Genetic analyses reveal a role for vitamin D insufficiency in HCV-associated hepatocellular carcinoma development

BACKGROUND

Vitamin D insufficiency has been associated with the occurrence of various types of cancer, but causal relationships remain elusive. We therefore aimed to determine the relationship between genetic determinants of vitamin D serum levels and the risk of developing hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC).

METHODOLOGY/PRINCIPAL FINDINGS

Associations between CYP2R1, GC, and DHCR7 genotypes that are determinants of reduced 25-hydroxyvitamin D (25[OH]D3) serum levels and the risk of HCV-related HCC development were investigated for 1279 chronic hepatitis C patients with HCC and 4325 without HCC, respectively. The well-known associations between CYP2R1 (rs1993116, rs10741657), GC (rs2282679), and DHCR7 (rs7944926, rs12785878) genotypes and 25(OH)D3 serum levels were also apparent in patients with chronic hepatitis C. The same genotypes of these single nucleotide polymorphisms (SNPs) that are associated with reduced 25(OH)D3 serum levels were found to be associated with HCV-related HCC (P = 0.07 [OR = 1.13, 95% CI = 0.99-1.28] for CYP2R1, P = 0.007 [OR = 1.56, 95% CI = 1.12-2.15] for GC, P = 0.003 [OR = 1.42, 95% CI = 1.13-1.78] for DHCR7; ORs for risk genotypes). In contrast, no association between these genetic variations and liver fibrosis progression rate (P>0.2 for each SNP) or outcome of standard therapy with pegylated interferon-α and ribavirin (P>0.2 for each SNP) was observed, suggesting a specific influence of the genetic determinants of 25(OH)D3 serum levels on hepatocarcinogenesis.

CONCLUSIONS/SIGNIFICANCE

Our data suggest a relatively weak but functionally relevant role for vitamin D in the prevention of HCV-related hepatocarcinogenesis.

Replication and infectivity of a novel genotype 1b hepatitis C virus clone

Hepatitis C virus infection is a major public health problem because of an estimated 170 million carriers worldwide. Genotype 1b is the major subtype of HCV in many countries and is resistant to interferon therapy. Study of the viral life cycle is important for understanding the mechanisms of interferon resistance of genotype 1b HCV strains. For such studies, genotype 1b HCV strains that can replicate and produce infectious virus particles in cultured cells are required. In the present study, we isolated HCV cDNA, which we named the NC1 strain, from a patient with acute severe hepatitis. Subgenomic replicon experiments revealed that several mutations enhanced the colony-formation efficiency of the NC1 replicon. The full-length NC1 genome with these adaptive mutations could replicate in cultured cells and produce infectious virus particles. The density gradient profile and morphology of the secreted virus particles were similar to those reported for the JFH-1 virus. Further introduction of a combination of mutations of the NS3 and NS5a regions into the NC1 mutants further enhanced secreted core protein levels and infectious virus titers in the culture medium of HCV-RNA-transfected cells. However, the virus infection efficiency was not sufficient for autonomous virus propagation in cultured cells. In conclusion, we established a novel cell culture-adapted genotype 1b HCV strain, termed NC1, which can produce infectious virus when the viral RNA is transfected into cells. This system provides an important opportunity for studying the life cycle of the genotype 1b HCV.

Serum ferritin levels are associated with a distinct phenotype of chronic hepatitis C poorly responding to pegylated interferon-alpha and ribavirin therapy

Elevated serum ferritin levels may reflect a systemic inflammatory state as well as increased iron storage, both of which may contribute to an unfavorable outcome of chronic hepatitis C (CHC). We therefore performed a comprehensive analysis of the role of serum ferritin and its genetic determinants in the pathogenesis and treatment of CHC. To this end, serum ferritin levels at baseline of therapy with pegylated interferon-alpha and ribavirin or before biopsy were correlated with clinical and histological features of chronic hepatitis C virus (HCV) infection, including necroinflammatory activity (N = 970), fibrosis (N = 980), steatosis (N = 886), and response to treatment (N = 876). The association between high serum ferritin levels (> median) and the endpoints was assessed by logistic regression. Moreover, a candidate gene as well as a genome-wide association study of serum ferritin were performed. We found that serum ferritin ≥ the sex-specific median was one of the strongest pretreatment predictors of treatment failure (univariate P < 0.0001, odds ratio [OR] = 0.45, 95% confidence interval [CI] = 0.34-0.60). This association remained highly significant in a multivariate analysis (P = 0.0002, OR = 0.35, 95% CI = 0.20-0.61), with an OR comparable to that of interleukin (IL)28B genotype. When patients with the unfavorable IL28B genotypes were stratified according to high versus low ferritin levels, SVR rates differed by > 30% in both HCV genotype 1- and genotype 3-infected patients (P < 0.001). Serum ferritin levels were also independently associated with severe liver fibrosis (P < 0.0001, OR = 2.67, 95% CI = 1.68-4.25) and steatosis (P = 0.002, OR = 2.29, 95% CI = 1.35-3.91), but not with necroinflammatory activity (P = 0.3). Genetic variations had only a limited impact on serum ferritin levels.

