Reconstitution of hepatitis C virus-specific T-cellmediated immunity after liver transplantation

Increased Sensitivities of Peripheral Blood Mononuclear Cells to Immunosuppressive Drugs in Cirrhosis Patients Awaiting Liver Transplantation

Successful immunosuppressive therapy is critical for liver transplantation. However, a considerable number of patients show clinical resistance to the therapy and experience rejection episodes, or alternatively exhibits serious adverse effects of drugs. We examined the in vitro response of peripheral blood mononuclear cells (PBMCs) to immunosuppressive drugs in cirrhosis patients awaiting liver transplantation. We evaluated the suppressive efficacy of prednisolone, methylprednisolone, cyclosporine, and tacrolimus on the in vitro blastogenesis of PBMCs obtained from 22 cirrhosis patients and 31 healthy subjects. In vitro drug concentrations giving 50% inhibition of PBMC blastogenesis (IC50s) were calculated. Two out of these 22 patients received liver transplantation from living donors, and their clinical courses were surveyed until 5 weeks after operation. The median IC50 values for prednisolone, cyclosporine, and tacrolimus against blastogenesis of PBMCs from cirrhosis patients were significantly lower than those of PBMCs from healthy subjects (p < 0.01). However, large individual differences were observed in the IC50 values of the immunosuppressive drugs examined, especially in the cirrhosis patients. One recipient exhibiting high PBMC sensitivity to tacrolimus (IC50 = 0.001 ng/ml) showed good clinical course without rejection until 5 weeks after liver transplantation. The other recipient exhibiting relatively low PBMC sensitivity to taclolimus (IC50 = 0.30) showed allograft rejection at 1 week after operation. We concluded from these observations that PBMCs of cirrhosis patients are vulnerable to the immunosuppressive effects of prednisolone and calcineurin inhibitors. However, large individual variations in the IC50 values suggest that patients exhibiting relatively lower sensitivity to these drugs may have risks of rejection, whereas highly sensitive patients are possibly able to reduce the dose of immunosuppressive drugs to avoid serious drug-adverse effects, after liver transplantation.

Functional Behavior of NKp46-Positive Intrahepatic Natural Killer Cells Against Hepatitis C Virus Reinfection After Liver Transplantation

BACKGROUND

NKp46 expression in natural killer (NK) cells has recently been shown to affect the responsiveness to antiviral treatment in hepatitis C virus (HCV)-infected patients. However, the density of NKp46 on intrahepatic NK cells is remarkably higher than that on peripherally circulating NK cells, whereas the biophylactic function of intrahepatic NK cells against HCV reinfection remains unclear.

METHODS

We analyzed the phenotypic and functional properties of intrahepatic NK cells using mononuclear cells extracted from ex vivo liver perfusates from living liver transplantation donors. To investigate the role of intrahepatic NK cells in relation to HCV infection, we evaluated posttransplant HCV load kinetics in HCV-related patients.

RESULTS

Intrahepatic NK cells from healthy donors showed a distinctive phenotype even in each of the CD56 and CD56 fractions compared with peripheral blood NK cells. In the assays using a Huh7-HCV replicon system, anti-HCV activity was induced via recognition of the NK cell receptors, including NKp46, NKp30, and NKG2D, which was demonstrated by the use of monoclonal antibodies that neutralized neutralizing molecules. Unexpectedly, the density of NKp46 on intrahepatic NK cells varied considerably among individuals, allowing us to demonstrate that HCV reload in the early posttransplant period was delayed in recipients of liver allografts containing a higher proportion of NKp46 NK cells.

CONCLUSIONS

Intrahepatic NKp46 NK cells exhibited anti-HCV activity via cell-to-cell contact. The variation of the NKp46 proportion in individuals could be attributed to the diversity of HCV resistance observed in these individuals, which possibly reflects the clinical outcome of infection in patients.

Immunopathogenesis of Hepatitis C Virus Infection

Despite advances in therapy, hepatitis C virus infection remains a major global health issue with 3 to 4 million incident cases and 170 million prevalent chronic infections. Complex, partially understood, host-virus interactions determine whether an acute infection with hepatitis C resolves, as occurs in approximately 30% of cases, or generates a persistent hepatic infection, as occurs in the remainder. Once chronic infection is established, the velocity of hepatocyte injury and resultant fibrosis is significantly modulated by immunologic as well as environmental factors. Immunomodulation has been the backbone of antiviral therapy despite poor understanding of its mechanism of action.

HCV-induced immune responses influence the development of operational tolerance after liver transplantation in humans

Pathogen-induced immune responses prevent the establishment of transplantation tolerance in experimental animal models. Whether this occurs in humans as well remains unclear. The development of operational tolerance in liver transplant recipients with chronic hepatitis C virus (HCV) infection allows us to address this question. We conducted a clinical trial of immunosuppression withdrawal in HCV-infected adult liver recipients to elucidate (i) the mechanisms through which allograft tolerance can be established in the presence of an ongoing inflammatory response and (ii) whether anti-HCV heterologous immune responses influence this phenomenon. Of 34 enrolled liver recipients, drug withdrawal was successful in 17 patients (50%). Tolerance was associated with intrahepatic overexpression of type I interferon and immunoregulatory genes and with an expansion of exhausted PD1/CTLA4/2B4-positive HCV-specific circulating CD8(+) T cells. These findings were already present before immunosuppression was discontinued and were specific for HCV infection. In contrast, the magnitude of HCV-induced proinflammatory gene expression and the breadth of anti-HCV effector T cell responses did not influence drug withdrawal outcome. Our data suggest that in humans, persistent viral infections exert immunoregulatory effects that could contribute to the restraining of alloimmune responses, and do not necessarily preclude the development of allograft tolerance.

Post-liver transplant hepatitis C virus recurrence: an unresolved thorny problem

Hepatitis C virus (HCV)-related cirrhosis represents the leading cause of liver transplantation in developed, Western and Eastern countries. Unfortunately, liver transplantation does not cure recipient HCV infection: reinfection universally occurs and disease progression is faster after liver transplant. In this review we focus on what happens throughout the peri-transplant phase and in the first 6-12 mo after transplantation: during this crucial period a completely new balance between HCV, liver graft, the recipient's immune response and anti-rejection therapy is achieved that will deeply affect subsequent outcomes. Nearly all patients show an early graft reinfection, with HCV viremia reaching and exceeding pre-transplant levels; in this setting, histological assessment is essential to differentiate recurrent hepatitis C from acute or chronic rejection; however, differentiating the two patterns remains difficult. The host immune response (mainly cellular mediated) appears to be crucial both in the control of HCV infection and in the genesis of rejection, and it is also strongly influenced by immunosuppressive treatment. At present no clear immunosuppressive strategy could be strongly recommended in HCV-positive recipients to prevent HCV recurrence, even immunotherapy appears to be ineffective. Nonetheless it seems reasonable that episodes of rejection and over-immunosuppression are more likely to enhance the risk of HCV recurrence through immunological mechanisms. Both complete prevention of rejection and optimization of immunosuppression should represent the main goals towards reducing the rate of graft HCV reinfection. In conclusion, post-transplant HCV recurrence remains an unresolved, thorny problem because many factors remain obscure and need to be better determined.

