Photopheresis - Extracorporeal photopheresis is an immunomodulatory technique in which a patien'ts leukocytes are exposed to ultraviolet-A light after pretreatment with 8-methoxypsoralen(methoxsalen).

The UVARXTS system being used in the photopheresis research is currently for investigational use only, pemding FDA approval. Photo Credit : Courtesy Therakos, a Johnson & Johnson Company

USC researchers light up the immune system to help heart transplant patients.  by Eva Emerson

Capping more than a decade of work, USC associate professor of cardiothoracic surgery Mark L. Barr, M.D., says that a new kind of therapy helps prevent rejection of heart transplants.The therapy, called photopheresis, combines ultra-violet light and a light-activated drug to suppress certain key immune cells.Combing photopheresis with standard therapy can reduce the number of serious organ rejections, without increasing side effects, Barr reported in a recent issue of the New England Journal of Medicine."It is a much more targeted therapy than what is currently used. Instead of suppressing the entire immune system, photopheresis allows us to suppress primarily those immune cells responsible for rejecting a donated organ," says Barr, who led an international trial of the therapy. "I expect that, in the future, photopheresis will be used for both prevention and treatment of rejection in patients who receive virtually any kind of solid organ transplant."In the study, a total of 60 heart transplant patients were randomly assigned to receive either photopheresis with standard therapy or standard therapy alone. Patients treated with photopheresis were more than twice as likely to have no episodes of rejection than were patients in the control group. What's more, those receiving standard therapy alone were more than twice as likely to have multiple rejections.Although transplant medicine has advanced considerably in recent years, some problems remain. Despite the use of powerful drugs to dampen the immune system, many patients experience life-threatening bouts of rejection. In addition, the intense immunosuppression necessary to battle rejection often leaves patients vulnerable to opportunistic infections from viruses like cytomegalovirus (CMV).The beauty of photopheresis, notes Barr, is it appears to only destroy the cells responsible for attacking the donor organ, leaving the rest of the immune system robust enough to fight off viruses and bacterial infections."Patients in the photopheresis group had lower levels of CMV in the bloodstream. That supports the idea that the procedure helps the patient's own immune system to clear the virus," he says.Photopheresis involves removing blood from patients and then collecting the white cells including T-lymphocytes, or T-cells. T-cells play a key role in mounting a defense against foreign molecules-including a transplanted heart.The treatment involves mixing the T-cells with a drug called methoxsalen. Exposing the mix to a UV-A light box-similar to something that might be found in a tanning salon-activates the drug, which binds to the T-cells in an irreversible fashion. Patients are then re-injected with their own altered T-cells. Like a vaccine, the inactivated T-cells alert the immune system to destroy any similar T-cells still in the blood.Photopheresis "changes the way the body views its own cells, so that the immune system will recognize-and eliminate-the very cells that are attacking the transplanted organ," Barr says."We see this study as proof of principle, that photopheresis works to change the complicated immune response of transplant patients," says Barr, who has helped move the therapy from an idea to a viable, and sometimes life-saving, therapy.The study's implications go beyond heart transplant recipients, Barr says. "This therapy may have a dramatic impact on the treatment of potentially lethal rejection in other solid organ transplants, including lung, small bowel and kidney. It has also been applied in bone marrow transplantation to treat or prevent Graft vs. Host Disease," Barr says.Outside of the present study, he and other researchers have successfully used photopheresis in transplant patients who have been in the midst of near-fatal rejection episodes."Some of our patients have clearly been saved by this therapy," he says.

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Extracorporeal Photopheresis in the Treatment of Persistent Rejection in a Pediatric Lung Transplant Recipient

Lung transplantation is an accepted therapy for children with end-stage lung disease. One-year lung transplant survival rates of 86% have been reported by the United Network for Organ Sharing. Allograft rejection is a common cause of death following transplantation. Extracorporeal photopheresis is a novel therapy used to treat solid-organ rejection; this therapy involves separating the leukocyte-rich fraction from whole blood, treating with psoralen and ultraviolet light A exposure. The objective of therapy is to reverse progressive and persistent rejection. Working collaboratively with an institution that offers extracorporeal photo-pheresis may provide an alternative or additional therapy in the management of ongoing rejection following solid-organ transplantation. Treatment for rejection is dire at suppressing donor T-cell clones to decrease the number and frequency of rejection episodes. A variety of therapies have been proposed to treat persistent or recurrent rejection (3 or more consecutive episodes) including antilymphocyte antibodies, total lymphoid irradiation, and methotrexate. However, all of these therapies increase the risk of developing infections and lymphoproliferative disease. Extracorporeal photo-pheresis (ECP) is an apheresis-based therapy that alters cell-mediated immunity to produce a clone-specific antilymphocytic immune response.Repeated episodes of acute rejection can predispose the recipient to chronic rejection and potentially limits long-term survival in lung transplantation. 

