Lymphotropism of hepatitis B and C viruses: an update and a newcomer

Hepatitis B Virus Replication in CD34+ Hematopoietic Stem Cells From Umbilical Cord Blood

BACKGROUND Hepatitis B virus (HBV) is a hepatotropic virus that can infect extrahepatic tissue. Whether hematopoietic stem cells (HSCs) can be infected by HBV and serve as a potential virus reservoir is still unknown. In this study, the susceptibility of CD34+ HSCs to HBV was investigated. MATERIAL AND METHODS Cord blood-derived CD34+ HSCs were exposed to HBV in vitro, and immunocytochemistry, transmission electron microscopy, and RT-PCR were used to identify viral-related proteins and specific viral genomic sequences. Then, CD34+ HSCs were challenged by different titers of HBV, and intracellular and supernatant HBV DNA, and hepatitis B surface antigen (HBsAg) levels, were examined. In addition, CD34+ peripheral blood stem cells (PBSCs) from chronic HBV carriers were isolated and cultured, and HBV DNA levels were measured. RESULTS HBV-infected CD34+ cells showed positive signals for HBsAg by DAB staining and TRITC staining, and HBV particles were identified. RT-PCR results showed that the 403 bp PCR products corresponding to the amplified hepatitis B S gene fragment were observed in CD34+ HSCs infected by HBV. In addition, supernatant and intracellular HBV DNA increased with the proliferation of CD34+ HSCs. Similar results were obtained from intracellular HBsAg quantification tests. In addition, HBV DNA levels both in cells and in supernatants of CD34+ PBSCs increased proportionally, and the increments of HBV DNA in the supernatants paralleled those found in cells. CONCLUSIONS HBV can replicate in CD34+ HSCs in cord blood or peripheral blood of chronic HBV carriers.

HCV-Induced Oxidative Stress: Battlefield-Winning Strategy

About 150 million people worldwide are chronically infected with hepatitis C virus (HCV). The persistence of the infection is controlled by several mechanisms including the induction of oxidative stress. HCV relies on this strategy to redirect lipid metabolism machinery and escape immune response. The 3β-hydroxysterol Δ24-reductase (DHCR24) is one of the newly discovered host markers of oxidative stress. This protein, as HCV-induced oxidative stress responsive protein, may play a critical role in the pathogenesis of HCV chronic infection and associated liver diseases, when aberrantly expressed. The sustained expression of DHCR24 in response to HCV-induced oxidative stress results in suppression of nuclear p53 activity by blocking its acetylation and increasing its interaction with MDM2 in the cytoplasm leading to its degradation, which may induce hepatocarcinogenesis.

Effects of hepatitis B virus X protein on human T cell cytokines

Chronic infection with hepatitis B virus (HBV) plays a significant role in hepatocellular carcinoma development. To investigate the effect of hepatitis B virus X protein (HBx) on inflammatory cytokines of human T cell, a eukaryotic expression vector, HBx-pEGFP-C1, was constructed and transfected into the Jurkat human T-cell line. Jurkat cells were transfected transiently using Lipofectamine 2000 and activated by phytohemagglutinin (PHA). Interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), IL-4, IL-10, IL-13, and IL-14 mRNA was measured. The results showed that the vector HBx-pEGFP-C1 was successfully constructed, and HBx was expressed in Jurkat cells. Compared with a control group, mRNA of IL-1β and TNF-α was significantly elevated in the HBx-pEGFP-C1 group (p < 0.05), while IL-4, IL-10, IL-13, and IL-14 mRNA was decreased (p < 0.05). Therefore, transient overexpression of HBx promoted PHA-induced pro-inflammatory cytokine secretion and repressed anti-inflammatory cytokine secretion in human T cells.