Brassinosteroids regulate plant growth through distinct signaling pathways in Selaginella and Arabidopsis

Brassinosteroids (BRs) are growth-promoting steroid hormones that regulate diverse physiological processes in plants. Most BR biosynthetic enzymes belong to the cytochrome P450 (CYP) family. The gene encoding the ultimate step of BR biosynthesis in Arabidopsis likely evolved by gene duplication followed by functional specialization in a dicotyledonous plant-specific manner. To gain insight into the evolution of BRs, we performed a genomic reconstitution of Arabidopsis BR biosynthetic genes in an ancestral vascular plant, the lycophyte Selaginella moellendorffii. Selaginella contains four members of the CYP90 family that cluster together in the CYP85 clan. Similar to known BR biosynthetic genes, the Selaginella CYP90s exhibit eight or ten exons and Selaginella produces a putative BR biosynthetic intermediate. Therefore, we hypothesized that Selaginella CYP90 genes encode BR biosynthetic enzymes. In contrast to typical CYPs in Arabidopsis, Selaginella CYP90E2 and CYP90F1 do not possess amino-terminal signal peptides, suggesting that they do not localize to the endoplasmic reticulum. In addition, one of the three putative CYP reductases (CPRs) that is required for CYP enzyme function co-localized with CYP90E2 and CYP90F1. Treatments with a BR biosynthetic inhibitor, propiconazole, and epi-brassinolide resulted in greatly retarded and increased growth, respectively. This suggests that BRs promote growth in Selaginella, as they do in Arabidopsis. However, BR signaling occurs through different pathways than in Arabidopsis. A sequence homologous to the Arabidopsis BR receptor BRI1 was absent in Selaginella, but downstream components, including BIN2, BSU1, and BZR1, were present. Thus, the mechanism that initiates BR signaling in Selaginella seems to differ from that in Arabidopsis. Our findings suggest that the basic physiological roles of BRs as growth-promoting hormones are conserved in both lycophytes and Arabidopsis; however, different BR molecules and BRI1-based membrane receptor complexes evolved in these plants.

Intravenous interferon administered during liver transplantation is not effective in preventing hepatitis C reinfection

BACKGROUND

Post-transplant hepatitis C is a major challenge after liver transplantation (LT). Antiviral therapy is associated with lower efficacy in the post-transplant setting.

AIMS

The purpose of this study was to determine the safety and effect of intravenous interferon (IFN) during the anhepatic phase of LT on hepatitis C viral load.

METHODS

Fifteen consecutive subjects undergoing liver transplant for hepatitis C cirrhosis were enrolled in the study, ten of which received study drug and five subjects served as controls. Cases received weight-based ribavirin and subcutaneous IFN at time of incision followed by intravenous IFN at the start of the anhepatic phase. Adverse events and viral levels were recorded. Repeated measures ANOVA was employed to test for differences over time, between the groups, and time by group interaction.

RESULTS

All subjects had genotype 1 virus. Hepatitis C viral load was lower at week 4 in cases compared to controls (769,004 ± 924,082 IU/ml and 2,329,896 ± 3,731,749 IU/ml, respectively), but did not reach statistical significance (p = 0.50). Three subjects developed adverse events related to IFN including pulmonary edema, rejection, and neutropenia.

CONCLUSIONS

Intravenous IFN administered during the anhepatic phase of liver transplant did not prevent graft reinfection and was associated with manageable adverse events. This regimen could be further studied if direct acting antiviral agents alone are insufficient for treating post-transplant hepatitis C.

Spontaneous clearance of hepatitis C infection after liver transplantation from IL28B rs12979860 CC donors

Genetic polymorphisms adjacent to IL28B have been previously associated with spontaneous clearance of hepatitis C virus (HCV) and a higher rate of sustained virological response to interferon-based treatment in HCV genotype 1-infected patients. A recent study has shown that patients with the CC genotype of the rs12979860 single nucleotide polymorphism upstream from the IL28B gene are more likely to clear HCV spontaneously relative to the CT or TT genotype. In the liver transplant cohort, HCV recurs almost universally in patients with detectable HCV RNA at the time of transplantation. The spontaneous clearance of HCV infection after transplant is very rare. We report two cases of spontaneous clearance of HCV genotype 1 infection after liver transplantation from homozygous IL28B CC donors. This finding may be explained by alterations in the host immune responses to HCV after transplantation with a CC donor liver, which has potential implications for donor selection in HCV-positive recipients.

Hepatitis C virus recurrence and immunosuppression-free state after liver transplantation

HCV-related disease is the most common indication for liver transplantation (LT). HCV recurrence, which is almost universal, has a significant impact on patient and graft survival after LT and still represents a great unsolved issue for the liver transplant community. Several treatment strategies have been proposed. Since antiviral therapy has limited efficacy and can be administrated only in selected transplant recipients and additionally that immunosuppressive drugs have a negative impact on HCV re-infection, the achievement of an immunosuppression-free state after LT could play a central role in the avoidance of rapid HCV recurrence.

Case report of successful peginterferon, ribavirin, and daclatasvir therapy for recurrent cholestatic hepatitis C after liver retransplantation

A recurrent hepatitis C virus (HCV) infection after liver transplantation (LT) can lead to accelerated allograft injury and fibrosis. The aim of this article is to report the first ever use of daclatasvir (DCV; also known as BMS-790052), a potent orally administered nonstructural 5A replication complex inhibitor, in combination with peginterferon α (PEG-IFNα) and ribavirin in an LT recipient. A 49-year-old female developed a severe recurrent HCV genotype 1b infection 4 months after transplantation with severe cholestasis on biopsy, an HCV RNA level of 10,000,000 IU/mL, an alkaline phosphatase level of 1525 IU/mL, and a total bilirubin level of 8.4 mg/dL. Despite partial virological suppression with PEG-IFNα and ribavirin, progressive allograft failure ensued and culminated in retransplantation at 9 months. Three months after the second transplant, DCV (20 mg/day), PEG-IFNα2a (180 μg/week), and ribavirin (800 mg/day) were prescribed for early recurrent cholestatic HCV. Serum HCV RNA became undetectable at week 3 of treatment and remained undetectable during 24 weeks of triple therapy and during the posttreatment follow-up. DCV was well tolerated, and the trough drug levels were within the targeted range throughout the treatment. The cyclosporine trough levels were also stable during and after therapy. In conclusion, the lack of anticipated drug-drug interactions between DCV and calcineurin inhibitors and the potent antiviral efficacy of DCV make this agent (in combination with PEG-IFN and ribavirin) an attractive antiviral regimen worthy of further study in LT recipients with recurrent HCV.

Risk for immune-mediated graft dysfunction in liver transplant recipients with recurrent HCV infection treated with pegylated interferon

BACKGROUND & AIMS

Patients with recurrent hepatitis C virus infection treated with pegylated interferon (PEG) after liver transplantation can develop severe immune-mediated graft dysfunction (IGD) characterized by plasma cell hepatitis or rejection.

