGD risk could inform donor approaches and perioperative care planning. We sought to develop a clinically useful, generalizable PGD prediction model to aid in transplant decision-making.

METHODS

We derived a predictive model in a prospective cohort study of subjects from 2012 to 2018, followed by a single-center external validation. We used regularized (lasso) logistic regression to evaluate the predictive ability of clinically available PGD predictors and developed a user interface for clinical application. Using decision curve analysis, we quantified the net benefit of the model across a range of PGD risk thresholds and assessed model calibration and discrimination.

RESULTS

The PGD predictive model included distance from donor hospital to recipient transplant center, recipient age, predicted total lung capacity, lung allocation score (LAS), body mass index, pulmonary artery mean pressure, sex, and indication for transplant; donor age, sex, mechanism of death, and donor smoking status; and interaction terms for LAS and donor distance. The interface allows for real-time assessment of PGD risk for any donor/recipient combination. The model offers decision-making net benefit in the PGD risk range of 10% to 75% in the derivation centers and 2% to 10% in the validation cohort, a range incorporating the incidence in that cohort.

CONCLUSION

We developed a clinically useful PGD predictive algorithm across a range of PGD risk thresholds to support transplant decision-making, posttransplant care, and enrich samples for PGD treatment trials.

The impact of human leukocyte antigen mismatch on recipient outcomes in living-donor liver transplantation

Donor-recipient human leukocyte antigen (HLA) compatibility has not been considered to significantly affect liver transplantation (LT) outcomes; however, its significance in living-donor LT (LDLT), which is mostly performed between blood relatives, remains unclear. This retrospective cohort study included 1954 LDLTs at our institution (1990-2020). The primary and secondary endpoints were recipient survival and the incidence of T cell-mediated rejection (TCMR) after LDLT, respectively, according to the number of HLA mismatches at all five loci: HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ. Subgroup analyses were also performed in between-siblings that characteristically have widely distributed 0-10 HLA mismatches. A total of 1304 cases of primary LDLTs were finally enrolled, including 631 adults (recipient age at LT ≥18 years) and 673 children (<18 years). In adult-to-adult LDLT, the more HLA mismatches at each locus, the significantly worse the recipient survival was (p = 0.03, 0.01, 0.03, 0.001, and <0.001 for HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ, respectively). This trend was more pronounced when multiple loci were combined (all p < 0.001 for A + B + DR, A + B + C, DR + DQ, and A + B + C + DR + DQ). Notably, a total of three or more HLA-B + DR mismatches was an independent risk factor for both TCMR (hazard ratio [HR] 2.66, 95% confidence interval [CI] 1.21-5.87; p = 0.02) and recipient survival (HR 2.44, 95% CI 1.11-5.35; p = 0.03) in between-siblings. By contrast, HLA mismatch did not affect pediatric LDLT outcomes at any locus or in any combinations; however, it should be noted that all donor-recipient relationships are parent-to-child that characteristically possesses one or less HLA mismatch at each locus and maximally five or less mismatches in total. In conclusion, HLA mismatch significantly affects not only TCMR development but also recipient survival in adult LDLT, but not in children.

Determining Clinical Thresholds for Donor HLA Eplet Compatibility to Predict Best Outcomes Following Lung Transplantation

Currently, the assessment of immunological risk in lung transplantation (LTx) does not completely consider HLA compatibility at the molecular level. We have previously demonstrated the association of HLA eplets in predicting chronic lung allograft dysfunction following LTx; however, the associations between HLA eplet mismatch (epMM) loads and overall survival are unknown.

Markers of rejection of a lung allograft: state of the art

Chronic lung allograft dysfunction (CLAD) affects approximately 50% of all lung transplant recipients by 5 post-operative years and is the leading cause of death in lung transplant recipients. Early CLAD diagnosis or ideally prediction of CLAD is essential to enable early intervention before significant lung injury occurs. New technologies have emerged to facilitate biomarker discovery, including epigenetic modification and single-cell RNA sequencing. This review examines new and existing technologies for biomarker discovery and the current state of research on biomarkers for identifying lung transplant rejection.

The impact of HLA-DR mismatch status on retransplant-free survival and bronchiolitis obliterans syndrome‒free survival among sensitized lung transplant recipients

INTRODUCTION

Donor‒recipient HLA-DR locus matching may be protective against bronchiolitis obliterans syndrome (BOS) in lung transplant recipients. It is unknown whether this benefit is more significant among sensitized (calculated panel reactive antibodies (CPRAs) of >0%) and highly sensitized (CPRAs of ≥80%) recipients who may be at a higher risk for BOS.

METHODS

This was a retrospective cohort study of adults in the Scientific Registry of Transplant Recipients who underwent lung transplantation between May 5, 2005 and May 31, 2019. Retransplant-free survival and BOS-free survival were compared among recipients with 0 vs ≥1 DR mismatches, grouped according to sensitization.

RESULTS

Among all 20,355 included recipients, 0 DR mismatch status was associated with improved retransplant-free survival (hazard ratio [HR] = 0.83, 95% CI = 0.74-0.93, p = 0.002) and BOS-free survival (HR = 0.86, 95% CI = 0.77-0.96, p = 0.007). Among sensitized recipients, 0 DR mismatch status was also associated with improved retransplant-free survival (HR = 0.79, 95% CI = 0.65-0.97, p = 0.02) and BOS-free survival (HR = 0.82, 95% CI = 0.67-1.00, p = 0.04). There was however no difference in retransplant-free or BOS-free survival between sensitized and non-sensitized recipients with 0 DR mismatches. Among highly sensitized recipients, 0 DR mismatch status was not associated with retransplant-free or BOS-free survival. Among sensitized and highly sensitized recipients, 0 DR mismatch status was not associated with reduced use of plasmapheresis or reduced biopsy-proven, treated acute cellular rejection compared with non-sensitized recipients.