Hepatitis C virus activates Bcl-2 and MMP-2 expression through multiple cellular signaling pathways

Hepatitis C virus (HCV) infection is associated with numerous liver diseases and causes serious global health problems, but the mechanisms underlying the pathogenesis of HCV infections remain largely unknown. In this study, we demonstrate that signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase-2 (MMP-2), and B-cell lymphoma 2 (Bcl-2) are significantly stimulated in HCV-infected patients. We further show that HCV activates STAT3, MMP-2, Bcl-2, extracellular regulated protein kinase (ERK), and c-Jun N-terminal kinase (JNK) in infected Huh7.5.1 cells. Functional screening of HCV proteins revealed that nonstructural protein 4B (NS4B) is responsible for the activation of MMP-2 and Bcl-2 by stimulating STAT3 through repression of the suppressor of cytokine signaling 3 (SOCS3). Our results also demonstrate that multiple signaling cascades, including several members of the protein kinase C (PKC) family, JNK, ERK, and STAT3, play critical roles in the activation of MMP-2 and Bcl-2 mediated by NS4B. Further studies revealed that the C-terminal domain (CTD) of NS4B is sufficient for the activation of STAT3, JNK, ERK, MMP-2, and Bcl-2. We also show that amino acids 227 to 250 of NS4B are essential for regulation of STAT3, JNK, ERK, MMP-2, and Bcl-2, and among them, three residues (237L, 239S, and 245L) are crucial for this regulation. Thus, we reveal a novel mechanism underlying HCV pathogenesis in which multiple intracellular signaling cascades are cooperatively involved in the activation of two important cellular factors, MMP-2 and Bcl-2, in response to HCV infection.

Inhibitory effects of cyclosporine on human regulatory T cells in vitro

BACKGROUND

Inevitable hepatitis C virus (HCV) recurrence after liver transplantation is a major barrier to the survival of a transplanted liver. It may be promoted by immunosuppression and the emergence of CD4+CD25+ regulatory T cells (Treg). Treg cells can mediate the induction and maintenance of immunological self-tolerance as well as transplant tolerance. We investigated the effects of cyclosporine (CsA), a widely used immunosuppressive agent, on human CD4+CD25+ Treg cells.

METHODS

Human CD4+CD25+ cells isolated from healthy donors were cultured in the presence of 40 or 400 ng/mL CsA. The suppressive activity of Treg was assessed in mixed leukocyte reactions (MLR) using CD25+ and autologous activated peripheral blood mononuclear cells (PBMC). Phenotype analysis (flow cytometric, Q-PCR) and cytokine production (ELISA) of Treg cells were then performed on cultures.

RESULTS

CsA (40 or 400 ng/mL) inhibited the proliferative capacity of PBMC and CD4+CD25+ Treg in a dose-dependent manner. Interestingly, addition of 40 ng/mL CsA in MLR impaired the suppressive activity of CD4+CD25+ cells, whereas a higher dose of CsA had no effect on Treg function. It appears that a therapeutic dose of CsA (40 ng/mL) did not change the phenotype of CD4+CD25+ T cells, but altered Treg activity by switching the regulatory to an inflammatory cytokine profile.

CONCLUSION

CsA significantly impaired the function of CD4+CD25+ Treg cells by inducing interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) secretion. The present studies suggested that CsA may block the induction of immune tolerance and decrease the risk of hepatitis C recurrence.

The hepatitis C virus enigma

Hepatitis C virus (HCV) has a high propensity to establish chronic infection with end-stage liver disease. The high turnover of virus particles and high transcription error rates due to lack of proof-reading function of the viral polymerase imply that HCV exists as quasispecies, thus enabling the virus to evade the host immune response. Clearance of the virus is characterized by a multispecific, vigorous and persistent T-cell response, whereas T-cell responses are weak, narrow and transient in patients who develop chronic infection. At present, standard treatment is a combination of pegylated interferon-alpha and ribavirin, with a sustained viral response rate of 40-80%, depending on genotype. The mechanisms for the observed synergistic effects of the two drugs are still not known in detail, but in addition to direct antiviral mechanisms, the immunomodulatory effects of both drugs seem to be important, with a shift from Th2- to Th1-cytokine profiles in successfully treated patients. This article describes virus-host relations in the natural course of HCV infection and during treatment.

Enlarged lymph nodes in porta hepatis: sonographic sign of chronic hepatitis B and C infections

PURPOSE

Enlarged lymph nodes in the hepatoduodenal ligament are prevalent in chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV); however, the clinical significance of this sonographic finding in an endemic area is unknown.

