Hepatocyte-induced CD4+ T cell alloresponse is associated with major histocompatibility complex class II up-regulation on hepatocytes and suppressible by regulatory T cells

Single-cell landscape of functionally cured chronic hepatitis B patients reveals activation of innate and altered CD4-CTL-driven adaptive immunity

BACKGROUND & AIMS

Hepatitis B surface antigen (HBsAg) loss or functional cure (FC) is considered the optimal therapeutic outcome for patients with chronic hepatitis B (CHB). However, the immune-pathological biomarkers and underlying mechanisms of FC remain unclear. In this study we comprehensively interrogate disease-associated cell states identified within intrahepatic tissue and matched PBMCs (peripheral blood mononuclear cells) from patients with CHB or after FC, at the resolution of single cells, to provide novel insights into putative mechanisms underlying FC.

METHODS

We combined single-cell transcriptomics (single-cell RNA sequencing) with multiparametric flow cytometry-based immune phenotyping, and multiplexed immunofluorescence to elucidate the immunopathological cell states associated with CHB vs. FC.

RESULTS

We found that the intrahepatic environment in CHB and FC displays specific cell identities and molecular signatures that are distinct from those found in matched PBMCs. FC is associated with the emergence of an altered adaptive immune response marked by CD4 cytotoxic T lymphocytes, and an activated innate response represented by liver-resident natural killer cells, specific Kupffer cell subtypes and marginated neutrophils. Surprisingly, we found MHC class II-expressing hepatocytes in patients achieving FC, as well as low but persistent levels of covalently closed circular DNA and pregenomic RNA, which may play an important role in FC.

CONCLUSIONS

Our study provides conceptually novel insights into the immuno-pathological control of HBV cure, and opens exciting new avenues for clinical management, biomarker discovery and therapeutic development. We believe that the discoveries from this study, as it relates to the activation of an innate and altered immune response that may facilitate sustained, low-grade inflammation, may have broader implications in the resolution of chronic viral hepatitis.

IMPACT AND IMPLICATIONS

This study dissects the immuno-pathological cell states associated with functionally cured chronic hepatitis B (defined by the loss of HBV surface antigen or HBsAg). We identified the sustained presence of very low viral load, accessory antigen-presenting hepatocytes, adaptive-memory-like natural killer cells, and the emergence of helper CD4 T cells with cytotoxic or effector-like signatures associated with functional cure, suggesting previously unsuspected alterations in the adaptive immune response, as well as a key role for the innate immune response in achieving or maintaining functional cure. Overall, the insights generated from this study may provide new avenues for the development of alternative therapies as well as patient surveillance for better clinical management of chronic hepatitis B.

The effect of hepatitis B virus on T lymphocyte and its subsets in chronic hepatitis B patients in different ALT stages: A new concept ALT in HBV infection

The aim of the present study was to explore the effect of hepatitis B virus on T lymphocyte and its subsets in different ALT states, and elucidate the immunological mechanism of ALT basing antiviral therapy for hepatitis B. 363 chronic hepatitis B patients were selected as the study subjects. According to ALT abnormalities, the patients were divided into three study groups. ALT normal group 131 cases, normal≦ ALT < 2 times of upper limit group 110 cases, ALT ≥ 2 times of upper limit group 122 cases. Entecavir was given to the ALT ≥ 2 times of upper limit group patients and followed up for 24 weeks. The hepatitis B antigen antibody parameters were measured by chemiluminescence immunoassay analyzer, the liver function parameters were measured by automatic biochemical analyzer, the hepatitis B virus load were measured by quantitative PCR analyzer, T lymphocytes were detected by flow cytometry, the level of IL-2, IFN-γ, IL-4 and IL-10 were detected by enzyme-linked immunosorbent assay. Detecting the influence of different hepatitis B viru loads in different groups on immunological indexes, and the virological and immunological indexes changes in before and after antiviral therapy patients. In the ALT normal group, different virus load hepatitis B virus had minor effect on T lymphocytes and their subsets (P > 0.05). In the ALT ≥ double upper limit of normal group. with the virus load increased, The total number of T lymphocytes, CD3+ CD4 + T lymphocytes decreased, (P < 0.05)CD3+ CD8 + T lymphocytes increased(P < 0.05). With the virus load increased the cytokines IL-2, IFN-γ which reflect the Th1 lymphocytes increased(P < 0.05), the cytokines IL-4、IL-10 which reflect the Th2 lymphocytes decreased(P < 0.05). Before and after 24 weeks of entecavir treatment, the patient's HBV-DNA decreased significantly(P < 0.05) and the body's immune function improved significantly. (P < 0.05)The influence of hepatitis B virus on immune function is different in different ALT states. Therefore, the scientific significance of ALT grouping in the hepatitis B treatment can be clarified from the immunological point.

Tumor Necrosis Factor Directs Allograft-Related Innate Responses and Its Neutralization Improves Hepatocyte Engraftment in Rats

The innate immune system plays a critical role in allograft rejection. Alloresponses involve numerous cytokines, chemokines, and receptors that cause tissue injury during rejection. To dissect these inflammatory mechanisms, we developed cell transplantation models in dipeptidylpeptidase-deficient F344 rats using mycophenolate mofetil and tacrolimus for partial lymphocyte-directed immunosuppression. Syngeneic hepatocytes engrafted in liver, whereas allogeneic hepatocytes were rejected but engrafted after immunosuppression. These transplants induced mRNAs for >40 to 50 cytokines, chemokines, and receptors. In allografts, innate cell type-related regulatory networks extended to granulocytes, monocytes, and macrophages. Activation of Tnfa and its receptors or major chemokine receptor-ligand subsets persisted in the long term. An examination of the contribution of Tnfa in allograft response revealed that it was prospectively antagonized by etanercept or thalidomide, which resolved cytokine, chemokine, and receptor cascades. In bioinformatics analysis of upstream regulator networks, the Cxcl8 pathway exhibited dominance despite immunosuppression. Significantly, Tnfa antagonism silenced the Cxcl8 pathway and decreased neutrophil and Kupffer cell recruitment, resulting in multifold greater engraftment of allogeneic hepatocytes and substantially increased liver repopulation in retrorsine/partial hepatectomy model. We conclude that Tnfa is a major driver for persistent innate immune responses after allogeneic cells. Neutralizing Tnfa should help in avoiding rejection and associated tissue injury in the allograft setting.