CONCLUSIONS

HLA-DR matching is associated with a similar improvement in retransplant-free and BOS-free survival among non-sensitized and sensitized lung transplant recipients. DR matching does not confer a more substantial retransplant-free or BOS-free survival benefit to highly sensitized recipients than to non-sensitized recipients.

Autoantibodies in lung transplantation

Chronic lung allograft dysfunction (CLAD) comprises both bronchiolitis obliterans syndrome and restrictive allograft syndrome as subtypes. After lung transplantation, CLAD remains a major limitation for long-term survival, and lung transplant recipients therefore have poorer outcomes compared with recipients of other solid organ transplants. Although the number of lung transplants continues to increase globally, the field demands detailed understanding of immunoregulatory mechanisms and more effective individualized therapies to combat CLAD. Emerging evidence suggests that CLAD is multifactorial and involves a complex, delicate interplay of multiple factors, including perioperative donor characteristics, inflammation induced immediately following transplant, post-transplant infection and interplay between allo- and autoimmunity directed to donor antigens. Recently, identification of stress-induced exosome release from the transplanted organ has emerged as an underlying mechanism in the development of chronic rejection and promises to prompt novel strategies for future therapeutic interventions. In this review, we will discuss recent studies and ongoing research into the mechanisms for the development of CLAD, with emphasis on immune responses to lung-associated self-antigens-that is, autoimmunity.

Early Identification of Chronic Lung Allograft Dysfunction: The Need of Biomarkers

A growing number of patients with end-stage lung disease have benefited from lung transplantation (LT). Improvements in organ procurement, surgical techniques and intensive care management have greatly increased short-term graft survival. However, long-term outcomes remain limited, mainly due to the onset of chronic lung allograft dysfunction (CLAD), whose diagnosis is based on permanent loss of lung function after the development of irreversible lung lesions. CLAD is associated with high mortality and morbidity, and its exact physiopathology is still only partially understood. Many researchers and clinicians have searched for CLAD biomarkers to improve diagnosis, to refine the phenotypes associated with differential prognosis and to identify early biological processes that lead to CLAD to enable an early intervention that could modify the inevitable degradation of respiratory function. Donor-specific antibodies are currently the only biomarkers used in routine clinical practice, and their significance for accurately predicting CLAD is still debated. We describe here significant studies that have highlighted potential candidates for reliable and non-invasive biomarkers of CLAD in the fields of imaging and functional monitoring, humoral immunity, cell-mediated immunity, allograft injury, airway remodeling and gene expression. Such biomarkers would improve CLAD prediction and allow differential LT management regarding CLAD risk.

Impact of human leukocyte antigen mismatch on lung transplant outcome

OBJECTIVES

Human leucocyte antigen (HLA) mismatch between donor and recipient has a differential impact on the outcome after transplant (Tx) among transplantable solid organs. Although the lung is considered a highly antigenic organ, the impact of HLA matching between the donor and the recipient has been shown to be heterogeneous on lung Tx outcome. To provide further evidence that HLA matching should be considered in the decision process prior to lung Tx, we evaluated the impact of donor/recipient HLA mismatch on the outcome after lung Tx at our institution.

METHODS

All patients who underwent lung Tx were analysed in this retrospective single-cohort study between 1994 and 2013 for HLA (-A, -B or -DR) matching between the donor and the recipient and their association with overall survival, the incidence of acute cellular rejection (ACR) and the development of chronic lung allograft dysfunction (CLAD).

RESULTS

In total, 371 (197 men) patients were included. Of these, 117 patients had no HLA match (0/6), 143 had a 1/6 match, 77 had 2/6 matches, 28 had 3/6 matches and 6 had 4/6 matches. One hundred and twenty-two (33%) patients experienced at least 1 episode of ACR and 172 (46%) patients developed CLAD. Univariate analysis showed a significant correlation between HLA mismatch and the development of CLAD, whereas multivariate analysis revealed that the number of HLA matches (hazard ratio 0.76; P = 0.002), antibodies to cytomegalovirus in either donors or recipients (hazard ratio 1.52; P = 0.036) and donor age (hazard ratio 1.03; P < 0.001) were independent risk factors for the development of CLAD. On the other hand, HLA matches did not correlate with the incidence of ACR and with the overall survival rate.

CONCLUSIONS

The number of HLA mismatches between donors and recipients after lung Tx did not correlate with ACR or with the overall survival. In contrast, HLA mismatch correlated with the development of CLAD and should therefore be considered a risk factor.

Prevalence of pre-transplant anti-HLA antibodies and their impact on outcomes in lung transplant recipients

Background

Previous studies have suggested that antibodies against human leukocyte antigen (HLA) are associated with worse outcomes in lung transplantation. However, little is known about the factors associated with outcomes following lung transplantation in Asia. Accordingly, we investigated the prevalence of anti-HLA antibodies in recipients before transplantation and assessed their impact on outcomes in Korea.

Methods

A single-center retrospective study was conducted. The study included 76 patients who received a lung transplant at a tertiary hospital in South Korea between January 2010 and March 2015.

