CD56+ T cells inhibit hepatitis C virus replication in human hepatocytes

Embryonic growth and effect of embryonic age on quantitative and functional characteristics of duck primary hepatocytes

Primary hepatocytes (PH) have been widely used in metabolic and disease-resistance mechanism research. However, hepatocyte isolation (HI) remains challenging in ducks. This study aimed to explore embryonic growth and the effect of embryonic age (EA) on the quantitative and functional characteristics of PH in ducks. For embryonic growth, the size and weight of the embryo and liver were determined from 6 to 28 EA (E6-E28, similar below). As EA increased, the corresponding size and weight grew significantly. Specifically, embryonic length varied from 12.5 mm to 133.0 mm, and liver width varied from 2.0 mm to 26.2 mm. Embryonic weight ranged from 0.259 g to 53.58 g, and liver weight ranged from 0.007 g to 1.765 g. Liver index initially decreased and then increased with a ratio ranging from 1.06 to 3.29%. For quantitative and functional characteristics, they were determined from E6 to E22, as there were no obvious liver features before E6 and few cells obtained after E22. The number of cells isolated in liver increased from E6 to E16 and then sharply decreased from E16 to E22. The viability remained relatively stable from E6 to E10 and then decreased from E12 to E22. The comprehensive intensity of hepatic glycogen was stronger at E8 and E14. Albumin expression increased markedly from E6 to E18 by qPCR, and the overall albumin expression was stronger at E8 and E14 by immunofluorescence assay. Hepatocyte purity exceeded 90% except for E20 and E22. During culture, cell clusters appeared after 24-h culture, which were identified as nonhepatocytes. The growth curve showed an initial increase in cell quantity followed by a decrease, another increase, and then remaining stable. In conclusion, EA had a significant effect on the quantitative and functional characteristics of PH, and the suitable EA for HI were E8 and E14. Considering better operability and quantity, E14 was the optimal EA, laying a solid foundation for further hepatocyte purification, nutrient metabolism, and disease-resistance mechanism explorations in ducks.

Human CD8+ T-Cell Populations That Express Natural Killer Receptors

CD8⁺ T cells are activated by TCRs that recognize specific cognate Ags, while NK-cell activation is regulated by a balance between signals from germline-encoded activating and inhibitory NK receptors. Through these different processes of Ag recognition, CD8⁺ T cells and NK cells play distinct roles as adaptive and innate immune cells, respectively. However, some human CD8⁺ T cells have been found to express activating or inhibitory NK receptors. CD8⁺ T-cell populations expressing NK receptors straddle the innate-adaptive boundary with their innate-like features. Recent breakthrough technical advances in multi-omics analysis have enabled elucidation of the unique immunologic characteristics of these populations. However, studies have not yet fully clarified the heterogeneity and immunological characteristics of each CD8⁺ T-cell population expressing NK receptors. Here we aimed to review the current knowledge of various CD8⁺ T-cell populations expressing NK receptors, and to pave the way for delineating the landscape and identifying the various roles of these T-cell populations.

Identification of a distinct NK-like hepatic T-cell population activated by NKG2C in a TCR-independent manner

BACKGROUND & AIMS

The liver provides a unique niche of lymphocytes enriched with a large proportion of innate-like T cells. However, the heterogeneity and functional characteristics of the hepatic T-cell population remain to be fully elucidated.

METHODS

We obtained liver sinusoidal mononuclear cells from the liver perfusate of healthy donors and recipients with HBV-associated chronic liver disease (CLD) during liver transplantation. We performed a CITE-seq analysis of liver sinusoidal CD45⁺ cells in combination with T cell receptor (TCR)-seq and flow cytometry to examine the phenotypes and functions of liver sinusoidal CD8⁺ T cells.

RESULTS

We identified a distinct CD56^hiCD161^-CD8⁺ T-cell population characterized by natural killer (NK)-related gene expression and a uniquely restricted TCR repertoire. The frequency of these cells among the liver sinusoidal CD8⁺ T-cell population was significantly increased in patients with HBV-associated CLD. Although CD56^hiCD161^-CD8⁺ T cells exhibit weak responsiveness to TCR stimulation, CD56^hiCD161^-CD8⁺ T cells highly expressed various NK receptors, including CD94, killer immunoglobulin-like receptors, and NKG2C, and exerted NKG2C-mediated NK-like effector functions even in the absence of TCR stimulation. In addition, CD56^hiCD161^-CD8⁺ T cells highly respond to innate cytokines, such as IL-12/18 and IL-15, in the absence of TCR stimulation. We validated the results from liver sinusoidal CD8⁺ T cells using intrahepatic CD8⁺ T cells obtained from liver tissues.

CONCLUSIONS

In summary, the current study found a distinct CD56^hiCD161^-CD8⁺ T-cell population characterized by NK-like activation via TCR-independent NKG2C ligation. Further studies are required to elucidate the roles of liver sinusoidal CD56^hiCD161^-CD8⁺ T cells in immune responses to microbial pathogens or liver immunopathology.

LAY SUMMARY

The role of different immune cell populations in the liver is becoming an area of increasing interest. Herein, we identified a distinct T-cell population that had features similar to those of natural killer (NK) cells - a type of innate immune cell. This distinct population was expanded in the livers of patients with chronic liver disease and could thus have pathogenic relevance.

Hepatic iNKT cells produce type 2 cytokines and restrain antiviral T cells during acute hepacivirus infection

Chronic hepatitis C virus (HCV) infection is a curable disease, but the absence of a vaccine remains a major problem in infection prevention. The lack of small animal models and limited access to human liver tissue impede the study of hepatic antiviral immunity and the development of new vaccine strategies. We recently developed an immune-competent mouse model using an HCV-related rodent hepacivirus which shares immunological features with human viral hepatitis. In this study, we used this new model to investigate the role of invariant natural killer T (iNKT) cells during hepacivirus infection in vivo. These cells are enriched in the liver, however their role in viral hepatitis is not well defined. Using high-dimensional flow cytometry and NKT cell deficient mice we analyzed a potential role of iNKT cells in mediating viral clearance, liver pathology or immune-regulation during hepacivirus infection. In addition, we identified new immune-dominant MHC class I restricted viral epitopes and analyzed the impact of iNKT cells on virus-specific CD8+ T cells. We found that rodent hepacivirus infection induced the activation of iNKT cell subsets with a mixed NKT1/NKT2 signature and significant production of type 2 cytokines (IL-4 and IL-13) during acute infection. While iNKT cells were dispensable for viral clearance, the lack of these cells caused higher levels of liver injury during infection. In addition, the absence of iNKT cells resulted in increased effector functions of hepatic antiviral T cells. In conclusion, our study reports a regulatory role of hepatic iNKT cells during hepacivirus infection in vivo. Specifically, our data suggest that iNKT cells skewed towards type 2 immunity limit liver injury during acute infection by mechanisms that include the regulation of effector functions of virus-specific T cells.

