Call it BOS, call it CLAD--the need for prospective clinical trials and elucidating the mechanism of extracorporeal photopheresis

Mechanisms of Action of Extracorporeal Photopheresis in the Control of Bronchiolitis Obliterans Syndrome (BOS): Involvement of Circulating miRNAs

Clinical evidence suggests an improvement or stabilization of lung function in a fraction of patients with bronchiolitis obliterans syndrome (BOS) treated by extracorporeal photopheresis (ECP); however, few studies have explored the epigenetic and molecular regulation of this therapy. The aim of present study was to evaluate whether a specific set of miRNAs were significantly regulated by ECP. Total RNA was isolated from serum of patients with established BOS grade 1–2 prior to the start and after 6 months of ECP treatment. We observed a significant downregulation of circulating hsa-miR-155-5p, hsa-miR-146a-5p and hsa-miR-31-5p in BOS patients at the start of ECP when compared to healthy subjects. In responders, increased miR-155-5p and decreased miR-23b-3p expression levels at 6 months were found. SMAD4 mRNA was found to be a common target of these two miRNAs in prediction pathways analysis, and a significant downregulation was found at 6 months in PBMCs of a subgroup of ECP-treated patients. According to previous evidence, the upregulation of miR-155 might be correlated with a pro-tolerogenic modulation of the immune system. Our analysis also suggests that SMAD4 might be a possible target for miR-155-5p. Further longitudinal studies are needed to address the possible role of miR-155 and its downstream targets.

Extracorporeal Photopheresis for Bronchiolitis Obliterans Syndrome After Lung Transplantation

BACKGROUND

Lung transplantation is a therapeutic option for select patients with end-stage lung disease. However, successful lung transplantation is hampered by chronic lung allograft dysfunction, in particular bronchiolitis obliterans syndrome (BOS). Although there is no approved or standard treatment for BOS, which may have several distinct phenotypes, extracorporeal photopheresis (ECP) has shown promising results in patients who develop BOS refractory to azithromycin treatment.

METHODS

We reviewed all relevant clinical data indexed on PubMed from 1987 to 2017 to evaluate the role of ECP in patients with BOS.

RESULTS

Seven small studies investigated the immunomodulatory effects of ECP in patients after solid organ transplant, and 12 studies reported clinical data specific to ECP therapy for BOS. Studies indicate that ECP triggers an apoptotic cellular cascade that exerts various immunomodulatory effects mediated via increases in anti-inflammatory cytokines, a decrease in proinflammatory cytokines, and an increase in tolerogenic regulatory T cells. Clinical evidence derived from relatively small single-center studies suggests that ECP therapy is associated with improvement or stabilization in lung function and sustainable, statistically significant, decreases in the rate of lung function decline in patients with BOS. Additionally, when adverse event data were reported, ECP was generally well tolerated. None of the comparative studies were randomized.

CONCLUSIONS

Immunomodulation mediated via ECP is a rational therapeutic option that may improve clinical outcomes in patients with BOS, particularly in the context of in-depth patient phenotyping as part of a stratified approach to treatment; good quality randomized controlled trials are needed to confirm observational findings.

Long-Term Off-Line Extracorporeal Photochemotherapy in Patients with Chronic Lung Allograft Rejection Not Responsive to Conventional Treatment: A 10-Year Single-Centre Analysis

BACKGROUND

Extracorporeal photochemotherapy (ECP) for chronic lung allograft dysfunction (CLAD) has been reported as beneficial in a few short-term studies.

OBJECTIVES

In this retrospective cohort study on 48 CLAD patients treated by ECP (off-line technique) for a period of >8 years (compared to 58 controls), we explored potential predictors of survival and response.

METHODS

Failures were defined as a decrease in forced expiratory volume in 1 s (FEV1) of >10% from ECP initiation.

RESULTS

ECP patients were enrolled between February 2003 and December 2013; 14 (29.2%) with restrictive allograft syndrome (RAS) and 34 with bronchiolitis obliterans syndrome. Grade 1 severity was indicated in 58.3%, grade 2 in 20.8%, and grade 3 in 20.8% of patients. The median follow-up was 65 months (cumulative 2,284.4 person-months). Twenty (41.7%) patients died, including 17 (85%) CLAD-related deaths. Among the controls, there were 42 deaths (72.4%), of which 32 (76.2%) were CLAD related, over a median of 51 months (cumulative 3,066.5 person-months; p = 0.09). Among ECP patients, the FEV1 slope flattened out after a decline in the initial months (slope -19 ml/month in months 0-6, +4 in months 36-48 and later; p = 0.001). RAS was associated with poorer survival, whereas a 'rapid decline in the previous 6 months' was not. No ECP side effects or complications were observed.

CONCLUSION

Long-term ECP for CLAD is safe and reduces FEV1 decline over time; the RAS phenotype might show a poorer response. ECP deserves to be evaluated in a randomized controlled trial.

Current views on chronic rejection after lung transplantation

Chronic lung allograft dysfunction (CLAD) was recently introduced as an overarching term mainly to classify patients with chronic rejection after lung transplantation, although other conditions may also qualify for CLAD. Initially, only the development of a persistent and obstructive pulmonary function defect, clinically identified as bronchiolitis obliterans syndrome (BOS), was considered as chronic rejection, if no other cause could be identified. It became clear in recent years that some patients do not qualify for this definition, although they developed a chronic and persistent decrease in FEV1 , without another identifiable cause. As the pulmonary function decline in these patients was rather restrictive, this was called restrictive allograft syndrome (RAS). In the present review, we will further elaborate on these two CLAD phenotypes, with specific attention to the diagnostic criteria, the role of pathology and imaging, the risk factors, outcome, and the possible treatment options.

ECP and solid organ transplantation

Since its introduction in photomedicine in 1983 ECP (extracorporeal photopheresis) has over the past decades been established as a safe and effective treatment approach for the palliative management of patients with cutaneous T-cell lymphoma, the Sezary syndrome variant in particular. Subsequently its effectiveness has been well documented in a number of additional T-cell-mediated diseases, particularly in the treatment and prevention of acute and chronic graft-vs. -host disease. More recently, ECP has been successfully used to treat acute heart allograft rejection and chronic allograft dysfunction after lung transplantation without increasing infectious complications. As recently documented ECP was also used as a part of CNI (calcineurin inhibitors) sparing or staggering protocols. For this group of patients it is proposed that its efficacy may be partly attributed through direct induction of lymphocyte apoptosis (Tambur et al., 2000) [1] and subsequent production of regulatory T cells (Treg) (Lamioni et al., 2007) [2,3] without causing general immunosuppression. However, the exact indications for use of ECP within this framework are not yet finalized.