Results

Nine patients (11.8%) had class I and/or class II panel-reactive antibodies greater than 50%. Twelve patients (15.8%) had anti-HLA antibodies with a low mean fluorescence intensity (MFI, 1000–3000), 7 (9.2%) with a moderate MFI (3000–5000), and 12 (15.8%) with a high MFI (> 5000). Ten patients (13.2%) had suspected donor-specific antibodies (DSA), and 60% (6/10) of these patients had antibodies with a high MFI. In an analysis of outcomes, high-grade (≥2) primary graft dysfunction (PGD) was more frequent in patients with anti-HLA antibodies with moderate-to-high MFI values than in patients with low MFI values (39.4% vs. 14.0%, p = 0.011). Of 20 patients who survived longer than 2 years and evaluated for pBOS after transplant, potential bronchiolitis obliterans syndrome (pBOS) or BOS was more frequent in patients with anti-HLA antibodies with moderate-to-high MFI than in patients with low MFI, although this difference was not statistically significant (50.0% vs. 14.3%, p = 0.131).

Conclusions

The prevalence of anti-HLA antibodies with high MFI was not high in Korea. However, the MFI was relatively high in patients with DSA. Anti-HLA antibodies with moderate-to-high MFI values were related to high-grade PGD. Therefore, recipients with high MFI before lung transplantation should be considered for desensitization and close monitoring.

HLA Mismatching Strategies for Solid Organ Transplantation - A Balancing Act

HLA matching provides numerous benefits in organ transplantation including better graft function, fewer rejection episodes, longer graft survival, and the possibility of reduced immunosuppression. Mismatches are attended by more frequent rejection episodes that require increased immunosuppression that, in turn, can increase the risk of infection and malignancy. HLA mismatches also incur the risk of sensitization, which can reduce the opportunity and increase waiting time for a subsequent transplant. However, other factors such as donor age, donor type, and immunosuppression protocol, can affect the benefit derived from matching. Furthermore, finding a well-matched donor may not be possible for all patients and usually prolongs waiting time. Strategies to optimize transplantation for patients without a well-matched donor should take into account the immunologic barrier represented by different mismatches: what are the least immunogenic mismatches considering the patient’s HLA phenotype; should repeated mismatches be avoided; is the patient sensitized to HLA and, if so, what are the strengths of the patient’s antibodies? This information can then be used to define the HLA type of an immunologically optimal donor and the probability of such a donor occurring. A probability that is considered to be too low may require expanding the donor population through paired donation or modifying what is acceptable, which may require employing treatment to overcome immunologic barriers such as increased immunosuppression or desensitization. Thus, transplantation must strike a balance between the risk associated with waiting for the optimal donor and the risk associated with a less than optimal donor.

HLA Matching at the Eplet Level Protects Against Chronic Lung Allograft Dysfunction

Donor selection in lung transplantation (LTx) is historically based upon clinical urgency, ABO compatibility, and donor size. HLA matching is not routinely considered; however, the presence or later development of anti-HLA antibodies is associated with poorer outcomes, particularly chronic lung allograft dysfunction (CLAD). Using eplet mismatches, we aimed to determine whether donor/recipient HLA incompatibility was a significant predictor of CLAD. One hundred seventy-five LTx undertaken at the Alfred Hospital between 2008 and 2012 met criteria. Post-LTx monitoring was continued for at least 12 months, or until patient death. HLA typing was performed by sequence-based typing and Luminex sequence-specific oligonucleotide. Using HLAMatchmaker, eplet mismatches between each donor/recipient pairing were analyzed and correlated against incidences of CLAD. HLA-DRB1/3/4/5+DQA/B eplet mismatch was a significant predictor of CLAD (hazard ratio [HR] 3.77, 95% confidence interval [CI]: 1.71-8.29 p < 0.001). When bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS) were analyzed independently, HLA-DRB1/3/4/5 + DQA/B eplet mismatch was shown to significantly predict RAS (HR 8.3, 95% CI: 2.46-27.97 p < 0.001) but not BOS (HR 1.92, 95% CI: 0.64-5.72, p = 0.237). HLA-A/B eplet mismatch was shown not to be a significant predictor when analyzed independently but did provide additional stratification of results. This study illustrates the importance of epitope immunogenicity in defining donor-recipient immune compatibility in LTx.

Human leukocyte antigen-DR13 and DR15 are associated with short-term lung transplant outcomes

BACKGROUND

Lung transplantation outcomes are among the least favorable, with most recipients eventually developing bronchiolitis obliterans syndrome (BOS) and subsequent graft failure. The presence of human leukocyte antigen (HLA)-DR has been implicated in the pathogenesis of BOS and may play a role in these poor outcomes.

METHODS

Lung transplant donor and recipient data were retrospectively gathered from the United Network for Organ Sharing database from January 2006 to June 2013. Donor and recipient characteristics, proportion of recipients treated for first year rejection, and 5-y rates of survival and freedom from BOS were determined according to HLA-DR1, -DR7, -DR13, and -DR15 status in both donor and recipient. Each HLA-DR allele was stratified by donor-recipient pair positivity status.

RESULTS

A total of 7402 lung transplant recipients met the inclusion and exclusion criteria. There were significant but small differences in donor and recipient characteristics for each HLA-DR group. The recipients in the D(-)R(+) pairing for HLA-DR13 and those in the D(+)R(-) pairing for HLA-DR15 had significantly higher rates of receiving treatment for rejection within the first year after transplant (P = 0.024 and P = 0.001, respectively). There were no differences in 5-y survival or freedom from BOS for any of the four HLA-DR alleles studied.

CONCLUSIONS

There are higher rates of patients treated for rejection within the first year who are either negative for the HLA-DR15 allele but received a donor-positive lung or positive for the HLA-DR13 allele but received a donor-negative lung for that allele. However, these differences do not appear to affect long-term outcomes.