Strategies Targeting the Innate Immune Response for the Treatment of Hepatitis C Virus-Associated Liver Fibrosis

Direct-acting antivirals eliminate hepatitis C virus (HCV) in more than 95% of treated individuals and may abolish liver injury, arrest fibrogenesis, and reverse fibrosis and cirrhosis. However, liver regeneration is usually a slow process that is less effective in the late stages of fibrosis. What is more, fibrogenesis may prevail in patients with advanced cirrhosis, where it can progress to liver failure and hepatocellular carcinoma. Therefore, the development of antifibrotic drugs that halt and reverse fibrosis progression is urgently needed. Fibrosis occurs due to the repair process of damaged hepatic tissue, which eventually leads to scarring. The innate immune response against HCV is essential in the initiation and progression of liver fibrosis. HCV-infected hepatocytes and liver macrophages secrete proinflammatory cytokines and chemokines that promote the activation and differentiation of hepatic stellate cells (HSCs) to myofibroblasts that produce extracellular matrix (ECM) components. Prolonged ECM production by myofibroblasts due to chronic inflammation is essential to the development of fibrosis. While no antifibrotic therapy is approved to date, several drugs are being tested in phase 2 and phase 3 trials with promising results. This review discusses current state-of-the-art knowledge on treatments targeting the innate immune system to revert chronic hepatitis C-associated liver fibrosis. Agents that cause liver damage may vary (alcohol, virus infection, etc.), but fibrosis progression shows common patterns among them, including chronic inflammation and immune dysregulation, hepatocyte injury, HSC activation, and excessive ECM deposition. Therefore, mechanisms underlying these processes are promising targets for general antifibrotic therapies.

Modulation of Immune Cell Subsets by Hepatitis C Virus and Antiviral Therapy in Early Virological Response HCV Genotype 4-Infected Patients with Compensated Liver Disease

BACKGROUND

Resolution of chronic hepatitis C virus (HCV) infection requires a complicated interaction between immune cell subsets. The effect of antiviral therapy on immune cell subsets remains to be defined. This study aimed to investigate the absolute count of certain immune cell subsets during therapy with pegylated interferon-α and ribavirin (PegIFN/RBV).

MATERIALS AND METHODS

Sixty HCV genotype 4-infected patients with compensated liver disease were treated with PegIFN/RBV therapy for 52 weeks. Efficacy was measured by studying the early virological response (EVR) at post-therapy week 12. Absolute counts of mature T cells, T helper cells, T cytotoxic cells, activated T cells, natural killer cells, natural killer/T (NKT) cells, B cells, and T regulatory cells (Treg), and the ratio of T helper to T cytotoxic cells were longitudinally analyzed by flow cytometry throughout the treatment and follow-up course.

RESULTS

Of the 60 genotype 4-infected subjects, 39 (65%) had EVR and 21 (35%) were non-EVR patients. In the first part of this study, there were significantly lower mean absolute count values of mature T, T cytotoxic, B, and NKT cells. Also, we detected statistically significantly lower mean values for the percentages of T cytotoxic, NKT, Treg, and activated T cells of HCV-infected patients at baseline values when compared with healthy subjects. After the initiation of PegIFN/RBV therapy, frequencies of T helper cells, activated T cells, Treg cells, B cells, and T helper:T cytotoxic ratio were found to be significantly lower in EVR patients than in non-EVR patients (p < 0.05). In contrast, frequencies of T cytotoxic and NKT cells were significantly increased in EVR patients when compared to non-EVR patients (p < 0.05).

CONCLUSION

These results suggest a pattern of higher levels of T cytotoxic and NKT cells, and lower levels of T helper, activated T, Treg, and B cell populations in patients who respond favorably to PegIFN/RBV therapy.

Prolactin Induces IL-2 Associated TRAIL Expression on Natural Killer Cells from Chronic Hepatitis C Patients In vivo and In vitro

BACKGROUND

Natural killer cells (NKC) are a major component of the innate immune response to HCV, mediating their effects through TRAIL and IFN-γ. However, their function is diminished in chronic HCV patients (HCVp). Prolactin is an immunomodulatory hormone capable of activating NKC.

OBJECTIVE

The study aims to explore if hyperprolactinemia can activate NKC in HCVp.

METHODS

We treated twelve chronic HCVp (confidence level =95%, power =80%) for 15 days with Levosulpiride plus Cimetidine to induce mild hyperprolactinemia. Before and after treatment, we determined TRAIL and NKG2D expression on peripheral blood NKC, along with cytokine profiles, viral loads and liver function. We also evaluated in vitro effects of prolactin and/or IL-2 on NKC TRAIL or NKG2D expression and IFN-γ levels on cultured blood mononuclear cells from 8 HCVp and 7 healthy controls.

RESULTS

The treatment induced mild hyperprolactinemia and increased TRAIL expression on NKC as well as the secretion of IL-1ra, IL-2, PDGF and IFN-γ. Viral loads decreased in six HCVp. IL-2 and TRAIL together explained the viral load decrease. In vitro, prolactin plus IL-2 synergized to increase TRAIL and NKG2D expression on NKC from HCVp but not in controls.

CONCLUSION

Levosulpiride/Cimetidine treatment induced mild hyperprolactinaemia that was associated with NKC activation and Th1-type cytokine profile. Also, an increase in TRAIL and IL-2 was associated with viral load decrease. This treatment could potentially be used to reactivate NKC in HCVp.

The Role of CD1d and MR1 Restricted T Cells in the Liver

The liver is one of the most important immunological organs that remains tolerogenic in homeostasis yet promotes rapid responses to pathogens in the presence of a systemic infection. The composition of leucocytes in the liver is highly distinct from that of the blood and other lymphoid organs, particularly with respect to enrichment of innate T cells, i.e., invariant NKT cells (iNKT cells) and Mucosal-Associated Invariant T cells (MAIT cells). In recent years, studies have revealed insights into their biology and potential roles in maintaining the immune-environment in the liver. As the primary liver-resident immune cells, they are emerging as significant players in the human immune system and are associated with an increasing number of clinical diseases. As such, innate T cells are promising targets for modifying host defense and inflammation of various liver diseases, including viral, autoimmune, and those of tumor origin. In this review, we emphasize and discuss some of the recent discoveries and advances in the biology of innate T cells, their recruitment and diversity in the liver, and their role in various liver diseases, postulating on their potential application in immunotherapy.

Alterations of the NK cell pool in HIV/HCV co-infection

BACKGROUND

A relevant proportion of human immunodeficiency virus (HIV) infected patients is co-infected with the hepatitis C virus (HCV). HCV co-infection in HIV-positive patients is associated with faster progression of liver disease in comparison to HCV mono-infection. Natural killer (NK) cells critically modulate the natural course of HCV infection. Both HIV and HCV mono-infection are associated with alterations of the NK cell pool. However, little data is available concerning phenotype and function of NK cells in HIV/HCV co-infection.

METHODS

A total of 34 HIV/HCV co-infected, 35 HIV and 39 HCV mono-infected patients and 43 healthy control persons were enrolled into this study. All HIV-positive patients were under effective antiretroviral therapy. NK cell phenotype, IFN-γ production and degranulation were studied by flow cytometry.

RESULTS

NK cell frequency in HIV/HCV co-infection was significantly lower than in healthy individuals but did not differ from HIV and HCV mono-infection. HIV/HCV co-infection was associated with significantly decreased expression of the maturation/differentiation markers CD27/62L/127 on NK cells but increased expression of CD57 compared to healthy controls. Of note, expression also differed significantly from HCV mono-infection but was similar to HIV mono-infection, suggesting a pronounced impact of HIV on these alterations. Similar findings were made with regard to the NK cell receptors NKG2A/C and NKp30. More importantly, NK cells in co-infection displayed a highly impaired functional activity with significantly lower IFN-γ production and degranulation than in healthy donors as well as HIV and HCV mono-infection, suggesting a synergistic effect of both viruses.

CONCLUSIONS

Our data indicate that HIV/HCV co-infection is associated with significant alterations of the NK cell pool, which might be involved in the rapid progression of liver disease in co-infected patients and which mainly reflect alterations observed in HIV mono-infection.

