Characterization of virus-specific T-cell immunity in liver allograft recipients with HCV-induced cirrhosis

Immune Responses to Tissue-Restricted Nonmajor Histocompatibility Complex Antigens in Allograft Rejection

Chronic diseases that result in end-stage organ damage cause inflammation, which can reveal sequestered self-antigens (SAgs) in that organ and trigger autoimmunity. The thymus gland deletes self-reactive T-cells against ubiquitously expressed SAgs, while regulatory mechanisms in the periphery control immune responses to tissue-restricted SAgs. It is now established that T-cells reactive to SAgs present in certain organs (e.g., lungs, pancreas, and intestine) are incompletely eliminated, and the dysregulation of peripheral immuneregulation can generate immune responses to SAgs. Therefore, chronic diseases can activate self-reactive lymphocytes, inducing tissue-restricted autoimmunity. During organ transplantation, donor lymphocytes are tested against recipient serum (i.e., cross-matching) to detect antibodies (Abs) against donor human leukocyte antigens, which has been shown to reduce Ab-mediated hyperacute rejection. However, primary allograft dysfunction and rejection still occur frequently. Because donor lymphocytes do not express tissue-restricted SAgs, preexisting Abs against SAgs are undetectable during conventional cross-matching. Preexisting and de novo immune responses to tissue-restricted SAgs (i.e., autoimmunity) play a major role in rejection. In this review, we discuss the evidence that supports autoimmunity as a contributor to rejection. Testing for preexisting and de novo immune responses to tissue-restricted SAgs and treatment based on immune responses after organ transplantation may improve short- and long-term outcomes after transplantation.

Contradictory immune response in post liver transplantation hepatitis B and C

Hepatitis B and C often progress to decompensated liver cirrhosis requiring orthotopic liver transplantation (OLT). After OLT, hepatitis B recurrence is clinically controlled with a combination of hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogues. Another approach is to induce self-producing anti-hepatitis B virus (HBV) antibodies using a HBV envelope antigen vaccine. Patients who had not been HBV carriers such as acutely infected liver failure or who received liver from HBV self-limited donor are good candidate. For chronic HBV carrier patients, a successful response can only be achieved in selected patients such as those treated with experimentally reduced immunosuppression protocols or received an anti-HBV adaptive memory carrying donor liver. Hepatitis C virus (HCV) reinfects transplanted livers at a rate of >90%. HCV reinfected patients show different severities of hepatitis, from mild and slowly progressing to severe and rapidly progressing, possibly resulting from different adaptive immune responses. More than half the patients require interferon treatment, although the success rate is low and carries risks for leukocytopenia and rejection. Managing the immune response has an important role in controlling recurrent hepatitis C. This study aimed to review the adaptive immune response in post-OLT hepatitis B and C.

Perioperative blood transfusion affects hepatitis C virus (HCV)-specific immune responses and outcome following liver transplantation in HCV-infected patients

OBJECTIVES

Perioperative factors can affect outcomes of liver transplantation (LT) in recipients with hepatitis C virus (HCV) infection. This study was conducted to investigate whether the immunomodulatory effects of packed red blood cells (PRBC) and platelets administered in the perioperative period might affect immune responses to HCV and thus outcomes in LT recipients.

METHODS

Data for a total of 257 HCV LT recipients were analysed. Data on clinical demographics including perioperative transfusion (during and within the first 24 h), serum cytokine concentration, HCV-specific interferon-γ (IFN-γ) and interleukin-17 (IL-17) producing cells, and outcomes including graft and patient survival were analysed.

RESULTS

Patient survival was higher in HCV LT recipients who did not receive transfusions (Group 1, n = 65) than in those who did (Group 2, n = 192). One-year patient survival was 95% in Group 1 and 88% in Group 2 (P = 0.02); 5-year survival was 77% in Group 1 and 66% in Group 2 (P = 0.05). Group 2 had an increased post-transplant viral load (P = 0.032) and increased incidence of advanced fibrosis at 1 year (P = 0.04). After LT, Group 2 showed increased IL-10, IL-17, IL-1β and IL-6, and decreased IFN-γ, and a significantly increased rate of IL-17 production against HCV antigen. Increasing donor age (P = 0.02), PRBC transfusion (P < 0.01) and platelets administration were associated with worse survival.