Pre-transplant Panel Reactive Antibody and Survival in Adult Cystic Fibrosis Patients After Lung Transplantation

BACKGROUND

Survival implications of pre-transplant antibodies to human leukocyte antigens prior to lung transplantation (LTx) in adult cystic fibrosis (CF) patients are unknown.

METHODS

Data from the United Network for Organ Sharing Registry (1987-2013) were used to compare survival differences in adult CF patients with pre-transplant class I and II panel reactive antibody (PRA) levels ≤10 versus >10 %.

RESULTS

Of 3149 CF LTx recipients, 1526 and 1399 were included in univariate survival analyses of class I and II PRA, respectively, while 1106 and 1001 were included in multivariate Cox analyses for class I and class II, respectively. Kaplan-Meier survival functions failed to demonstrate significant differences in survival with PRA >10 % for class I (Log-rank test: χ (2) (df = 1): 1.11, p = 0.293) or class II (Log-rank test: χ (2) (df = 1): 0.99, p = 0.320). Adjusting for covariates, multivariate Cox models demonstrated that class II PRA >10 % was associated with a significant increase in mortality hazard (HR 1.918; 95 % CI 1.128, 3.261; p = 0.016), whereas class I PRA >10 % was uncorrelated with this outcome.

CONCLUSIONS

Pre-transplant PRA class II >10 % in adult CF patients is associated with elevated mortality hazard after LTx.

Influence of human leukocyte antigen mismatching on bronchiolitis obliterans syndrome in lung transplantation

BACKGROUND

Varying results have been reported in the investigation of human leukocyte antigen (HLA) mismatching and bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTx).

METHODS

The UNOS database was queried for the period 1997 to 2013 to examine HLA mismatching and its association with BOS in LTx.

RESULTS

Of 16,959 first-time adult LTx recipients, 16,854 were included in the univariate Cox analysis and Kaplan-Meier survival function evaluation, and 14,578 were included in multivariate Cox models. Multivariate Cox analysis showed that the number of total HLA mismatches was significantly associated with greater hazard of BOS (HR = 1.060; 95% CI 1.013 to 1.108; p = 0.011), as was the presence of 2 HLA-A mismatches, when compared with 0 or 1 mismatch at that locus (HR = 1.128; 95% CI 1.026 to 1.240; p = 0.012). These results were confirmed using competing-risks regression models that adjusted for death before BOS diagnosis. Multivariate Cox models identified no significant association with BOS hazard for HLA-B (HR = 1.014; 95% CI 0.914 to 1.126; p = 0.785) or HLA-DR (HR = 1.085; 95% CI 0.987 to 1.193; p = 0.090) mismatches. Higher body mass index was associated with increased risk for BOS, whereas older age was protective against BOS. Induction with alemtuzumab (HR = 0.343; 95% CI 0.252 to 0.467; p < 0.001) or basiliximab (HR = 0.862; 95% CI 0.758 to 0.980; p = 0.023) and longer ischemic time (HR = 0.909; 95% CI 0.877 to 0.942; p < 0.001) were associated with lower hazard of BOS.

CONCLUSIONS

Total HLA mismatches are associated with increased risk for BOS, specifically at the A locus. Induction with alemtuzumab or basiliximab reduced the risk, whereas greater ischemic time appears to also be protective.

Human leukocyte antigen mismatching and survival after lung transplantation in adult and pediatric patients with cystic fibrosis

INTRODUCTION

The influence of human leukocyte antigen (HLA) mismatching on survival in adult and pediatric patients with cystic fibrosis (CF) after lung transplantation (LTx) is unknown.

METHODS

The United Network for Organ Sharing database was queried from 1987 to 2013 to determine the influence of HLA mismatching on survival in adult and pediatric CF LTx recipients by assessing the association of HLA mismatching with survival in first-time adult (aged ≥ 18 years) and pediatric (aged <18 years) recipients.

RESULTS

Of 3149 adult and 489 pediatric patients with CF, 3145 and 489 were used for univariate Cox analysis, 2687 and 363 for Kaplan-Meier survival analysis, and 2073 and 257 for multivariate Cox analysis, respectively. Univariate analyses in adult and pediatric patients with CF demonstrated conflicting associations between HLA mismatching and survival (adult hazard ratio [HR], 1.0; 95% confidence interval [CI], 0.97-1.1; P = .45 vs pediatric HR, 0.87; 95% CI, 0.77-0.99; P = .032). Multivariate Cox models including both pediatric and adult patients confirmed that HLA mismatching had an initially protective effect at young ages (HR, 0.85; 95% CI, 0.73-0.99; P = .044) and that this protective effect diminished at older ages and was no longer associated with survival at P < .05 beyond age 10 years.

CONCLUSIONS

HLA mismatching has significantly different implications for survival after LTx in adult compared with pediatric patients with CF.

Interplay between immune responses to HLA and non-HLA self-antigens in allograft rejection

Recent studies strongly suggest an increasing role for immune responses against self-antigens (Ags) which are not encoded by the major histocompatibility complex in the immunopathogenesis of allograft rejection. Although, improved surgical techniques coupled with improved methods to detect and avoid sensitization against donor human leukocyte antigen (HLA) have improved the immediate and short term function of transplanted organs. However, acute and chronic rejection still remains a vexing problem for the long term function of the transplanted organ. Immediately following organ transplantation, several factors both immune and non immune mechanisms lead to the development of local inflammatory milieu which sets the stage for allograft rejection. Traditionally, development of antibodies (Abs) against mismatched donor HLA have been implicated in the development of Ab mediated rejection. However, recent studies from our laboratory and others have demonstrated that development of humoral and cellular immune responses against non-HLA self-Ags may contribute in the pathogenesis of allograft rejection. There are reports demonstrating that immune responses to self-Ags especially Abs to the self-Ags as well as cellular immune responses especially through IL17 has significant pro-fibrotic properties leading to chronic allograft failure. This review summarizes recent studies demonstrating the role for immune responses to self-Ags in allograft immunity leading to rejection as well as present recent evidence suggesting there is interplay between allo- and autoimmunity leading to allograft dysfunction.