METHODS

We conducted a multicenter case-control study of 52 liver transplant recipients with hepatitis C to assess the incidence of, risk factors for, and outcomes of PEG-IGD. Data from each patient were compared with those from 2 matched patients who did not develop PEG-IGD (n = 104). We performed a multivariate analysis of risk factors and analyzed treatment and outcomes of graft dysfunction subtypes.

RESULTS

Overall incidence of PEG-IGD during a 10-year study period was 7.2%. Risk factors included no prior PEG therapy (odds ratio = 5.3; P < .0001), therapy with PEGα-2a (odds ratio = 4.7; P = .03), and immune features (mainly plasma cell hepatitis) on pre-PEG therapy liver biopsies (odds ratio = 3.9; P = .005). The PEG-IGD group had lower long-term patient (61.5% vs 91.3% of controls) and graft (38.5% vs 85.6% of controls) survival and higher rates of retransplantation (34.6% vs 6.7% of controls) (all, P < .0001), without increases in sustained virologic response. Variables associated with increased mortality included acute rejection as the PEG-IGD sub-type (hazard ratio [HR] = 2.4; P = .002), a high level of alkaline phosphatase at PEG initiation (HR = 1.003; P = .005), and lack of a sustained virologic response (HR = 3.3; P = .04). Variables associated with graft failure included a high level of alkaline phosphatase at PEG initiation (HR = 1.002; P = .04) and lack of a sustained virologic response (HR = 2.1; P = .04).

CONCLUSIONS

PEG-IGD has high morbidity and mortality and is not associated with increased rates of virologic response. It is important to avoid PEG therapy in liver transplant recipients with specific clinical, biochemical, and histologic risk factors for PEG-IGD.

Hepatic transplant and HCV: a new playground for an old virus

Hepatitis C virus (HCV) infection is a major global health problem affecting 170 million people worldwide. The majority of infected individuals fail to resolve their infection, with a significant number developing chronic, progressive HCV-related liver disease. HCV infection is the leading indication for liver transplantation and unfortunately, all patients with detectable viral load before transplantation will have rapid, recurrent infection. What remain to be determined are factors contributing to the severity of HCV recurrence. Such factors are unique to the posttransplant setting and include: viral genetic diversity and composition, immunosuppression, donor/recipient age and sex, genetic factors and the liver microenvironment. Importantly, the possibility that the severity of HCV recurrence might be also influenced by factors related to the primary course of disease (i.e. viral set point, previously acquired adaptations of the virus) must be further evaluated. In this sense, recurrent HCV infection should not be regarded merely as another acute infection, but rather, it should be cautioned that problems first arising during the primary course of disease may be accentuated during recurrence. Development of novel therapeutic approaches will require a thorough understanding of viral and host determinants of infection resolution and how these factors may change in the posttransplant setting.

Immunosuppression, liver injury and post-transplant HCV recurrence

Hepatitis C virus (HCV) infection is a major cause for liver transplantation worldwide. Still, HCV re-infection of the graft occurs in almost all cases. Most liver transplant recipients experience episodes of graft hepatitis associated with fibrosis progression and graft failure. Clinical management of graft hepatitis can be challenging as in addition to rejection and HCV-induced hepatitis various other factors might be involved including toxic liver injury, steatohepatitis, ischaemic bile duct lesions or infections with other pathogens. Treatment options are often contradictory for different causes of graft hepatitis, and the role of distinct immunosuppressive drugs has been discussed controversially. Corticosteroids increase the infectivity of HCV by altering expression levels of entry factors and other immunosuppressive agents may have diverse effects on HCV replication and fibrosis progression. Interferon alpha-therapy of hepatitis C shows limited efficacy and tolerability in liver transplant recipients and may also cause rejection. In this review we summarize the current knowledge on mechanisms of liver injury in post-transplant hepatitis C, discuss the pros and cons of immunosuppressive agents in this specific setting and describe potential novel approaches to prevent HCV reinfection.

Explanted liver inflammatory grade predicts fibrosis progression in hepatitis C recurrence

Factors present prior to liver transplantation (LT) that predict fibrosis progression in recurrent hepatitis C infection (HCV) after LT would be important to identify. This study sought to determine if histologic grade of HCV in the explant predicts fibrosis progression in recurrent HCV. The clinical and histologic data of all 159 patients undergoing their first LT for HCV at our center from 1998 to 2001 were retrospectively reviewed with follow-up through June 2008. Twenty-five cases were excluded for: non-HCV-related graft loss <90 days (19), recidivism (4), or unavailable explant or follow-up biopsies (2). A single pathologist scored (Ishak) explants in a blinded fashion. Patients were grouped by explant inflammatory grade ≤ 4 (group1) and >4 (group 2). Prospectively scored liver biopsies (protocol months 1 and 4, annually, and as indicated clinically) were reviewed for development of advanced fibrosis (bridging or cirrhosis). Cox proportional hazard regression was used to analyze the association of explant grade, donor, viral and LT factors with progression to advanced fibrosis. The groups were well-matched for patient, viral, donor, and transplant factors. Five-year advanced fibrosis-free survival in group 1 versus group 2 was 63% versus 28%, P < 0.001. Explant grade >4 was associated with increased HCV-related graft loss at 1 (6% versus 3%) and 5 (36% versus 14%) years post-LT (P = 0.003). On univariate and multivariate Cox regression analysis, predictors of advanced fibrosis were explant grade >4 (hazard ratio [HR] = 3.3, 95% confidence interval [CI] = 1.9-5.6, P < 0.001) donor age >50 (HR = 3.3, 95% CI = 1.9-5.7, P < 0.001) and viral load at LT of >158,730 IU/mL (HR = 1.8, 95% CI = 1.05-3.1, P = 0.03).

CONCLUSION

Explant histologic grade can identify patients requiring more aggressive monitoring and intervention for HCV recurrence post-LT.

NK cells, innate immunity and hepatitis C infection after liver transplantation

Liver transplantation in patients with active hepatitis C virus (HCV) infection is followed by almost universal recurrence of viral infection. The control of HCV infection has been characterized largely in terms of the HCV-specific function of T-lymphocytes and the adaptive immune response. Emerging data suggest that components of the innate immune system, including natural killer cells, have a central role in determining the nature of posttransplant HCV infection and the likelihood of response to antiviral therapy. This review examines the emerging evidence implicating innate immunity in the pathogenesis of posttransplant HCV infections and the potential therapeutic implications of these observations.

Clinical characterization of patients developing histologically-proven fibrosing cholestatic hepatitis C post-liver transplantation

AIM

  Fibrosing cholestatic hepatitis C (FCH) post-liver transplantation (LT) is an uncommon disorder with extremely poor outcome. Using stringent histological criteria, we sought to identify cases of FCH to better characterize its incidence, clinical features and outcomes.

METHODS

  From January 1991 to December 2007, 973 LT for hepatitis C virus (HCV) were performed at our center. Using the pathology database, 51 cases with a provisional diagnosis of FCH were identified. FCH was diagnosed histologically by cholestasis accompanied by thin periportal fibrous septa, ductular reaction and mild inflammation.

