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

Efficacy of tacrolimus versus cyclosporine after lung transplantation: an updated systematic review, meta-analysis, and trial sequential analysis of randomized controlled trials

BACKGROUND

Little data supports using tacrolimus versus cyclosporin for immunosuppression concerning acute rejection and bronchiolitis obliterans syndrome/Chronic Lung Allograft Dysfunction CLAD complications following lung transplantation (LTx). Our goal was to evaluate the use of tacrolimus versus cyclosporine in preventing these complications after LTx.

METHODS

We included randomized controlled trials (RCTs) by searching PubMed, Web of Science, SCOPUS, and Cochrane through January 10th, 2024. We pooled dichotomous data using the risk ratio (RR) and continuous data using the mean difference (MD) with a 95% confidence interval (CI).

RESULTS

We included Four RCTs with a total of 677 patients. Tacrolimus was significantly associated with decreased risk of acute rejection (RR: 1.21, 95% CI [1.03, 1.42], I2 = 25%, P = 0.02) compared with cyclosporine, bronchiolitis obliterans syndrome/CLAD (RR: 1.87, 95% CI [1.26, 2.77], I2 = 52%, P = 0.002), and treatment withdrawal (RR: 3.11, 95% CI [2.06, 4.70], I2 = 0%, P =  < 0.00001). However, tacrolimus significantly increased the risk of new-onset diabetes (RR: 0.33, 95% CI [0.12, 0.91], I2 = 0%, P = 0.03), and kidney dysfunction (RR: 0.79, 95% CI [0.66, 0.93], I2 = 0%, P = 0.006). In contrast, there was no difference in the incidence of all-cause mortality (RR: 91, 95% CI [0.68, 1.22], I2 = 0%, P = 0.53), arterial hypertension (RR: 2.40, 95% CI [0.41, 14.21], I2 = 92%, P = 0.33), and new cancer (RR: 1.57, 95% CI [0.79, 3.10], I2 = 4%, P = 0.20).

CONCLUSION

Tacrolimus has decreased acute rejection episodes and CLAD rate than cyclosporine, but it increased the risk of new-onset diabetes and kidney dysfunction.

Predicting Primary Graft Dysfunction in Lung Transplantation: Machine Learning-Guided Biomarker Discovery

BACKGROUND –

There is an urgent need to better understand the pathophysiology of primary graft dysfunction (PGD) so that point-of-care methods can be developed to predict those at risk. Here we utilize a multiplex multivariable approach to define cytokine, chemokines, and growth factors in patient-matched biospecimens from multiple biological sites to identify factors predictive of PGD.

METHODS –

Biospecimens were collected from patients undergoing bilateral LTx from three distinct sites: donor lung perfusate, post-transplant bronchoalveolar lavage (BAL) fluid (2h), and plasma (2h and 24h). A 71-multiplex panel was performed on each biospecimen. Cross-validated logistic regression (LR) and random forest (RF) machine learning models were used to determine whether analytes in each site or from combination of sites, with or without clinical data, could discriminate between PGD grade 0 (n = 9) and 3 (n = 8).

RESULTS –

Using optimal AUROC, BAL fluid at 2h was the most predictive of PGD (LR, 0.825; RF, 0.919), followed by multi-timepoint plasma (LR, 0.841; RF, 0.653), then perfusate (LR, 0.565; RF, 0.448). Combined clinical, BAL, and plasma data yielded strongest performance (LR, 1.000; RF, 1.000). Using a LASSO of the predictors obtained using LR, we selected IL-1RA, BCA-1, and Fractalkine, as most predictive of severe PGD.

CONCLUSIONS –

BAL samples collected 2h post-transplant were the strongest predictors of severe PGD. Our machine learning approach not only identified novel cytokines not previously associated with PGD, but identified analytes that could be used as a point-of-care cytokine panel aimed at identifying those at risk for developing severe PGD.

