Cell culture systems for the hepatitis C virus

Since the discovery of HCV in 1989, the lack of a cell culture system has hampered research progress on this important human pathogen. No robust system has been obtained by empiric approaches, and HCV cell culture remained hypothetical until 2005. The construction of functional molecular clones has served as a starting point to reconstitute a consensus infectious cDNA that was able to transcribe infectious HCV RNAs as shown by intrahepatic inoculation in a chimpanzee. Other consen- sus clones have been selected and established in a hu- man hepatoma cell line as replicons, i.e. self-replicating subgenomic or genomic viral RNAs. However, these repli- cons did not support production of infectious virus. Inter- estingly, some full-length replicons could be established without adaptive mutations and one of them was able to replicate at very high levels and to release virus particles that are infectious in cell culture and in vivo. This new cell culture system represents a major breakthrough in the HCV field and should enable a broad range of basic and applied studies to be achieved.

Cloning of the non-structural gene 3 of hepatitis C virus and its inducible expression in cultured cells

AIM To study the inducible expression of hepatitis C virus ns3 gene (HCV ns3) in eukaryotic cells.METHODS The ns3 gene was obtained from plasmid pBns3 by polymerase chain reaction and inserted into the cloning vector pGEM-T. Then, the ns3 was subcloned into the vector pMSG to generate dexamethasone (DM)-inducible expression plasmid pMSG-ns3. CHO cells were transfected by pMSG-ns3 using calcium phosphate precipitation method and cultivated for 12 h-24 h. The transfected cells were induced with DM and the transient expression of NS3 protein was analyzed by ELISA and Western-blot methods.RESULTS After treated with 3×10-8mol/ L DM, the expression of NS3 was observed in the transfected CHO cells. A slightly higher level of NS3 was shown along with the time of DM treatment.CONCLUSION The inducible expressing vector pMSG-ns3 might be helpful for further studies of the characteristics of the ns3 gene in vivo.

Cladogynos orientalis Zipp. extracts inhibit cell culture-derived hepatitis C virus genotype 2a replication in Huh-7 cells through NS5B inhibition

Objective: To evaluate the potential anti-hepatitis C virus (HCV) activities of Cladogynos orientalis Zipp. ex Span and to investigate the molecular mode of action. Methods: Ethanolic and water extracts from various parts of Cladogynos orientalis were examined for cytotoxicity by MTT assay. Sub-cytotoxic concentrations of the extracts were used for further determining anti-HCV activity using cell culture-derived HCV genotype 2a propagated in HepaRG cell line. Immunofluorescence assay was performed to observe the effect on viruses at the pre-entry step. Mode of action at the post-entry step was investigated for the viral RNA and protein expressions by real time RT-PCR and Western blotting assays, respectively. Results: Although Cladogynos orientalis water extracts exhibited lower cytotoxicity than ethanolic extracts, all ethanolic extracts from roots, stems, and leaves of Cladogynos orientalis exhibited higher anti-HCV activities than water extracts. The highest anti-HCV activity was observed in infected cells treated with the extracts 5 h after absorption. No extracts showed pre-viral entry effect. At the post-viral entry step, only leaf ethanolic extracts inhibited NS5B expression, while all extracts did not inhibit HCV NS3 expression. Conclusions: Cladogynos orientalis ethanolic extracts could be further studied and the major active compound needs to be identified as a promising source for anti-HCV agents.

Hepatitis C virus infection of human hepatoma cell line 7721 in vitro

AIM: To establish a cell culture system with long-term replication of hepatitis C virus in vitro. METHODS: Human hepatoma cell line 7721 was tested for its susceptibility to HCV by incubating with a serum from a patient with chronic hepatitis C. Cells and supernatant were harvested at various phases during the culturing periods. The presence of HCV RNA, the expression of HCV antigens in cells and/or supernatant were examined by RTPCR, in situ hybridization and immunohistochemistry respectively. RESULTS: The intracellular HCV RNA was first detected on d2 after infection and then could be intermittently detected in both cells and supernatant over a period of at least three months. The expression of HCV NS3,CP10 antigens could be observed in cells. The fresh cells could be infected by supernatant from cultured infected cells and the transmission of viral genome from HCV-infected 7721 cells to PBMCs was also observed. CONCLUSION: The hepatoma line 7721 is not only susceptible to HCV but also supports its long-term replication in vitro.