RESULTS

  FCH was reconfirmed in 24 recipients; seven had concurrent biliary problems. Twenty-seven cases were excluded; biopsy was unavailable in nine cases, 15 did not meet the histological criteria of FCH and three had missing clinical information. All received deceased donors at a mean age of 64.4 years (15/17 aged >50 years). Mean time from LT to FCH was 7.6 months with 16 of 17 diagnosed within 1 year of LT. At diagnosis, mean viral load was 14.4 million IU/mL, bilirubin 16.2 mg/dL, aspartate aminotransferase 262 IU/mL, alanine aminotransferase 192 IU/mL and alkaline phosphatase 299 IU/mL. All 17 patients died or required re-LT a mean of 7.8 months after the FCH diagnosis.

CONCLUSION

  FCH occurs infrequently and is typified by hyperbilirubinemia, donor age of more than 50 years, extremely high HCV RNA and specific histological changes occurring within the first several months post-LT with extremely poor patient and graft survival. Histology alone is not reliable for the diagnosis of FCH, especially in the setting of recurrent HCV with concurrent biliary problems.

Measurement of CD4+ T-cell function in predicting allograft rejection and recurrent hepatitis C after liver transplantation

Recurrence of hepatitis C virus (HCV) can be difficult to distinguish from acute cellular rejection (ACR) following liver transplantation. The Cylex Immune Function Assay (ImmuKnow) provides objective measure of recipient's immune function. The goal is to assess the ability of this assay to distinguish these similar conditions. A retrospective review was performed in 54 recipients with HCV. ImmuKnow assays were measured with allograft biopsies. Levels of adenosine triphosphate (ATP) release from CD4+ T cells (ng/mL) were compared with the following biopsy result classifications: 365 ± 130 with ACR (n = 11), 152 ± 100 with recurrent HCV (n = 26), 240 ± 71 with normal biopsies (n = 12), and 157 ± 130 with overlapping features of ACR and recurrent HCV (n = 5). Recipients with recurrent HCV had lower immune response than those with ACR (p < 0.0001).Using a cutoff level of 220, the sensitivity and specificity for distinguishing two conditions were 88.5% and 90.9%, respectively. When recipients with overlapping features had low immune response, three of four recipients' subsequent biopsies showed recurrent HCV. In conclusion, the ImmuKnow assay can be a sensitive and specific additional test for distinguishing recurrent HCV from ACR and may be useful for predicting which recipients may be most vulnerable to recurrent HCV.

Hepatitis C virus recurrence after liver transplantation: biomarkers of disease and fibrosis progression

End-stage liver disease due to hepatitis C virus infection (HCV) is the principal indication for liver transplantation. In the USA, over a third of available liver allografts are transplanted into recipients with chronic HCV infection. Reinfection of the graft is universal, but the impact of reinfection on short- and long-term liver function is highly variable. HCV infection in liver transplantation recipients is characterized by an accelerated fibrogenesis, with approximately a third of patients developing cirrhosis within 5 years of follow-up. HCV is associated with decreased patient and graft survival when compared with other indications of orthotopic liver transplantation. The mechanisms responsible for the accelerated liver damage in HCV-infected orthotopic liver transplantation recipients remain largely unknown.

Mutations in hepatitis C virus genotype 1b and the sensitivity of interferon-ribavirin therapy after liver transplantation

BACKGROUND & AIMS

The results of post-transplant antiviral therapy for recurrent hepatitis C virus (HCV) are poor, and significant pre-transplant predictors for sustained viral response (SVR) have not yet been identified.

METHODS

Pegylated interferon/ribavirin therapy was performed for more than 48 weeks in 50 patients who underwent liver transplantation (LT) for HCV genotype 1-related liver disease. Of these, 22 patients achieved SVR. The predictive potential of the viral mutations, including amino acids (aa) 70 and 91 in the Core region, interferon sensitivity-determining region (ISDR, aa 2209-2248) and interferon/ribavirin resistance-determining region (IRRDR, aa 2334-2379) in NS5A, was evaluated.

RESULTS

In 16 patients, the sequences in the pre- and post-transplant samples were the same, except for aa 70 in the Core of 1 patient. The SVR achievement percentage was significantly lower in the Non-double wild (DW) at aa 70 and 91, the ISDR<2 and IRRDR<6 groups than in the DW (30% vs. 65%, p=0.015), the ISDR2 (35% vs. 69%, p=0.035) and IRRDR6 (25% vs. 78%, p<0.001) groups, respectively. Predictive scoring with these three items provides a newly established and significant predictor for SVR after LT (p=0.015).

CONCLUSION

DW, ISDR2 and IRRDR6 were found to be significant predictors for SVR after LT. In addition, it is possible that the establishment of a new scoring system consisting of these three factors may be a useful marker to predict interferon sensitivity for recurrent HCV after LT.

Monitoring peripheral blood CD4+ adenosine triphosphate activity in recurrent hepatitis C and its correlation to fibrosis progression

The recurrence of hepatitis C virus (HCV) after orthotopic liver transplantation (OLT) is often associated with rapid fibrosis progression attributed to the state of impaired cellular immunity. At present, there are no means to predict those at risk for progression. Peripheral blood CD4+ adenosine triphosphate (ATP) release (the ImmuKnow assay) correlates with immunoreactivity and has been used to monitor global cellular immune function in transplant recipients. The aim of this study was to assess the relationship between cellular immune function measured by the ImmuKnow assay and fibrosis progression in patients with HCV recurrence after OLT. The ImmuKnow assay was prospectively performed in adult HCV patients at 4 and 12 months post-OLT. Protocol liver biopsies were performed (on day 7, in month 4, and yearly) after OLT. The first biopsy that showed fibrosis post-OLT was used to determine the time interval for developing fibrosis. Sixty-two patients met the inclusion criteria. The median follow-up time was 12 (6.5-12.1) months. Fibrosis progression was observed in 61.3% of the patients. ATP levels were lower in patients with fibrosis progression in comparison with patients without progression at 4 months (145 versus 259 ng/mL, P < 0.001) and at 12 months (152 versus 264 ng/mL, P = 0.008). ATP levels at 4 and 12 months post-OLT were found to be significantly associated with a higher hazard of progression. For each 25-unit increase in ATP levels at 4 and 12 months after transplantation, the hazard of fibrosis progression decreased by 22% (P = 0.001) and 12% (P = 0.015), respectively. In conclusion, greater suppression of cellular immunity, as measured by the ImmuKnow assay, is associated with more rapid progression of fibrosis in patients with recurrent HCV post-OLT. Post-OLT monitoring of CD4+ ATP activity may identify a subset of patients at greatest risk for early fibrosis progression.

Preservation of immune function and anti-hepatitis C virus (HCV) immune responses after liver transplantation in HIV-HCV coinfected patients (ANRS-HC08 "THEVIC" trial)

BACKGROUND/AIMS

Liver transplantation (LT) in immune-suppressed human immunodeficiency virus (HIV) and hepatitis C virus (HCV) coinfected patients is feasible but raises questions regarding the severity of HCV recurrence on the liver graft and preservation of immune function. We investigated whether LT is deleterious to the immune system.