Lung transplantation: Current insights and outcomes

Until now, the ability to predict or retard immune-mediated rejection events after lung transplantation is still limited due to the lack of specific biomarkers. The pressing need remains to early diagnose or predict the onset of chronic lung allograft dysfunction (CLAD) and its differential phenotypes that is the leading cause of death. Omics technologies (mainly genomics, epigenomics, and transcriptomics) combined with advanced bioinformatic platforms are clarifying the key immune-related molecular routes that trigger early and late events of lung allograft rejection supporting the biomarker discovery. The most promising biomarkers came from genomics. Both unregistered and NIH-registered clinical trials demonstrated that the increased percentage of donor-derived cell-free DNA in both plasma and bronchoalveolar lavage fluid showed a good diagnostic performance for clinically silent acute rejection events and CLAD differential phenotypes. A further success arose from transcriptomics that led to development of Molecular Microscope® Diagnostic System (MMDx) to interpret the relationship between molecular signatures of lung biopsies and rejection events. Other immune-related biomarkers of rejection events may be exosomes, telomer length, DNA methylation, and histone-mediated neutrophil extracellular traps (NETs) but none of them entered in registered clinical trials. Here, we discuss novel and existing technologies for revealing new immune-mediated mechanisms underlying acute and chronic rejection events, with a particular focus on emerging biomarkers for improving precision medicine of lung transplantation field.

Acute rejection post lung transplant

PURPOSE OF REVIEW

To review what is currently known about the pathogenesis, diagnosis, treatment, and prevention of acute rejection (AR) in lung transplantation.

RECENT FINDINGS

Epigenomic and transcriptomic methods are gaining traction as tools for earlier detection of AR, which still remains primarily a histopathologic diagnosis.

SUMMARY

Acute rejection is a common cause of early posttransplant lung graft dysfunction and increases the risk of chronic rejection. Detection and diagnosis of AR is primarily based on histopathology, but noninvasive molecular methods are undergoing investigation. Two subtypes of AR exist: acute cellular rejection (ACR) and antibody-mediated rejection (AMR). Both can have varied clinical presentation, ranging from asymptomatic to fulminant ARDS, and can present simultaneously. Diagnosis of ACR requires transbronchial biopsy; AMR requires the additional measuring of circulating donor-specific antibody (DSA) levels. First-line treatment in ACR is increased immunosuppression (pulse-dose or tapered dose glucocorticoids); refractory cases may need antibody-based lymphodepletion therapy. First line treatment in AMR focuses on circulating DSA removal with B and plasma cell depletion; plasmapheresis, intravenous human immunoglobulin (IVIG), bortezomib, and rituximab are often employed.

Single-Cell RNA Sequencing in Organ and Cell Transplantation

Single-cell RNA sequencing is a high-throughput novel method that provides transcriptional profiling of individual cells within biological samples. This method typically uses microfluidics systems to uncover the complex intercellular communication networks and biological pathways buried within highly heterogeneous cell populations in tissues. One important application of this technology sits in the fields of organ and stem cell transplantation, where complications such as graft rejection and other post-transplantation life-threatening issues may occur. In this review, we first focus on research in which single-cell RNA sequencing is used to study the transcriptional profile of transplanted tissues. This technology enables the analysis of the donor and recipient cells and identifies cell types and states associated with transplant complications and pathologies. We also review the use of single-cell RNA sequencing in stem cell implantation. This method enables studying the heterogeneity of normal and pathological stem cells and the heterogeneity in cell populations. With their remarkably rapid pace, the single-cell RNA sequencing methodologies will potentially result in breakthroughs in clinical transplantation in the coming years.

Pulmonary and esophageal function in lung transplantation: Fundamental principles and clinical application

The lungs and esophagus have a close anatomical and physiological relationship. Over the years, reflux-induced pulmonary injury has gained wider recognition, but the full effects of pulmonary disease on esophageal function are still unknown. Intrathoracic pressure dynamics potentially affect esophageal function, especially in patients with end-stage lung disease, both obstructive and restrictive. Lung transplantation is the only viable option for patients with end-stage pulmonary disease and has provided us with a unique opportunity to study these effects as transplantation restores the intrathoracic environment. Esophageal and foregut functional testing before and after transplantation provide insights into the pathophysiology of the foregut-pulmonary axis, such as how underlying pulmonary disease and intrathoracic pressure changes affect esophageal physiology. This review summarizes the available literature and shares the research experience of a lung transplant center, covering topics such as pre- and posttransplant foregut function, esophageal motility in lung transplant recipients, immune-mediated mechanisms of graft rejection associated with gastroesophageal reflux, and the role of antireflux surgery in this population.