A longitudinal analysis of T-cell epitope-coding regions of hepatitis C virus after liver transplantation

Analysis of Post-Liver Transplant Hepatitis C Virus Recurrence Using Serial Cluster of Differentiation Antibody Microarrays

BACKGROUND

Hepatitis C virus (HCV) reinfection of the liver allograft after transplantation is universal, with some individuals suffering severe disease recurrence. Predictive markers of recurrent disease severity are urgently needed. In this study, we used a cluster of differentiation (CD) microarray to predict the severity of HCV recurrence after transplantation.

METHODS

The CD antibody microarray assays of live leukocytes were performed on peripheral blood taken in the first year after transplantation. The results were grouped into phases defined as; Pre-transplant (day 0), Early (day 3 to week 2), Mid (week 4 to week 10), and Late (week 12 to week 26). Hepatitis C virus severity was based on fibrosis stages in the first 2 years (F0-1 mild and F2-4 severe).

RESULTS

Serial blood samples from 16 patients were taken before and after liver transplantation. A total of 98 assays were performed. Follow-up was 3 years or longer. Comparing recurrence severity, significantly greater numbers of CD antigens were differentially expressed on the pretransplant samples compared to any posttransplant timepoints. Five differentially expressed CD antigens before transplantation (CD27 PH, CD182, CD260, CD41, and CD34) were significantly expressed comparing severe to mild recurrence, whereas expression of only CD152 was significant in the late phase after transplantation. No relationship was observed between the donor or recipient interleukin-28B genotypes and HCV recurrence severity.

CONCLUSIONS

This study shows that circulating leukocyte CD antigen expression has utility in assessing recurrent HCV disease severity after liver transplantation and serves as a proof of principle. Importantly, pretransplant CD antigen expression is most predictive of disease outcome.

Challenges of recurrent hepatitis C in the liver transplant patient

Cirrhosis secondary to hepatitis C virus (HCV) is a very common indication for liver transplant. Unfortunately recurrence of HCV is almost universal in patients who are viremic at the time of transplant. The progression of fibrosis has been shown to be more rapid in the post-transplant patients than in the transplant naïve, hence treatment of recurrent HCV needs to be considered for all patients with documented recurrent HCV. Management of recurrent HCV is a challenging situation both for patients and physicians due to multiple reasons as discussed in this review. The standard HCV treatment with pegylated interferon and Ribavarin can be considered in these patients but it leads to a lower rate of sustained virologic clearance than in the non-transplanted population. Some of the main challenges associated with treating recurrent HCV in post-transplant patients include the presence of cytopenias; need to monitor drug-drug interactions and the increased incidence of renal compromise. In spite of these obstacles all patients with recurrent HCV should be considered for treatment since it is associated with improvement in survival and a delay in fibrosis progression. With the arrival of direct acting antiviral drugs there is renewed hope for better outcomes in the treatment of post-transplant HCV recurrence. This review evaluates current literature on this topic and identifies challenges associated with the management of post-transplant HCV recurrence.

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.

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.

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.

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

Hepatitis C virus (HCV)-related liver failure is the leading indication for liver transplantation worldwide. After transplantation, virological recurrence is the rule, but the spectrum of histological injury is wide, ranging from the development of allograft cirrhosis within a few years to minimal hepatitis despite long-term follow-up. The immunological correlates of this variable natural history are poorly understood. Here, we studied the kinetics of the cellular immune responses, viral replication, and allograft histology in 24 patients who had undergone liver transplantation for HCV-related liver failure. Using direct ex vivo methodologies (i.e., interferon-gamma ELISPOT and major histocompatibility complex class I-peptide tetrameric complexes), we found that patients who experienced viral eradication after antiviral therapy showed restoration of HCV-specific T-cell responses, whereas patients with progressive HCV recurrence that failed to respond to therapy showed declining frequencies of these viral-specific effector cells. The cytotoxic T lymphocytes that peripherally reconstituted after transplantation were clonotypically identical to those present within the recipient explant liver, defined at the level of the T-cell receptor beta chain (one epitope/one clone). Moreover, the subset of patients who spontaneously demonstrated minimal histologic recurrence had more vigorous CD4+ T-cell responses in the first 3 months, particularly targeting nonstructural proteins. We provide evidence that T-cell responses emerge after liver transplantation, and their presence correlates with improved histological and clinical outcomes. In conclusion, these results may help identify patients more likely to develop severe HCV recurrence and therefore benefit from current antiviral therapy, as well as provide a rationale for the future use of novel immunotherapeutic approaches. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience. wiley.com/jpages/0270-9139/suppmat/index.html).

