Vascular rejection in cardiac transplantation

Extracorporeal photopheresis and its role in heart transplant rejection: prophylaxis and treatment

Heart transplantation is the gold standard therapeutic option for select patients with end-stage heart failure. Unfortunately, successful long-term outcomes of heart transplantation can be hindered by immune-mediated rejection of the cardiac allograft, specifically acute cellular rejection, antibody-mediated rejection, and cardiac allograft vasculopathy. Extracorporeal photopheresis is a cellular immunotherapy that involves the collection and treatment of white blood cells contained in the buffy coat with a photoactive psoralen compound, 8-methoxy psoralen, and subsequent irradiation with ultraviolet A light. This process is thought to cause DNA and RNA crosslinking, ultimately leading to cell destruction. The true mechanism of therapeutic action remains unknown. In the last three decades, extracorporeal photopheresis has shown promising results and is indicated for a variety of conditions. The American Society for Apheresis currently recommends the use of extracorporeal photopheresis for the treatment of cutaneous T-cell lymphoma, scleroderma, psoriasis, pemphigus vulgaris, atopic dermatitis, graft-versus-host disease, Crohn's disease, nephrogenic systemic fibrosis, and solid organ rejection in heart, lung, and liver transplantation. In this review, we aim to explore the proposed effects of extracorporeal photopheresis and to summarize published data on its use as a prophylactic and therapy in heart transplant rejection.

Antibody-mediated rejection in the cardiac allograft: diagnosis, treatment and future considerations

PURPOSE OF REVIEW

This review summarizes the latest publications dealing with antibody-mediated rejection (AMR) and defines areas of controversy and future steps that may improve the outcome for patients with this virulent form of rejection.

RECENT FINDINGS

Recent progress includes publication of standardized pathologic criteria for acute AMR by the International Society for Heart and Lung Transplantation (ISHLT) and guidelines for treatment of acute AMR by the American Heart Association, endorsed by ISHLT as well. Recently published review articles emphasize the important role of innate immune mechanisms, clarify the role of viral infection and provide insights into vascular biology and the role of innate effector populations, macrophages and dendritic cells.

SUMMARY

Strategies for future studies are discussed in the context of these new findings and similar efforts undertaken by renal and liver allograft investigators.

Donor-specific antibodies to class II antigens are associated with accelerated cardiac allograft vasculopathy: a three-dimensional volumetric intravascular ultrasound study

BACKGROUND

Although a link between donor-specific antibodies against human leukocyte antigens type II (DSA II+) and transplant glomerulopathy has been clearly established, its role in cardiac allograft vasculopathy (CAV) is unclear.

METHODS

Donor-specific antibodies were evaluated using solid-phase single-antigen bead assay before transplantation in 51 heart transplant recipients. Coronary angiography and three-dimensional intravascular ultrasound were performed at baseline and approximately 1 year after the baseline examination.

RESULTS

There were 4 (7.8 %), 11 (21.5%), and 2 (3.9%) patients who had DSA against donor class I (DSA I+), DSA II+, or both, respectively. All patients had negative complement-dependent cytotoxic crossmatch. There was accelerated progression of CAV in the DSA II+ group demonstrated by accelerated progression in plaque index (plaque volume/vessel volume) compared to patients with no DSA II+ antibodies (13.8% [12%] vs. -7.9% [37%], P=0.01). The development of any angiographic CAV was also more common in DSA II+ patients as compared to the DSA- patients at 4 years (100% [0%] vs. 64.2% [10%], P=0.05). All other traditional risk factors for CAV or immunosuppression were similar between the groups (P>0.2 for all).

CONCLUSIONS

This is the first preliminary study demonstrating that heart transplant recipients with preformed class II DSA may be at an increased risk for accelerated CAV as detected by consecutive volumetric three-dimensional intravascular ultrasound.

The long-term outcome of treated sensitized patients who undergo heart transplantation

BACKGROUND

Sensitized patients prior to heart transplantation are reportedly at risk for hyperacute rejection and for poor outcome after heart transplantation. It is not known whether the reduction of circulating antibodies pre-transplant alters post-transplant outcome.

METHODS AND RESULTS

Between July 1993 and July 2003, we reviewed 523 heart transplant patients of which 95 had pre-transplant panel reactive antibody (PRAs) >10%; 21/95 were treated pre-transplant for circulating antibodies. These 21 patients had PRAs > 10% (majority 50-100%) and were treated with combination therapy including plasmapheresis, intravenous gamma globulin and rituximab to reduce antibody counts. The 74 untreated patients with PRAs > 10% (untreated sensitized group) and those patients with PRAs < 10% (control group) were used for comparison. Routine post-transplant immunosuppression included triple-drug therapy. After desensitization therapy, circulating antibody levels pre-transplant decreased from a mean of 70.5 to 30.2%, which resulted in a negative prospective donor-specific crossmatch and successful heart transplantation. Compared to the untreated sensitized group and the control group, the treated sensitized group had similar five-yr survival (81.1% and 75.7% vs. 71.4%, respectively, p = 0.523) and freedom from cardiac allograft vasculopathy (74.3% and 72.7% vs. 76.2%, respectively, p = 0.850).

CONCLUSION

Treatment of sensitized patients pre-transplant appears to result in acceptable long-term outcome after heart transplantation.