Cytokeratin 8 is increased in hepatitis C virus cells and its ectopic expression induces apoptosis of SMMC7721 cells

AIM:To investigate cytokeratin 8(CK8)overexpression during hepatitis C virus(HCV)infection and its pathogenesis,and the effect of ectopic CK8 expression on hepatoma cell lines.METHODS:We successfully established an in vitro HCV cell culture system(HCVcc)to investigate the different expression profiles of CK8 in Huh-7-HCV and Huh-7.5-HCV cells.The expression of CK8 at the mRNA level was determined by real-time polymerase chain reaction(RT-PCR).The expression of CK8 at the protein level was evaluated by Western blotting.We then constructed a eukaryotic expression combination vector containing the coding sequence of human full length CK8 gene.CK8cDNA was amplified by reverse transcription-PCR and inserted into pEGFP-C1 and the positive clone pEGFPCK8 was obtained.After confirming the sequence,the recombinant plasmid was transfected into SMMC7721cells with lipofectamine2000 and CK8 expression was detected using inverted fluorescence microscopy,RTPCR and Western blotting.Besides,we identified biological function of CK8 on SMMC7721 cells,including cell proliferation,cell cycle and apoptosis detection.RESULTS:RT-PCR showed that the expression level of CK8 in Huh-7-HCV and Huh-7.5-HCV cells was 2.88and 2.95 times higher than in control cells.Western blot showed that CK8 expression in Huh-7-HCV and Huh-7.5-HCV cells was 2.53 and 3.26 times higher than that in control cells,respectively.We found that CK8at mRNA and protein levels were both significantly increased in HCVcc.CK8 was up-regulated in SMMC7721cells.CK8 expression at the mRNA level was significantly upregulated in SMMC7721/pEGFP-CK8 cells.CK8expression in SMMC7721/pEGFP-CK8 cells was 2.69times higher than in SMMC7721 cells,and was 2.64times higher than in SMMC7721/pEGFP-C1 cells.CK8expression at the protein level in SMMC7721/pEGFPCK8 cells was 2.46 times higher than in SMMC7721cells,and was 2.29 times higher than in SMMC7721/pEGFP-C1 cells.Further analysis demonstrated that forced expression of CK8 slowed cell growth and induced apoptosis of SMMC7721 cells.CONCLUSION:CK8 up-regulation might have a functional role in HCV infection and pathogenesis,and could be a promising target for the treatment of HCV infection.

Ribavirin contributes to eradicate hepatitis C virus through polarization of T helper 1/2 cell balance into T helper 1 dominance

The mechanism of action of ribavirin(RBV) as an immunomodulatory and antiviral agent and its clinical significance in the future treatment of patients with hepatitis C virus(HCV) infection are reviewed.RBV up-regulates type 1 and/or 2 cytokines to modulate the T helper(Th) 1/2 cell balance to Th1 dominance.Examination of co-stimulatory signaling indicated that RBV down-modulates inducible co-stimulator on Th cells,which contributes to differentiating na?ve Th cells into Th2 cells while reducing their interleukin-10 production.The effects on T-regulatory(Treg) cells were also investigated,and RBV inhibited the differentiation of na?ve Th cells into adaptive Treg cells by downmodulating forkhead box-P3.These findings indicate that RBV mainly down-regulates the activity of Th2 cells,resulting in the maintenance of Th1 activity that contributes to abrogating HCV-infected hepatocytes.Although an interferon-free treatment regimen exhibits almost the same efficacy without serious complications,regimens with RBV will be still be used because of their ability to facilitate the cellular immune response,which may contribute to reducing the development of hepatocellular carcinogenesis in patients infected with HCV.