METHODS

Fourteen HIV-HCV coinfected patients (HIV viral load [VL] <50 copies/ml; median CD4 count of 276/mm(3) pretransplantation) were grafted for HCV-cirrhosis and followed over 2 years. Nine patients received anti-HCV therapy post-transplantation. HCV and HIV VLs and degree of acute and chronic hepatitis were monitored. Peripheral blood T-cell phenotypes and interferon-gamma (IFN-gamma) immune responses against opportunistic pathogens, HCV, and HIV-1 p24 were evaluated.

RESULTS

Median HCV VLs, CD4 counts, T-cell subsets, and IFN-gamma-producing T-cell frequencies against opportunistic pathogens and HIV-1 p24 did not change over time. HCV-specific T cells were observed ex vivo in two patients pretransplantation and in two others post-transplantation. HCV-specific in vitro amplification enabled the detection of HCV-specific IFN-gamma-producing responses in three further patients post-transplantation. Anti-HCV responses were observed independently of anti-HCV therapy and were undetectable in patients with severe hepatitis or liver fibrosis.

CONCLUSIONS

These results demonstrate that LT in HIV-HCV coinfected patients is not deleterious to the immune system and does not alter immune responses directed against HCV, HIV, or opportunistic pathogens.

Human liver transplantation as a model to study hepatitis C virus pathogenesis

Hepatitis C is a leading etiology of liver cancer and a leading reason for liver transplantation. Although new therapies have improved the rates of sustained response, a large proportion of patients (approximately 50%) fail to respond to antiviral treatment, thus remaining at risk for disease progression. Although chimpanzees have been used to study hepatitis C virus biology and treatments, their cost is quite high, and their use is strictly regulated; indeed, the National Institutes of Health no longer supports the breeding of chimpanzees for study. The development of hepatitis C virus therapies has been hindered by the relative paucity of small animal models for studying hepatitis C virus pathogenesis. This review presents the strengths of human liver transplantation and highlights the advances derived from this model, including insights into viral kinetics and quasispecies, viral receptor binding and entry, and innate and adaptive immunity. Moreover, consideration is given to current and emerging antiviral therapeutic approaches based on translational research results.

Molecular and cellular aspects of hepatitis C virus reinfection after liver transplantation: how the early phase impacts on outcomes

Hepatitis C virus (HCV)-related liver disease postliver transplantation is associated with an accelerated course in comparison with that observed in the nonimmunosuppressed individual. Outcomes in transplantation for this indication have, therefore, been a major area of clinical interest in the field of liver transplantation. The factors underlying the rapid progression of HCV-related liver disease posttransplantation are complex and multifactorial. Nevertheless, recent data indicate a range of parameters assessable early posttransplantation that may be useful in the prediction of outcome of transplantation for this condition. This overview, therefore, concentrates on the early events occurring postliver transplantation in the HCV-infected patient, and the implications of these recent observations for the pathogenesis of the various forms of HCV-related allograft injury.

Clinical Significance of the Cellular Pharmacodynamics of Tacrolimus in Living-Donor Liver Transplantation

Successful immunosuppressive therapy is critical for liver transplantation; however, a considerable number of patients experience fatal rejection or alternatively exhibit serious infection resulting from excessive immunosuppression. The in vitro tacrolimus response of peripheral blood mononuclear cells (PBMCs) before transplantation was compared to the clinical outcome up to 4 weeks after operation in 28 living-donor liver transplant recipients treated with tacrolimus. The tacrolimus IC50 values against concanavalin A-induced PBMC blastogenesis in vitro were calculated. These recipients were classified into two groups with the mean tacrolimus IC50 (0.18 ng/ml) as the cutoff point, after which the clinical outcome between the patient groups was compared. The allograft rejection incidence in the low-sensitivity group (IC50 < 0.18 ng/ml; n = 16) was 6/12 (50.0%), which was significantly higher than the incidence of 2/16 (12.5%) in the high-sensitivity group (IC50 > 0.18 ng/ml; n = 12) ( p = 0.0297). In contrast, the infection incidence in the high-sensitivity group was 6/16 (37.5%), which was significantly higher than that of the low-sensitivity group (1/12; 8.3%) ( p = 0.0401). These data suggest that patients exhibiting a low PBMC sensitivity to tacrolimus have a risk of rejection, whereas highly sensitive patients have a risk of infection in living-donor liver transplantations under tacrolimus therapy.

Hepatitis B virus-specific CD4 T cell immunity after liver transplantation for chronic hepatitis B

Cellular immunity plays an important role in the long-term control of hepatitis B virus (HBV) infection. We studied the changes in HBV-specific CD4 T cell immunity after orthotopic liver transplantation (OLT) for chronic hepatitis B under antiviral prophylaxis. T cell proliferation and interferon-gamma production in response to in vitro challenge with HBV-encoded antigens were tested in 40 OLT recipients without HBV recurrence and in 12 OLT recipients with HBV recurrence more than 1 year after transplantation, and they were compared to 40 subjects with chronic HBV infection and to 23 subjects with self-limited HBV infection. The frequency and magnitude of the HBV-specific CD4 T cell response were significantly lower in 40 OLT recipients with HBV clearance, but the T cell reactivity to mitogen (phytohemagglutinin) and recall antigen (tetanus toxoid) was maintained. In the 12 OLT recipients with HBV recurrence, however, the HBV-specific T cell immunity was enhanced to a level comparable to that of patients with chronic hepatitis B, and the level was dependent on the serum viral load. In conclusion, HBV-specific CD4 T cell immunity is antigen-driven and evanesces with viral clearance, hence providing a favorable milieu for reactivation once prophylaxis is withdrawn. The cellular immunity in recipients with recurrence is not significantly different from that of individuals with chronic hepatitis B.

Prospective study of natural killer cell phenotype in recurrent hepatitis C virus infection following liver transplantation

BACKGROUND/AIMS

Graft re-infection invariably occurs after liver transplantation (OLT) for chronic hepatitis C and disease progression is unpredictable. We prospectively examined peripheral blood mononuclear cells (PBMC) subsets and natural killer (NK) cell receptors (NKRs) in patients with recurrent hepatitis C post-OLT.

METHODS

PBMC were obtained at baseline and at different time points after OLT. NKRs were identified using monoclonal antibodies by flow cytometry.

RESULTS

The proportions of NK, natural T (NT), total and gammadelta T cells were significantly reduced (p<0.01) 7 days post-transplant, probably as a result of graft repopulation. NKG2D+ NK cells were significantly higher compared with healthy controls (p<0.01), declined post-OLT and subsequently returned to baseline values. This, together with a progressive increase in the proportion of CD94/NKG2C+ NK cells over time (p< or = 0.01), appeared to be related to hepatitis C recurrence. There was a statistically significant correlation between expression of the natural cytotoxicity receptors (NCRs) and ALT (p<0.05), supporting the hypothesis that NK cells participate in the necroinflammatory process.

CONCLUSIONS

The data are compatible with homing of immune cells to the liver allograft after surgery, most of which return to pre-OLT levels. HCV recurrence may cause variations in selected NKRs expression akin to other viral infections.