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.

[Long-term outcome of lung transplantation]

Lung transplantation (LTx) nowadays is an established therapeutic option for various end-stage lung diseases in despite of an optimal medical therapy in selected patients affected with various pathologies such as emphysema/chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and various forms of bronchiectasis, pulmonary fibrosis and pulmonary hypertension. Progress and refinement over the last two decades in both surgical techniques and medical management including especially the introduction of cyclosporine A, have been impressive. Patient survival improved significantly over time. According to the most recent data of the International Registry of Lung Transplantation (ISHLT), actuarial survival is 79%, 63%, 52% and 29% at 1, 3, 5 and 10 years respectively, with a current overall survival half-life of 5.3 years, and more than 7 years for those who survived 1 year or more. However, survival depends on different parameters such as the underlying disease, data relative to the donor, the recipient and/or the transplant procedure. Major limitation of long-term survival is still chronic allograft dysfunction, which is histologically represented by an obliterative bronchiolitis and functionally by the bronchiolitis obliterans syndrome (BOS). In uncomplicated cases near-normalization of pulmonary function is the rule, with more than 80% of survivors at 1, 3, 5 and 10 years reporting no activity limitations. Functional results after single LTx remain lower than those of the bilateral LTx, and depend on the potential worsening of the underlying disease and complications arising on the native lung. Exercise performance usually is approximately 50% of predicted, suggesting extrapulmonary causes such as side effects of immunosuppressive drugs. Quality of life improves significantly in all domains including employment status.

Bronchiolitis obliterans syndrome: alloimmune-dependent and -independent injury with aberrant tissue remodeling

Long-term success in lung transplantation continues to be challenged by chronic graft dysfunction, which is manifest as bronchiolitis obliterans syndrome (BOS). The mechanisms of BOS involve both immune-mediated pathways (rejection, autoimmune-like mechanisms), and alloimmune-independent pathways (infection, aspiration, ischemia, primary graft failure), which lead to a fibroproliferative responses. BOS correlates histologically with obliterative bronchiolitis in terminal bronchioles and evidence of aberrant remodeling in the airway epithelium, vasculature, stroma, and lymphoid system. A potentially important mechanism that supports the progressive and therapy-resistant nature of BOS is a continuous cycle of ongoing injury and aberrant remodeling. Namely, anatomical and functional abnormalities induce and exacerbate immune-mediated and alloimmune-independent pathways through various mechanisms (e.g., epithelial remodeling decreases mucociliary clearance that exacerbates aspiration-related injury). From this viewpoint, we review current therapeutic strategies and revisit the role of transplant surgeons in attenuating the initial transplant-related injuries to prevent the lung grafts from entering the remodeling-injury cycle.

IL-17-dependent cellular immunity to collagen type V predisposes to obliterative bronchiolitis in human lung transplants

Bronchiolitis obliterans syndrome (BOS), a process of fibro-obliterative occlusion of the small airways in the transplanted lung, is the most common cause of lung transplant failure. We tested the role of cell-mediated immunity to collagen type V [col(V)] in this process. PBMC responses to col(II) and col(V) were monitored prospectively over a 7-year period. PBMCs from lung transplant recipients, but not from healthy controls or col(IV)-reactive Goodpasture's syndrome patients after renal transplant, were frequently col(V) reactive. Col(V)-specific responses were dependent on both CD4+ T cells and monocytes and required both IL-17 and the monokines TNF-alpha and IL-1beta. Strong col(V)-specific responses were associated with substantially increased incidence and severity of BOS. Incidences of acute rejection, HLA-DR mismatched transplants, and induction of HLA-specific antibodies in the transplant recipient were not as strongly associated with a risk of BOS. These data suggest that while alloimmunity initiates lung transplant rejection, de novo autoimmunity mediated by col(V)-specific Th17 cells and monocyte/macrophage accessory cells ultimately causes progressive airway obliteration.

Early Posttransplant Inflammation Promotes the Development of Alloimmunity and Chronic Human Lung Allograft Rejection

BACKGROUND

Chronic human lung allograft rejection, represented by bronchiolitis obliterans syndrome (BOS), is the single most important factor that limits the long-term survival following lung transplantation (LT). However, the pathogenesis of BOS remains unclear. We hypothesized that the early posttransplant inflammation would promote the development of donor anti-human leukocyte antigen (HLA) alloimmunity and predispose to BOS.

METHODS

Serum levels of interleukin (IL)-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, Eotaxin, IP-10, MIG, MCP-1, MIP-1alpha, MIP-1beta, RANTES, tumor necrosis factor (TNF)-alpha, interferon (IFN)-alpha, IFN-gamma, granulocyte-macrophage colony-stimulating factor, IL-1Ralpha, and IL-2R were serially analyzed in 31 BOS+ and matched 31 BOS- patients using quantitative multiplex bead immunoassays. Donor-specific HLA class II cellular immunity was analyzed using enzyme-linked immunospot (ELISPOT) by testing recipient peripheral blood mononuclear cells against mismatched donor HLA-DR peptides. Anti-HLA class II antibodies were monitored using flow panel reactive antibodies.