CONCLUSION

In patients with CHC, elevated serum ferritin levels are independently associated with advanced liver fibrosis, hepatic steatosis, and poor response to interferon-alpha-based therapy.

Lymphotropic hepatitis C virus has an interferon-resistant phenotype

Hepatitis C virus (HCV) infects and associates with B cells, leading to abnormal B-cell activation and development of lymphoproliferative and autoimmune disorders. This immune perturbation may in turn be associated with the resistance of HCV against the host immune system. The objective of this study was to analyse the effects of HCV infection of B cells on the efficacy of interferon (IFN)-based therapy. The study enrolled 102 patients with chronic hepatitis C who were treated with pegylated IFN plus ribavirin. HCV RNA titres in B cells were compared in patients with rapid viral responder (RVR) vs non-RVR, sustained viral responder (SVR) vs non-SVR and null viral responder (NVR) vs VR. The levels of HCV RNA in B cells were significantly higher in non-RVR, non-SVR and NVR groups. Association between the therapy outcome and the positive B-cell HCV RNA was also investigated in relation to other known viral and host factors. Multivariable analyses showed that the positive B-cell HCV RNA and the minor single-nucleotide polymorphism near the IL28B gene (rs8099917) were independent factors associated with NVR in patients infected with HCV genotype 1. When these two factors were combined, the sensitivity, specificity, positive and negative predictive values for NVR were 92.3%, 98.2%, 92.3% and 98.2%, respectively. Genotype 1 and the presence of one or no mutations in the IFN-sensitivity determining region were associated with higher levels of B-cell HCV RNA. B-cell-tropic HCV appears to have an IFN-resistant phenotype. B-cell HCV RNA positivity is a predictive factor for resistance to IFN-based therapy.

Thin-section CT findings of patients with acute Streptococcus pneumoniae pneumonia with and without concurrent infection

OBJECTIVES

The aim of this study was to compare the pulmonary thin-section CT findings of patients with acute Streptococcus pneumoniae pneumonia with and without concurrent infection.

METHODS

The study group comprised 86 patients with acute S. pneumoniae pneumonia, 36 patients with S. pneumoniae pneumonia combined with Haemophilus influenzae infection, 26 patients with S. pneumoniae pneumonia combined with Pseudomonas aeruginosa infection and 22 patients with S. pneumoniae pneumonia combined with methicillin-susceptible Staphylococcus aureus (MSSA) infection. We compared the thin-section CT findings among the groups.

RESULTS

Centrilobular nodules and bronchial wall thickening were significantly more frequent in patients with pneumonia caused by concurrent infection (H. influenzae: p<0.001 and p<0.001, P. aeruginosa: p<0.001 and p<0.001, MSSA: p<0.001 and p<0.001, respectively) than in those infected with S. pneumoniae alone. Cavity and bilateral pleural effusions were significantly more frequent in cases of S. pneumoniae pneumonia with concurrent P. aeruginosa infection than in cases of S. pneumoniae pneumonia alone (p<0.001 and p<0.001, respectively) or with concurrent H. influenzae (p<0.05 and p<0.001, respectively) or MSSA infection (p<0.05 and p<0.05, respectively).

CONCLUSIONS

When a patient with S. pneumoniae pneumonia has centrilobular nodules, bronchial wall thickening, cavity or bilateral pleural effusions on CT images, concurrent infection should be considered.

Transcriptional activation of the anchoring protein SAP97 by heat shock factor (HSF)-1 stabilizes K(v) 1.5 channels in HL-1 cells

BACKGROUND AND PURPOSE

The expression of voltage-dependent K⁺ channels (K_v) 1.5 is regulated by members of the heat shock protein (Hsp) family. We examined whether the heat shock transcription factor 1 (HSF-1) and its inducer geranylgeranylacetone (GGA) could affect the expression of K_v1.5 channels and its anchoring protein, synapse associated protein 97 (SAP97).

