Preemptive treatment of de novo donor-specific antibodies in lung transplant patients reduces subsequent risk of chronic lung allograft dysfunction or death

The diagnosis and management of chronic lung allograft dysfunction

PURPOSE OF REVIEW

Chronic lung allograft dysfunction (CLAD) remains a life-threatening complication following lung transplantation. Different CLAD phenotypes have recently been defined, based on the combination of pulmonary function testing and chest computed tomography (CT) scanning and spurred renewed interests in differential diagnosis, risk factors and management of CLAD.

RECENT FINDINGS

Given their crucial importance in the differential diagnosis, we will discuss the latest development in assessing the pulmonary function and chest CT scan, but also their limitations in proper CLAD phenotyping, especially with regards to patients with baseline allograft dysfunction. Since no definitive treatment exists, it remains important to timely identify clinical risk factors, but also to assess the presence of specific patterns or biomarkers in tissue or in broncho alveolar lavage in relation to CLAD (phenotypes). We will provide a comprehensive overview of the latest advances in risk factors and biomarker research in CLAD. Lastly, we will also review novel preventive and curative treatment strategies for CLAD.

SUMMARY

Although this knowledge has significantly advanced the field of lung transplantation, more research is warranted because CLAD remains a life-threatening complication for all lung transplant recipients.

Fibrotic progression from acute cellular rejection is dependent on secondary lymphoid organs in a mouse model of chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) remains one of the major limitations to long-term survival after lung transplantation. We modified a murine model of CLAD and transplanted left lungs from BALB/c donors into B6 recipients that were treated with intermittent cyclosporine and methylprednisolone postoperatively. In this model, the lung allograft developed acute cellular rejection on day 15 which, by day 30 after transplantation, progressed to severe pleural and peribronchovascular fibrosis, reminiscent of changes observed in restrictive allograft syndrome. Lung transplantation into splenectomized B6 alymphoplastic (aly/aly) or splenectomized B6 lymphotoxin-β receptor-deficient mice demonstrated that recipient secondary lymphoid organs, such as spleen and lymph nodes, are necessary for progression from acute cellular rejection to allograft fibrosis in this model. Our work uncovered a critical role for recipient secondary lymphoid organs in the development of CLAD after pulmonary transplantation and may provide mechanistic insights into the pathogenesis of this complication.

Impact of Transient and Persistent Donor-Specific Antibodies in Lung Transplantation

Lung transplantation (LuTx) is an established treatment for patients with end-stage lung diseases, however, outcomes are limited by acute and chronic rejection. One aspect that has received increasing attention is the role of the host's humoral alloresponse, particularly the formation of de novo donor-specific antibodies (dnDSAs). The aim of this study was to investigate the clinical significance of transient and persistent dnDSAs and to understand their impact on outcomes after LuTx. A retrospective analysis was conducted using DSA screening data from LuTx recipients obtained at the Medical University of Vienna between February 2016 and March 2021. Of the 405 LuTx recipients analyzed, 205 patients developed dnDSA during the follow-up period. Among these, 167 (81%) had transient dnDSA and 38 (19%) persistent dnDSA. Persistent but not transient dnDSAs were associated with chronic lung allograft dysfunction (CLAD) and antibody-mediated rejection (AMR) (p < 0.001 and p = 0.006, respectively). CLAD-free survival rates for persistent dnDSAs at 1-, 3-, and 5-year post-transplantation were significantly lower than for transient dnDSAs (89%, 59%, 56% vs. 91%, 79%, 77%; p = 0.004). Temporal dynamics of dnDSAs after LuTx have a substantial effect on patient outcomes. This study underlines that the persistence of dnDSAs poses a significant risk to graft and patient survival.

Association of positive pre-transplant angiotensin II type 1 receptor antibodies with clinical outcomes in lung transplant recipients

INTRODUCTION

Autoantibodies against the angiotensin II type 1 receptor (AT1R-Ab) have been previously associated with de novo donor-specific antibody (DSA) formation in lung transplantation. However, data regarding the clinical significance of AT1R-Ab in long-term graft function after lung transplantation are lacking.

METHODS

Seventy-one patients who underwent lung transplantation between July 2016 and January 2020 were enrolled in this study. We examined the relationship between pre-transplant AT1R-Ab levels and graft function, clinical outcomes, and human leukocyte antigen (HLA) DSA levels during the first 3 years post-transplantation.

RESULTS

Seventeen (23.9%) patients were AT1R-Ab-positive, and 54 (76.1%) were AT1R-Ab-negative. The median antibody value of the AT1R-Ab-positive group was 18 [18-22.5] U/mL, while that of the AT1R-Ab-negative group was 5.1 [3.5-8.0] U/mL (p < 0.001). There was no significant difference in the median acute cellular rejection (ACR) scores between the two groups (median [interquartile range] 1 [0.8-3] vs. 0.7 [0-1]; p = 0.145). However, there was a significant difference in the distribution of the ACR scores between the two groups (p = 0.015). Most (41.2%) patients in the pre-transplant AT1R-positive group scored above 1. The incidence of de novo DSA was also higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (52.9% vs. 20.4%, p = 0.009). The incidence of chronic lung allograft dysfunction (CLAD) within 3 years was significantly higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (58.3% vs. 11.8%; p < 0.001). In the multivariate Cox regression analysis, AT1R-Ab positivity (hazard ratio, 9.46; 95% confidence interval, 2.89-30.94; p < 0.001) was significantly associated with early CLAD. Furthermore, Kaplan-Meier analysis showed that AT1R-Ab-positive patients had a shorter survival time (χ2 = 39.62, p < 0.001).

CONCLUSION

High AT1R-Ab levels in the pre-transplant serum of lung recipients were associated with the development of de novo HLA-DSA, ACR, early CLAD, and short survival.

Management of donor-specific antibodies in lung transplantation

The formation of antibodies against donor human leukocyte antigens poses a challenging problem both for donor selection as well as postoperative graft function in lung transplantation. These donor-specific antibodies limit the pool of potential donor organs and are associated with episodes of antibody-mediated rejection, chronic lung allograft dysfunction, and increased mortality. Optimal management strategies for clearance of DSAs are poorly defined and vary greatly by institution; most of the data supporting any particular strategy is limited to small-scale retrospective cohort studies. A typical approach to antibody depletion may involve the use of high-dose steroids, plasma exchange, intravenous immunoglobulin, and possibly other immunomodulators or small-molecule therapies. This review seeks to define the current understanding of the significance of DSAs in lung transplantation and outline the literature supporting strategies for their management.