CONCLUSIONS

Transfusion had a negative impact on LT recipients with HCV. The associated early increase in pro-HCV IL-17 and IL-6, with decreased IFN-γ, suggests that transfusion may be associated with the modulation of HCV-specific responses, increased fibrosis and poor transplant outcomes.

Peritransplant absolute lymphocyte count as a predictive factor for advanced recurrence of hepatitis C after liver transplantation

Lymphocytes play an active role in natural immunity against hepatitis C virus (HCV). We hypothesized that a lower absolute lymphocyte count (ALC) may alter HCV outcome after liver transplantation (LT). The aim of this study was to investigate the impact of peritransplant ALC on HCV recurrence following LT. A total of 289 LT patients between 2005 and 2011 were evaluated. Peritransplant ALC (pre-LT, 2-week, and 1-month post-LT) and immunosuppression were analyzed along with recipient and donor factors in order to determine risk factors for HCV recurrence based on METAVIR fibrosis score. When stratifying patients according to pre- and post-LT ALC (<500/μL versus 500-1,000/μL versus >1,000/μL), lymphopenia was significantly associated with higher rates of HCV recurrence with fibrosis (F2-4). Multivariate Cox regression analysis showed posttransplant ALC at 1 month remained an independent predictive factor for recurrence (P = 0.02, hazard ratio [HR] = 2.47 for <500/μL). When peritransplant ALC was persistently low (<500/μL pre-LT, 2-week, and 1-month post-LT), patients were at significant risk of developing early advanced fibrosis secondary to HCV recurrence (F3-4 within 2 years) (P = 0.02, HR = 3.16). Furthermore, severe pretransplant lymphopenia (<500/μL) was an independent prognostic factor for overall survival (P = 0.01, HR = 3.01). The use of rabbit anti-thymocyte globulin induction (RATG) had a remarkable protective effect on HCV recurrence (P = 0.02, HR = 0.6) despite its potential to induce lymphopenia. Subgroup analysis indicated that negative effects of posttransplant lymphopenia at 1 month (<1,000/μL) were significant regardless of RATG use and the protective effects of RATG were independent of posttransplant lymphopenia.

CONCLUSION

Peritransplant ALC is a novel and useful surrogate marker for prediction of HCV recurrence and patient survival. Immunosuppression protocols and peritransplant management should be scrutinized depending on peritransplant ALC.

Interplay between immune responses to HLA and non-HLA self-antigens in allograft rejection

Recent studies strongly suggest an increasing role for immune responses against self-antigens (Ags) which are not encoded by the major histocompatibility complex in the immunopathogenesis of allograft rejection. Although, improved surgical techniques coupled with improved methods to detect and avoid sensitization against donor human leukocyte antigen (HLA) have improved the immediate and short term function of transplanted organs. However, acute and chronic rejection still remains a vexing problem for the long term function of the transplanted organ. Immediately following organ transplantation, several factors both immune and non immune mechanisms lead to the development of local inflammatory milieu which sets the stage for allograft rejection. Traditionally, development of antibodies (Abs) against mismatched donor HLA have been implicated in the development of Ab mediated rejection. However, recent studies from our laboratory and others have demonstrated that development of humoral and cellular immune responses against non-HLA self-Ags may contribute in the pathogenesis of allograft rejection. There are reports demonstrating that immune responses to self-Ags especially Abs to the self-Ags as well as cellular immune responses especially through IL17 has significant pro-fibrotic properties leading to chronic allograft failure. This review summarizes recent studies demonstrating the role for immune responses to self-Ags in allograft immunity leading to rejection as well as present recent evidence suggesting there is interplay between allo- and autoimmunity leading to allograft dysfunction.

Role of antibodies to self-antigens in chronic allograft rejection: potential mechanism and therapeutic implications

Significant progress has been made in preventing acute allograft rejection following solid organ transplantation resulting in improved allograft survival. However, long term function still remains disappointing primarily due to chronic allograft rejection. Alloimmune responses primarily defined by the development of antibodies (Abs) to donor mismatched major histocompatibility antigens during the post-transplantation period have been strongly correlated to the development of chronic rejection. In addition, recent studies have demonstrated an important role for autoimmunity including the development of Abs to organ specific self-antigens in the pathogenesis of chronic allograft rejection. Based on this, a new paradigm has evolved indicating a possible cross-talk between the alloimmune responses and autoimmunity leading to chronic rejection. In this review, we will discuss the emerging concept for the role of cellular and humoral immune responses to self-antigens in the immunopathogenesis of chronic allograft rejection which has the potential to develop new strategies for the prevention and/or treatment of chronic rejection.