METHODS

Six hundred outpatients were categorized into 4 groups (nonviral, HBV, HCV, and HBV and HCV) using viral markers. The prevalence and size of enlarged lymph nodes were compared. Correlation between clinical parameters and nodal size was evaluated.

RESULTS

The incidence of detectable nodes in both the HBV group and the HCV group was significantly increased (56.9% and 69.4%, respectively; both p < 0.001) compared with the nonviral group; this rate was independent of aminotransferase levels. Nodal width was the only significant parameter when viral and nonviral groups were compared (p < 0.05). If a width of more than 5 mm was used to predict HBV or HCV infection, the positive predictive rate was 88% and the specificity was 89%.

CONCLUSIONS

Lymph nodes in the hepatoduodenal ligament, especially those wider than 5 mm, suggest chronic HBV or HCV infection instead of only chronic hepatitis, especially in an endemic area such as Taiwan.

Cyclosporine versus tacrolimus in patients with HCV infection after liver transplantation: Effects on virus replication and recurrent hepatitis

AIM: To determine the effects of the calcineurin inhibitors, cyclosporine and tacrolimus, on hepatitis C virus (HCV) replication and activity of recurrent hepatitis C in patients post liver transplantation.

METHODS: The data of a cohort of 107 patients who received liver transplantation for HCV-associated liver cirrhosis between 1999 and 2003 in our center were retrospectively analyzed. The level of serum HCV-RNA and the activity of recurrent hepatitis were compared between 47 patients who received either cyclosporine or tacrolimus as the primary immunosuppressive agent and an otherwise similar immunosuppressive regimen which did not lead to biliary complications within the first 12 mo after transplantation.

RESULTS: HCV-RNA increased within 3 mo after transplantation but the differences between the cyclosporine group and the tacrolimus group were insignificant (P = 0.49 at 12 mo). In addition, recurrent hepatitis as determined by serum transaminases and histological grading of portal inflammation and fibrosis showed no significant difference after 12 mo (P = 0.34).

CONCLUSION: Cyclosporine or tacrolimus as a primary immunosuppressive agent does not influence the induction or severity of recurrent hepatitis in HCV-infected patients after liver transplantation.

Clinical consequences of hepatitis C virus infection

Hepatitis C virus (HCV) is a positive strand RNA virus that belongs to the Hepacivirinae genus within the Flaviviridae family. HCV infection has a wide spectrum of cellular tropism and clinical presentations. This has major impacts in terms of pathogenesis and diagnosis. Consequently, a wide range of clinical consequences characterises this viral infection, including asymptomatic chronic carriage, acute hepatitis, chronic hepatitis, cirrhosis, hepatocellular carcinoma and extrahepatic manifestations. The latter are commonly observed and may represent the first sign of the disease. A better knowledge of the pathobiology of HCV and its clinical consequences will be important for developing better treatment strategies to cure HCV infection and extrahepatic manifestations.

The hepatitis B virus X protein binds to and activates the NH(2)-terminal trans-activation domain of nuclear factor of activated T cells-1

We have previously reported that the hepatitis B virus X protein (HBx) activates nuclear factor of activated T cells (NF-AT), a key regulator of the immune system, by a calcium/calcineurin-dependent pathway, involving dephosphorylation and nuclear translocation of this transcription factor. In addition, we showed that HBx synergizes with potent calcium-mobilizing stimuli to activate NF-AT-dependent transcription, suggesting that additional mechanisms might also be operative in the activation of NF-AT by HBx. Here we demonstrate that HBx activates the NH(2)-terminal transcription activation domain (TAD) of NF-AT1 by a mechanism involving protein-protein interaction. Targeting of HBx to the nucleus did not affect its ability to induce the transcriptional activity of NF-AT1. In contrast, mutations of HBx affecting its functional interaction with general transcription factors abrogated the HBx-induced activity of NF-AT1. Together these results indicate that HBx may exert its function by acting as a nuclear coactivator of NF-AT1.