Extracorporeal Photopheresis:  The therapy involves separating the plasma and leukocyte-rich fractions from whole blood by centrifugation and treating the lymphocytes obtained with 8-methoxypsoralen (methoxsalen, 8-MOP) followed by ultraviolet light (UV-A) exposure. Methoxsalen is added directly to the buffy coat collection bag after the leukapheresis collection phase. The use of methoxsalen allows selective activation of the drug when the cells are exposed to UV-A.[10]A large-bore catheter, such as a Davol double-lumen catheter (Davol, mc, Cranston, RI), is recommended in patients who undergo leukapheresis because venous flow rates of 25 to 50 mL/min are required. A sterile gauze with 10% povidone iodine is applied over the insertion site and changed daily for the first 7 days. After 7 days, a transparent dressing is applied to allow the insertion site to be observed for signs of infection. The sutures remain in place for 21 days. Each lumen of the catheter is flushed with 6 mL isotonic sodium chloride solution followed by 3 mL heparin 1:1000 units after the procedure. Once the leukocytes are treated, they are reinfused into the patient in an attempt to downregulate the immune response. It is not possible to treat individuals who weigh less than 40 kg with this device. In children who weigh less than 40 kg, the UV AR photopheresis system (Therakos, West Chester, Pa) may be used.  In children who weigh less than 20 kg, the amount of plasma or buffy coat should be reduced accordingly. Higher doses of heparin may be required in patients who are hypercoagulable. The blood is continuously circulating through a sterile cassette surrounded by UV-A-emitting light bulbs that permit 180 minutes of ultraviolet light exposure to ensure that all cells receive adequate exposure. The psoralen is added directly to the leukocytes avoiding a frequent side effect of nausea. The psoralen levels are monitored to maintain levels above 50 ng/mL. At the conclusion of the photoactivation process, the treated cells are returned to the patient. Once the cells are reinfused into the patient, the recipient is considered immunized with inactive autologous immunocompetent cells directed toward the graft.

Complications: Few toxic reactions or adverse events have been associated with ECP therapy. The recommended schedule for ECP is 2 consecutive day treatments on a weekly basis for the first month, then biweekly intervals for the second and third months, and then monthly for another 3 months.

Mechanism of Action:  The mechanism of action in ECP therapy is poorly understood. Several explanations have been proposed, including the induction of antigen-specific immunosuppression that is directed toward T cells. The UV-A activates psoralen in the leukocyte and stops the activity of proliferating T cells. The treated T cells mediate both the humoral and cellular rejection response, improving graft survival. In addition, photopheresis may stop the progression of bronchiolitis obliterans (BO), but does not reverse scarring that is already present.  Villanueva et al examined the results of ECP therapy in the treatment of acute rejection with BO in 14 adult lung transplant recipients. ECP stabilized the lung function in patients with early BO syndrome but had minimal impact on the outcome in patients with advanced BO (stage 2 or 3). Patients with early BO had an average survival of 4 years. Case Study  An 18-year-old woman diagnosed with CF, with pancreatic insufficiency and malabsorption, under-went a bilateral lung transplantation for end-stage lung disease. The immediate postoperative course was uneventful. Initial immunosuppression included daclizumab, tacrolimus, prednisone, and mycophenolate mofetil. She underwent monthly bronchoscopies with transbronchial biopsies per protocol and for clinical deterioration. An early biopsy obtained 3 months after transplantation demonstrated mild rejection (ISHL T grade 2A) with numerous eosinophils indicating a subacute inflammatory process. One month later, a transbronchial biopsy indicated minimal acute cellular rejection (ISHLT grade AI). The episodes of acute rejection were managed with steroid pulses over 3 days and maintenance immunosuppression. She developed worsening pulmonary function over the next 4 weeks and a transbronchial biopsy was obtained that revealed moderate to severe cellular rejection (ISHLT grade A3-4, Bl). Initially, she was treated with pulsed doses of methylprednisolone. In addition, she received a 14-day course of muromonab-CD3. Arrangements were therefore made to perform the pheresis procedure at our institution and transport the blood to HUP for ECP. The patient underwent pheresis using centrifugal apparatus.Villanueva examined the results of ECP therapy in the treatment of acute rejection with BO in 14 adult lung transplant recipients. ECP stabilized the lung function in patients with early BO syndrome but had minimal impact on the outcome in patients with advanced BO (stage 2 or 3). Patients with early BO had an average survival of 4years.

The entire procedure (leukapheresis, transport, irradiation, return transport, and reinfusion) took place within 16 to 18 hours. No transfusion reactions were reported; however, the patient complained of s,eyere fatigue with apheresis. A transbronchial biopsy was obtained 1 week after the third ECP procedure that indicated acute and chronic bronchitis with moderate acute rejection (ISHLT grade A3), no improvement from the previous biopsies. At this point, the patient became despondent and refused further treatments. A final transbronchial biopsy was

obtained 3 weeks later. The results indicated extensive BO with organizing pneumonia. This was associated with interstitial lymphocytic infiltrate. No acute rejection was found. Although ongoing pulmonary pathology was present, the absence of acute rejection suggests that the photo-pheresis may have reversed the acute rejection. Although the patient's clinical status had stabilized, she still refused further therapy.

Conclusions: Extracorporeal photopheresis is a potential new therapy for recurrent acute rejection. It has minimal side effects and specifically targets activated lymphocytes found during acute rejection episodes in transplant recipients. Although the exact mechanism of action is unknown, ECP seems to change the immune-mediated destruction of transplanted tissues. Although ECP is not available in many institutions, we have shown a novel approach to facilitate this therapy when the technology is not immediately available.

(Source: Barbara V. Wise, RN, PhD, Karen E. King, MD, Alain H. Rook, MD, Peter J. Mogayzel Jr, MD, PhDProg Transplant 13(1):61-64, 2003. @ 2003 North American Transplant