Suppression of autophagy by mycophenolic acid contributes to inhibition of HCV replication in human hepatoma cells

Previous studies have shown that mycophenolic acid (MPA) has an anti-HCV activity. However, the mechanism of MPA-mediated inhibition of HCV replication remains to be determined. This study investigated whether MPA has an effect on autophagy, a cellular machinery required for HCV replication, thereby, inhibits HCV replication in Huh7 cells. MPA treatment of Huh7 cells could suppress autophagy, evidenced by decreased LC3B-II level and conversion of LC3B-I to LC3B-II, decreased autophagosome formation, and increased p62 level compared to MPA-untreated cells. Tunicamycin treatment or HCV infection could induce cellular autophagy, however, MPA also exhibited its inhibitory effect on tunicamycin- or HCV infection-induced autophagy. The expression of three autophagy-related genes, Atg3, Atg5, and Atg7 were identified to be inhibited by MPA treatment. Over-expression of these genes could partly recover HCV replication inhibited by MPA; however, silencing their expression by siRNAs could enhance the inhibitory effect of MPA on HCV. Collectively, these results reveal that suppression of autophagy by MPA plays a role in its anti-HCV activity. Down-regulating the expression of three autophagy-related genes by MPA involves in its antiviral mechanism.

IFN-λ Inhibits Drug-Resistant HIV Infection of Macrophages

Type III interferons (IFN-λs) have been demonstrated to inhibit a number of viruses, including HIV. Here, we further examined the anti-HIV effect of IFN-λs in macrophages. We found that IFN-λs synergistically enhanced anti-HIV activity of antiretrovirals [azidothymidine (AZT), efavirenz, indinavir, and enfuvirtide] in infected macrophages. Importantly, IFN-λs could suppress HIV infection of macrophages with the drug-resistant strains, including AZT-resistant virus (A012) and reverse transcriptase inhibitor-resistant virus (TC49). Mechanistically, IFN-λs were able to induce the expression of several important anti-HIV cellular factors, including myxovirus resistance 2 (Mx2), a newly identified HIV post-entry inhibitor and tetherin, a restriction factor that blocks HIV release from infected cells. These observations provide additional evidence to support the potential use of IFN-λs as therapeutics agents for the treatment of HIV infection.

A different representation of natural T cells and natural killer cells between tumor-infiltrating and periphery lymphocytes in human hepatocellular carcinoma

Natural T cells [cluster of differentiation (CD) 3⁺CD56⁺] and natural killer (NK) cells (CD3^-CD56⁺) are particularly abundant in the human liver and serve an important role in immune responses in the liver. The aim of the present study was to extensively determine the phenotypic and functional characteristics of natural T and NK cells in human hepatocellular carcinoma (HCC). Tumorous and non-tumorous tissue infiltrating lymphocytes (TILs and NILs, respectively) and peripheral blood mononuclear cells (PBMCs) from patients with hepatocellular carcinoma (HCC) were obtained to determine the frequency and phenotype of natural T/NK cells by a multicolor fluorescence activated cell sorting analysis. The abundance of natural T cells and NK cells was decreased in TILs vs. NILs (natural T cells, 6.315±1.002 vs. 17.16±1.804; NK cells, 6.324±1.559 vs. 14.52±2.336, respectively). However such results were not observed in PBMCs from HCC patients vs. that of healthy donors. Notably, a substantial fraction of the natural T cells (21.96±5.283) in TILs acquired forkhead box P3 (FOXP3) expression, and the FOXP3⁺ natural T cells lost the expression of interferon-γ and perforin. Conversely, being similar to the conventional FOXP3⁺ regulatory T cells, the FOXP3⁺ natural T cells assumed a specific phenotype that was characteristic of CD25⁺, CD45RO⁺ and cytotoxic T-lymphocyte-associated protein 4⁺. Consistent with the phenotypic conversion, the present functional results indicate that FOXP3 expression in natural T cells contributes to the acquisition of a potent immunosuppressive capability. In conclusion, the present study describes a different representation of natural T cells and NK cells in local tumor tissues and in the periphery blood of patients with HCC, and identified a new type of FOXP3-expressing natural T cell spontaneously arising in the TILs of HCC.

Downregulation of autophagy-related gene ATG5 and GABARAP expression by IFN-λ1 contributes to its anti-HCV activity in human hepatoma cells

Type-III interferon (IFN-λ), the most recently discovered family of IFNs, shares common features with type I IFNs, but also has many distinctive activities. It is not clear that whether IFN-λ has additional antiviral mechanisms. In this study, we investigated the effects of IFN-λ on autophagy, a cellular process closely related to hepatitis C virus (HCV) infection in human hepatoma Huh7 cells. Our results showed that IFN-λ1 treatment inhibit autophagic activity in Huh7 cells, as evidenced by the decreased expression of microtubule-associated protein 1 light chain 3B (LC3B)-II and conversion of LC3B-I to LC3B-II, decreased formation of GFP-LC3 puncta and accumulation of autophagosomes. IFN-λ1 could also inhibit HCV-induced or tunicamycin (a known inducer of autophagy with similar mechanism to HCV infection) -induced LC3B-II expression and autophagosome formation. Through PCR array, real time RT PCR, and western blot, two autophagy-related genes, ATG5 and GABARAP, were identified and verified to be down-regulated by IFN-λ1 treatment, either in HCV-uninfected Huh7 cells or in HCV JFH-1-infected cells. Overexpression of ATG5 and/or GABARAP could partly recover the IFN-λ1-inhibited HCV replication. Mechanism research demonstrated that IFN-λ1 could induce the expression of miR-181a and miR-214 (targeting ATG5 and GABARAP respectively), by which down-regulates ATG5 and GABARAP expression. Taken together, our results indicate that suppression of the autophagy response by IFN-λ1 contributes to IFN-λ1 anti-HCV activity. The results also provide a theoretical basis for improving the effectiveness of IFN treatment of HCV infection through inhibition of the HCV-induced autophagy response.

Antibody-dependent CD56+ T cell responses are functionally impaired in long-term HIV-1 infection

Background

Antibody-dependent cellular cytotoxicity (ADCC), which mainly mediated by natural killer (NK) cells, may play a critical role in slowing human immunodeficiency virus type-1 (HIV-1) disease progression and protecting from HIV-1 infection. Besides classic NK cells, CD56+ T cells also have some NK cell-like properties, such as the large granular lymphocyte morphology and the capacity to destroy NK-sensitive target cells. However, little is known about the potentials of antibody-dependent CD56+ T cell responses and the association between antibody-dependent CD56+ T cell responses and HIV-1 disease progression.

Results

In the present study, we showed evidences that, in addition to NK cells, CD56+ T cells could generate degranulation upon CD16 cross-linking. Ex vivo study showed that FcγRIII (CD16)-mediated CD56+ T cell responses were distinctly induced by IgG antibody-bound P815 cells. Comparatively, CD56− T cells and invariant NKT (CD3+ 6B11+) failed to induce antibody-dependent activation. Antibody-dependent CD56+ T cell responses were mainly ascribed to CD4/CD8 double negative subset and were functionally impaired in long-term HIV-1-infected former plasma donors, regardless of hepatitis C virus (HCV) coinfection status. Also, CD56+ T cell-mediated HIV-1-specific antibody-dependent responses were declined in men who have sex with men with HIV-1 infection over 3 years. Finally, we showed that matrix metalloprotease (MMP) inhibitor GM6001 could partially restored antibody-dependent CD56+ T cell responses of chronic HIV-1-infected subjects.

