LATE ACUTE REJECTION IN LIVER TRANSPLANT: A SYSTEMATIC REVIEW

Introduction: Late acute rejection leads to worse patient and graft survival after liver transplantation. Aim: To analyze the reported results published in recent years by leading transplant centers in evaluating late acute rejection and update the clinical manifestations, diagnosis and treatment of liver transplantation. Method: Systematic literature review through Medline-PubMed database with headings related to late acute rejection in articles published until November 2013 was done. Were analyzed demographics, immunosuppression, rejection, infection and graft and patient survival rates. Results: Late acute rejection in liver transplantation showed poor results mainly regarding patient and graft survival. Almost all of these cohort studies were retrospective and descriptive. The incidence of late acute rejection varied from 7-40% in these studies. Late acute rejection was one cause for graft loss and resulted in different outcomes with worse patient and graft survival after liver transplant. Late acute rejection has been variably defined and may be a cause of chronic rejection with worse prognosis. Late acute rejection occurs during a period in which the goal is to maintain lower immunosuppression after liver transplantation. Conclusion: The current articles show the importance of late acute rejection. The real benefit is based on early diagnosis and adequate treatment at the onset until late follow up after liver transplantation.


INTRODUCTION
A cute cellular rejection has been a common cause of graft loss and an indication for re-transplantation. Advances in immunosuppression have improved the outcome of transplantation 7 . However, late acute rejection appears to result in a different outcome with worse patient and graft survival after liver transplantation 7,9 . Late acute rejection has been variably defined as ocurring more than one, three, or six months after transplantation. Therefore, it differs from early acute cellular rejection, which occurs less than three months after liver transplantation 7,9 . The focus of histologic findings may be portal, central, or both, but the central component is more frequently, and is often associated with poor compliance and is more often refractory to treatment 7 . Late acute rejection causes graft loss, decreased patient survival, chronic rejection and worse prognosis. Late acute rejection occurs during a period in which immunosuppression is lower months after liver transplantation 1,6,7,9 . It is important to pay more attention to this important clinical entity, which is associated with graft loss and patient death. The aim of this study was to systematically review the literature on late acute rejection.

METHODS
Systematic review was performed using electronic search in Medline-PubMed database in English. The search was completed in November 2013.
The research questions and the inclusion and exclusion criteria were developed using the PICO method, which includes data on patients, interventions, comparison classes or controls, outcome structures and inclusion/exclusion criteria. The interventions considered were those performed after liver transplantation with late acute rejection.
The terms for each group were sought in combination using the ''OR'' operator. The results for the search terms, which formed the ''P'' (Patients) group were combined with the result for searches that formed the ''I'' (Intervention) group using the ''AND'' operator and subsequently with the ''exclusion keywords'' using the ''NOT'' operator ( Figure 1).  The Medline search was performed through PubMed (www. ncbi.nlm.nih.gov/pubmed) and was adapted using the Meshterms (graft rejection OR rejection) AND (liver transplantation OR liver graft OR liver transplant) AND adult AND transplant recipient. After this initial search was realized, other selections with more specific terms and mesh terms using (rejection OR graft rejection AND late acute rejection) AND (liver transplantation OR liver graft OR liver transplant) were performed.
The studies were analyzed by two independent researchers (LSN and RAP), and a consensus meeting was held to reach a final decision. The study was approved by a Research Ethics Committee.

RESULTS
This systematic review initially showed 4377 articles, and after a specific search, 234 articles were selected ( Figure 2). Of these, 20 studies were selected according to inclusion criteria and nine were selected for this review. In this review, was noted the importance of late acute rejection in the post-liver transplant, mainly affecting patient and graft survival. Table 2 shows the overall analysis of the nine selected studies. The definition of late acute rejection is more than six months in most studies; however, the diagnosis of early acute rejection occurs within the first month after liver transplant, and that of late acute rejection occurs after three months. Almost all of these cohort studies were retrospective and descriptive. The incidence of late acute rejection was 7-40% in these studies. Only one related incidence was greater at 25%. Other significant findings were the significantly lower patient and graft survival. The evolution to chronic rejection is higher in patients who develop late acute rejection ( Table 2).
The immunosuppression regimen after liver transplantation and the therapeutics used during episodes of late acute rejection are shown in Table 2. The majority of papers reported therapy with steroid and tacrolimus with strict therapeutic drug monitoring after liver transplantation. More than six months after the surgery, tacrolimus or cyclosporine were maintained at 5 to 10 μg/l and 100 to 150 μg/l, respectively. During the episode, an intravenous bolus of 1 g of methylprednisolone was used daily for two days followed by oral prednisolone. Table  2 shows that some cases with steroid-resistance, persistent acute rejection or renal insufficiency have options to improve the results.

