Promising early results with immunosuppression using rabbit anti-thymocyte globulin and steroids with delayed introduction of tacrolimus in adult liver transplant recipients

Authors


Abstract

Induction therapy with T-cell depleting drugs in liver transplantation is controversial. This study examined the use of rabbit antithymocyte globulin (RATG) with delayed introduction of tacrolimus in liver transplant recipients. Additional subgroup analysis compared patients with or without hepatitis C (HCV) cirrhosis. Over 17 months, 116 adults received 120 liver allografts. Four patients who died before receiving RATG were excluded. Immunosuppression included steroids, 3 doses of RATG (2 mg/kg), and tacrolimus started on postoperative day 3 to 4. Ninety-six percent of patients were alive with a mean follow-up of 12.9±4.5 months. No graft was lost to rejection. Two patients developed hepatic artery thrombosis. Six percent of patients had acute rejection. No patient had steroid resistant or recurrent rejection. RATG related drug events were limited to fever, chills, tachycardia, and oxygen desaturation. There were no cases of lymphoproliferative disease. Forty-two percent of patients were transplanted for HCV. Thirty-two percent of HCV-patients had biopsy proven hepatitis C recurrence occurring at 4 weeks to 10 months posttransplant. RATG induction therapy is associated with good patient and graft survival, a low incidence of rejection, and minimal side effects. In addition, RATG induction is safe in patients transplanted for HCV. (Liver Transpl 2004;10:404–407.)

The delayed introduction of immunosuppression has several benefits. The use of calcineurin inhibitors is often associated with renal and neurologic side effects which are poorly tolerated in the immediate posttransplant period. Several of the biological induction agents may cause hemodynamic alterations in recipients. In the early postoperative period after liver transplantation, there may already be significant alterations in recipient hemodynamics, ventilation, renal function, acid base balance, and coagulation. Delaying the use of calcineurin inhibitors, as well as biological agents, allows the clinician to evaluate the fresh postoperative liver transplant recipient in the absence of confounding variables.1, 2

The use of high-dose immunosuppression in the immediate postoperative period in animal models where the graft is usually accepted without immunosuppression is associated with the inhibition of graft tolerance.3, 4 Immune activation rather than prevention of the initial immune response to the graft is associated with long-term tolerance in rat liver allografts. The delayed introduction of heavy immunosuppression might allow for the necessary immune activation to occur, enabling either elimination or significant reductions in chronic long-term immunosuppression after liver transplantation.5

The routine use of biological induction immunosuppression in liver transplantation is controversial. Induction therapy with rabbit antithymocyte globulin (RATG) has been used successfully in conjunction with triple immunosuppression and for steroid-free protocols in liver transplant recipients.6, 7 Elevated incidences of cytomegalovirus and posttransplant lymphoproliferative disease after use of biologic agents for the treatment of acute cellular rejection dampened enthusiasm for using these agents in induction protocols. The success with RATG in liver transplantation is tempered by the fact that increases in immunosuppression are associated with clinically significant hepatitis C (HCV) recurrence posttransplant, which occurs in 50% of patients by 1 year.8, 9

The most difficult time period in the management of the liver transplant recipient is in the first few postoperative months. Elevations in liver chemistries may be the result of significant reperfusion injury, vascular complications, biliary complications, and rejection. An ideal immunosuppressive protocol would have a very low incidence of rejection (especially in the first 8 weeks posttransplant), minimal infectious complications, and minimal impact on other organ systems.

The results described in this paper summarize our experience with an immunosuppression protocol that includes steroids given after graft reperfusion, 3 doses of RATG initiated on postoperative days 1 to 3, and tacrolimus started on postoperative day 3 or 4. Our results suggest that this protocol is safe, easy to use, and associated with a low incidence of rejection.

Abbreviations

RATG, rabbit anti-thymocyte globulin; HCV, hepatitis C virus.

Patients and Methods

Patient Population

Between July 2001 and December 2002, 120 adult liver transplants were performed at Indiana University Hospital with the intent to be immunosuppressed with RATG, tacrolimus, and steroids. Four patients died in the perioperative period before receiving ATG and are not considered in this paper. One hundred and twelve patients received 116 whole organ liver transplants and were included in the RATG, tacrolimus, and steroid protocol. Indications for transplant are shown in Table 1.