High seroprotection rate induced by low doses of a recombinant hepatitis B vaccine in healthy Iranian neonates

Low-dose vaccination has been proposed as a cost-saving strategy to implement mass vaccination of neonates with hepatitis B (HB) vaccine, world-wide, particularly in developing countries. The effectiveness of low vaccine doses, however, needs to be evaluated and verified in newborns from different ethnic backgrounds. In this study, a recombinant HB vaccine (Heberbiovac) was administered in three different doses, including the standard 10 microg together with 5 and 2.5 microg to three groups of healthy Iranian neonates. Each group, consisting of 230-260 subjects, received triple doses of vaccine given i.m. at 0, 1.5 and 9 month intervals. Serum samples were collected 2-4 weeks after completion of vaccination, and anti-HBs antibody was quantitated by a sandwich ELISA. Seroprotection (anti-HBs>10 IU/L) was detected in 92, 97.4 and 96.1% of 2.5, 5 and 10 microg vaccine dose recipients, with geometric mean titer (GMT) of 4502, 5824 and 6104 IU/L, respectively. No significant differences were observed in seroprotection rate and GMT between the 10 and 5 microg dose recipients. Both parameters, however, were significantly lower in neonates vaccinated with a 2.5 microg vaccine dose (P<0.05 and P<0.001, respectively). These findings indicate induction of a strong protective immune response in healthy Iranian neonates by a low dose (5 microg) of the recombinant HB vaccine.

Detection of hepatitis C virus RNA in alpha interferon derived from in vitro culture of leukocytes of human origin

In order to assure the virological safety of blood products, in addition to serological testing of individual donations and virus inactivation steps undertaken during manufacture, routine PCR testing for HCV RNA of starting materials (plasma, cells), intermediates or final product is necessary. The aim of this study was to determine the rate of HCV RNA positive batches of human native leukocyte interferon during large-scale production. Our findings indicate the presence of HCV RNA in 6.1% batches despite acidification of intermediates in order to inactivate Sendai virus.

HBV viral load within subpopulations of peripheral blood mononuclear cells in HBV infection using limiting dilution PCR

Extrahepatic viral load in peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B virus (HBV) is still under debate. In this study, HBV infection rates and viral titers were examined within all PBMC subpopulations using limiting dilution-PCR (LD-PCR). PBMCs of patients with acute or chronic hepatitis B were separated by magnetic beads in monocytes, B-cells, CD4+ T-cells, CD8+ T-cells, and NK cells. Using two-round nested PCR, HBV-DNA sequences were detected in all patients examined within each PBMC subpopulation. The frequencies of HBV-positive cells and viral loads were calculated by Poisson analysis of HBV PCR results from serial dilutions of cells and cell lysates. Highest infection rates were found in monocytes and B-cells followed by CD8 + T-cells, NK cells, and CD4+ T-cells. Concerning all subsets, frequencies of HBV-positive cells were 50- to 500-fold higher in chronic than in acute hepatitis B. Viral loads were mostly estimated at about one HBV genome per HBV-positive cell. Moreover, slightly elevated HBV titers were seen in B-cells, CD4+ T-cells, and NK cells in both acute and chronic hepatitis B. It was demonstrated that beside a generally more latent HBV infection in PBMCs, elevated HBV titers point to replication or selective viral uptake within particular PBMC subsets. Therefore, the data suggest that HBV-infected PBMCs may participate in persistence of HBV.

Differential antigen-processing pathways of the hepatitis B virus e and core proteins

BACKGROUND & AIMS

Hepatitis B e antigen (HBeAg) and hepatitis B core antigen (HBcAg) seem to play different roles in the induction and regulation of the antiviral immune response, although the two antigens share all major CD4(+) T-cell epitopes, and these epitopes can be processed from both antigens via the exogenous antigen-presenting pathway. The aim of this study was to test the ability of antigen-presenting cells to present epitopes from endogenously synthesized HBcAg/HBeAg on HLA class II molecules.

METHODS

Lymphoblastoid cell lines infected with recombinant vaccinia viruses containing various HBcAg or HBeAg constructs and stable transfectants were tested for their ability to stimulate HBcAg/HBeAg-specific CD4(+) T-cell clones.