The Role of Diverse Liver Cells in Liver Transplantation Tolerance

Liver transplantation is the ideal treatment approach for a variety of end-stage liver diseases. However, life-long, systemic immunosuppressive treatment after transplantation is required to prevent rejection and graft loss, which is associated with severe side effects, although liver allograft is considered more tolerogenic. Therefore, understanding the mechanism underlying the unique immunologically privileged liver organ is valuable for transplantation management and autoimmune disease treatment. The unique hepatic acinus anatomy and a complex cellular network constitute the immunosuppressive hepatic microenvironment, which are responsible for the tolerogenic properties of the liver. The hepatic microenvironment contains a variety of hepatic-resident immobile non-professional antigen-presenting cells, including hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, and hepatic stellate cells, that are insufficient to optimally prime T cells locally and lead to the removal of alloreactive T cells due to the low expression of major histocompatibility complex (MHC) molecules, costimulatory molecules and proinflammatory cytokines but a rather high expression of coinhibitory molecules and anti-inflammatory cytokines. Hepatic dendritic cells (DCs) are generally immature and less immunogenic than splenic DCs and are also ineffective in priming naïve allogeneic T cells via the direct recognition pathway in recipient secondary lymphoid organs. Although natural killer cells and natural killer T cells are reportedly associated with liver tolerance, their roles in liver transplantation are multifaceted and need to be further clarified. Under these circumstances, T cells are prone to clonal deletion, clonal anergy and exhaustion, eventually leading to tolerance. Other proposed liver tolerance mechanisms, such as soluble donor MHC class I molecules, passenger leukocytes theory and a high-load antigen effect, have also been addressed. We herein comprehensively review the current evidence implicating the tolerogenic properties of diverse liver cells in liver transplantation tolerance.

Alloresponses of Mixed Lymphocyte Hepatocyte Culture to Immunosuppressive Drugs as an In-Vitro Model of Hepatocyte Transplantation

Background

Hepatocyte transplantation (HCTx) has the potential for the treatment of end-stage liver disease. However, failure of engraftment and the long-term acceptance of cellular allografts remain significant challenges for its clinical application. The aim of this study was to investigate the efficacy of the immunosuppressive agents, Cyclosporine, Everolimus, and Belatacept to suppress the alloresponse of primary human hepatocytes in a mixed lymphocyte-hepatocyte culture (MLHC) and their potential hepatotoxicity in vitro.

Material/Methods

Primary human hepatocytes were co-cultured with allogeneic peripheral blood mononuclear cells (PBMCs) in an MLHC. Proliferative alloresponses were determined by flow cytometry, and cytokine secretion was measured using Luminex-based multiplex technology. Using an MLHC, the alloresponses of primary human hepatocytes were compared in the presence and absence of Cyclosporine, Everolimus, and Belatacept. Cultured primary human hepatocytes were assessed for the production of albumin, urea, aspartate transaminase (AST) and DNA content. Metabolic activity was determined with the MTT assay.

Results

Immune responses induced by primary human hepatocytes were effectively suppressed by Cyclosporine, Everolimus, and Belatacept. Everolimus significantly reduced the metabolic activity of primary human hepatocytes in vitro, suggesting impairment of cell viability. However, further functional analysis showed no significant differences between treated and untreated controls.

Conclusions

Cyclosporine, Everolimus, and Belatacept suppressed the alloresponse of primary human hepatocytes in an MLHC without significant cytotoxicity or functional cell impairment.

Silencing of HLA class I on primary human hepatocytes as a novel strategy for reduction in alloreactivity

In contrast to the whole liver, primary hepatocytes are highly immunogenic. Thus, alternative strategies of immunomodulation after hepatocyte transplantation are of special interest. Silencing of HLA class I expression is expected to reduce the strength of allogeneic immune responses and to improve graft survival. In this study, primary human hepatocytes (PHH) were isolated using a two-step-collagenase perfusion-technique and co-cultured with allogeneic lymphocytes in terms of a mixed lymphocyte hepatocyte culture. Expression of HLA class I on PHH was silenced using lentiviral vectors encoding for β2-microglobulin-specific short hairpin RNA (shβ2m) or non-specific shRNA (shNS) as control. The delivery of shβ2m into PHH caused a decrease by up to 96% in β2m transcript levels and a down-regulation of HLA class I cell surface expression on PHH by up to 57%. Proliferative T cell alloresponses against HLA-silenced PHH were significantly lower than those observed form fully HLA-expressing PHH. In addition, significantly lower secretion of pro-inflammatory cytokines was observed. Levels of albumin, urea and aspartate-aminotransferase did not differ in supernatants of cultured PHH. In conclusion, silencing HLA class I expression on PHH might represent a promising approach for immunomodulation in the transplant setting without compromising metabolic function of silenced hepatocytes.