Conclusions

Our results suggested that CD56+ T cells could mediate ADCC responses and the responses were impaired in chronic HIV-1 infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0313-6) contains supplementary material, which is available to authorized users.

Altered T cell phenotypes associated with clinical relapse of multiple sclerosis patients receiving fingolimod therapy

Multiple sclerosis (MS) is a T cell-mediated autoimmune disease. Fingolimod, a highly effective disease-modifying drug for MS, retains CCR7⁺ central memory T cells in which autoaggressive T cells putatively exist, in secondary lymphoid organs, although relapse may still occur in some patients. Here, we analyzed the T cell phenotypes of fingolimod-treated, fingolimod-untreated patients, and healthy subjects. The frequency of CD56⁺ T cells and granzyme B-, perforin-, and Fas ligand-positive T cells significantly increased during fingolimod treatment. Each T cell subpopulation further increased during relapse. Interestingly, T cells from fingolimod-treated patients exhibited interferon-γ biased production, and more myelin basic protein-reactive cells was noted in CD56⁺ than in CD56⁻ T cells. It is likely that the altered T cell phenotypes play a role in MS relapse in fingolimod-treated patients. Further clinical studies are necessary to investigate whether altered T cell phenotypes are a biomarker for relapse under fingolimod therapy.

Toll-like receptor 3-activated macrophages confer anti-HCV activity to hepatocytes through exosomes

Exosomes are a class of cell-released small vesicles that mediate intercellular communication by delivering functional factors to recipient cells. During hepatitis C virus (HCV) infection, the interaction between liver resident macrophages and hepatocytes is a key component in liver innate immunity. In this study, we explored the role of exosomes in the delivery of innate anti-HCV factors to hepatocytes from macrophages. We showed that supernatant from TLR3-activated macrophage cultures could efficiently inhibit HCV replication in Huh7 cells. This macrophage-mediated anti-HCV activity was through exosomes because inhibiting exosomes could abrogate the action of macrophages. Further analyses demonstrated that TLR3-activated macrophages release exosomes that contain anti-HCV microRNA (miRNA)-29 family members. Inhibiting miRNA29 could restore HCV replication. These findings suggest a novel antiviral mechanism in liver innate immunity against HCV infection and provide insights to support further studies on developing exosome-based delivery system for disease treatment.-Zhou, Y., Wang, X., Sun, L., Zhou, L., Ma, T.-C., Song, L., Wu, J.-G., Li, J.-L., Ho, W.-Z. Toll-like receptor 3-activated macrophages confer anti-HCV activity to hepatocytes through exosomes.

Donor-unrestricted T cells in the human CD1 system

The CD1 and MHC systems are specialized for lipid and peptide display, respectively. Here, we review evidence showing how cellular CD1a, CD1b, CD1c, and CD1d proteins capture and display many cellular lipids to T cell receptors (TCRs). Increasing evidence shows that CD1-reactive T cells operate outside two classical immunogenetic concepts derived from the MHC paradigm. First, because CD1 proteins are non-polymorphic in human populations, T cell responses are not restricted to the donor's genetic background. Second, the simplified population genetics of CD1 antigen-presenting molecules can lead to simplified patterns of TCR usage. As contrasted with donor-restricted patterns of MHC-TCR interaction, the donor-unrestricted nature of CD1-TCR interactions raises the prospect that lipid agonists and antagonists of T cells could be developed.

Immunological changes in different patient populations with chronic hepatitis C virus infection

AIM: To investigate killer inhibitory and activating receptor expression by natural killer (NK), natural killer T-like (NKT-like) and CD8+ T lymphocytes in patients with chronic hepatitis C virus (HCV) infection with elevated and with persistently normal alanine aminotransferase (PNALT).

METHODS: The percentage of peripheral blood Treg cells, KIR2DL3, ILT-2, KIR3DL1, CD160, NKG2D, NKG2C expressing NK, T and NKT-like cells, cytokine production and NK cytotoxicity were determined by flow cytometry. Twenty-one patients with chronic HCV infection with elevated alanine aminotransferase, 11 HCV carriers with persistently normal alanine aminotransferase and 15 healthy volunteers were enrolled.

RESULTS: No significant differences were observed in the percentage of total T, NK or NKT-like cells between study groups. Comparing the activating and inhibitory receptor expression by NK cells obtained from HCV carriers with PNALT and chronic HCV hepatitis patients with elevated alanine aminotransferase, NKG2D activating receptor expression was the only receptor showing a significant difference. NKG2D expression of NK cells was significantly lower in patients with elevated alanine aminotransferase. The expression of CD160, NKG2D and NKG2C activating receptor by CD8+ T cells were significantly lower in patients with chronic HCV hepatitis than in healthy controls and in HCV carriers with PNALT. Plasma TGF-β1 levels inversely correlated with NKG2D expression by NK cells. In vitroTGF-β1 treatment inhibited NK cells cytotoxic activity and downregulated NKG2D expression. CD8+ T cells from HCV carriers with PNALT showed significantly elevated expression of CD160, NKG2D and NKG2C activating receptors compared to chronic HCV patients with elevated alanine aminotransferase. Enhanced expression of inhibitory KIR2DL3 receptor, and decreased ILT-2 expression on NK cells were also found in chronic hepatitis C patients compared to healthy controls.

CONCLUSION: Our study demonstrated a complex dysregulation of activating and inhibitory receptor expression, such as decreased NKG2D and CD160 activating receptor expression and increased KIR2DL3 inhibitory receptor expression by NK and cytotoxic T cells and may provide further mechanism contributing to defective cellular immune functions in chronic hepatitis C. Increased NKG2D receptor expression in HCV patients with persistently normal ALT suggests an important pathway for sustaining NK and CD8 T cell function and a protective role against disease progression.

CD3(bright)CD56(+) T cells associate with pegylated interferon-alpha treatment nonresponse in chronic hepatitis B patients

Chronic hepatitis B (CHB) infection is a serious and prevalent health concern worldwide, and the development of effective drugs and strategies to combat this disease is urgently needed. Currently, pegylated interferon-alpha (peg-IFNα) and nucleoside/nucleotide analogues (NA) are the most commonly prescribed treatments. However, sustained response rates in patients remain low, and the reasons are not well understood. Here, we observed that CHB patients preferentially harbored CD3^brightCD56⁺ T cells, a newly identified CD56⁺ T cell population. Patients with this unique T cell population exhibited relatively poor responses to peg-IFNα treatment. CD3^brightCD56⁺ T cells expressed remarkably high levels of the inhibitory molecule NKG2A as well as low levels of CD8. Even if patients were systematically treated with peg-IFNα, CD3^brightCD56⁺ T cells remained in an inhibitory state throughout treatment and exhibited suppressed antiviral function. Furthermore, peg-IFNα treatment rapidly increased inhibitory TIM-3 expression on CD3^brightCD56⁺ T cells, which negatively correlated with IFNγ production and might have led to their dysfunction. This study identified a novel CD3^brightCD56⁺ T cell population preferentially shown in CHB patients, and indicated that the presence of CD3^brightCD56⁺ T cells in CHB patients may be useful as a new indicator associated with poor therapeutic responses to peg-IFNα treatment.