Recurrent hepatitis C virus after transplant and the importance of plasma cells on biopsy

Hepatitis C virus(HCV) is the leading indication for liver transplantation in the United States.It recurs universally after transplant but the rate of fibrosis and the development of graft failure is variable.Different donor and recipient features have been demonstrated to impact fibrosis.Plasma cell hepatitis,a histologic finding,is one feature associated with poor graft and patient outcomes.The pathogenic mechanism resulting in plasma cell hepatitis is poorly understood,with evidence suggesting a role for both the HCV and the immune system.A recent publication described plasma cell hepatitis in a larger context of immune medicated graft dysfunction in transplant recipients receiving interferon based therapy.This manuscript will highlight the topic of plasma cell hepatitis and provide commentary on the lack of recognition,the data regarding pathophysiologic mechanisms and the potential management options.

Circulating tumor and cancer stem cells in hepatitis C virusassociated liver disease

AIM: To assess the role of circulating tumor cells (CTCs) and cancer stem cells (CSCs) in hepatitis C virus (HCV)-associated liver disease.

Hepatitis C virus-related B cell subtypes in non Hodgkin's lymphoma

AIM:To evaluate if indolent B cell-non Hodgkin's lymphoma(B-NHL) and diffuse large B-cell lymphoma(DLBCL) in hepatitis C virus(HCV) positive patients could have different biological and clinical characteristics requiring different management strategies.METHODS:A group of 24 HCV related B-NHL patients(11 indolent,13 DLBCL) in whom the biological and clinical characteristics were described and confronted.Patients with DLBCL were managed with the standard of care of treatment.Patients with indolent HCV-related B-NHL were managed with antiviral treatment pegylated interferon plus ribavirin and their course observed.The outcomes of the different approaches were compared.RESULTS:Patients with DLBCL had a shorter duration of HCV infection and a higher prevalence of HCV genotype 1 compared to patients with indolent B-NHL in which HCV genotype 2 was the more frequent genotype.Five of the 9 patients with indolent HCV-relatedB-NHL treated with only antiviral therapy,achieved a complete response of their onco-haematological disease(55%).Seven of the 13 DLBCL patients treated with immunochemotheraphy obtained a complete response(54%).CONCLUSION:HCV genotypes and duration of HCV infection differed between B-NHL subtypes.Indolent lymphomas can be managed with antiviral treatment,while DLBCL is not affected by the HCV infection.

Induction of hepatitis C virus-specific cytotoxic T and B cell responses by dendritic cells expressing a modified antigen targeting receptor

AIM: To find a novel antigen (Ag) presentation strategy to improve the immune responses induced by dendritic cell (DC)vaccine expressing hepatitis C virus (HCV) core antigen (pcDNA3HCV C-Fc) in Balb/c mice (H-2d).METHODS: pcDNA3HCV C-Fc plasmid and eukaryotic expression vector pcDNA3 were injected into mice sc. Immune responses to pcDNA3HCV C-Fc were studied. Meanwhile the effect of pcDNA3HCV C-Fc on anti-translated subcutaneous tumor of SP2/0 cells stably expressing HCV C Ag (SP2/0-HCV C-FC) was also studied. Anti-HCV C in serum was detected by enzyme-linked immunoadsordent assay (ELISA) and HCV specific cytotoxic T lymphocyte (CTL) activity was measured by LDH release assay. After 3 wk of DNA immunization,the cells of SP2/0-HCV C-FC were inoculated into mice subcutaneously and tumor growth was measured every 5 d.The survival rate and living time of mice were also calculated.RESULTS: After 4 wk of DC immunization, the A450 nm values of sera in mice immunized with pcDNA3HCV C-Fc-DC and pcDNA3-DC were 0.56±0.17 and 0.12±0.03 respectively. The antibody titres in mice codeliveried with pcDNA3HCV C-Fc with DC were significantly higher than those of mice injected with pcDNA3-DC. The HCV specific CTL activities in mice coinjected with DC and pcDNA3HCV C-Fc or empty expression vectors were(73.2±3.1) % and (24.4±8.8) %, which were significantly higher than those of mice injected with water.The DC vaccine could evidently inhibit tumor growth, prolong the survival time of mice and improve the survival rate of mice and these effects could be improved by HCV C-Fc (pcDNA3HCV C-Fc) gene codelivered.CONCLUSION: DC vaccine has a strong antigenicity in humoral and cellular immunities, which can be promoted by transduced pcDNA3HCV C-Fc expressing HCV C or Fc.Thus, pcDNA3HCV C-Fc-transduced DCs may be a promising candidate for a CTL-based vaccine against HCV.