Using an immune functional assay to differentiate acute cellular rejection from recurrent hepatitis C in liver transplant patients

In transplant recipients transplanted for hepatitis C, presentation of abnormal transaminases can herald the presentation of recurrent hepatitis C, cellular rejection, or both. Given the sometimes ambiguous histology with these 2 entities, the ability to distinguish them is of great importance because misinterpretation can potentially affect graft survival. We used an immune functional assay to help assess the etiology of abnormal liver function test results in liver transplant recipients. Blood samples for the immune functional assay were taken from 42 recipients prospectively at various times post-transplant and compared with clinical and histologic findings. In patients whose liver biopsy showed evidence of cellular rejection, the immune response was noted to be very high, whereas in those with active recurrence of hepatitis C, the immune response was found to be very low. This finding was found to be statistically significant (P < 0.0001). In those patients in whom there was no predominant histologic features suggesting 1 entity over the other, the immune response was higher than in those with aggressive hepatitis C but lower than in those with cellular rejection. In conclusion, these data show the potential utility of the ImmuKnow assay as a means of distinguishing hepatitis C from cellular rejection and its potential usefulness as a marker for outlining the progression of hepatitis C.

Virology and pathogenesis of hepatitis C virus recurrence

1. In hepatitis C virus (HCV)-infected patients undergoing liver transplantation (LT), the virus infects the liver graft immediately after transplantation. The main source of HCV infection is circulating virions. Nevertheless, some data suggest that HCV present in extrahepatic compartments may contribute to HCV infection in some cases of hepatitis C recurrence. 2. Studies on early kinetics have shown that HCV replication starts a few hours after transplantation and that HCV-RNA concentrations increase a few hours or days after the procedure, suggesting that HCV has an enormous ability to adapt to the new environment. 3. The quasispecies population may change significantly after transplantation, most likely because of the need to adapt to a new environment. There are no conclusive data supporting the role of HCV quasispecies composition and disease outcomes. 4. Persistence of HCV infection is the rule after transplantation. This is due to immunosuppression and to the immune exhaustion of the previously exposed immune system. 5. In general, HCV is not thought to be directly cytopathic. Thus, it is believed that the immune response against HCV causes liver damage. However, understanding the mechanisms of liver damage in HCV-infected LT recipients is extremely complex because of the existence of a human leukocyte antigen-mismatched organ, the preexisting virus-specific T cells that may be dysfunctional and/or tolerized, and the immunosuppression. 6. Despite the possible effect of immune-mediated liver damage, it is clear that strong immunosuppression is associated with severe forms of hepatitis C recurrence (cholestatic hepatitis, fibrosing cholestatic hepatitis, and accelerated fibrosis progression). Thus, in the absence of a strong anti-HCV immune response, HCV is able to directly (HCV proteins) or indirectly (cytokines) produce liver damage. 7. The activation of stellate cells and accelerated deposition of fibrosis are the final consequences of HCV infection in the graft. There are several mechanisms that may act synergistically to activate and perpetuate stellate cell activation in the setting of LT: ischemia-reperfusion damage, old donor age, HCV proteins, cholestasis, rejection, infection with other viruses (cytomegalovirus), and immune-mediated injury.

The natural history of recurrent hepatitis C and what influences this

1. Liver failure and liver cancer from chronic hepatitis C are the most common indications for liver transplantation and numbers of both are projected to double over the next 20 years. 2. Recurrent hepatitis C infection of the allograft is universal and immediate following liver transplantation and associated with accelerated progression to cirrhosis, graft loss and death. 3. Graft and patient survival is reduced in liver transplant recipients with recurrent HCV infection compared to HCV-negative recipients. 4. The natural history of chronic hepatitis C is accelerated following liver transplantation compared C, with 20% progressing to cirrhosis by 5 years. However, the rate of fibrosis progression is not uniform and may increase over time. 5. The rates of progression from cirrhosis to decompensation and from decompensation to death are also accelerated following liver transplantation. 6. Multiple host, donor and viral factors are associated with rapid fibrosis progression and HCV-related graft failure. 7. Over the last decade, graft and patient survival rates have improved following liver transplantation for non-HCV disease but not for HCV-cirrhosis. This may reflect worsening donor quality and changes in immunosuppression strategies over recent years. 8. Viral eradication by antiviral therapy prevents disease progression and improves survival. 9. The severity of recurrent hepatitis C at one year post-transplant predicts subsequent progression to cirrhosis. Annual protocol biopsies are recommended to help determine need for antiviral therapy. 10. The projected impact of recurrent hepatitis C on graft and patient survival can only be avoided by the development of safe and effective antiviral strategies which can both prevent initial graft infection and eradicate established hepatitis C recurrence.

Pre- and post-transplant monitoring of granzyme B enzyme-linked immunosorbent spot assay in pediatric liver recipients

This study aims to investigate potential role of granzyme B enzyme-linked immunosorbent spot (GrB ELISPOT) for immunological monitoring in pediatric liver transplantation.

PATIENTS AND METHODS

Peripheral blood mononuclear cells from 28 pediatric recipients were serially tested for GrB-producing donor-reactive cells at day 0 pre-transplantation (baseline) and days 7, 14, and 28 post-transplantation.

RESULTS

At baseline, no difference of GrB value was found in acute rejection (14/28) compared to normal graft function patients (day 0: 4(3.9) spots versus 5(2.9) spots, respectively: p=0.65). At day 7 post-transplantation, acute rejection patients showed frequencies of GrB ELISPOT higher than those with normal graft function, but the differences observed were not statistically significant (day 7: 15(4.9) spots versus 10(4.0) spots, respectively: p=0.55). GrB increased significantly at day 7 from baseline in the rejection group (15(4.9) spots versus 4(3.9), respectively p=0.04), whereas corresponding changes were not significant in the group without rejection (10(4.0) versus 5(2.9), respectively: p=0.15).

CONCLUSION

GrB ELISPOT pre-transplantation could not predict the occurrence of early post-transplant acute rejection; similarly frequencies at days 7, 14 and 28 could not be correlated with acute rejection in pediatric liver recipients. However, a kinetic study of GrB ELISPOT could be helpful to predict or confirm early rejection in the small group of liver allograft recipients analyzed in this study.

Pretransplantation CD56(+) innate lymphocyte populations associated with severity of hepatitis C virus recurrence

Cluster of differentiation (CD)56(+) lymphocytes are believed to play important roles in the innate immune response to viral infections by production of interferon (IFN)-gamma and/or the recognition of virally infected cells, but their role in liver transplantation (LT) has not been characterized. Here, for the first time, we examine the phenotypic and functional features of these cells in patients undergoing LT for hepatitis C virus (HCV)-related liver failure. The study was comprised of four patient groups: patients with mild HCV recurrence (n = 9), severe HCV recurrence (n = 10), patients with non-HCV-related liver failure (n =10), and normal healthy subjects (n = 10). Pre-LT, the frequency of circulating CD56(+) lymphocytes was significantly lower in patients who subsequently developed severe HCV recurrence, relative to those patients who developed mild histologic recurrence, as well as non-HCV controls. HCV was associated with impaired lymphokine-activated killing and natural cytotoxicity. We found that natural T (NT) cells that coexpressed CD4/CD8 or expressed CD8 alone were more frequent in patients who subsequently developed severe recurrence. In contrast, NT cells that expressed only CD4 appeared to be depleted in HCV infection relative to controls. A significantly higher percentage of NTs in both HCV groups expressed the inhibitory receptor NKG2A relative to HCV-negative controls with liver disease. In conclusion, these results demonstrate a previously unappreciated association between pretransplantation CD56(+) lymphocytes and outcome of HCV recurrence and provide novel mechanistic insights into the immunopathogenesis of HCV recurrence, as well as potential targets for therapeutic manipulation.