NKT cell subsets as key participants in liver physiology and pathology

Natural killer T (NKT) cells are innate-like lymphocytes that generally recognize lipid antigens and are enriched in microvascular compartments of the liver. NKT cells can be activated by self- or microbial-lipid antigens and by signaling through toll-like receptors. Following activation, NKT cells rapidly secrete pro-inflammatory or anti-inflammatory cytokines and chemokines, and thereby determine the milieu for subsequent immunity or tolerance. It is becoming clear that two different subsets of NKT cells-type I and type II-have different modes of antigen recognition and have opposing roles in inflammatory liver diseases. Here we focus mainly on the roles of both NKT cell subsets in the maintenance of immune tolerance and inflammatory diseases in liver. Furthermore, how the differential activation of type I and type II NKT cells influences other innate cells and adaptive immune cells to result in important consequences for tissue integrity is discussed. It is crucial that better reagents, including CD1d tetramers, be used in clinical studies to define the roles of NKT cells in liver diseases in patients.

Genotype-Associated Differential NKG2D Expression on CD56+CD3+ Lymphocytes Predicts Response to Pegylated-Interferon/Ribavirin Therapy in Chronic Hepatitis C

Hepatitis C virus (HCV) genotype 1 infections are significantly more difficult to eradicate with PEG-IFN/ribavirin therapy, compared to HCV genotype 2. The aim of this work is to investigate the difference of immunological impairments underlying this phenomenon. Pre-treatment NKG2D expression on peripheral CD56+CD3+ lymphocytes and CD56+CD3- NK cells from cases of chronic hepatitis C were analyzed and assessed by treatment effect. Two strains of HCV were used to co-incubate with immune cells in vitro. NKG2D expression on peripheral CD56+CD3+ lymphocytes, but not NK cells, was significantly impaired in genotype 1 infection, compared to genotype 2. When peripheral blood mononuclear cells from healthy donors were co-incubated with TNS2J1, a genotype 1b/2a chimera strain, or with JFH1, a genotype 2a strain, genotype-specific decrease of NKG2D on CD56+CD3+ lymphocytes, but not NK cells, was observed.　Pre-treatment NKG2D expression on peripheral CD56+CD3+ lymphocytes significantly correlated with reduction in serum HCV RNA levels from week 0 to week 4, and predicted treatment response. Ex vivo stimulation of peripheral CD56+CD3+ lymphocytes showed NKG2D expression-correlated IFN-γ production. In conclusion, Decreased NKG2D expression on CD56+CD3+ lymphocytes in chronic HCV genotype 1 infection predicts inferior treatment response to PEG-IFN/ribavirin therapy compared to genotype 2.

The roles of endoplasmic reticulum overload response induced by HCV and NS4B protein in human hepatocyte viability and virus replication

Hepatitis C virus (HCV) replication is associated with endoplasmic reticulum (ER) and its infection triggers ER stress. In response to ER stress, ER overload response (EOR) can be activated, which involves the release of Ca²⁺ from ER, production of reactive oxygen species (ROS) and activation of nuclear factor κB (NF-κB). We have previously reported that HCV NS4B expression activates NF-κB via EOR-Ca²⁺-ROS pathway. Here, we showed that NS4B expression and HCV infection activated cancer-related NF-κB signaling pathway and induced the expression of cancer-related NF-κB target genes via EOR-Ca²⁺-ROS pathway. Moreover, we found that HCV-activated EOR-Ca²⁺-ROS pathway had profound effects on host cell viability and HCV replication. HCV infection induced human hepatocyte death by EOR-Ca²⁺-ROS pathway, whereas activation of EOR-Ca²⁺-ROS-NF-κB pathway increased the cell viability. Meanwhile, EOR-Ca²⁺-ROS-NF-κB pathway inhibited acute HCV replication, which could alleviate the detrimental effect of HCV on cell viability and enhance chronic HCV infection. Together, our findings provide new insights into the functions of EOR-Ca²⁺-ROS-NF-κB pathway in natural HCV replication and pathogenesis.

Circulating microRNA-196a as a candidate diagnostic biomarker for chronic hepatitis C

Previous studies have demonstrated the inhibitory effect of microRNA (miR)-196a on hepatitis C virus (HCV) expression in human hepatocytes. However, the clinical implications of aberrant miR-196a expression and the application of circulating miR-196a in the diagnosis and management of chronic hepatitis C (CHC) require further investigation. The present study aimed to examine the possibility of using serum miR-196a as a biomarker for CHC. The Affymetrix miRNA array platform was used for miRNA expression profiling in adenovirus (Ad)-HCV core-infected (HepG2-HCV) and Ad-enhanced green fluorescence protein (EGFP)-infected HepG2 cells (HepG2-control). miR-196a downregulation and levels were analyzed using stem-loop reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis of the sera of 43 patients with CHC and 22 healthy controls. A total of six miRNAs were identified as significantly different (≥1.5 fold; P≤0.05) between the two groups. Of note, significant miR-196a downregulation was observed in HepG2-HCV as compared with HepG2-EGFP. Furthermore, as compared with that of the healthy control group, serum miR-196a was demonstrated to be significantly lower in patients with CHC. In addition, analysis of the receiver operating characteristic (ROC) curve for serum miR-196a revealed an area under the ROC curve of 0.849 (95% confidence interval, 0.756–0.941; P<0.001) with 81.8% sensitivity and 76.7% specificity in discriminating chronic HCV infection from healthy controls at a cut-off value of 6.115×10^‒5, demonstrating significant diagnostic value for CHC. However, no correlation was identified between serum miR-196a and alanine aminotransferase, aspartate aminotransferase or HCV-RNA. In conclusion, the present study identified circulating miR-196a as a specific and noninvasive candidate biomarker for the diagnosis of CHC.

The role of hepatic expression of STAT1, SOCS3 and PIAS1 in the response of chronic hepatitis C patients to therapy

BACKGROUND

The underlying mechanisms of hepatitis C virus (HCV) resistance to treatment are unknown. Signal transducers and activators of transcription (STAT) proteins play a critical role in antiviral defense.

OBJECTIVE

To explore some of the mechanisms of HCV resistance to interferon, the expression of STAT1 and its negative regulators, protein inhibitor of activated STAT (PIAS1) and suppressor of cytokine signalling (SOCS3), in liver tissues of both inteferon responders and nonresponders in chronic HCV patients.

METHODS

Sixty patients were divided into the following groups: group 1a comprised 38 treatment-responder chronic HCV patients; group 1b consisted of 22 treatment-nonresponder chronic HCV patients; and group 2 consisted of six control subjects. Liver biopsies were examined for histological scoring; STAT1, SOCS3 and PIAS1 expression was analyzed using Western blotting methods.

RESULTS

STAT1 expression in the liver tissue of patients in group 1 was significantly increased compared with group 2 patients (P=0.001), while no significant difference in expression was observed between group 1a and group 1b patients (P=0.747). However, phosphorylated STAT1 protein was expressed at a significantly higher level in liver tissue of patients in group 1a compared with patients in group 1b (P=0.001). Western blot analysis of PIAS1 and SOCS3 protein expression in liver tissues from groups 1 and 2 revealed significantly increased expression in group 1 compared with group 2 (P=0.001). In addition, PIAS1 and SOCS3 protein expression was significantly higher in the liver tissues of patients in group 1b compared with patients in group 1a.

CONCLUSION

Levels of STAT1 and⁄or the protein expression of its negative regulators, PIAS1 and SOCS3, may be a good predictor of response to therapy. These could be used as biomarkers that are easily detected by Western blotting or immunostaining during standard histopathological liver biopsy analysis.