CD4+ T cell responses in hepatitis C virus infection

Hepatitis C virus (HCV) infection is a major cause of liver damage, with virus-induced end-stage disease such as liver cirrhosis and hepatocellular carcinoma resulting in a high rate of morbidity and mortality worldwide. Evidence that CD4+ T cell responses to HCV play an important role in the outcome of acute infection has been shown in several studies. However, the mechanisms behind viral persistence and the failure of CD4+ T cell responses to contain virus are poorly understood. During chronic HCV infection, HCV-specific CD4+ T cell responses are rela- tively weak or absent whereas in resolved infection these responses are vigorous and multispecific. Persons with a T-helper type I profile, which promotes cellular effec- tor mechanisms are thought to be more likely to experi- ence viral clearance, but the overall role of these cells in the immunopathogenesis of chronic liver disease is not known. To define this, much more data is required on the function and specificity of virus-specific CD4+ T cells, especially in the early phases of acute disease and in the liver during chronic infection. The role and possible mechanisms of action of CD4+ T cell responses in deter- mining the outcome of acute and chronic HCV infection will be discussed in this review.

Liver angiogenesis as a risk factor for hepatocellularcarcinoma development in hepatitis C virus cirrhotic patients

AIM： To evaluate the predictive value of hepatocyte proliferation and hepatic angiogenesis for the occurrence of Hepatocellular carcinoma （HCC） in hepatitis C virus （HCV） cirrhotic patients.METHODS： One hundred-five patients （69 males, 36 females; age range, 51-90 year; median 66 year） with biopsy proven HCV cirrhosis were prospectively monitored for HCC occurrence for a median time of 64 too. Angiogenesis was assessed by using microvessel density （MVD）, hepatocyte turnover by MIB1 and PCNA indexes at inclusion in liver biopsies.RESULTS： Forty six patients （43.8%） developed HCC after a median time of 55 （6-120） mo while 59 （56.2%） did not. Patients were divided into two groups according to the median value of each index. The difference between patients with low （median MVD = 3; range 0-20） and high （median MVD = 7; range 1-24） MVD was statist（caUy s（gn（ficant （χ^2= 22.06; P 〈 0.0001） wh（ch was not the case for MIB1 or PCNA （MIB-I： χ^2 = 1.41; P = 0.2351; PCNA： χ^2 = 1.27; P = 0.2589）. The median MVD was higher in patients who developed HCC than in those who did not. HOe-free interval was significantly longer in patients with the MVD ≤ 4 （P = 0.0006）. No relationship was found between MIB1 or PCNA and MVD （MIB-1 r^2 = 0.00007116, P = 0.9281; PCNA： P =0.001950; P = 0.6692）. MVD only was able to predict the occurrence of HCC in these patients. Among other known risk factors for HCC, only male sex was statistically associated with an increased risk. CONCLUSION： Liver angiogenesis has a role for in HCV- related liver carcinogenesis and for defining patients at higher risk.