Evolution of the NS3 and NS5B regions of the hepatitis C virus during disease recurrence after liver transplantation

In patients with hepatitis C virus (HCV)-related cirrhosis, infection recurrence is universal after liver transplantation (LT). The relevance of host and virus-related factors on the outcome of hepatitis C recurrence is poorly understood. This study analyzed the relationship between the genetic evolution of the Non-Structural (NS)3 protease and NS5B polymerase regions of HCV and the severity of hepatitis C recurrence. Thirty-three patients were classified as having mild (n = 16) or severe recurrence (n = 17), according to the degree of fibrosis in liver biopsies obtained 1 year after transplantation. Viral load and consensus sequences of the NS3 and NS5B domains were determined in a pre-LT and in four post-LT sequential serum samples. At week 12 after LT, viremia was significantly higher in patients with severe recurrence. NS3 and NS5b regions evolved independently after LT. The genetic evolution of NS3 domain was not related to the severity of the recurrence. However, the diversification in the NS5B region later than 12 weeks after LT was greater in patients with mild than in those with severe recurrence, suggesting a stronger immune pressure in the first group. These observations highlight the complex interplay between viral evolution and clinical outcomes in the LT setting.

Selective decrease in hepatitis C virus-specific immunity among African Americans and outcome of antiviral therapy

Hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, end-stage liver disease, and hepatocellular carcinoma throughout the world. Considerable evidence indicates that the risk of viral persistence, natural history, and response to antiviral therapy varies among racial groups, but limited data exist on potential mechanisms to account for these differences. Type 1 helper (Th1) responses to HCV proteins and cytomegalovirus (CMV) antigens were examined using a sensitive interferon (IFN)-gamma enzyme-linked immunospot (ELISPOT) assay in 187 Caucasian American (CA) and 187 African American (AA) patients with chronic genotype 1 infection. ELISPOT responses were examined relative to human leukocyte antigen (HLA) class II alleles and outcome of therapy with pegylated IFN and ribavirin. Th1 responses specific to hepatitis C core protein and combined HCV antigens were significantly lower in AAs compared to CAs, but CMV responses were comparable in the 2 races. The HCV difference in immunity remained after adjusting for gender, serum alanine aminotransferase, histologic severity, and viral level, and was not accounted for by the differential prevalence of human leukocyte antigen class II alleles. Pretreatment total HCV-specific CD4+ T cell response was associated with sustained virologic response (SVR) to pegylated IFN and ribavirin; 43% of patients who had more than 168 ELISPOTs/10(6) peripheral blood mononuclear cells (above background) experienced SVR compared to 28% of those who did not (P= 0.007). ELISPOT response was independently associated with SVR by multivariable analysis.

CONCLUSION

Compared to CAs, AAs have weaker HCV-specific immunity. Pretreatment HCV-specific immunity is associated with response to combination antiviral therapy.

Acute rejection in HCV-infected liver transplant recipients: The great conundrum

1. In hepatitis C virus (HCV)-infected patients, treatment of acute rejection is associated with worse outcomes (increased risk of allograft cirrhosis and mortality). 2. Whether patients with HCV are at higher risk for rejection remains controversial. 3. The mechanisms mediating acute rejection and recurrence of HCV are distinct, and as such, it should be possible to develop techniques based on these molecular differences that are diagnostically useful. 4. Liver biopsy is considered the gold-standard for diagnosing acute rejection and recurrent HCV; however, given histopathological similarities between the two conditions, discrimination can be extremely difficult. 5. At the present time, there are no reliable, noninvasive tools available to distinguish between HCV recurrence alone and acute rejection plus HCV recurrence. 6. Mild rejection per se is not associated with graft loss and treatment of rejection with steroids and OKT3 is associated with worse outcome in HCV; thus, it seems logical that we should no longer treat mild rejection.

Monitoring tolerance after human liver transplantation

The validation of reliable, non-invasive immunological assays evaluating anti-donor responsiveness in allograft recipients would provide a clinically relevant tool for the early detection of ongoing rejection process as well as for the identification of operational tolerance in the long term. A sequential approach towards immunological monitoring of allografts is proposed in this review: (i) investigations exploring the initial donor-recipient alloresponses, including the analysis of the cytokine network; (ii) investigations regarding graft acceptance and operational tolerance in long-term transplant patients, consisting in the analysis of regulatory T cells and of circulating precursors of dendritic cells, in the measurement of T cell alloreactivity as well as in the study of T cell receptor repertoires. Beside the conventional in vivo and in vitro immunological techniques, the potential applications of molecular imaging in transplantation also deserve further exploration, with particular respect to allograft immune monitoring. Enforced collaboration between transplant clinicians and immunologists will be required to develop the translational research protocols required for the development of immunological monitoring, within an international multicentric network.

Sensitivity to antiviral therapy may change after liver transplantation in patients with chronic hepatitis C virus infection

In hepatitis C virus (HCV)-infected patients, it is generally assumed that the pattern of response to antiviral therapy remains unaltered after liver transplantation (LT). However, changes in the circulating HCV quasispecies and in the gene expression profiles of the graft might influence response to treatment after LT. We evaluated 22 HCV-infected patients who received antiviral treatment while awaiting LT and in whom HCV infection recurred. Eleven of these patients underwent a new antiviral treatment course. Our study analyses the early virological response to both treatment courses to assess the influence of the changes in HCV on the response to therapy. Patients were considered early virological responders (EVR) if viral load declined > or = 2 log10 during the first 12 weeks of therapy. The remaining individuals were considered nonresponders (NR). HCV sequences from hypervariable region 1 and nonstructural 5A (NS5A) region before both treatment regimens were compared. Of 11 patients, 8 (73%) showed identical early response to both courses of therapy (group A: five EVR-EVR, three NR-NR). Interestingly, the response changed in three patients (27%) (group B): two NR became EVR after transplantation, whereas one EVR became NR. Fixation of mutations within the NS5A occurred preferentially in group B (100%) compared with group A (37%)(P = 0.12). However, the number of fixed mutations was not significantly different between groups, suggesting that the changes in sensitivity to therapy after LT are not exclusively dependent on variations in HCV strains. In conclusion, in HCV-infected patients undergoing LT, the pattern of response to antiviral treatment may change after transplantation, and this possibility needs to be incorporated in clinical practice.

