Immunosuppression for liver transplantation in HCV-infected patients: mechanism-based principles

Abstract

We retrospectively analyzed 42 hepatitis C virus (HCV)-infected patients who underwent cadaveric liver transplantation under two strategies of immunosuppression: (1) daily tacrolimus (TAC) throughout and an initial cycle of high-dose prednisone (PRED) with subsequent gradual steroid weaning, or (2) intraoperative antithymocyte globulin (ATG) and daily TAC that was later space weaned. After 36 +/- 4 months, patient and graft survival in the first group was 18/19 (94.7%) with no examples of clinically serious HCV recurrence. In the second group, the three-year patient survival was 12/23 (52%), and graft survival was 9/23 (39%); accelerated recurrent hepatitis was the principal cause of the poor results. The data were interpreted in the context of a recently proposed immunologic paradigm that is equally applicable to transplantation and viral immunity. In the framework of this paradigm, the disparate hepatitis outcomes reflected different equilibria reached under the two immunosuppression regimens between the relative kinetics of viral distribution (systemically and in the liver) and the slowly recovering HCV-specific T-cell response. As a corollary, the aims of treatment of the HCV-infected liver recipients should be to predict, monitor, and equilibrate beneficial balances between virus distribution and the absence of an immunopathologic antiviral T-cell response. In this view, favorable equilibria were accomplished in the nonweaned group of patients but not in the weaned group. In conclusion, since the anti-HCV response is unleashed when immunosuppression is weaned, treatment protocols that minimize disease recurrence in HCV-infected allograft recipients must balance the desire to reduce immunosuppression or induce allotolerance with the need to prevent antiviral immunopathology.

Figure 1

Patient and graft survival (months). Patient (black diamonds) and graft (gray squares) survival to three years for HCV-infected liver recipients (top panels) and uninfected recipients (bottom panels) under the TAC-PRED and ATG-TAC immunosuppression regimens. The P values calculated by log-rank between the charts show that all other survival results were similar except in HCV-positive recipients under ATG-TAC immunosuppression. The current mean serum bilirubin of surviving primary grafts in the different groups (subscripts) is not significantly different. Horizontal axis in months.

Figure 2

The effect of two strategies of immunosuppression (TAC-PRED and ATG-TAC) in HCV-mfected liver recipients (continuous lines of A-D). The dashed lines in C and D also depict the hepatic fibrosis scores and time to first rejection in noninfected contemporaneous liver recipients. Note that severe hepatic fibrosis occurred only in the HCV-infected patients treated with ATG-TAC (C). Horizontal axis in months.

Figure 3

(A) Interrelation of noncytopathic antigen quantity and the antigen-specific cytolytic T-cell (CTL) response after a primary HCV infection or, alternatively, after primary liver transplantation. (B) Liver transplantation (Tx) in a patient with chronic aggressive hepatitis long after the viral/CTL balance shown in panel A is reached. The potential effect of immunosuppression on the quantity of the preexisting viral antigen, the de novo transplant antigen, and their respective CTL responses are shown schematically and described in the text. Horizontal axis = time.