EXPERIMENTAL APPROACH

Transfected mouse atrial cardiomyocytes (HL-1 cells) and COS7 cells were subjected to luciferase reporter gene assay and whole-cell patch clamp. Protein and mRNA extracts were subjected to Western blot and quantitative real-time polymerase chain reaction.

KEY RESULTS

Heat shock of HL-1 cells induced expression of Hsp70, HSF-1, SAP97 and K_v1.5 proteins. These effects were reproduced by wild-type HSF-1. Both heat shock and expression of HSF-1, but not the R71G mutant, increased the SAP97 mRNA level. Small interfering RNA (siRNA) against SAP97 abolished HSF-1-induced increase of K_v1.5 and SAP97 proteins. A luciferase reporter gene assay revealed that the SAP97 promoter region (from −919 to −740) that contains heat shock elements (HSEs) was required for this induction. Suppression of SIRT1 function either by nicotinamide or siRNA decreased the level of SAP97 mRNA. SIRT1 activation by resveratrol had opposing effects. A treatment of the cells with GGA increased the level of SAP97 mRNA, K_v1.5 proteins and I_Kur current, which could be modified with either resveratrol or nicotinamide.

CONCLUSIONS AND IMPLICATIONS

HSF-1 induced transcription of SAP97 through SIRT1-dependent interaction with HSEs; the increase in SAP97 resulted in stabilization of K_v1.5 channels. These effects were mimicked by GGA.

Meticillin-resistant Staphylococcus aureus and meticillin-susceptible S. aureus pneumonia: comparison of clinical and thin-section CT findings

OBJECTIVES

The purpose of this study was to compare the clinical and thin-section CT findings in patients with meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-susceptible S. aureus (MSSA).

METHODS

We retrospectively identified 201 patients with acute MRSA pneumonia and 164 patients with acute MSSA pneumonia who had undergone chest thin-section CT examinations between January 2004 and March 2009. Patients with concurrent infectious disease were excluded from our study. Consequently, our study group comprised 68 patients with MRSA pneumonia (37 male, 31 female) and 83 patients with MSSA pneumonia (32 male, 51 female). Clinical findings in the patients were assessed. Parenchymal abnormalities, lymph node enlargement and pleural effusion were assessed.

RESULTS

Underlying diseases such as cardiovascular were significantly more frequent in the patients with MRSA pneumonia than in those with MSSA pneumonia. CT findings of centrilobular nodules, centrilobular nodules with a tree-in-bud pattern, and bronchial wall thickening were significantly more frequent in the patients with MSSA pneumonia than those with MRSA pneumonia (p = 0.038, p = 0.007 and p = 0.039, respectively). In the group with MRSA, parenchymal abnormalities were observed to be mainly peripherally distributed and the frequency was significantly higher than in the MSSA group (p = 0.028). Pleural effusion was significantly more frequent in the patients with MRSA pneumonia than those with MSSA pneumonia (p = 0.002).

CONCLUSIONS

Findings from the evaluation of thin-section CT manifestations of pneumonia may be useful to distinguish between patients with acute MRSA pneumonia and those with MSSA pneumonia.

Production and characterization of HCV particles from serum-free culture

Hepatitis C virus (HCV) is a major cause of liver cancer, and it is therefore important to develop a prophylactic strategy for HCV infection. In recent years, a system for cell culture of the infectious HCV particle has been established, and the inactivated particle has potential as an antigen for vaccine development. In this study, we aimed to establish highly efficient HCV particle purification procedures using the following serum-free culture of HCV particles. First, naïve human hepatoma Huh7 cells were grown in serum-free medium that was supplemented with human-derived insulin, transferrin and sodium selenite. Then, in vitro transcribed JFH-1 or J6/JFH-1 chimeric HCV-RNA was transfected into the serum-free conditioned Huh7 cells. Infectious HCV was secreted into the culture supernatant with the same efficiency as that from cells cultured in FBS-containing medium. The HCV-core protein and RNA continued to be detected in the culture supernatant when the infected cells were subcultured in serum-free medium. Sucrose gradient centrifugation analyses indicated that the profiles of HCV-core, HCV-RNA and the infectivity of HCV particles were almost identical between HCV from FBS-supplemented and serum-free cultures. We further determined that anti-CD81, anti-SR-BI and anti-E2 antibodies inhibited infection by serum-free cultured HCV to a greater extent than infection by HCV from FBS-supplemented cultures. These HCV particles also differed in the level of associated apoplipoproteins: the ApoE level was lower in serum-free cultured HCV. ApoB and ApoE antibody-depletion assays suggested that infection of serum-free cultured HCV was independent of ApoB and ApoE proteins. These data suggest that lipids conjugated with HCV affect infection and neutralization.