Donor graft steatosis influences immunity to hepatitis C virus and allograft outcome after liver transplantation

BACKGROUND

Hepatitis C virus (HCV) recurrence after orthotopic liver transplantation (OLT) is universal, often with accelerated allograft fibrosis. Donor liver steatosis is frequently encountered and often associated with poor early postoperative outcome. The aim of this study was to test the hypothesis that allograft steatosis alters immune responses to HCV and self-antigens promoting allograft fibrosis.

METHODS

Forty-eight HCV OLT recipients (OLTr) were enrolled and classified based on amount of allograft macrovesicular steatosis at time of OLT. Group 1: no steatosis (0%-5% steatosis, n=21), group 2: mild (5%-35%, n=16), and group 3: moderate (>35%, n=11). Cells secreting interleukin (IL)-17, IL-10, and interferon gamma (IFN-γ) in response to HCV antigens were enumerated by Enzyme Linked Immunospot Assay. Serum cytokines were measured by Luminex, antibodies to Collagen I, II, III, IV, and V by ELISA.

RESULTS

OLTr of moderate steatotic grafts had the highest incidence of advanced fibrosis in protocol 1 year post-OLT biopsy (10.8% vs. 15.8% vs. 36.6%, r=0.157, P<0.05). OLTr from groups 2 and 3 had increased HCV-specific IL-17 (P<0.05) and IL-10 (P<0.05) with reduced IFN-γ (P<0.05) secreting cells when compared with group 1. This was associated with increase in serum IL-17, IL-10, IL-1β, IL-6, IL-5, and decreased IFN-γ. In addition, there was development of antibodies to Collagen I, II, III and V in OLTr with increased steatosis (P<0.05).

CONCLUSION

The results demonstrate that allograft steatosis influences post-OLT HCV-specific immune responses leading to an IL-17 T-helper response and activation of humoral immune responses to liver-associated self-antigens that may contribute to allograft fibrosis and poor outcome.

Immune response to extracellular matrix collagen in chronic hepatitis C-induced liver fibrosis

Hepatitis C virus (HCV) infection and its recurrence after orthotopic liver transplantation (OLT) are associated with the remodeling of extracellular matrix (ECM) components [particularly collagen (Col)], which leads to fibrosis. Our aim was to determine whether the development of antibodies (Abs) to self-antigen Col in HCV-infected patients correlates with the fibrosis stage and the peripheral cytokine response. Patients with chronic HCV infection, patients with HCV recurrence after OLT who had undergone a biopsy procedure, and healthy control subjects were enrolled. The HCV subjects (n = 70) were stratified as follows: (1) a non-OLT group without fibrosis (Scheuer stages 0-2), (2) a non-OLT group with fibrosis (Scheuer stages 3-4), (3) a post-OLT group without fibrosis (Scheuer stages 0-2), and (4) a post-OLT group with fibrosis (Scheuer stages 3-4). Serum samples were analyzed for Abs against Col1, Col2, Col4, Col5, and vimentin with enzyme-linked immunosorbent assays. Serum levels of cytokines were measured with multiplex bead immunoassays. The levels of Abs to Col1 were higher in the fibrosis groups versus the no-fibrosis groups and the controls for both non-OLT patients (P < 0.001) and post-OLT patients (P = 0.01). There were increased levels of Abs to Col2, Col4, Col5, and vimentin in the non-OLT fibrosis group (Col2, P = 0.0001; Col4, P = 0.122; Col5, P < 0.0001; vimentin, P = 0.36) and in the post-OLT fibrosis group (Col2, P = 0.006; Col4, P = 0.19; Col5, P < 0.0001; vimentin, P = 0.24) in comparison with the no-fibrosis groups. The non-OLT and post-OLT fibrosis groups demonstrated significantly higher T helper 2 (T(h) 2) and T helper 17 (T(h) 17) cytokine levels and lower T helper 1 cytokine levels in comparison with the no-fibrosis groups. Our results demonstrate that in HCV-infected patients, the levels of Abs to ECM Col1, Col2, and Col5 positively correlate with liver fibrosis, which is associated with a predominantly T(h) 2 and T(h) 17 cytokine profile.