Sex mismatch in heart transplantation is associated with increased number of severe rejection episodes and shorter long-term survival

BACKGROUND

Heart transplantation is the criterion standard for treating end-stage heart failure. Male sex of both the donor organ and the recipient is advantageous for survival, possibly owing to hemodynamic or immunologic reasons. The effect of sex mismatch on long-term survival in male heart transplant recipients is less known.

PATIENTS AND METHODS

In this prospective single-center study, we reviewed follow-up data for 57 sex-mismatched and 179 sex-matched men who underwent orthotopic heart transplantation between 1990 and 2002.

RESULTS

Median survival was significantly shorter in the sex-mismatched group (8.1 vs 12.9 years; P < .04). Subgroup analysis revealed that this was even more pronounced in male heart recipients with coronary artery disease (2.4 vs 12.9 years; P < .001). Female donor organs were significantly smaller (left ventricular end-diastolic diameter 49 vs 51 mm; P < .05), and recipients more often experienced clinically relevant episodes of cellular rejection during the first 3 months posttransplantation (International Society for Heart and Lung Transplantation grade 3, 5.6% vs 3.1%; P < .001). Global left ventricular function, and immunosuppressive and inflammatory parameters did not differ.

CONCLUSION

In male orthotopic heart transplant recipients, sex mismatch is associated with adverse outcome owing to increased number and severity of episodes of graft rejection.

Anti-HLA antibodies in heart transplantation

We have analyzed the relationship between the development of transplant-related coronary artery disease (TRCAD) and the following potential risk factors: (a). number of HLA mismatches between recipient and donor; (b). production of anti-HLA antibodies; (c). growth of lymphocytes infiltrating the graft; and (d). frequency of biopsy proven episodes of acute rejection. The study population consisted of 285 adult heart allograft recipients who were monitored over a period of two years or more. The results demonstrate a significant correlation between TRCAD, generation of anti-HLA class II antibodies and potential of lymphocytes infiltrating the graft to proliferate ex-vivo in medium containing IL-2. Humoral and cellular immune responses to HLA-DR antigens expressed by the graft seem to underlie the development of TRCAD.

Immunosuppression for cardiac transplantation—the past, present and future

The field of cardiac transplant immunosuppression is rapidly developing and has evolved over the past 35 years. Anecdote, experience and registry based practice is giving way to an increasing bounty of well designed, randomized controlled trials which will guide future therapy. Current therapy is based on triple therapy with corticosteroids, a calcineurin inhibitor and an antimetabolite, but these regimens may be replaced by substitution or addition of newer antiproliferative agents. The true nemesis is coronary graft vasculopathy, which affects 50% of patients at 5 years and until recently had very few preventive therapeutic options. Renal toxicity remains among the most challenging adverse effects of immunosuppression to be overcome.

Humoral rejection in cardiac transplantation: risk factors, hemodynamic consequences and relationship to transplant coronary artery disease

BACKGROUND

Acute cellular rejection is the mechanism of most immune-related injury in cardiac transplant recipients. However, antibody-mediated humoral rejection (HR) has also been implicated as an important clinical entity following orthotopic heart transplantation. Humoral rejection has been reported to play a role in graft dysfunction in the early post-transplant period, and to be a risk factor for the development of transplant coronary artery disease. Some involved in transplantation pathology doubt the existence of clinically significant humoral rejection in cardiac allografts. Those who recognize its existence disagree on its possible role in graft dysfunction or graft coronary artery disease. In this study, we report clinical features of patients with the pathologic diagnosis of HR at our institution since July 1997, when we began systematic surveillance for humoral rejection.

METHODS

We reviewed medical records of patients with the pathologic diagnosis of HR without concurrent cellular rejection between July 1997 and January 2001. Diagnosis was based on routine histology ("swollen cells" distending capillaries, interstitial edema and hemorrhage) and immunofluorescence (capillary deposition of immunoglobulin and complement with HLA-DR positivity), or immunoperoxidase staining of paraffin-embedded tissue (numerous CD68-positive macrophages and fewer swollen endothelial cells distending capillaries).

RESULTS

A total of 44 patients (4 to 74 years old) showed evidence of HR without concurrent cellular rejection at autopsy or on one or more biopsies. Although females comprised only 26% of our transplant population, 23 patients (52%) with HR were female. A positive peri-operative flow cytometry T-cell crossmatch was observed in 32% of HR patients compared with 12% of controls (p = 0.02). Hemodynamic compromise consisting of shock, hypotension, decreased cardiac output/index and/or a rise in capillary wedge or pulmonary artery pressure was observed in 47% of patients at the time of diagnosis of HR. Six patients (5 females) died (14% mortality) with evidence of HR at or just before autopsy, 6 days to 16 months after transplantation. The incidence of transplant coronary artery disease was 10% greater at 1 year, and 36% greater at 5 years, in patients with HR when compared with non-HR patients.

CONCLUSIONS

Humoral rejection was associated with acute hemodynamic compromise in 47% of patients, and was the direct cause of death in 6 patients (13%). Humoral rejection is a clinicopathologic entity with a high incidence in women and is associated with acute hemodynamic compromise, accelerated transplant coronary artery disease and death.