Table 1. Indications for Liver Transplantation
Diagnosisn
Hepatitis C cirrhosis57
Primary sclerosing cholangitis11
Autoimmune hepatitis9
Others35
Total112

Immunosuppression

Induction immunosuppression consisted of 500 mg of methylprednisolone given intravenously after graft reperfusion or in the intensive care unit immediately after surgery. A standard steroid taper was used in all patients so that by 1 week posttransplant all patients were on 20 mg of oral prednisone daily. Three doses of intravenous RATG (2 mg/kg/dose) were given on alternating days starting on postoperative days 1 to 3. The timing of the first dose was dependent upon the patient situation, and was delayed if the patient was still being weaned from the ventilator on the first postoperative day, or if the patient was hemodynamically unstable. RATG administration was also delayed if the patient had renal dysfunction requiring continuous venovenous hemodialysis in anticipation of prolonging the duration that tacrolimus could be withheld. Tacrolimus was usually initiated on postoperative day 3 or 4 with target trough levels between 8 and 12 ng/ml for the first 3 months and then 5 to 8 ng/ml thereafter. Adjustments in tacrolimus dosing more than 2 months after the transplant were made only if patients had evidence of renal dysfunction (dose was lowered), or if there was biopsy confirmed rejection (dose was increased).

Infectious Prophylaxis

Valganciclovir 900 mg twice daily and fluconazole 100 mg once daily were given to all patients for 3 months. Patients were also started on pneumocystis carinii prophylaxis, usually with Septra SS daily, for life.

Work-up of Abnormal Liver Tests and Diagnosis of Rejection in the First 8 Weeks Posttransplant

In the immediate postoperative period, elevations in transaminases were evaluated with Doppler ultrasound to exclude vascular complications. If this failed to reveal the cause, then patients were evaluated for signs of biliary obstruction or leak by endoscopic retrograde cholangiopancreatography in patients with duct-to-duct anastamosis or by transhepatic cholangiogram for patients that had a choledochojejunostomy. Elevations in the cholestatic markers (total bilirubin, alkaline phosphatase, and γ-glutamyl transferase) were primarily evaluated by endoscopic retrograde cholangiopancreatography or transhepatic cholangiogram. If biliary pathology was identified, then a biliary stent was placed across the anastamosis. If Doppler ultrasound and endoscopic retrograde cholangiopancreatography failed to reveal a cause for enzyme elevations, a percutaneous liver biopsy was performed. Liver biopsies were evaluated by a pathologist in conjunction with a transplant surgeon, and graded for rejection using the Banff criteria for allograft rejection. Biopsies in patients with hepatitis C were also evaluated for hepatitis recurrence using the hepatitis activity index. A diagnosis of recurrent hepatitis required elevated HCV RNA by polymerase chain reaction and biopsy confirmation demonstrating a lobular hepatitis suggesting reinfection of the graft. Patients who had rejection confirmed by biopsy were pulsed with intravenous steroids.

Results

Patient and Graft Survival

Patient and graft survival were excellent with a mean follow-up of 12.9±4.5 months (Fig. 1). There was no difference in graft or patient survival in those who were transplanted for HCV (55 of 57 patients alive) versus those patients transplanted with non-HCV disease (52 of 55 patients alive). No patient or graft was lost to rejection. Causes of death are shown in Table 2,  , with only 1 patient dying from causes that might be attributed to over immunosuppression. This patient was transplanted for fulminant hepatic failure secondary to amoxicillin clavulanate, and went home within 2 weeks posttransplant. She returned 2 months postoperatively with fever, marrow suppression, and later elevations of the transaminases to greater than 2500. Doppler ultrasound revealed patent hepatic vessels, and a liver biopsy revealed massive hepatocyte necrosis with parenchymal hemorrhage. There were no signs of rejection, and autopsy findings were inconclusive.

Figure 1.

Patient and graft survival curves in 112 liver transplant recipients that were immunosuppressed with steroids, rabbit anti-thymocyte globulin induction, and delayed introduction of tacrolimus.

Table 2. Causes of Death Post-Transplant
DiagnosisNumber of Deaths
Acute pancreatitis1
Hepatic artery thrombosis1
Biliary leak1
Pancreatic carcinoma1
Unknown1
Table  . Other Causes of Graft Loss
DiagnosisNumberInterval from Transplant (Days)
Hepatic artery thrombosis119
Portal vein disruption12
Primary non-function12
Intrahepatic strictures1210

Incidence of Rejection and its Treatment

Biopsy confirmed rejection occurred in 5 of 112 patients (4.5%) within the first 2 months posttransplant. Overall, 7 of 112 patients (6.2%) experienced rejection at some point posttransplant during the follow-up period. One of 57 (1.8%) patients transplanted for HCV disease had an episode of rejection. No patient had recurrent episodes of rejection. All episodes of rejection were treated by either increases in tacrolimus doses or a steroid pulse. No episode of rejection required the use of biological agents.