RESULTS

There was early posttransplant elevation in basal serum levels of proinflammatory chemokines IP-10 and MCP-1 and Th1-cytokines IL-1beta, IL-2, IL-12, and IL-15 in BOS+ patients, compared to BOS- and normal subjects. In addition, a threefold decline in IL-10 levels was found during BOS development. BOS+ patients revealed increased development of HLA class II alloantibodies and Th1-predominant donor-specific cellular immunity with high frequency of IFN-gamma and low IL-5 producing T-cells.

CONCLUSION

Early posttransplant elevation of proinflammatory mediators is associated with alloimmunity and chronic human lung allograft rejection.

Extended Ganciclovir Prophylaxis in Lung Transplantation

BACKGROUND

Positive cytomegaloviral status of the donor or of the recipient adversely affects survival and enhances the development of bronchiolitis obliterans syndrome (BOS) in lung transplant recipients. The role of ganciclovir prophylaxis in cytomegalovirus infection in respect to obliterative bronchiolitis or to BOS development is not known.

METHODS

From the Papworth transplant database, we identified 146 patients who received organs from cytomegalovirus-positive donors. We classified patients into 3 groups as follows: Group 1 consisted of 42 patients who underwent transplantation between 1990 and 1992 when no prophylaxis was given; Group 2 consisted of 49 patients who underwent transplantation between 1992 and 1995 when 4 weeks of IV ganciclovir was given as prophylaxis; and Group 3 consisted of 55 patients who underwent transplantation between 1995 and 1998 when cytomegalovirus prophylaxis consisted of IV (1 week) followed by oral ganciclovir for a total of 3 months. Donor management, recipient management during and after surgery, and pharmacotherapy were uniform during the study period. We used survival and regression methods to compare these groups, adjusting for the transplantation type (single lung, double lung, or heart-lung) and for HLA typing.

RESULTS

We found a significant difference among all 3 groups in numbers of cytomegaloviral disease episodes in the 1st year after transplantation. The number of rejection episodes in the 3 groups during the 1st post-transplant year gradually decreased from Group 1 to Group 3. We identified no statistically significant benefit in the time to BOS occurrence or in actuarial survival.

CONCLUSION

Extended prophylaxis with IV and oral ganciclovir practically abolishes cytomegaloviral disease and is related to a decreased incidence of rejection episodes. However, ganciclovir prophylaxis is not related to a decreased incidence or progression of BOS or survival.

Impact of MHC class II incompatibility on localization of mononuclear cell infiltrates to the bronchiolar compartment of orthotopic lung allografts

Chronic pathological changes in transplanted lungs are unique because they center on the airways. We examined the relative role of MHC class I and II antigens in causing bronchial pathology in orthotopic lung transplants to rats maintained on cyclosporin A (CsA). Transplants mismatched for MHC class II antigens had significantly more peri-bronchiolar infiltrates than MHC class I incompatible transplants. No significant increase in infiltrates was found in lung transplants incompatible for MHC class I plus II antigens compared to MHC class II antigens alone. Immunohistochemistry demonstrated that MHC class II antigen expression was confined to macrophages in MHC class I incompatible transplants, but was upregulated on bronchial epithelium in transplants with MHC class II incompatibilities. Vascular endothelium was notably devoid of MHC class II antigen expression in all transplants. However, both peri-bronchial and peri-vascular infiltrates were frequently cuffed by alveolar macrophages and type II pneumocytes that expressed MHC class II antigens. PCR analysis demonstrated that IFN-gamma and regulated on activation, normal T cells expressed and secreted (RANTES) were upregulated in MHC class II incompatible transplants. Thus, MHC class II incompatible orthotopic lung transplants in rats maintained on CsA immunosuppression undergo a bronchiolcentric upregulation of alloantigens.

Immune mechanisms in the pathogenesis of bronchiolitis obliterans syndrome after lung transplantation

Lung transplantation is recognized as the only viable treatment option in a variety of end-stage pulmonary diseases. However, the long-term survival after lung transplantation is limited by the development of obliterative bronchiolitis, and its clinical correlate bronchiolitis obliterans syndrome (BOS), which is considered to represent chronic lung allograft rejection. Histopathologically, BOS is an inflammatory process that leads to fibrous scarring of the terminal and respiratory bronchioles and subsequent total occlusion of the airways. The specific etiology and pathogenesis of BOS are not well understood. The current premise is that BOS represents a common lesion in which different inflammatory insults such as ischemia-reperfusion, rejection, and infection can lead to a similar histological and clinical outcome. However, the low incidence of BOS in non-transplanted individuals and the observation that early development of BOS is predicted by the frequency and severity of acute rejection episodes indicate that alloimmune-dependent mechanisms play a crucial role in the pathogenesis of BOS. The evidence presented in this review indicates that BOS is the result of humoral and cellular immune responses developed against major histocompatibility complex molecules expressed by airway epithelial cells of the lung allograft. This process is aggravated by alloimmune-independent mechanisms such as ischemia-reperfusion and infection. Currently, treatment of BOS is frequently unsuccessful. Therefore, a better understanding of the immunopathogenesis of BOS is of paramount importance toward improving long-term patient and graft survival after lung transplantation.

