Weaning of immunosuppression in long-term liver transplant recipients

Weaning of immunosuppression in liver transplant recipients

Immunosuppression has been sporadically discontinued by noncompliant liver allograft recipients for whom an additional 4 1/2 years of follow-up is provided. These anecdotal observations prompted a previously reported prospective drug withdrawal program in 59 liver recipients. This prospective series has been increased to 95 patients whose weaning was begun between June 1992 and March 1996, 8.4+/-4.4 (SD) years after liver replacement. A further 4 1/2 years follow-up was obtained of the 5 self-weaned patients. The prospectively weaned recipients (93 livers; 2 liver/kidney) had undergone transplantation under immunosuppression based on azathioprine (AZA, through 1979), cyclosporine (CsA, 1980-1989), or tacrolimus (TAC, 1989-1994). In patients on CsA or TAC based cocktails, the adjunct drugs were weaned first in the early part of the trial. Since 1994, the T cell-directed drugs were weaned first. Three of the 5 original self-weaned recipients remain well after drug-free intervals of 14 to 17 years. A fourth patient died in a vehicular accident after 11 years off immunosuppression, and the fifth patient underwent retransplantation because of hepatitis C infection after 9 drug-free years; their allografts had no histopathologic evidence of rejection. Eighteen (19%) of the 95 patients in the prospective series have been drug free for from 10 months to 4.8 years. In the total group, 18 (19%) have had biopsy proved acute rejection; 7 (7%) had a presumed acute rejection without biopsy; 37 (39%) are still weaning; and 12 (13%, all well) were withdrawn from the protocol at reduced immunosuppression because of noncompliance (n=8), recurrent PBC (n=2), pregnancy (n=1), and renal failure necessitating kidney transplantation (n=1). No patients were formally diagnosed with chronic rejection, but 3 (3%) were placed back on preexisting immunosuppression or switched from cyclosporine (CsA) to tacrolimus (TAC) because of histopathologic evidence of duct injury. Two patients with normal liver function died during the trial, both from complications of prior chronic immunosuppression. No grafts suffered permanent functional impairment and only one patient developed temporary jaundice. Long surviving liver transplant recipients are systematically overimmunosuppressed. Consequently, drug weaning, whether incomplete or complete, is an important management strategy providing it is done slowly under careful physician surveillance. Complete weaning from CsA-based regimens has been difficult. Disease recurrence during drug withdrawal was documented in 2 of 13 patients with PBC and could be a risk with other autoimmune disorders.

The lost chord: microchimerism and allograft survival

Recent evidence suggests that passenger leukocytes migrate after organ transplantation and produce persistent chimerism, which is essential for sustained survival of the allografts. Here, Thomas Starzl and colleagues argure that this hematolymphopoietic chimerism provides an important framework for the interpretation of basic and therapeutically oriented transplantataion research.

The two-way paradigm of transplantation immunology

The events following organ transplantation require a reciprocal cell interaction which includes both the conventional host-versus-graft reaction and a graft-versus-host component. With all successful transplantation, both graft and recipient become genetic composites. Where donors were available, chimerism has been confirmed in 30-year kidney-recipient survivors, as well as in several liver and lung recipients. A majority of liver recipients have been able to acquire an immunosuppressant-free state after 10-year survival. Animal models suggest that donor-derived cells may exert a tolerogenic effect.

Prevention of Transplant Rejection: Can Tolerance be Achieved with Immunosuppressive Treatment?

Successful solid organ transplantation is generally attributed to the increasingly precise ability of drugs to control rejection. However, it was recently shown that a few donor haematolymphoid cells can survive for decades in recipients of successful organ allografts, a phenomenon called microchimaerism. The association for decades of haematolymphoid chimaerism with allograft tolerance in experimental transplantation suggests that immunosuppressive drugs merely create a milieu that enables an allograft and its complement of passenger leucocytes to prime the recipient for graft acceptance.Exploitation of this concept requires a fundamental shift in the classical view of passenger leucocytes only as initiators of rejection. Microchimaerism has taught us that solid organ transplantation involves the transfer of two donor organ systems to the recipient: the allograft parenchyma and the donor haematolymphoid system in the form of donor stem cells contained within the passenger leucocyte compartment. Each has the potential to integrate with the corresponding recipient system and carry out normal physiological functions, such as immunological self definition. Resistance to initial integration by mature T cells requires some form of immunosuppression, but maintenance of donor immune system function will depend on renewable supply of cells, which can be provided by engrafted progenitors. Successful clinical application will depend on the development of low morbidity methods to enhance engraftment of donor haemopoietic stem cells.

An analysis of late deaths after liver transplantation

Late deaths (after more than 1 year) after liver transplantation were analyzed in a series of 464 consecutive patients who received liver grafts between 1982 and 1993. Recipients who survived the first posttransplant year (n = 365) had actuarial 5- and 10-year survival rates of 92% and 84%, respectively. Thirty-five patients died between 1.1 and 7.6 years after transplantation (mean, 3.2 +/- 1.9 years). The most common causes of death were related to immunosuppression (40%), namely, chronic rejection, opportunistic infection, and lymphoma. The second most common causes of death were related to the primary disease for which liver transplantation was performed (34.3%), mainly recurrence of hepatobiliary malignancy and hepatitis B. Eight patients (22.9%) died of unrelated and unpredicted causes, most commonly of cardiovascular disease. Although the survival of liver recipients who live beyond the first posttransplant year is excellent, control of rejection and the consequences of chronic immunosuppression are continual threats. Modification of immunosuppression may help in decreasing the mortality of long-term survivors. In addition, better selection of recipients and effective adjuvant therapies (antiviral and antineoplastic) are needed in patients in whom the primary liver disease is notorious for recurrence.