Accurate representation of the hepatitis C virus quasispecies in 5.2-kilobase amplicons

Hepatitis C virus (HCV) exists as a swarm of genetically distinct but related variants, or a quasispecies, whose complexity and sequence evolution are critical to studies of viral pathogenesis. Because most studies of the HCV quasispecies have focused on a relatively small genomic segment, the first hypervariable region of the E2 gene, it is possible that viral complexity is occasionally underestimated (due to primer mismatch) and that sequence evolution is misperceived due to unrecognized covariation. This report describes a sensitive and reproducible method to amplify most of the HCV genome as a single 5.2-kb amplicon by using primers directed at relatively conserved genomic segments. Using 52 specimens obtained during acute infection over a range of viral RNA concentrations, the overall rate of successful amplification was 94% and varied in a concentration-dependent manner, with successful amplification in 26 of 26 (100%) specimens at greater than 10(5) IU/ml, 15 of 16 (94%) at 10(4) to 10(5) IU/ml, 6 of 7 (86%) at 10(3) to 10(4) IU/ml, and 2 of 3 (67%) at less than 10(3) IU/ml. Quasispecies complexity, determined by using this novel long-amplicon method followed by heteroduplex mobility assay combined with single-stranded conformational polymorphism (HDA+SSCP) analysis, was very high, even during acute HCV infection, when 10 to 21 (median, 16) different HDA+SSCP patterns were detected among 33 cDNA clones examined. Replicate analyses indicate that this diversity is not dominated by random errors generated during amplification. Therefore, the HCV quasispecies is highly complex even during acute infection and is accurately represented in amplicons representing more than half of the viral genome.

Genetic variability of hepatitis C virus NS3 protein in human leukocyte antigen-A2 liver transplant recipients with recurrent hepatitis C

The association between the severity of chronic hepatitis C and the variability of the hepatitis C virus (HCV) genome remains controversial, but to our knowledge few data are available to date regarding T-cell epitope coding regions in transplant patients. In the current study, we identified 21 human leukocyte antigen (HLA)-A2-positive Spanish patients with chronic hepatitis C, 14 immunosuppressed liver transplant recipients, and 7 immunocompetent controls. Alanine aminotransferase, aspartate aminotransferase, viral load, and rate of fibrosis progression were determined. Genetic distances of HCV isolates and variations in epitopes of the HCV nonstructural 3 protein (NS3-1393 LIFCHSKKK and NS3-1406 KLVALGINAV) were compared between patients with slow or fast progression of fibrosis. Isolates from transplant patients with fast progression were found to be more divergent (P =.03), had a higher mean value of synonymous (dS) variations (P =.02), and some were differentiated in a phylogenetic tree, compared with isolates from patients with slow progression. The HLA-A2-restricted NS3-1406 epitope was found to be more variable (20 of 21 isolates differed from the prototype) compared with the A3-restricted NS3-1392 epitope (19% vs. 1.25% variation). A shift in the viral peptide was not detected in a subset of transplant patients, but was evident in two of three nontransplant patients with follow-up. There was no correlation noted between a particular amino acid variation and fibrosis progression (slow or fast) in either transplant or nontransplant patients. The results of the current study suggest that 1) there may be different HCV-1b strains in our geographic area, 2) immunosuppression appears to have little effect in amino acid variation at the HCV NS3-1406 epitope, and 3) variations over time might be more frequent in nonimmunosuppressed patients.

