CD11c+ dendritic cells mediate antigen-specific suppression in extracorporeal photopheresis

Extracorporeal photopheresis and the cellular mechanisms: Effects of 8-methoxypsoralen and UVA treatment on red blood cells, platelets and reactive oxygen species

BACKGROUND AND OBJECTIVES

Extracorporeal photopheresis (ECP) is a widespread cellular therapy for graft-versus-host disease, autoimmune diseases and Sézary disease. One of the main effects of ECP is the apoptosis of leukocytes, but the therapeutic mechanisms are not completely known. The aim of this study was to investigate the effects on red blood cells, platelets and the induction of reactive oxygen species.

MATERIALS AND METHODS

We used human cells from healthy blood donors to simulate in vitro the composition in an apheresis bag. Cells were treated with 8-methoxypsoralen (8-MOP) and UVA. Red blood cell stability, platelet activity and induction of reactive oxygen species were analysed.

RESULTS

After 8-MOP and UVA treatment, the red blood cells showed high cell integrity with low levels of eryptosis and no increase of free haemoglobin or red blood cell distribution width (RDW). Red blood cell immune-associated antigens CD59 and CD147 were hardly affected by the treatment. Platelet glycoproteins CD41, CD62P and CD63 indicated strong platelet activation after 8-MOP and UVA treatment. Reactive oxygen species were slightly but not significantly induced by the treatment.

CONCLUSION

The effect of the ECP therapy is probably not exclusively mediated by leukocytes. Platelet activation is another striking effect caused by the treatment of the apheresis product with 8-MOP/UVA. However, since we could hardly identify any evidence for eryptosis or haemolysis, it is unlikely that red blood cell eryptosis is part of the therapeutic mechanism. Further research on this topic seems to be promising.

Extracorporeal photopheresis as graft-versus-host disease prophylaxis: a randomized controlled trial: Prophylactic extracorporeal photopheresis to prevent graft-versus-host disease

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative option for many patients diagnosed with hematological malignancies. A major obstacle is graft-versus-host disease (GvHD) causing significant morbidity and mortality. Extracorporeal photopheresis (ECP) is an increasingly applied GvHD treatment, partly due to its favourable safety profile. In contrast, the use of ECP in preventing GvHD is sparse, and randomized controlled trials (RCTs) are lacking.

OBJECTIVE

We therefore conducted a RCT to assess if ECP applied post-transplant, could prevent the development of GvHD within the first year of transplantation.

STUDY DESIGN

We enrolled 157 patients (18-74 years) with a hematological malignancy receiving first allo-HSCT: 76 randomized to the intervention group and 81 to the control group. ECP was initiated directly upon engraftment and was planned twice weekly for two weeks, then once weekly for four weeks. GvHD, relapse, and death were analyzed with Cox regression analysis.

RESULTS

During the first year, 45 patients in the intervention and 52 control patients developed GvHD (HR=0.82, 95% CI 0.55-1.22, P=0.32). There were no differences in acute or chronic GvHD or its organ distribution in this intention-to-treat RCT. A per-protocol analysis revealed a significant difference in GvHD between the intervention (per-protocol; n=39 of 76) and the control group (n=77), 46% vs 68%, respectively, (HR 0.47, 95% CI 0.27-0.80, P=0.006). Relapse occurred in 15 patients in the intervention group and in 11 patients among the controls (HR=1.38, 95% CI 0.64-3.01, P=0.42). GvHD-free relapse-free (GRFS) survival, event-free survival, overall survival and non-relapse mortality did not differ significantly between the two study groups. No significant difference in immune reconstitution between the two study groups was revealed.

CONCLUSION

This first intention-to-treat RCT, investigating ECP as GvHD prophylaxis in allo-HSCT for hematological malignancy does not support the use of ECP as adjunct to standard drug-based GvHD-prophylaxis. This trial was registered at www.

CLINICALTRIALS

gov as #NCT03204721.