The evolution of immunosuppression with FK506 in pediatric living-related liver transplantation

The effects of three FK506 induction regimens on pediatric living-related liver transplantation (LRLT) were studied retrospectively in terms of patient survival and adverse side effects. The patients consisted of 120 children, ranging from 3 to 210 months of age, who underwent a total of 122 LRLTs with a minimum follow-up of 6 months. Immunosuppression consisted of FK506 and low-dose steroids. FK506 was given in 3 ways: (1) high-dose intravenous (i.v.) induction, with FK506 begun at a dose of 0.15 mg/kg/day for the first 16 patients; (2) low-dose i.v. induction, with FK506 begun at a dose of 0.06 mg/kg/day for the next 45 patients; and (3) per os (p.o.) induction, with FK506 begun orally from the day prior to LRLT and continued postoperatively. Whole-blood trough levels of FK506 were monitored daily. Trough levels in the high induction group were often as high as 100 ng/ml compared with the level of 20 ng/ml in the p.o. induction group. Patient survivals were 75%, 89%, and 80% in the high-i.v. vs. low-i.v. vs. p.o. groups. The incidences of acute rejection were 12.5%, 22.2%, and 26.4%, and the incidences of viral infection were 56%, 38%, and 11% in the respective groups. Major adverse effects occurred with higher frequency in the high-i.v. induction group. Oral FK506 induction therapy at a dose of 0.15 mg/kg/day starting from the day before LRLT was safer and associated with a lower incidence of viral infection than therapy with i.v. FK506.

The current status of hepatic transplantation at the University of Pittsburgh

Tacrolimus is a more potent and satisfactory immunosuppressant than CyA for combination therapy with prednisone. In randomized trials comparing the 2 drugs, the ability of tacrolimus to rescue intractably rejecting grafts on the competing CyA arm allowed equalization of patient and graft survival on both arms when the intent-to-treat analytic methodology was applied. The ability of tacrolimus to systematically rescue the treatment failures of CyA suggested, as a matter of common sense, that it is the preferred baseline drug for hepatic transplantation. This conclusion was supported by analysis of secondary end points, including the ability to prevent rejection. Hepatic-intestinal, multivisceral and isolated intestinal transplantation became feasible on a practical basis only after the advent of tacrolimus. Nevertheless, better management strategies must be devised before intestinal transplantation, alone or with other abdominal viscera, will meet its potential. One such strategy is based on the discovery of the presence of previously unsuspected, low-level donor leukocyte chimerism in long-surviving allograft recipients. We believe that this chimerism is the essential explanation for the feasibility of organ transplantation and a link to the acquired neonatal tolerance demonstrated by Billingham, Brent and Medawar (32). The hematolymphopoietic chimerism in organ recipients explains why weaning to a drug-free state in selected long-term survivors is frequently feasible and particularly if the allograft is a liver. Weaning should never be attempted without a stepwise protocol and careful monitoring of graft function. Recognition of the natural chimerism that develops after whole organ transplantation has led to efforts to augment it with perioperative donor BM infusion. This procedure has been shown to be free of significant complications (including GVHD) in all kinds of whole organ recipients, including those given intestine. The prospects of clinical xenotransplantation must be evaluated in the same context of chimerism as that delineated for allotransplantation with the discovery of spontaneous chimerism. Before addressing chimerism-related questions in xenotransplantation, the additional barrier of the complement activation syndromes that cause hyperacute rejection will have to be surmounted. Although measures to effectively transplant xenografts have so far eluded us, the availability of the more potent drug, tacrolimus, and recognition of the seminal basis of allograft (or xenograft) acceptance via chimerism has inserted an element of reality into the largely wishful thinking that has been evident in discussions about the future of xenotransplantation.

Hepatic transplantation at the University of Pittsburgh: new horizons and paradigms after 30 years of experience

In the 1993 edition of this book, we described 4 major initiatives in liver transplantation: First, the evaluation of the new immunosuppressive drug FK506 (tacrolimus); second, the feasibility of combined liver-intestinal and multivisceral transplantation; third, 2 clinical attempts at hepatic xenotransplantation; and fourth, beginning attempts to enhance donor-specific nonreactivity with adjuvant bone marrow infusion. These and other new clinical studies during the last 12 months are the concerns of this update. The topics will be considered separately because of the unique design of each and the heterogeneity of the enrolled patient population.

The patient and graft survival curves were estimated by the Kaplan-Meier method and the comparisons were done by the log-rank test. Survival time for patients was defined as the time that elapsed from the transplantation date until death, or the date of the last follow-up evaluation. For calculating graft survival, the date of graft removal was also considered. Cox’s proportional hazards model was used to analyze different causes of mortality and graft failure. Single variable comparison for qualitative data was made by chi-square analysis. The one-way analysis of variance was used for 3-way comparison.