Nonstructural protein 3-4A: the Swiss army knife of hepatitis C virus

Hepatitis C virus (HCV) nonstructural protein 3-4A (NS3-4A) is a complex composed of NS3 and its cofactor NS4A. It harbours serine protease as well as NTPase/RNA helicase activities and is essential for viral polyprotein processing, RNA replication and virion formation. Specific inhibitors of the NS3-4A protease significantly improve sustained virological response rates in patients with chronic hepatitis C when combined with pegylated interferon-α and ribavirin. The NS3-4A protease can also target selected cellular proteins, thereby blocking innate immune pathways and modulating growth factor signalling. Hence, NS3-4A is not only an essential component of the viral replication complex and prime target for antiviral intervention but also a key player in the persistence and pathogenesis of HCV. This review provides a concise update on the biochemical and structural aspects of NS3-4A, its role in the pathogenesis of chronic hepatitis C and the clinical development of NS3-4A protease inhibitors.

Mineral trioxide aggregate inhibits osteoclastic bone resorption

Mineral trioxide aggregate (MTA), a commonly used endodontic repair material, is useful for both basic and clinical research, and the effect of MTA on osteoblast differentiation has been well-defined. However, the effects of MTA on osteoclastic bone resorption are not fully understood. Hence, the aim of this study is to examine the effect of MTA solution in the regulation of osteoclast bone-resorbing activity using osteoclasts formed in co-cultures of primary osteoblasts and bone marrow cells. MTA solution dose-dependently reduced the total area of pits formed by osteoclasts. The reduction of resorption induced by 20% MTA treatment was due to inhibition of osteoclastic bone-resorbing activity and had no effect on osteoclast number. A 20% MTA solution disrupted actin ring formation, a marker of osteoclastic bone resorption, by reducing phosphorylation and kinase activity of c-Src, and mRNA expressions of cathepsin K and mmp-9. A high concentration of MTA solution (50%) induced apoptosis of osteoclasts by increasing the expression of Bim, a member of the BH3-only (Bcl-2 homology) family of pro-apoptotic proteins. Taken together, our results suggest that MTA is a useful retrofilling material for several clinical situations because it both stimulates osteoblast differentiation and inhibits bone resorption.

Magnitude of CD8 T-cell responses against hepatitis C virus and severity of hepatitis do not necessarily determine outcomes in acute hepatitis C virus infection

AIM

We investigated the relationship between the magnitude of comprehensive hepatitis C virus (HCV)-specific CD8(+) T-cell responses and the clinical course of acute HCV infection.

METHODS

Six consecutive patients with acute HCV infection were studied. Analysis of HCV-specific CD8(+) T-cell responses was performed using an interferon-gamma-based enzyme-linked immunospot assay using peripheral CD8(+) T-cells, monocytes and 297 20-mer synthetic peptides overlapping by 10 residues and spanning the entire HCV sequence of genotype 1b.

RESULTS

Five patients presented detectable HCV-specific CD8(+) T-cell responses against a single and different peptide, whereas 1 patient showed responses against three different peptides. Neither the magnitude of HCV-specific CD8(+) T-cell responses nor the severity of hepatitis predicts the outcome of acute hepatitis. The maximum number of HCV-specific CD8(+) T-cells correlated with maximum serum alanine aminotransferase level during the course (r = 0.841, P = 0.036).

CONCLUSIONS

HCV-specific CD8(+) T-cell responses were detectable in all 6 patients with acute HCV infection, and 6 novel HCV-specific CTL epitopes were identified. Acute HCV infection can resolve with detectable HCV-specific CD8(+) T-cell responses, but without development of antibody against HCV.