Factors that influence the severity of recurrent hepatitis C virus following liver transplantation

Poor outcomes following OLT for HCV disease have been associated with several host, viral, and non-host/non-viral factors. As is evident from the literature, there is confounding data in favor of and against these factors in the pathogenesis of severe recurrent HCV. Nevertheless, from a viral perspective, the patient most likely to achieve a good outcome following OLT is someone with low-level (< or = 10(9) copies/mL) HCV RNA viremia both pre- and post-OLT and a genotype other than lb. In terms of host factors, the patients with best outcomes are: whites, men, less than 49 years of age, receiving a donor liver less than 40 years of age, not coinfected with CMV, and have low HAI or histologic activity indices during the early stage of follow-up. Host recipient immune homology may or may not be a major factor in outcomes. A non-host, non-viral factor favoring less severe recurrence of HCV is a shorter warm ischemia time. Finally, features that may influence outcomes over which there is no control include: recipient age, recipient gender, and donor age (in the case of cadaveric donors). Unfortunately, the best-case scenario is uncommon.

Screening and identification of genes trans-regulated by hepatitis C virus NC3 protein with microarray assay

AIM

To understand the target genes up-regulated or down-regulated by NS3 protein, we compared the differentially expressed genes between the hepatoblastoma cell line HepG2 transfected by pcDNA3.1(-) and pcDNA3.1-NS3, respectively by cDNA microarray technique.

METHODS

The NS3 coding DNA fragment was amplified with polymerase chain reaction (PCR) technique by using pBRTM3011 containing the full length of HCV-H cDNA as the template. The expressive vector of pcDNA3.1-NS3 was constructed by routine molecular biological methods. The HepG2 cells were transfected by pcDNA3.1(-) and pcDNA3.1-NS3, respectively using lipofectamine. The total RNA was isolated and reverse transcribed. The cDNAs were subjected for microarray screening with 1 152 cDNA probes.

RESULTS

The expressive vector has been constructed and confirmed by restriction enzyme digestion and DNA sequencing analysis. The expression of NS3 protein has been confirmed by Western blot with single chain variable region (scFv) antibody. High quality mRNA and cDNA had been prepared and successful microarray screening had been conducted. From the scanning results, it was found 34 genes were up-regulated and 37 genes were down-regulated by NS3 protein of HCV.

CONCLUSION

NS3 protein is a transactivator. The expression of NS3 protein affected the expression spectrum of HCV infected hepatocyte. The microarray is an important technique for the study of transactivating effects for viral proteins.

Hepatitis C virus in the human liver transplantation model

Hepatitis C virus-related liver failure is the single leading indication for liver transplantation, and the study of HCV in the transplant setting has enhanced the understanding of the natural history of disease and putative mechanisms by which HCV causes liver injury. In a subset of patients, allograft cirrhosis develops within a few years after transplantation, and recent findings suggest these individuals are immunologically impaired compared with individuals with mild HCV recurrence at long-term follow-up. Fig. 9 shows a conceptual paradigm of mechanisms potentially involved in shaping HCV outcome after transplantation. It is possible that relative antiviral control by innate and adaptive immune responses (to maintain HCV replication below a certain threshold) prevents direct cytopathic injury and induction of oxidative stress and apoptosis of cells. Additional phenomena that may contribute to induction of apoptosis (eg, genetic polymorphisms within the donor organ. CMV coinfection, and ischemic-preservation injury) may augment the initial cascade of liver injury. Recruitment to the allograft of nonspecific cells may decrease viral replication by way of noncytolytic mechanisms or augment viral replication (eg, Th2 phenotype) and direct cytopathic injury. The immune response is likely insufficiently vigorous to keep viral replication under control, but may maintain chronic liver injury. The liver transplant model is unique in that distinct phenotypic outcomes can be observed over a short period of time. A consideration of the temporal evolution of different mechanisms is also important, because mechanisms that initially predominate may become less important over time, and conversely, as suggested with the inverse correlation between viral load at 5 years and allograft fibrosis, new immune responses may emerge that modify the host-virus interaction. Prospective characterization of the immunoregulatory and virologic mechanisms involved in the liver transplantation model hopefully will help unravel the causal basis of reported associations, lead to the development of highly specific therapeutic strategies, and ultimately diminish the rate of graft loss from recurrent disease.