RESULTS

Only antigen-presenting cells infected with HBeAg constructs but not those infected with HBcAg constructs were able to stimulate HBcAg/HBeAg-specific CD4(+) T-cell clones. T-cell activation by HBeAg constructs was completely inhibited by brefeldin A but not affected by chloroquin. In contrast, T-cell activation by exogenous, recombinant HBcAg was inhibited by chloroquin but not by brefeldin A.

CONCLUSIONS

The findings indicate that processing and HLA class II-associated presentation of endogenously synthesized HBeAg in virus-infected cells, including hepatocytes, may occur. This mechanism may be involved in the regulation of the CD4(+) T-cell response to HBcAg/HBeAg.

Hepatitis C virus infection, mixed cryoglobulinemia, and non-Hodgkin's lymphoma: an emerging picture

Hepatitis C virus (HCV) is a single-stranded RNA agent which expresses its genetic informations in the form of a single, large polyprotein encoded by an open reading frame (ORF) that extends through most of its genomic RNA. Proteolytic cleavage of the ORF product is essential for the virogenesis and the production of viral progeny. HCV is responsible for chronic liver disease, cirrhosis and possibly hepatocellular carcinoma. Viral persistence is considered the greatest problem in the management of HCV infection. It may result from several mechanisms, two of which are established. In the first, the high rate of genetic variations during viral replication results in the production of mutants capable of escaping the immune attack. In the second, the virus infects cells of the immune system itself, which represent a privileged site that cannot be reached by virus-specific T cell response. Involvement of lymphoid cells in the early stages of HCV infection may provide insight into the pathobiologic patterns of extrahepatic dissemination (lymph nodes, major salivary glands, kidneys, blood vessels). Dissemination of HCV-infected lymphoid cells throughout the organism is likely to maintain a mobile and extensive reservoir of the virus. In this respect, extrahepatic sites may act as a source of continuous reinfection of hepatocytes. Studies of intrahepatic B lymphocytes indicate that they are infected with HCV, clonally expanded and activated to secrete IgM molecules with rheumatoid factor activity. This strongly suggests that HCV directly stimulates B cell expansion, which may result in an indolent stage of lymphoproliferation (i.e., mixed cryoglobulinemia) or in frank B cell non-Hodgkin's lymphoma (NHL). The frequency of NHL, however, is much lower than that of HCV infection, suggesting that HCV alone is not able to induce tumors and that cellular events, in addition to the presence of virus and virus-encoded products, are necessary in order to obtain a malignant B cell phenotype. The demonstration of HCV productive infection in bone marrow-recruited and circulating pluripotent hematopoietic CD34+ stem cells indicates that HCV replication occurs in the early differentiation stages of hematopoietic progenitors. These are stable cell populations and are likely to represent the initial site of infection and a continuous source of virus production.

Activation of the envelope proteins by a metalloproteinase enables attachment and entry of the hepatitis B virus into T-lymphocyte

Previously, we identified an HBV binding factor (HBV-BF), a 50-kDa serum glycoprotein which interacts with HBV envelope proteins and which is also located in the membrane of normal human hepatocyte (A. Budkowska et al. (1993) J. Virol. 67, 4316). Here we show that HBV-BF is a neutral metalloproteinase which shares substrate specificity and properties with a newly described family of membrane type matrix metalloproteinases. HBV-BF treatment of the HBV resulted in the cleavage of the N-terminal part of the middle HBV envelope protein at the pre-S2(136-141) amino acid sequence VRGLYF/L (containing a single arginine cleavage site). HBV-BF affected the reactivity of the large HBV protein with pre-S1-specific MAbs, probably inducing the conformational change of the pre-S1 domain. The HBV-BF-digested virus remained morphologically intact with unchanged S antigenic determinants. The structural modifications of the viral envelope proteins induced by HBV-BF enabled cell membrane attachment and viral entry into the T-lymphocyte. Both processes were blocked by the metalloproteinase inhibitor 1,10 phenanthroline. Thus, the host-dependent proteolytic activation of the envelope proteins seems to be essential for the HBV entry into the cell. HBV-BF under a membrane bound or a secreted form could be (one of) the molecule(s) responsible for the HBV proteolytic activation.