Treating hepatitis C infection in liver transplant recipients

Chronic infection with hepatitis C virus (HCV) is a growing problem worldwide, with up to 300 million individuals infected, and those with chronic infection are at risk for cirrhosis and hepatocellular carcinoma. HCV infection is the most common indication for liver transplantation in the United States and Europe. Unfortunately, although transplantation is effective for treating decompensated cirrhosis and limited hepatocellular carcinoma associated with hepatitis C, HCV reinfection is virtually the rule among transplant recipients. Reinfection of the graft is associated with more rapidly progressive disease, with a median time to cirrhosis of 8 to 10 yr. Unfortunately, treatment of chronic HCV in liver transplant recipients is suboptimal. Combination therapy with interferon (pegylated and nonpegylated forms) plus ribavirin appears to provide maximum benefits. Drug therapy is usually administered for recurrent disease. No prophylactic therapy is available. Preemptive regimens offer no distinctive advantages over treatments begun for recurrent disease. Overall, treatment is poorly tolerated, with frequent need for dose reductions, especially from cytopenias, and drug discontinuations in up to 50% of patients. Optimizing drug doses is important in maximizing sustained virological response rates. Future therapies may include ribavirin alternatives with lower rates of anemia, alternative interferons with lower rates of cytopenias, and new antiviral drugs that can be used alone or in combination with either interferon or ribavirin to enhance sustained virological response rates and improve tolerability. Liver Transpl 12:1192-1204, 2006. (c) 2006 AASLD.

HBV and HCV infections and acute rejection differentially modulate CD95 and CD28 expression on peripheral blood lymphocytes after liver transplantation

Hepatitis B virus (HBV) and hepatitis C virus (HCV) generally reinfect liver graft early posttransplantation and lead to poorer graft and patient survivals. In the present study the influence of acute rejection (AR), HBV and HCV infections, and human leukocyte antigen (HLA) class-I compatibility on the expression of CD28 (in 237 liver recipients) and CD95 (in 114 liver recipients) on peripheral blood cells were evaluated by flow cytometry during the first month after transplantation. HBV/HCV infections induced strong CD95 upregulation on CD3+ lymphocytes. Maximal CD95 upmodulation was found in infected recipients showing partial HLA class-I compatibility. AR and virus reinfection could be distinguished because CD28 was upregulated on CD4+ lymphocytes only in recipients with AR, irrespective of their status regarding HBV/HCV infections. In conclusion, cytometric co-evaluation of CD95 and CD28 expression on peripheral blood lymphocytes could be useful to discriminate AR from cellular activation induced by viral reinfection of the liver graft.

Immunomodulatory Activities of IFN-γ1b in Combination with Type I IFN: Implications for the Use of IFN-γ1b in the Treatment of Chronic HCV Infections

The standard of care for chronic hepatitis C, pegylated interferon-alpha (IFN-alpha) and ribavirin (RBV), causes a sustained virologic response (SVR) in approximately 50% of patients. SVR is correlated with innate and adaptive immune system responses, such as natural killer (NK) cell activation, production of IFN-alpha from immature plasmocytoid dendritic cells (pDC), and polarization of CD4(+) cells to a T helper 1 (Th1) cell phenotype. To examine how these immunologic responses vary with currently available regimens for chronic hepatitis C, cell populations purified from human peripheral blood mononuclear cells (PBMC) were treated with the clinically available combinations of pegylated IFN-alpha2b (PEG-IFN-alpha2b) + RBV, IFN-alphacon1 + RBV, or IFN- alphacon1 + IFN-gamma1b, and activation of cellular immune system components was monitored. The magnitude of NK cell activation depended on regimen, with IFN-alphacon1 + IFN-gamma1b > IFN-alphacon1 + RBV > PEG-IFN- alphaa2b + RBV. The maximum human serum concentrations of IFN-alphacon1 + IFN-gamma1b saturated NK cell activation, whereas the maximum human serum concentrations of IFN-alphacon1 + RBV or PEG-IFN-alpha2b + RBV did not. IFN-gamma1b also enhanced the production of IFN-alpha from immature pDCs, which are the dominant source of IFN-alpha upon viral infection. The rank order for induction of Th1 cell phenotype and repression of Th2 cell phenotype by the cocktails described was identical to that observed for NK cell activation. Additionally, IFN- gamma1b suppressed the ability of the hepatitis C virus (HCV) NS4 protein to enhance monocyte secretion of interleukin- 10 (IL-10), a cytokine whose expression level is correlated with viral persistence. These results suggest that addition of IFN-gamma1b to HCV treatment regimens may provide unique benefits.

HLA-DRB1 donor-recipient mismatch affects the outcome of hepatitis C disease recurrence after liver transplantation

BACKGROUND & AIMS

This study extends our previously reported observations that various immunological factors are associated with the occurrence of histologically proven recurrent hepatitis C. The two specific issues investigated were to confirm the associations of MHC alleles and donor/recipient mismatch with the occurrence of recurrent hepatitis C in an independent cohort of newly transplanted patients and to look for immunologic and nonimmunologic variables affecting the severity of the recurrent disease.

METHODS

Two separate cohorts of consecutive patients were studied: a look-back cohort (LC) of 120 patients and a cohort for studying the disease progression (CSDP) of 190 patients. Protocol liver biopsies were obtained at least 1, 3, 5, 7, and 10 years after liver transplantation (LT).

RESULTS

A fully mismatched donor/recipient pair at the DRB1 locus was confirmed to be associated with both the recurrence of histologic hepatitis in the LC (59% vs 23%, P = .0002) and its progression beyond stage 3 in the CSPD (71.4% vs 39.3%, P = .0003). Relevant immunologic and nonimmunologic variables were included into a multivariate Cox proportional model and three variables, namely, donor age, full HLA-DRB1 donor-recipient mismatch, and HLA B14, resulted in independent risk factors for the development of severe fibrosis.

CONCLUSION

This study provides evidence that DRB1 donor-recipient mismatch affects both the occurrence and progression of recurrent hepatitis C disease. This information is clinically relevant as it may help to better allocate organs and to recognize patients at risk for progression so that specific interventions can be implemented.

The immunological monitoring of alloreactive responses in liver transplant recipients: a review

The aim of this work is to review the current knowledge in the field of immunological monitoring of allogenic responsiveness in clinical liver transplantation. When compared to other solid-organ transplants, liver allografts are considered as immunologically privileged, and, accordingly, constitute a favorable setting to develop experimental as well as clinical strategies for minimization of immunosuppression and even induction of operational tolerance. The validation of simple, reliable, noninvasive assays exploring antidonor alloreactivity will constitute a crucial step toward implementing such approaches in the clinic. In contrast to research in rodents claiming the development of donor-specific tolerance in case of graft survivals of over 100 days without immunosuppression, it is impractical to confirm tolerance induction in this way in humans. Promising candidate assays include the detection of post-transplant immune deviation, of circulating precursors of dendritic cells subtypes, and of regulatory T cells. A conceptual framework for the development of tolerance assays in clinical liver transplantation is also proposed.

Sustained, spontaneous disappearance of serum HCV-RNA under immunosuppression after liver transplantation for HCV cirrhosis

Immunosuppression is a main determinant for the increased Hepatitis C Virus (HCV) replication after liver transplantation and the accelerated course of recurrent HCV liver disease. We present two patients both with diabetes, renal dysfunction with proteinuria converted to sirolimus therapy, who cleared serum HCV RNA without antiviral treatment. This is a potentially important observation that should stimulate study into factors that may help viral clearance from blood.