HBsAg stimulates NKG2D receptor expression on natural killer cellsand inhibits hepatitis C virus replication

Background： Higher hepatitis B surface antigen （HBsAg） facilitates hepatitis C virus （HCV） clearance inpatients with hepatitis B virus （HBV）/HCV co-infection. We investigated the effect of exogenous HBsAgon the inhibition of HCV replication mediated by natural killer （NK） cells.

CD4+ T cells and natural killer cells: Biomarkers for hepatic fibrosis in human immunodeficiency virus/hepatitis C virus-coinfected patients

AIM To characterize peripheral blood natural killer(NK) cells phenotypes by flow cytometry as potential biomarker of liver fibrosis in human immunodeficiency virus(HIV)/hepatitis C virus(HCV) coinfected patients.METHODS Peripheral mononuclear cells from 24 HIV/HCV(HBVnegative) coinfected and 5 HIV/HCV/HBV seronegative individuals were evaluated. HIV/HCV coinfected patients were divided in to groups: G1, patients with METAVIR F0-F2 and G2, patients with METAVIR F3-F4. NK surface cell staining was performed with: AntiCD3(APC/Cy7), anti-CD56(PE/Cy5), anti-CD57(APC), anti-CD25(PE), anti-CD69(FITC), anti-NKp30(PE), antiNKp46(PE/Cy7), anti-NKG2D(APC), anti-DNAM(FITC); anti-CD62L(PE/Cy7), anti-CCR7(PE), anti-TRAIL(PE), anti-Fas L(PE), anti CD94(FITC). Flow cytometry data acquisition was performed on BD FACSCanto, analyzed using Flow Jo software. Frequency of fluorescence was analyzed for all single markers. Clinical records were reviewed, and epidemiological and clinical data were obtained.RESULTS Samples from 11 patients were included in G1 and from 13 in G2. All patients were on ARV, with undetectable HIV viral load. Liver fibrosis was evaluated by transient elastography in 90% of the patients and with biopsy in 10% of the patients. Mean HCV viral load was(6.18 ± 0.7 log10). Even though, no major significant differences were observed between G1 and G2 regarding NK surface markers, it was found that patients with higher liver fibrosis presented statistically lower percentage of NK cells than individual with low to mild fibrosis and healthy controls(G2: 5.4% ± 2.3%, G1: 12.6% ± 8.2%, P = 0.002 and healthy controls 12.2% ± 2.7%, P = 0.008). It was also found that individuals with higher liver fibrosis presented lower CD4 LT count than those from G1(G2: 521 ± 312 cells/μL, G1: 770 ± 205 cells/μL; P = 0.035).CONCLUSION Higher levels of liver fibrosis were associated with lower percentage of NK cells and LTCD4+ count; and they may serve as noninvasive biomarkers of liver damage.

Hepatitis C virus core proteins derived from different quasispecies of genotype 1b inhibit the growth of Chang liver cells

AIM: To investigate the influence of different quasispecies of hepatitis C virus (HCV) genotype 1b core protein on growth of Chang liver cells. METHODS: Three eukaryotic expression plasmids (pEGFP-N1/core) that contained different quasispecies truncated core proteins of HCV genotype 1b were constructed. These were derived from tumor (T) and non- tumor (NT) tissues of a patient infected with HCV and C191 (HCV-J6). The core protein expression plasmids were transiently transfected into Chang liver cells. At different times, the cell cycle and apoptosis was assayed by flow cytometry, and cell proliferation was assayed by methyl thiazolyl tetrazolium (MTT) assay. RESULTS: The proportion of S-phase Chang liver cells transfected with pEGFP-N1/core was significantly lower than that of cells transfected with blank plasmid at three different times after transfection (all P < 0.05). The proliferation ratio of cells transfected with pEGFP-N1/corewas significantly lower than that of cells transfected with blank plasmid. Among three different quasispecies, T, NT and C191 core expression cells, there was no significant difference in the proportion of S- and G0/G1-phase cells. The percentage of apoptotic cells was highest for T (T > NT > C191), and apoptosis was increased in cells transfected with pEGFP-N1/core as the transfection time increased (72 h > 48 h > 24 h). CONCLUSION: These results suggest that HCV genotype 1b core protein induces apoptosis, and inhibits cell- cycle progression and proliferation of Chang liver cells. Different quasispecies core proteins of HCV genotype 1b might have some differences in the pathogenesis of HCV persistent infection and hepatocellular carcinoma.