Selective unresponsiveness to HBsAg vaccine in newborns related with an in utero passage of hepatitis B virus DNA

Thirty four out of 158 (22%) newborns to mothers chronically infected by the hepatitis B virus (HBV) did not produce antibodies (Ab) to HBsAg 1 month after the last injection of the HBV vaccine supplemented with HBV specific immunoglobulins. At birth, HBV genome was detected by polymerase chain reaction (PCR) in the peripheral blood mononuclear cells (PBMC) of a large majority (28 out of 34) of these non-responder newborns but never in the other newborns who responded to the HBsAg vaccine. HBV genome was detected in serum, only in some cases (nine out of 34) and never in the absence of HBV DNA in PBMC. For nine out of 14 followed newborns, the absence of response was transitory since anti-HBs Abs appeared after 15 months, without booster, while the HBV genome had disappeared. Unresponsiveness was specific to the HBV envelope protein since all late responders and 15-months-non-responders to the HBsAg vaccine produced normal levels of Abs to the three poliovirus serotypes, to tetanus toxoid and to the pneumococcus polysaccharides. An in utero induced immune tolerance to low doses of HBsAg appears as the most plausible hypothesis to explain this unresponsiveness to HBV vaccine.

Quantification of hepatitis C virus RNA in peripheral blood mononuclear cells: a comparison between patients chronically infected by HCV and patients coinfected by HIV

In patients chronically infected by hepatitis C virus (HCV), peripheral blood mononuclear cells (PBMCs) were shown to be targets for virus replication and in those coinfected with HIV, HCV viraemia was considerably increased. The purpose of this study was to quantify HCV RNA in PBMCs from 25 patients infected by HCV and from 25 patients coinfected by HCV and HIV. We used the branched DNA assay after extraction of total RNA on 5 x 10(6) cells to quantify HCV RNA, and the Inno LiPA assay to determine the HCV genotype. HCV RNA in PBMCs could be quantified in 8/25 patients in each group, but the HCV RNA concentration was very low in comparison with viraemia, since the highest result was 8.1 x 10(4) Eq genome/10(6) cells. In 10 ml of total blood, there was approximately 100 to 5,000 times less HCV RNA in PBMCs than in the plasma. It is therefore likely that PBMCs play only a minor part in the viral load present in the plasma. There was no preferential genotype associated with quantifiable HCV RNA in the PBMCs. In the case of HIV coinfection, there was no increase in the HCV-RNA concentration in PBMCs that could explain the increased viraemia observed in these patients. On the contrary, HCV RNA could not even be detected by RT-PCR in some of our coinfected patients.

Detection of hepatitis C virus (HCV) proteins by immunofluorescence and HCV RNA genomic sequences by non-isotopic in situ hybridization in bone marrow and peripheral blood mononuclear cells of chronically HCV-infected patients

Immunofluorescence (IF) to detect HCV antigens and non-isotopic in situ hybridization (NISH) to detect HCV RNA genome were carried out on bone marrow (BM) and peripheral blood (PB) mononuclear cells (MC) of 11 chronically HCV-infected patients. In four patients (36.4%) HCV antigens were detected in monocytes/macrophages as well as in B lymphocytes in both BMMC and PBMC. Positive T lymphocytes in BMMC were found in three of them, but only one patient showed positive T cells in PBMC. NISH invariably demonstrated minus and plus HCV RNA genomic strands either in monocytes/macrophages or B and T lymphocytes in BMMC and PBMC in the four HCV antigen-positive patients and in two further patients not expressing viral proteins in blood MC. IF signals appeared diffusely distributed within the cytoplasm, or as brilliant granules in distinct submembrane areas or else in cytoplasm membrane. Nuclei never stained. Similarly, NISH displayed HCV RNA accumulation restricted to MC cytoplasm only, nuclei being persistently negative. NISH, however, was unable to detect cell membrane signal. Infection of blood MC is a common event in naturally acquired HCV infection, since none of these patients was conditioned by immunomodulating or immunosuppressive therapies. No difference was found in terms of age, length of disease, anti-HCV immune response, type and severity of chronic liver damage between patients with HCV-infected MC and patients without cell infection. These results demonstrate that HCV can infect BMMC and PBMC that represent important extrahepatic sites of virus replication, and may help to explain the immunological abnormalities observed in chronic HCV carriers.