Characterization of infectious hepatitis C virus from liver-derived cell lines

The efficient production of infectious HCV from the JFH-1 strain is restricted to the Huh7 cell line and its derivatives. However, the factors involved in this restriction are unknown. In this study, we examined the production of infectious HCV from other liver-derived cell lines, and characterized the produced viruses. Clones of the Huh7, HepG2, and IMY-N9, harboring the JFH-1 full-genomic replicon, were obtained. The supernatant of each cell clone exhibited infectivity for naïve Huh7. Each infectious supernatant was then characterized by sucrose density gradient. For all of the cell lines, the main peak of the HCV-core protein and RNA exhibited at approximately 1.15g/mL of buoyant density. However, the supernatant from the IMY-N9 differed from that of Huh7 in the ratio of core:RNA at 1.15g/mL and significant peaks were also observed at lower density. The virus particles produced from the different cell lines may have different characteristics.

Trans-encapsidation of hepatitis C virus subgenomic replicon RNA with viral structure proteins

A trans-packaging system for hepatitis C virus (HCV) subgenomic replicon RNAs was developed. HCV subgenomic replicon was efficiently encapsidated by the HCV structural proteins that were stably expressed in trans under the control of a mammalian promoter. Infectious HCV-like particles (HCV-LPs), established a single-round infection, were produced and released into culture medium in titers of up to 10(3) focus forming units/ml. Expression of NS2 protein with structural proteins (core, E1, E2, and p7) was shown to be critical for the infectivity of HCV-LPs. Anti-CD81 treatment decreased the number of infected cells, suggesting that HCV-LPs infected cells in a CD81-dependent manner. The packaging cell line should be useful both for the production of single-round infectious HCV-LPs to elucidate the mechanisms of HCV assembly, particle formation and infection to host cells, and for the development of HCV replicon-based vaccines.

Experiment study on fracture fixation with low rigidity titanium alloy: plate fixation of tibia fracture model in rabbit

In order to investigate bone tissue reaction to the low rigidity titanium alloy of TNTZ in bone plate fixation, animal experiment with rabbit was performed with X-ray follow-up and histological observation. Experimental fractures were made in rabbit tibiae, and fixed by different bone plates of SUS316L, Ti-6Al-4V and TNTZ. Although there was no significant difference in fracture healing, bone atrophy was observed in cortical bone especially under the bone plate, which was different in time course among three materials. The bone atrophy under the bone plate was confirmed as porous or poor bone tissue in histological observation. In addition, the diameter of the tibia bone was increased in TNTZ as the result of bone remodeling with a new cortical bone. It is confirmed that the elastic modulus of the bone plate will naturally influence bone tissue reaction to the bone plate fixation according to the Wolff's law of functional restoration.

Cell culture and infection system for hepatitis C virus

Hepatitis C virus (HCV) infection causes chronic liver disease and is a worldwide health problem. Despite ever-increasing demand for knowledge on viral replication and pathogenesis, detailed analysis has been hampered by a lack of efficient viral culture systems. We isolated HCV genotype 2a strain JFH-1 from a patient with fulminant hepatitis. This strain replicates efficiently in Huh7 cells. Efficient replication and secretion of recombinant viral particles can be obtained in cell culture by transfection of in vitro-transcribed full-length JFH-1 RNA into Huh7 cells. JFH-1 virus generated in cell culture is infectious for both naive Huh7 cells and chimpanzees. The efficiency of viral production and infectivity of generated virus is substantially improved with permissive cell lines. This protocol describes how to use this system, which provides a powerful tool for studying viral life cycle and for the construction of antiviral strategies and the development of effective vaccines. Viral particles can be obtained in 12 days with this protocol.

The roles of CD81 and glycosaminoglycans in the adsorption and uptake of infectious HCV particles

Because appropriate cell-culture systems or small-animal models have been lacking, the early steps in the HCV life cycle have been difficult to study. A cell culture system was developed recently that allows production of infectious HCV. In this study, infectious HCV particles produced in cultured cells were used. To clarify the role of CD81 in HCV attachment and entry, the effect of anti-CD81 antibody was examined. The antibody blocked HCV virion entry but not particle attachment. Only the fraction bound to a heparin affinity column and eluted with 0.3 M NaCl productively infected Huh7 cells, indicating that infectious HCV particles bind to heparin. Both heparin treatment of the virus particles and heparinase treatment of the Huh7 cells reduced virus-cell binding without substantially inhibiting HCV infectivity. Finally, to confirm the role of both heparin sulfate proteoglycan (HSPG) and CD81 in HCV entry, the effects of heparinase I and anti-CD81 antibody were analyzed. No productive RNA replication was detected in the Huh7 cells in the presence of both heparinase I and anti-CD81 antibody. In conclusion, these data suggested that both HSPG and CD81 are important for HCV entry. HSPG may play a role in the initial cell surface binding of infectious HCV particles and CD81 is conceivably correlated with HCV entry after viral attachment.