Optimierung der extrakorporalen Photopherese

Die Extrakorporale Photopherese ist ein etabliertes Therapieverfahren für Patienten mit T-Zell vermittelten Erkrankungen. Dabei besteht das Verfahren aus der Gewinnung autologer mononukleärer Zellen, deren Behandlung mit 8-Methoxypsoralen und UVA-Licht und die Retransfusion der behandelten Zellen.

Die Wirkmechanismen der Photopherese sind zwar noch nicht vollständig geklärt, ein zentraler Mechanismus stellt jedoch die Apoptose mononukleärer Zellen dar. Das Ziel der Studie war eine Optimierung der Photopherese im Hinblick auf die Behandlung der Zellen mit 8-Methoxypsoralen/UVA und der daraus induzierten verstärkten Apoptose der Lymphozyten. Dabei sind einige Faktoren bekannt, welche die Effektivität der 8-Methoxypsoralen/UVA-Behandlung der Zellen beeinflussen können, wie z.B. der Hämatokrit oder die UVA-Dosis. Unser Fokus lag auf der Verfügbarkeit der photoaktiven Substanz und dem Einfluss der Zellsuspensionsmatrix auf die Apoptose der Lymphozyten.

Die Verfügbarkeit von 8-Methoxypsoralen für die Aufnahme in die Zellen reduzierte sich durch Absorption an Kunststoffe der Bestrahlungssysteme sowie durch Bindung an Proteine bei der Verwendung von autologem Plasma bei der Suspendierung der Zellen. Eine Steigerung der Zugabe von 8-Methoxypsoralen auf 340 ng/mL anstelle von 200 ng/mL führte zu einem Anstieg der T-Zell Apoptose, die sich unter Verwendung von physiologischer Kochsalzlösung als Zellsuspensionsmatrix weiter erhöhte. Eine Anpassung des Verfahrens mit NaCl anstelle von Plasma und die Verwendung einer höheren 8-Methoxypsoralen Konzentration führte zu einer gesteigerten Apoptoseinduktion der T-Zellen. Inwiefern sich eine Erhöhung der Apoptose auf die klinische Wirksamkeit auswirkt, bedarf hingegen noch weiterer klinischen Untersuchungen.

A simplified extracorporeal photopheresis procedure based on single high-dose ultraviolet A light irradiation shows similar in vitro efficacy

BACKGROUND

Extracorporeal photopheresis (ECP) is one of the most widely used and effective cell-based therapies for the treatment of T-cell-mediated diseases. The patients' white blood cells (WBCs) are collected by apheresis and exposed to the photosensitizer 8-methoxypsoralen (8-MOP) and ultraviolet A (UVA) light before retransfusion. The UVA/8-MOP combination has been in use in ECP for more than 4 decades; however, whether ECP can be simplified by UVA light irradiation only has never been analyzed.

STUDY DESIGN AND METHODS

Peripheral blood mononuclear cells were treated with classical ECP or different UVA light doses only (UVA^only ). Treatment efficacy was investigated by apoptosis induction in WBC subsets, inhibition of T-cell proliferation, and the ability of monocytes to induce allogeneic T-cell expansion and to respond to lipopolysaccharide and interferon-γ stimulation in vitro.

RESULTS

High-dose UVA^only treatment (5 J/cm² ) was as efficient as ECP to induce apoptosis within 48 hours. UVA^only treatment modulated the composition of the surviving cells by improving monocyte survival and promoting CD8⁺ T-cell apoptosis. Both ECP and UVA^only treatment inhibited anti-CD3/anti-CD28 triggered T-cell proliferation. Interestingly, whereas ECP-treated monocytes exhibited a markedly reduced capacity to respond to stimulation and to induce allogeneic T-cell proliferation, UVA^only treatment preserved monocyte functionality to some degree.

CONCLUSIONS

High-dose UVA^only and standard ECP showed comparable efficacy in inducing apoptosis and inhibiting direct T-cell proliferation. Hence, UVA^only treatment can be a simplified alternative to ECP therapy. Furthermore, increased monocyte survival with partially preserved functionality after UVA^only treatment may provide a novel method for immunoregulation.