DISCUSSION
The importance of this study involved early diagnosis and successful treatment, both of which are essential for improving the prognosis and survival rate of the graft and the patient 5,7 .
In the reviewed literature, was observed a small number of specific studies in this area, with most of the articles being retrospective and descriptive cohort.
Late acute rejection occurred primarily with an incidence rate of 7-23% 1,7,6 . Only one study reported an incidence of 41% 5 . The definition for the time period for late acute rejection is obscure. There is no consensus on the time period, and most of the studies used 3-6 months 6,9 . One used more than one year 2 but did not show a survival difference between late and early acute rejection. Another used one month as the beginning of the time period for late acute rejection 5 . A long-term retrospective study 9 showed incidence of 19% and significantly lower patient and graft survival 9 . Other long-term papers showed similar results, with an incidence rate of 11% and lower survival (10 year follow up) with late acute rejection than without acute rejection 7 .
Wang et al. 10 performed 40 biopsies and demonstrated an increase in blood eosinophil count as a valuable biomarker for predicting late acute rejection after liver transplantation 10 . Neil et al. 5 presented data on early diagnosis that evaluated the delay in diagnosis based on biopsy and reported no difference between early and late acute rejection in the severity and rejection acute index (RAI) 5 .
Regarding the use of an immunosuppressive regimen, therapy may affect survival. Tacrolimus and cyclosporine showed a significant difference and better results in the tacrolimus group 1,6 . Another important finding is that mycophenolate mofetil with tacrolimus and steroid decreased the risk of late acute rejection in patients with hepatitis virus C, hepatitis virus B and no viral disease 8,11 . CsA target levels (ng/dL) were routinely maintained post-LT between 300 and 400 the first month, 250 and 350 the second and third months, 200 and 300 between months 3 and 12, and 100 and 200 after 1 year. TAC target levels (ng/dL) were routinely maintained post-LT between 15 and 20 the first month, 10 and 15 between the second and third months, approximately 10 between 3 and 12 months, and between 5 and 10 after 1 year.
ST taper was used in all patients. Induction therapy with OKT3 was used in only patients with pre-existing renal failure at the time of transplant. CsA target levels (ng/mL) were routinely maintained post-LT between 250 and 350 in the first month and tapered down to 100 and 200 after one year.
Intravenous bolus of 1 g of methylprednisolone daily for two days followed by recycles of prednisolone. If clinical and histological evidence of persistent acute rejection remained, OKT3 or thymoglobulin was administered intravenously for a total of seven to 14 day followed by a liver biopsy. 24 patients (24%) were on monotherapy with a calcineurin inhibitor (21 on TAC and 3 on CsA), 56 patients (57%) were on two immunosuppressors, with the most common combination consisting of an antimetabolite and a CNI (19 azathioprine and TAC, 16 TAC and MMF), 9 patients were on prednisolone and TAC and 18 patients (18%) were on a triple-therapy regimen of CNI, antimetabolites, and corticosteroids.
The immunosuppression therapy was steroid and tacrolimus strictly controlled with therapeutic drug monitoring. More than six months after liver transplantation, tacrolimus and cyclosporine were maintained at 5 to 10 μg/l and 100 to 150 μg/l, respectively 1 .
An episode of late acute rejection should be treated with a bolus of corticosteroids, which was prescribed for 81% 3 and 73% 6 of patients. In addition to intravenous steroid boluses, patients can be treated with steroid recycle 2 and oral steroids 9 and pulsed high-dose prednisolone at 200 mg/day for three days 7 . High-dose methylprednisolone (20 mg/kg per day) followed by recycling is another option 1 .
Modifications of the immunosuppression (Cyclosporine to Tacrolimus) can be used for different types of rejection. Higher acute rejection than grade 1 was treated with steroid bolus therapy (11%) or a modification of the immunosuppression (30%) 3 . In 6% of late acute rejection episodes, steroid-resistance was encountered and required treatment with anti-T-cell monoclonal antibody (OKT3) 6 in a few cases 2,6 . Patients with steroid-resistant cellular rejection were treated with mycophenolate mofetil and anti-T-cell monoclonal antibody 1 . If clinical and histological evidence of persistent acute rejection remained, OKT3 or Thymoglobulin was administered intravenously for a total of 7 to 14 days 9 .
Nacif et al. 4 analyzed the blood samples over time 30 days after the liver transplantation and showed a significant correlation between the Tacrolimus blood level and the deterioration of glomerular filtration rate and serum creatinine. Patients with infections had a higher serum level of Tacrolimus. The dose and presence of rejection were significantly different. Blood Tacrolimus levels greater than 10 ng/ml were associated with impaired renal function. Doses greater than 0.15 mg/kg/day were associated with the prevention of acute cellular rejection but predisposed patients to infectious disease 4 .
Patients with renal dysfunction or other calcineurin toxicity received azathioprine at 1-2 mg/kg/d or mycophenolate mofetil at 0.5-2 g/d, and a steroid taper was used in all patients. Induction therapy with OKT3 was used in only patients with pre-existing renal failure at the time of liver transplant. Cyclosporine target levels (ng/ml) were routinely maintained post liver transplantation between 250 and 350 during the first month and tapered down to 100 and 200 after one year 9 .

CONCLUSION
The current articles show the importance of late acute rejection. In addition, the data support the benefit of early diagnosis and the appropriate treatment of the episode and maintenance therapy during the late period after the liver transplantation.