Incidence of Postoperative Opportunistic Infections

Five patients developed cytomegalovirus infections including 2 patients with systemic infectons as evidenced by positive serologies and 1 patient each with gastritis, colitis, and pneumonitis as proven by biopsy. All patients responded to treatment with oral valgancyclovir and decreased immunosuppression.

Incidence of Postoperative Cancers

One patient died 6 months postoperatively of pancreatic adenocarcinoma. One other patient with a long smoking history is being treated for a bronchogenic squamous cell cancer. No patient has developed a posttransplant lymphoproliferative disorder during the follow-up period.

Recurrence of HCV

Biopsy confirmed recurrent hepatitis C has occurred in 18 of 57 (32%) patients 1 to 10 months posttransplant. Three of 57 (5%) patients have had severe recurrence, 1 of whom has progressed to fibrosis, 1 was treated with pegylated interferon and ribaviran and recovered, and another is currently receiving treatment with pegylated interferon and ribavirin. Liver chemistries (alanine aminotransferase [U/L] and bilirubin [mg/dl]) were similar in the patients transplanted for HCV and for non-HCV liver disease.

Postoperative Renal Function

Nine of 112 (8%) of patients required perioperative continuous venovenous hemodialysis. The renal function in this group was similar to that of the group of patients that did not require continuous venovenous hemodialysis (data not shown). No patient in either group requires permanent hemodialysis.

Discussion

The administration of immunosuppression in the immediate postoperative period has wide-ranging effects on the patient in terms of hemodynamic stability, renal function, and potentially long-term graft acceptance. The delayed introduction of immunosuppression might allow for immune activation, which is thought to be critical for long term graft accepatance in tolerant rodent liver transplant models.5

The use of biological induction in liver transplantation has not achieved widespread acceptance. RATG has been used with good results in liver transplantation as induction therapy followed by triple immunosuppression with calcineurin inhibitors, antimetabolites, and steroids.6 More recently, RATG has been used in steroid sparing protocols.10, 11 Humanized anti-CD25 mAbs antibodies block the interaction of IL-2 with its receptor, and have been used in induction protocols with cyclosporine, steroids, and azathioprine, or cyclosporine and steroids. Biopsy-confirmed acute rejection rates during the first 6 posttransplant months ranged from 23 to 35%. Acute rejection rates were higher in patients transplanted for HCV.12, 13 The results in our series with delayed introduction of RATG and tacrolimus compare favorably with other immunosuppressive protocols. Delayed introduction of RATG and tacrolimus minimized the incidence of rejection so that the use of steroid pulses is minimal. In addition, there were minimal complications related to over immunosuppression, especially with regards to cytomegalovirus infection and posttransplant cancers.

HCV related liver disease is the most common indication for liver transplantation. Recurrent hepatitis C viremia is universal and clinically significant HCV recurrence after liver transplant occurs in up to 50% of recipients within 1 year posttransplant. The 32% clinically significant recurrence rate in our series suggests that the use of RATG and tacrolimus is not more prone to cause clinically significant HCV recurrence than other immunosuppressive regimens. It is possible that the reduced incidence of clinically significant HCV recurrence in our regimen occurs because there is minimal rejection, and the use of steroid pulses is nearly eliminated.

Renal function following liver transplant is often impaired, with a significant subset of patients going on to develop posttransplant renal failure requiring dialysis and renal transplantation. The delayed introduction of RATG and tacrolimus was associated with normal creatinine levels at 1 year posttransplant, and no patient requires chronic hemodialysis. The inclusion of RATG allowed for the use of tacrolimus with targeted trough levels of 10 ng/ml or less in the immediate posttransplant period, possibly avoiding nephrotoxicity caused by higher targeted trough levels of tacrolimus.

Delayed introduction of RATG and tacrolimus can be used in nearly all patients, and is easy to use. This protocol is associated with good patient and graft survival, as well as good postoperative renal function. In addition, the incidence of rejection is minimal and the posttransplant recurrence of HCV is on the lower end of reported series.

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