Hepatitis C virus impairs TLR3 signaling and inhibits IFN-λ 1 expression in human hepatoma cell line

Toll-like receptor 3 (TLR3) activation plays an important role in the innate immune responses to viral infections. We show here that the activation of TLR3 signaling pathway by poly I:C, a synthetic mimic of dsRNA, could induce high-level expression of interferon (IFN)-λ1 in a hepatoma cell line. The induced IFN-λ1 contributed to poly I:C-mediated inhibition of hepatitis C virus (HCV) Japanese fulminant hepatitis-1 (JFH-1) replication in Huh7 cells. This inhibitory effect of poly I:C on HCV replication, however, was compromised by HCV infection of Huh7 cells. Investigation of the mechanisms showed that HCV infection suppressed the expression of poly I:C-induced IFN-λ1 and IFN-stimulated genes [IFN-stimulated gene 56 (ISG-56), myxovirus resistance A (MxA) and 2'-5'-oligoadenylate synthetase 1 (OAS-1))], the key antiviral elements in IFN signaling pathway. Among the HCV nonstructural (NS) proteins tested, NS3/4A, NS5A and NS5B had the ability to inhibit poly I:C-induced IFN-λ1 expression in Huh7 cells. These observations provide the experimental evidence that HCV and its proteins impair TLR3 signaling and inhibit intracellular IFN-λ1/ISG expression in a hepatoma cell line, which may account for HCV persistence in the liver.

Induction of interferon-λ contributes to Toll-like receptor-3-activated hepatic stellate cell-mediated hepatitis C virus inhibition in hepatocytes

There is limited information about the role of hepatic stellate cells (HSC) in liver innate immunity against hepatitis C virus (HCV). We thus examined whether HSC can produce antiviral factors that inhibit HCV replication in human hepatocytes. HSC expressed functional Toll-like receptor 3 (TLR-3), which could be activated by its ligand, polyinosine-polycytidylic acid (poly I:C), leading to the induction of interferon-λ (IFN-λ) at both mRNA and protein levels. TLR-3 signalling of HSC also induced the expression of IFN regulatory factor 7 (IRF-7), a key regulator of IFN signalling pathway. When HCV JFH-1-infected Huh7 cells were co-cultured with HSC activated with poly I:C or incubated in media conditioned with supernatant (SN) from poly I:C-activated HSC, HCV replication was significantly suppressed. This HSC SN action on HCV inhibition was mediated through IFN-λ, which was evidenced by the observation that antibody to IFN-λ receptors could neutralize the HSC-mediated anti-HCV effect. The role of IFN-λ in HSC-mediated anti-HCV activity is further supported by the observation that HSC SN treatment induced the expression of IRF-7 and IFN-stimulated genes (ISGs), OAS-1 and MxA in HCV-infected Huh7 cells. These observations indicate that HSC may be a key regulatory bystander, participating in liver innate immunity against HCV infection using an IFN-λ-dependent mechanism.

Retinoic acid inducible gene-I (RIG-I) signaling of hepatic stellate cells inhibits hepatitis C virus replication in hepatocytes

Retinoic acid inducible gene-I (RIG-I) is critical in the activation of the type I IFN-dependent antiviral innate immune response to hepatitis C virus (HCV) infection. We examined whether hepatic stellate cells (HSC; LX-2) possess a functional RIG-I signaling pathway and produce antiviral factors that can inhibit HCV. We showed that LX-2 cells treated with the RIG-I ligand (5'ppp-dsRNA) expressed significantly higher levels of IFN-β and IFN-λ than the control cells. The RIG-I activation in LX-2 cells also induced the expression of Toll-like receptor 3 (TLR3) and IFN regulatory factor-7 (IRF-7), the key regulators of the IFN signaling pathway. When HCV Japanese fulminant hepatitis (JFH)-1-infected hepatocytes were co-cultured with LX-2 cells stimulated with 5'ppp-dsRNA or incubated in media conditioned with supernatant (SN) from 5'ppp-dsRNA-stimulated LX-2 cells, HCV replication in hepatocytes was suppressed significantly. This LX-2 cell action on HCV replication was mediated through both IFN-β and IFN-λ, as Abs to IFN-α/β or IFN-λ receptors could neutralize the LX-2 SN-mediated anti-HCV effect. The role of IFNs in LX-2 cell-mediated anti-HCV activity is further supported by the observation that LX-2 SN treatment induced the expression of IFN stimulated genes, 2'-5'-oligoadenylate synthase-1 (OAS-1) and myxovirus resistance A (MxA), in HCV-infected Huh7 cells. These observations highlight the importance of HSC in liver innate immunity against HCV infection via a RIG-I-mediated signaling pathway.

TLR3 activation efficiency by high or low molecular mass poly I:C

Toll-like receptor 3 (TLR3) plays a critical role in initiating type I IFN-mediated innate immunity against viral infections. TLR3 recognizes various forms of double stranded (ds) RNA, including viral dsRNA and a synthetic mimic of dsRNA, poly I:C, which has been used extensively as a TLR3 ligand to induce antiviral immunity. The activation efficiency of TLR3 by poly I:C is influenced by various factors, including size of the ligands, delivery methods and cell types. In this study, we examined the stimulatory effect of two commercially-available poly I:Cs [high molecular mass (HMM) and low molecular mass (LMM)] on TLR3 activation in various human cell types by determining the induction of type I and type III IFNs, as well as the antiviral effect. We demonstrated that the direct addition of both HMM- and LMM-poly I:C to the cultures of primary macrophages or a neuroplastoma cell line could activate TLR3. However, the transfection of poly I:C was necessary to induce TLR3 activation in other cell types studied. In all the cell lines tested, the efficiency of TLR3 activation by HMM-poly I:C was significantly higher than that by LMM-poly I:C. These observations indicate the importance and necessity of developing effective TLR3 ligands for antiviral therapy.

Mycophenolate mofetil inhibits hepatitis C virus replication in human hepatic cells

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation and the major cause of graft failure. A widely used immunosuppressant, cyclosporine A (CsA), for people who receive organ transplantation, has been recognized to have the ability to inhibit HCV replication both in vivo and in vitro. In this study, we investigated the effects of several other immunosuppressants, including mycophenolate mofetil (MMF), rapamycin and FK506, on HCV replication in human hepatic cells. MMF treatment of hepatic cells before or during HCV infection significantly suppressed full cycle viral replication, as evidenced by decreased expression of HCV RNA, protein and production of infectious virus. In contrast, rapamycin and FK506 had little effect on HCV replication. Investigation of the mechanism(s) disclosed that the inhibition of HCV replication by MMF was mainly due to its depletion of guanosine, a purine nucleoside crucial for synthesis of guanosine triphosphate, which is required for HCV RNA replication. The supplement of exogenous guanosine could reverse most of anti-HCV effect of mycophenolate mofetil. These data indicate that MMF, through the depletion of guanosine, inhibits full cycle HCV JFH-1 replication in human hepatic cells. It is of interest to further determine whether MMF is indeed beneficial for HCV-infected transplant recipients in future clinical studies.