Bronchiolitis Obliterans Syndrome

Post-transplantation bronchiolitis obliterans syndrome (BOS) is a clinicopathological syndrome characterised histologically by obliterative bronchiolitis (OB) and physiologically by airflow limitation. It affects long-term survival with no consistently effective treatment strategy.An updated review of risk factors for OB/BOS, and approaches to prevention and treatment was performed through a systematic review of relevant studies between January 1990 and February 2005. The initial search identified 853 publications, with 56 articles reviewed after exclusions. Early acute rejection is the most significant risk factor, with late rejection (> or =3 months) also significant. Lymphocytic bronchitis/bronchiolitis is relevant, with later onset associated with greater risk. Viral infections are identified as significant risk factors. Human leukocyte antigen matching and OB/BOS development is a weaker association, but is stronger with acute rejection. Recipient and donor characteristics have a minor role. There is limited evidence that altering immunosuppression is effective in reducing the rate of decline in lung function. BOS reflects an allo-immunological injury, possibly triggered by cytomegalovirus and respiratory viral infections, or noninfectious injury. Immunological susceptibility may be reflected by more frequent acute rejection episodes. Preventative and therapeutic modifications in immunosuppression remain important. Identifying markers of immunological susceptibility and, hence, risk stratification requires further research.

Bronchiolitis obliterans syndrome: Pathogenesis and management

Over the past 15 years, lung transplantation has become an established treatment for a variety of end-stage lung diseases, but medium- and long-term success has been limited by a high incidence of bronchiolitis obliterans syndrome (BOS). Immune mediated injury has been recognized as the leading cause of BOS, and the term is synonymous with chronic rejection. But recently, nonimmune mechanisms, such as gastroesophageal reflux, have been recognized as potential culprits. The results of various treatment options have generally been disappointing, and BOS has emerged as the leading cause of late morbidity and mortality after lung transplantation.

Lung transplantation. Donor selection

The demand for donor lungs currently exceeds the supply of suitable grafts by a significant margin. Legal backgrounds and organizational and logistic issues are of major impact on the available donor pool. Re-evaluation of the donor criteria currently in use and new, innovative approaches such as living donor lung transplantation and non-heart-beating donation will hopefully contribute to improve this situation and reduce waiting time and waiting list mortality.

Predictors of lung transplant survival in eurotransplant

This study was undertaken to assess the influence of patient/donor and center factors on lung transplantation outcome. Outcomes of all consecutive first cadaveric lung transplants performed at 21 Eurotransplant centers in 1997-99 were analyzed. The risk-adjusted center effect on mortality was estimated. A Cox model was built including donor and recipient age and gender, primary disease, HLA mismatches, patient's residence, cold ischemic time, donor's cause of death, serum creatinine, type of lung transplant, respiratory support status, clinical condition and percentage predicted FEV1. The center effect was calculated (expressed as the standardized difference between the observed and expected survival rates), and empirical and full Bayes methods were applied to evaluate between-center differences. A total of 590 adults underwent lung transplantation. The primary disease (p=0.01), HLA-mismatches (p = 0.02), clinical condition(p < 0.0001) and the patient's respiratory support status (p = 0.05) were significantly associated with survival. After adjusting for case-mix, no between-center differences could be found. An in-depth empirical Bayes analysis showed the between-center variation to be zero. Similar results were obtained from the full Bayes analysis. Based on these data, there is no scientific basis to support a hypothesis of possible association between center volume and lung survival rates.

Statin use is associated with improved function and survival of lung allografts

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are widely used antilipidemic agents that are also immunomodulatory. We evaluated possible effects of these agents after lung transplantation by comparing outcomes of 39 allograft recipients, who were prescribed statins for hyperlipidemia, with those of 161 contemporaneous control recipients who did not receive these drugs. Acute rejection (>or= Grade II) was less frequently found in the statin group (15.1 versus 25.6% of biopsies, p < 0.01). None of 15 recipients started on statins during postoperative Year 1 developed obliterative bronchiolitis, whereas the cumulative incidence of this complication among control subjects was 37% (p < 0.01). Total cellularity, as well as proportions of inflammatory neutrophils and lymphocytes, were significantly lower in bronchoalveolar lavages of statin recipients. Among double lung recipients, those taking statins had significantly better spirometry: FVC (80 +/- 2 versus 70 +/- 1%) and FEV1 (87 +/- 2 versus 70 +/- 1%), as percentages of predicted values, and absolute FEV1/FVC (83.4 +/- 1.2 versus 78.6 +/- 0.5) (all p < 0.01). The 6-year survival of recipients taking statins (91%) was much greater than that of control subjects (54%) (p < 0.01). These data suggest statin use may have substantial clinical benefits after pulmonary transplantation.

Concomitant allorecognition of mismatched donor HLA class I- and class II-derived peptides in pediatric lung transplant recipients with bronchiolitis obliterans syndrome

BACKGROUND

The authors' previous studies with 2 different adult patient populations demonstrated a correlation between indirect allorecognition of mismatched donor HLA Class I- and Class II-derived peptides and the development of bronchiolitis obliterans syndrome (BOS) after lung transplantation. The aim of this study was to determine whether a parallel allorecognition of mismatched donor HLA Class I- and Class II-derived peptides occurs after lung transplantation and to determine its correlation with the development of BOS after lung transplantation in a group of pediatric patients.

METHODS

Peripheral blood mononuclear cells from 7 BOS-positive and 6 BOS-negative pediatric lung transplant recipients (age, 11.5 +/- 4.4 years) were cultured in the presence of synthetic peptides corresponding to the alpha-chain hypervariable regions of a mismatched donor HLA Class I molecule and the beta-chain hypervariable region of a mismatched donor HLA-DR molecule. The frequencies of HLA Class I and Class II alloreactive T cells were determined using limiting dilution analysis.