Direct effects of hepatitis C virus on the lymphoid cells

It has been reported that the direct binding of hepatitis C virus(HCV)and/or the replication of HCV in the extrahepatic organs and,especially,lymphoid cells,might affect the pathogenesis of extrahepatic diseases with HCV infection.More than one decade ago,several reports described the existence of HCV-RNA in peripheral blood mononuclear cells.Moreover,many reports describing the existence of HCV in B lymphocytes and B cell lymphoma have been published.In addition to B lymphocytes,it was reported that HCV replication could be detected in T lymphocytes and T cell lines.Among the extrahepatic diseases with HCV infection,mixed cryoglobulinemia-related diseases and autoimmunerelated diseases are important for understanding the immunopathogensis of HCV persistent infection.Moreover,HCV persistent infection can cause malignant lymphoma.The biological significance of lymphotropic HCV has not yet become clear.However,several candidates have been considered for a long time.One is that lymphotropic HCV is an HCV reservoir that might contribute to the recurrence of HCV infection and difficultto-treat disease status.The other important issue is the carcinogenesis of the lymphoid cells and disturbances of the immune responses.Therefore,the extrahepatic diseases might be induced by direct interaction between HCV and lymphoid cells.In this article,we summarize various studies showing the direct effect of HCV on lymphoid cells and discuss the biological significance of lymphotropic HCV.

HepG2 cells support viral replication and gene expression of hepatitis C virus genotype 4 in vitro

AIM： TO establish a cell culture system with longterm replication of hepatitis C virus （HCV） genome and expression of viral antigens in vitro. METHODS： HepG2 cell line was tested for its susceptibility to HCV by incubation with a serum from a patient with chronic hepatitis C. Cells and supernatant were harvested at various time points during the culture. Culture supernatant was tested for its ability to infect na＇ive cells. The presence of minus （antisense） RNA strand, and the detection of core and E1 antigens in cells were examined by RT-PCR and immunological techniques （flow cytometry and Western blot） respectively. RESULTS： The intracellular HCV RNA was first detected on d 3 after infection and then could be consistently detected in both cells and supernatant over a period of at least three months. The fresh cells could be infected with supernatant from cultured infected cells. Flow cytometric analysis showed surface and intracellular HCV antigen expression using in house made polyclonal antibodies （anti-core, and anti-E1）. Western blot analysis showed the expression of a cluster of immunogenic peptides at molecular weights extended between 31 and 45 kDa in an one month old culture of infected cells whereas this cluster was undetectable in uninfected HepG2 cells. CONCLUSION： HepG2 cell line is not only susceptible to HCV infection but also supports its replication in vitro. Expression of HCV structural proteins can be detected in infected HepG2 cells. These cells are also capable of shedding viral particles into culture media which in turn become infectious to uninfected cells.

Genetic vaccination with Flt3-L and GM-CSF as adjuvants: Enhancement of cellular and humoral mmune responses that results in protective immunity in a murine model of hepatitis C virus infection