CD56+ T cells inhibit HIV-1 infection of macrophages

CD56+ T cells, the crucial component of the host innate immune system, play an important role in defense against viral infections. We investigated the noncytolytic anti-HIV-1 activity of primary CD56+ T cells. SNs collected from CD56+ T cell cultures inhibited HIV-1 infection and replication. This CD56+ T SN-mediated anti-HIV-1 activity was broad-spectrum, as CD56+ T SNs could inhibit infections by laboratory-adapted and clinical strains of HIV-1. The antibody to IFN-γ could partially block the CD56+ T SN-mediated anti-HIV effect. Investigation of mechanism(s) of the CD56+ T cell action on HIV-1 showed that although CD56+ T SN had little effect on HIV-1 entry coreceptor CCR5 expression, CD56+ T SN induced the expression of CC-chemokines, the ligands for CCR5. The antibodies to CC-chemokines also significantly blocked CD56+ T SN-mediated anti-HIV activity. Furthermore, CD56+ T SN up-regulated the expression of STAT-1/-2 and enhanced the expression of IRF1, -3, -7, and -9, resulting in the induction of endogenous IFN-α/β expression in macrophages. Moreover, CD56+ T SN up-regulated intracellular expression of APOBEC3G/3F, the recently identified HIV-1 restriction factors. These findings provide compelling evidence that CD56+ T cells may have a critical role in innate immunity against HIV-1 infection.

Virus stimulation of human mast cells results in the recruitment of CD56⁺ T cells by a mechanism dependent on CCR5 ligands

The trafficking of effector cells to sites of infection is crucial for antiviral responses. However, the mechanisms of recruitment of the interferon-γ-producing and cytotoxic CD56(+) T cells are poorly understood. Human mast cells are sentinel cells found in the skin and airway and produce selected proinflammatory mediators in response to multiple pathogen-associated signals. The role of human mast cell-derived chemokines in T-cell recruitment to virus infection was examined. Supernatants from primary human cord blood-derived mast cells (CBMCs) infected with mammalian reovirus were examined for chemokine production and utilized in chemotaxis assays. Virus-infected CBMCs produced several chemokines, including CCL3, CCL4, and CCL5. Supernatants from reovirus-infected CBMCs selectively induced the chemotaxis of CD8(+) T cells (10±1%) and CD3(+)CD56(+) T cells (19±5%). CD56(+) T-cell migration was inhibited by pertussis toxin (65±9%) and met-RANTES (56±7%), a CCR1/CCR5 antagonist. CD56(+) T cells expressed CCR5, but little CCR1. The depletion of CCL3, CCL4, and CCL5 from reovirus-infected CBMC supernatants significantly (41±10%) inhibited CD56(+) T-cell chemotaxis. This study demonstrates a novel role for mast cells and CCR5 in CD56(+) T-cell trafficking and suggests that human mast cells enhance immunity to viruses through the selective recruitment of cytotoxic effector cells to virus infection sites. These findings could be exploited to enhance local T-cell responses in chronic viral infection and malignancies at mast cell-rich sites.

Tetherin has negligible activity in restricting hepatitis C virus in hepatocytes

We investigated the ability of tetherin, a recently identified antiviral factor, in restricting hepatitis C virus (HCV) in the Japanese fulminant hepatitis-1 (JFH-1) infectious cell culture system. Human hepatocytes (Huh7, Huh7.5.1) expressedlow levels of endogenous tetherin, which could be induced by IFN-α. However, tetherin contributes little to IFN-α-mediated anti-HCV JFH-1 activity. Although tetherin could inhibit Vpu-deleted HIV-1 release, it had negligible activity in restricting HCV JFH-1 release from hepatocytes, which was evidenced by unaffected levels of intracellular/extracellular HCV RNA and infectious virus. The failure of tetherin's anti-HCV activity could not be related to the counteraction of HCV, as HCV infection of hepatocytes affected neither tetherin expression nor anti-HIV function of tetherin. These observations imply that tetherin has negligible activity in the restriction of HCV JFH-1 in human hepatocytes.

MicroRNA-196: critical roles and clinical applications in development and cancer

The discovery of microRNAs (miRNAs) represents one of the most significant advances in biological and medical sciences in the last decade. Hundreds of miRNAs have been identified in plants, viruses, animals and human beings, and these tiny, non-coding RNA transcripts have been found to play crucial roles in important biological processes involved in human health and disease. Recently, many studies have demonstrated that miR-196 plays critical roles in normal development and in the pathogenesis of human disease processes such as cancer. Several investigations have implemented cell culture and animal models to explore the potential molecular mechanisms of miR-196. This review provides updated information about the structure of the miR-196 gene and the roles of miR-196 in development, cancer and disease formation. Importantly, we discuss the possible molecular mechanisms whereby miR-196 regulates cellular functions including targeting molecules and gene regulation pathways; potential clinical applications are addressed, as well as future directions for investigation. miR-196a may prove to be a novel therapeutic target for several cancers.

IL-29/IL-28A suppress HSV-1 infection of human NT2-N neurons

The newly identified cytokines, IL-28/IL-29 (also termed type III IFNs), are able to inhibit a number of viruses. Here, we examined the antiviral effects of IL-29/IL-28A against herpes simplex virus type 1 (HSV-1) in human NT2-N neurons and CHP212 neuronal cells. Both IL-29 and IL-28A could efficiently inhibit HSV-1 replication in neuronal cells, as evidenced by the reduced expression of HSV-1 DNA and proteins. This inhibitory effect of IL-29 and IL-28A against HSV-1 could be partially blocked by antibody to IL-10Rβ, one of the key receptors for IL-29 and IL-28A. To explore the underlying antiviral mechanisms employed by IL-29/IL-28A, we showed that IL-29/IL-28A could selectively induce the expression of several Toll-like receptors (TLRs) as well as activate TLR-mediated antiviral pathway, including IFN regulatory factor 7, IFN-α, and the key IFN-α stimulated antiviral genes.

Fibrosis severity and mannan-binding lectin (MBL)/MBL-associated serine protease 1 (MASP-1) complex in HCV-infected patients

BACKGROUND AND STUDY AIMS

Mannan-binding lectin (MBL) is a collectin synthesised in the liver and secreted into the bloodstream. It binds micro-organisms via interactions with glycans on the target surface. Bound MBL subsequently activates MBL-associated serine protease proenzymes (MASPs). Several studies have investigated the possible role for MBL in hepatitis C virus (HCV) infection by examining MBL levels and polymorphisms in relation to disease progression and in response to treatment. The aim of this study was to investigate the relation of the activity of MBL and MBL/MASP-1 complex in sera of patients with mild and severe chronic HCV infection and outcome of HCV infection.

PATIENTS AND METHODS

Serum level of MBL and functional assays for MBL/MASP-1 complex activity were assayed in sera of 80 patients with chronic HCV infection. Patients were divided into two groups according to the results of the liver biopsy, group I (40 HCV patients had mild hepatic fibrosis, Ishak fibrosis stages 0-1) and group II (40 HCV patients had severe hepatic fibrosis, Ishak fibrosis stages 5-6), in addition to 20 control subjects as group III. The analysis of the MBL/MASP-1 complex activity at 0, 3 and 6 months was performed in all patients.

RESULTS

Serum levels of MBL and MBL/MASP-1 complex activity were higher in sera of patients with chronic HCV liver disease compared to those in control subjects. There was a correlation between the activity of the MBL/MASP-1 complex and the severity of fibrosis (P=0.003). MBL/MASP-1 complex activity was associated more significantly with severe fibrosis in comparison to MBL concentration.

CONCLUSION

MBL and MBL/MASP-1 complex activities play a key role in first-line host defence mechanism against certain infectious agents including HCV infection. However, it is also likely that the role of MBL and MBL/MASP-1 complex activity extends beyond this restricted infection-related view in that it appears to be a key regulator of inflammation.

The Need for New Anti-Hepatitis C Virus Therapeutic Strategies: Targeting the cellular micro-ribonucleic acids?