RESULTS

A significant increase (p = 0.025) in HLA Class I-alloreactive T cells was observed in BOS-positive patients (7.1 x 10(-5) +/- 4.3 x 10(-5)) compared with BOS-negative patients (2.1 x 10(-5) +/- 1.8 x 10(-6)). In addition, a significant increase (p = 0.033) in HLA Class II-alloreactive T cells also was observed in BOS-positive patients (9.6 x 10(-5) +/- 7.9 x 10(-5)) compared with BOS-negative patients (1.3 x 10(-5) +/- 2.1 x 10(-6)).

CONCLUSIONS

This study indicates that a parallel CD4+ T-cell alloreactivity to both donor HLA Class I and Class II molecules may play a role in the pathogenesis of BOS both in adult and pediatric lung transplant recipients.

Interleukin-6 and interferon-gamma gene polymorphisms in the development of bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

A number of genetic polymorphisms have been shown to regulate the production and secretion of tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, interferon (IFN)-gamma, interleukin (IL)-6, and IL-10. Several of these genetic polymorphisms have been shown to be associated with either acute or chronic rejection of kidney, liver, and heart allografts and with development of allograft fibrosis after lung transplantation. The aim of this study was to assess the effect of these genetic polymorphisms on the development of bronchiolitis obliterans syndrome (BOS) after lung transplantation.

METHODS

Genetic polymorphisms were detected by means of polymerase chain reaction in 93 lung allograft recipients for functional polymorphisms in the TNF-alpha (-308), TGF-beta1 (+869 and +915), IL-6 (-174), IFN-gamma (+874), and IL-10 (-1082, -819, and -592) genes. Then, a correlation between BOS development and the presence of these cytokine genotypes was determined using Kaplan-Meier actuarial analysis.

RESULTS

A significant correlation was detected between the presence of high-expression polymorphisms of the IL-6 and IFN-gamma genes and BOS development after lung transplantation (P =0.045 and 0.039, respectively). Also, patients with high-expression polymorphisms in both genes developed BOS significantly earlier than patients with low-expression polymorphisms in one or both genes, suggesting a synergistic effect of the alleles during BOS pathogenesis (P =0.016). No correlation was detected between polymorphisms of the TNF-alpha, TGF-beta1, and IL-10 genes and development of BOS after lung transplantation.

CONCLUSIONS

The presence of high-expression polymorphisms at position -174 of the IL-6 gene and position +874 of the IFN-gamma gene significantly increases the risk for BOS development after lung transplantation.

Evidence for immune responses to a self-antigen in lung transplantation: role of type V collagen-specific T cells in the pathogenesis of lung allograft rejection

We have reported that lung allograft rejection involves an immune response to a native protein in the lung, type V collagen (col(V)), and that col(V)-induced oral tolerance prevented acute and chronic rejection. In support of these findings col(V) fragments were detected in allografts during rejection, but not in normal lungs. The purpose of the current study was to isolate and characterize col(V)-specific allograft-infiltrating T cells and to determine their contribution to the rejection response in vivo. Two col(V)-specific T cell lines, LT1 and LT3, were isolated from F344 (RT1(lv1)) rat lung allografts during rejection that occurred after transplantation into WKY (RT1(l)) recipients. Both cell lines, but not normal lung lymphocytes, proliferated in response to col(V). Neither LT1 nor LT3 proliferated in response to alloantigens. LT1 and LT3 were CD4(+)CD25(-) and produced IFN-gamma in response to col(V). Compared with normal CD4(+) T cells, both cell lines expressed a limited V-beta TCR repertoire. Each cell strongly expressed V-beta 9 and 16, but differed in expression of other V-betas. Adoptive transfer of each cell line did not induce pathology in lungs of normal WKY rats. In contrast, adoptive transfer of LT1, but not LT3, caused marked peribronchiolar and perivascular inflammation in isograft (WKY) lungs and abrogated col(V)-induced oral tolerance to allograft (F344) lungs. Collectively, these data show that lung allograft rejection involves both allo- and autoimmune responses, and graft destruction that occurs during the rejection response may expose allograft-infiltrating T cells to potentially antigenic epitopes in col(V).

Survival benefit of cardiopulmonary bypass support in bilateral lung transplantation for emphysema patients

BACKGROUND

This study is designed to examine a possible association of cardiopulmonary bypass (CPB) support and outcome of lung transplantation in a well-balanced group of emphysema patients.

METHODS

We performed a retrospective analysis of 62 consecutive primary bilateral lung transplantations for emphysema. Risk factors for their possible association with patient survival were analyzed by multivariate logistic regression.

RESULTS

The use of CPB support was associated with improved survival (odds ratio=0.25; P=0.038). The actuarial survival at 1 year was 97% for patients treated with CPB and 77% for patients treated without CPB support. In 28 patients (45%), 2 human leukocyte antigen (HLA)-DR mismatches between donor and recipient occurred, whereas 34 patients had 0 or 1 HLA-DR mismatches. The use of CPB support in the group with two HLA-DR mismatches was associated with improved survival (odds ratio=0.06; P=0.020). This association was not present in the group with 0 or 1 HLA-DR mismatches.

CONCLUSIONS

These results demonstrate a significant survival benefit of CPB support during bilateral lung transplantation in emphysema patients. The difference in survival benefit of CPB support between the patients with 0 or 1 HLA-DR mismatches and the patients with 2 HLA-DR mismatches indicates that the immunosuppressive effect of CPB support might be responsible for this survival benefit. The underlying immunological mechanism might be important in the future treatment of organ transplantation.