Characterization of HCV-specific CD4+Th17 immunity in recurrent hepatitis C-induced liver allograft fibrosis

Hepatitis C virus (HCV) recurrence with accelerated fibrosis following orthotopic liver transplantation (OLT) is a universal phenomenon. To evaluate mechanisms contributing to HCV induced allograft fibrosis/cirrhosis, we investigated HCV-specific CD4+Th17 cells and their induction in OLT recipients with recurrence utilizing 51 HCV+ OLT recipients, 15 healthy controls and 9 HCV- OLT recipients. Frequency of HCV specific CD4+ Tcells secreting IFN-γ, IL-17 and IL-10 was analyzed by ELISpot. Serum cytokines and chemokines were analyzed by LUMINEX. Recipients with recurrent HCV induced allograft inflammation and fibrosis/cirrhosis demonstrated a significant increase in frequency of HCV specific CD4+Th17 cells. Increased pro-inflammatory mediators (IL-17, IL-1β, IL-6, IL-8 and MCP-1), decreased IFN-γ, and increased IL-4, IL-5 and IL-10 levels were identified. OLT recipients with allograft inflammation and fibrosis/cirrhosis demonstrated increased frequency of Foxp3+ regulatory T cells (Tregs) that inhibited HCV specific CD4+Th1 but not Th17 cells. This suggests that recurrent HCV infection in OLT recipients induces an inflammatory milieu characterized by increased IL-6, IL-1β and decreased IFN-γ which facilitates induction of HCV specific CD4+Th17 cells. These cells are resistant to suppression by Tregs and may mediate an inflammatory cascade leading to cirrhosis in OLT recipients following HCV recurrence.

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.

Alloimmunity and autoimmunity in chronic rejection

PURPOSE OF REVIEW

Recent studies demonstrate an increasing role for alloimmune responses in the disruption of self-tolerance leading to immune responses to self-antigens that play a role in the immunopathogenesis of chronic rejection following solid organ transplantation. This review summarizes recent studies and implications for the alloimmune-response-induced de-novo development of autoimmune responses following solid organ transplantations.

RECENT FINDINGS

Immediately following organ transplantation, several factors lead to enduring an inflammatory milieu. Studies from our laboratory and others have demonstrated that development of antihuman leukocyte antigen antibodies precedes the development of chronic rejection. Using an in-vivo murine model, we have demonstrated that administration of anti-major histocompatibility complex (MHC) class I directly into the native lungs leads to chronic rejection pathology. Further, the in-vitro ligation of epithelial cell surface MHC class I molecules by specific anti-MHC can lead to cell activation and production of fibrinogenic growth factors.

SUMMARY

On the basis of these findings, we hypothesized that alloimmune responses can lead to autoimmunity, thus playing an important role in chronic rejection. Characterization of both the temporal occurrence and functional significance of antibodies to self-antigens may provide insight into the pathogenesis of chronic rejection and these antibodies can serve as clinically useful biomarkers.

Recipient age affects long-term outcome and hepatitis C recurrence in old donor livers following transplantation

We studied the role of donor and recipient age in transplantation/ischemia-reperfusion injury (TIRI) and short- and long-term graft and patient survival. Eight hundred twenty-two patients underwent deceased donor liver transplantation, with 197 donors being > or = 60 years old. We evaluated markers of reperfusion injury, graft function, and clinical outcomes as well as short- and long-term graft and patient survival. Increased donor age was associated with more severe TIRI and decreased 3- and 5-year graft survival (73% versus 85% and 72% versus 81%, P < 0.001) and patient survival (77% versus 88% and 77% versus 82%, P < 0.003). Hepatitis C virus (HCV) infection and recipient age were the only independent risk factors for graft and patient survival in patients receiving an older graft. In the HCV(+) cohort (297 patients), patients > or = 50 years old who were transplanted with an older graft versus a younger graft had significantly decreased 3- and 5-year graft survival (68% versus 83% and 64% versus 83%, P < 0.009). In contrast, HCV(+) patients < 50 years old had similar 3- and 5-year graft survival if transplanted with either a young graft or an old graft (81% versus 82% and 81% versus 82%, P = 0.9). In conclusion, recipient age and HCV status affect the graft and patient survival of older livers. Combining older grafts with older recipients should be avoided, particularly in HCV(+) patients, whereas the effects of donor age can be minimized in younger recipients.