Infection with the hepatitis C virus (HCV) is a worldwide problem. Patients with chronic HCV infection who are non-responders to standard therapy represent a growing population within the HCV epidemic. Novel, more efficient and tolerable therapies are urgently needed. This review discusses the recent results showing that targeting miR-122, a micro-ribonucleic acid (MicroRNA) that enhances HCV replication, is a new anti-HCV therapy with a high barrier to resistance.

Increased natural killer cell cytotoxicity and NKp30 expression protects against hepatitis C virus infection in high-risk individuals and inhibits replication in vitro

CD56(pos) natural killer (NK)/natural T (NT) cells are important innate effectors providing the first line of defense against viral infection. Enhanced NK activity has been shown to protect from human immunodeficiency virus-1 infection. However, the role played by these innate effectors in protection against or development of hepatitis C virus (HCV) infection is unknown. We characterized CD56(pos) populations in 11 injection drug users (IDUs) who remained uninfected despite being repeatedly exposed to HCV. NK profiles in exposed but uninfected (EU) individuals were compared with preinfection samples (median 90 days prior to HCV seroconversion) collected from 14 IDUs who were exposed and subsequently became infected (EI) and unexposed normal control subjects (n = 8). Flow cytometric analysis of CD56(pos) populations demonstrated that EUs had a higher proportion of CD56(low) mature (P = 0.0011) NK cells compared with EI subjects. Bead-isolated NKs ( > 90% purity) from EUs had significantly higher interleukin-2 (IL-2)-induced cytolytic activity against the NK-sensitive cell line K562 at an effector-to-target ratio of 10:1 (P < 0.0001). NKp30, a natural cytotoxicity receptor involved in NK activation, is highest on NK/NT cells in EUs relative to infected subjects. Using the JFH-1 infection system, we demonstrated that NKp30(high) cells in the absence of exogenous stimulation significantly reduce infection of hepatocytes.

CONCLUSION

CD56(pos) populations in EUs are enriched for effector NKs displaying enhanced IL-2-induced cytolytic activity and higher levels of the natural cytotoxicity receptor NKp30-activating receptor. In addition, NKp30(high) cells are more effective in preventing infection of Huh-7.5 cells than their NKp30(low/neg) counterparts. These data support the hypothesis that NK cells contribute to anti-HCV defense in vivo in the earliest stages of infection, providing innate protection from HCV acquisition.

Cyclosporin A inhibits hepatitis C virus replication and restores interferon-alpha expression in hepatocytes

Hepatitis C virus (HCV) infection is the leading indication for liver transplantation and a major cause of graft failure. This study investigated whether cyclosporin A (CsA), a widely used immunosuppressant for organ transplantation, inhibits full cycle HCV replication and restores type I interferon (IFN) signaling pathway in human hepatocytes. CsA treatment of hepatocytes before, during, and after HCV infection significantly inhibited full cycle viral replication, which is evidenced by decreased expression of HCV RNA, protein, and infectious viruses in human hepatocytes. The suppression of HCV replication by CsA was associated with elevated levels of endogenous IFN-α in infected hepatocytes. Although CsA had little effect on IFN-α signaling pathway in uninfected hepatocytes, CsA treatment of HCV-infected hepatocytes specifically upregulated the expression of IFN regulatory factor-1 and inhibited the expression of suppressor of cytokine signaling-1 and protein inhibitor of activated signal transducers and activators of transcription-x, the primary negative regulators of IFN signaling pathway. These findings provide additional evidence to support the development of CsA-based prevention/treatment of HCV infection for transplant recipients.

Upregulation of SOCS-3 and PIAS-3 impairs IL-12-mediated interferon-gamma response in CD56 T cells in HCV-infected heroin users

Background

CD56⁺ T cells are abundant in liver and play an important role in host innate immunity against viral infections, including hepatitis C virus (HCV) infection, a common infection among heroin abusers. We thus investigated the in vivo impact of heroin use or heroin use plus HCV infection on the CD56⁺ T cell frequency and function.

Methodology/Principal Findings

A total of 37 heroin users with (17) or without (20) HCV infection and 17 healthy subjects were included in the study. Although there was no significant difference in CD56⁺ T cell frequency in PBMCs among three study groups, CD56⁺ T cells isolated from the heroin users had significantly lower levels of constitutive interferon-gamma (IFN-γ) expression than those from the normal subjects. In addition, when stimulated by interleukin (IL)-12, CD56⁺ natural T cells from HCV-infected heroin users produced significantly lower levels of IFN-γ than those from the normal subjects. This diminished ability to produce IFN-γ by CD56⁺ T cells was associated with the increased plasma HCV viral loads in the HCV-infected heroin users. Investigation of the mechanisms showed that although heroin use or heroin use plus HCV infection had little impact on the expression of the key positive regulators (IL-12 receptors, STAT-1, 3, 4, 5, JAK-2, and TYK-2) in IL-12 pathway, heroin use or heroin use plus HCV infection induced the expression of suppressor of cytokine signaling protein-3 (SOCS-3) and protein inhibitors of activated STAT-3 (PIAS-3), two key inhibitors of IL-12 pathway.

Conclusion/Significance

These findings provide compelling in vivo evidence that heroin use or heroin use plus HCV infection impairs CD56⁺ T cell-mediated innate immune function, which may account for HCV infection and persistence in liver.

Systematic identification of microRNA and messenger RNA profiles in hepatitis C virus-infected human hepatoma cells

In order to investigate the global and dynamic host microRNAs (miRNAs)/messenger RNAs (mRNAs) expression alteration during in vitro acute HCV infection, a comprehensive microarray analysis was performed using human hepatoma cells. Totally, 108 human miRNAs and 1247 mRNAs were identified whose expression levels changed for more than 2.0-fold in response to HCV infection. Upon HCV infection, signature from the unique miRNA expression pattern reflected the involvement of miRNA-regulated host cellular physiology and antiviral mechanism, whereas a preponderance of differentially regulated genes associated with metabolism, cell growth, apoptosis and cytokine/chemokine pathways. Furthermore, a reverse regulatory association of differentially expressed miRNAs and their predicted targets was constructed. Finally, the differentially expressed miRNAs such as miR-24, miR-149, miR-638 and miR-1181 were identified to be involved in HCV entry, replication and propagation. These results suggest that combined miRNA and mRNA profiling may have superior potential as a diagnostic and mechanistic feature in HCV infection.

Liver natural killer and natural killer T cells: immunobiology and emerging roles in liver diseases

Hepatic lymphocytes are enriched in NK and NKT cells that play important roles in antiviral and antitumor defenses and in the pathogenesis of chronic liver disease. In this review, we discuss the differential distribution of NK and NKT cells in mouse, rat, and human livers, the ultrastructural similarities and differences between liver NK and NKT cells, and the regulation of liver NK and NKT cells in a variety of murine liver injury models. We also summarize recent findings about the role of NK and NKT cells in liver injury, fibrosis, and repair. In general, NK and NKT cells accelerate liver injury by producing proinflammatory cytokines and killing hepatocytes. NK cells inhibit liver fibrosis via killing early-activated and senescent-activated stellate cells and producing IFN-gamma. In regulating liver fibrosis, NKT cells appear to be less important than NK cells as a result of hepatic NKT cell tolerance. NK cells inhibit liver regeneration by producing IFN-gamma and killing hepatocytes; however, the role of NK cells on the proliferation of liver progenitor cells and the role of NKT cells in liver regeneration have been controversial. The emerging roles of NK/NKT cells in chronic human liver disease will also be discussed.Understanding the role of NK and NKT cells in the pathogenesis of chronic liver disease may help us design better therapies to treat patients with this disease.