AIM： To investigate whether transfection of plasmid DNA encoding these cytokines enhances both humoral and cellular immune responses to hepatitis C virus （HCV） in a murine model. METHODS： We established a tumor model of HCV infection using syngenic mouse myeloma cells stably transfected with NS5. Co-vaccination of DNA encoding granulocyte macrophage colony-stimulating factor （GM- CSF） and Flt-3 ligand together with a plasmid encoding for the HCV NS5 protein was carried out. Mice were sacrificed 14 d after the last immunization event with collection of spleen cells and serum to determine humoral and cellular immune responses. RESULTS： Co-vaccination of DNA encoding GM-CSF and Fit-3 ligand together with a plasmid encoding for the HCV NS5 protein induced increased antibody responses and CD4＋ T cell proliferation to this protein, Vaccination with DNA encoding GM-CSF and FIt-3L promoted protection against tumor formation and/or reduction in mice co- immunized with cytokine-encoding DNA constructs, This suggests this strategy is capable of generating cytotoxic T lymphocyte activity in vivo, Following inoculation with plasmid DNA encoding Flt-3L, no increase in spleen size or in dendritic cell （DC） and natural killer cell numbers was observed. This was in contrast to a dramatic increase of both cell types after administration of recombinant Flt3-L in vivo. This suggests that vaccination with plasmid DNA encoding cytokines that regulate DC generation and mobilization may not promote unwanted side effects, such as autoimmunity, splenic fibrosis or hematopoietic malignancies that may occur with administration of recombinant forms of these proteins. CONCLUSION： Our data support the view that plasmid DNA vaccination is a promising approach for HCV immunization, and may provide a general adjuvant vaccination strategy against malignancies and other pathogens.

Mononuclear phagocyte system in hepatitis C virus infection

The mononuclear phagocyte system （MPS）, which con-sists of monocytes, dendritic cells （DCs）, and macro-phages, plays a vital role in the innate immune defense against pathogens. Hepatitis C virus （HCV） is effcient in evading the host immunity, thereby facilitating its devel-opment into chronic infection. Chronic HCV infection is the leading cause of end-stage liver diseases, liver cirrhosis, and hepatocellular carcinoma. Acquired im-mune response was regarded as the key factor to era-dicate HCV. However, innate immunity can regulate the acquired immune response. Innate immunity-derived cytokines shape the adaptive immunity by regulating T-cell differentiation, which determines the outcome of acute HCV infection. Inhibition of HCV-specific T-cell responses is one of the most important strategies for im-mune system evasion. It is meaningful to illustrate the role of innate immune response in HCV infection. With the MPS being the important factor in innate immunity, therefore, understanding the role of the MPS in HCV infection will shed light on the pathophysiology of chronic HCV infection. In this review, we outline the impact of HCV infection on the MPS and cytokine production. We discuss how HCV is detected by the MPS and describe the function and impairment of MPS components in HCV infection.

PI3K/SHIP2/PTEN pathway in cell polarity and hepatitis C virus pathogenesis

Hepatitis C virus(HCV) infects hepatocytes, polarized cells in the liver. Chronic HCV infection often leads to steatosis, fibrosis, cirrhosis and hepatocellular carcinoma, and it has been identified as the leading cause of liver transplantation worldwide. The HCV replication cycle is dependent on lipid metabolism and particularly an accumulation of lipid droplets in host cells. Phosphoinositides(PIs) are minor phospholipids enriched in different membranes and their levels are tightly regulated by specific PI kinases and phosphatases. PIs are implicated in a vast array of cellular responses that are central to morphogenesis, such as cytoskeletal changes, cytokinesis and the recruitment of downstream effectors to govern mechanisms involved in polarization and lumen formation. Important reviews of the literature identified phosphatidylinositol(Ptd Ins) 4-kinases, and their lipid products Ptd Ins(4)P, as critical regulators of the HCV life cycle. SH2-containing inositol polyphosphate 5-phosphatase(SHIP2), phosphoinositide 3-kinase(PI3K) and their lipid products Ptd Ins(3,4)P2 and Ptd Ins(3,4,5)P3, respectively, play an important role in the cell membrane and are key to the establishment of apicobasal polarity and lumen formation. In this review, we will focus on these new functions of PI3 K and SHIP2, and their deregulation by HCV, causing a disruption of apicobasal polarity, actin organization and extracellular matrix assembly. Finally we will highlight the involvement of this pathway in the event of insulin resistance and nonalcoholic fatty liver disease related to HCV infection.