An infectious and selectable full-length replicon system with hepatitis C virus JFH-1 strain

AIM

The hepatitis C virus (HCV) strain JFH-1 was cloned from a patient with fulminant hepatitis. A JFH-1 subgenomic replicon and full-length JFH-1 RNA efficiently replicate in cultured cells. In this study, an infectious, selectable HCV replicon containing full-length JFH-1 cDNA was constructed.

METHODS

The full-genome replicon was constructed using the neomycin-resistant gene, EMCV IRES and wild-type JFH-1 cDNA. Huh7 cells were transfected with RNA synthesized in vitro, and then cultured with G418. Independent colonies were cloned to establish cell lines that replicate the full-length HCV replicon.

RESULTS

HCV RNA replication was detected in each isolated cell line. HCV proteins and HCV RNA were secreted into culture medium, and exhibited identical density profiles. Interestingly, culture supernatants of the replicon cells were infectious for naïve Huh7 cells. Long-term culture did not affect replication of replicon RNA in the replicon cells, but it reduced core protein secretion and infectivity of culture supernatant. Culture supernatant obtained after serial passage of replicon virus was infectious for Huh7 cells.

CONCLUSIONS

Selectable infection was established using HCV replicon containing full-length genotype 2a JFH-1 cDNA. This system might be useful for HCV research.

The NS3 helicase and NS5B-to-3'X regions are important for efficient hepatitis C virus strain JFH-1 replication in Huh7 cells

The JFH-1 strain of hepatitis C virus (HCV) is a genotype 2a strain that can replicate autonomously in Huh7 cells. The J6 strain is also a genotype 2a strain, but its full genomic RNA does not replicate in Huh7 cells. However, chimeric J6/JFH-1 RNA that has J6 structural-protein-coding regions and JFH-1 nonstructural-protein-coding regions can replicate autonomously and produce infectious HCV particles. In order to determine the mechanisms underlying JFH-1 RNA replication, we constructed various J6/JFH-1 chimeras and tested their RNA replication and virus particle production abilities in Huh7 cells. Via subgenomic-RNA-replication assays, we found that both the JFH-1 NS5B-to-3'X (N5BX) and the NS3 helicase (N3H) regions are important for the replication of the J6CF replicon. We applied these results to full-length genomic RNA replication and analyzed replication using Northern blotting. We found that a chimeric J6 clone with JFH-1 N3H and N5BX could replicate autonomously but that a chimeric J6 clone with only JFH-1 N5BX had no replication ability. Finally, we tested the virus production abilities of these clones and found that a chimeric J6 clone with JFH-1 N3H and N5BX could produce infectious HCV particles. In conclusion, the JFH-1 NS3 helicase and NS5B-to-3'X regions are important for efficient replication and virus particle formation of HCV genotype 2a strains.

Arsenic in various foods: Cumulative data

Data for the arsenic content in various foods were collated. The number of collected values was about 2500 columns, which enables an estimation of the range of arsenic contents in each food group. Data were categorized into six groups (crops, milk/meat/egg, fish, algae, seafood, others) and expressed as a percentile graph. In addition, the inorganic arsenic ratio of each food group was estimated. This approach enabled the authors to understand the arsenic contents of some food groups at a glance. The intake of inorganic arsenic seems to be mostly from seafood. The contribution from other categories of food is small.

CD81 expression is important for the permissiveness of Huh7 cell clones for heterogeneous hepatitis C virus infection

Huh7 cells constitute a permissive cell line for cell culture of hepatitis C virus (HCV) particles. However, our Huh7 line shows limited permissiveness for HCV. Thus, in this study we set out to determine which host factors are important for conferring permissiveness. To analyze the limited permissiveness of our Huh7 cells, 70 clones were obtained after single-cell cloning of parental Huh7 cells. The cloned Huh7 cells exhibited various levels of HCV pseudoparticles and JFH-1 virus infection efficiency, and some clones were not permissive. A subgenomic replicon was then transfected into the cloned Huh7 cells. While the replication efficiencies differed among the cloned Huh7 cells, these efficiencies did not correlate with infectious permissibility. Flow cytometry showed that CD81, scavenger receptor class B type I, and low-density-lipoprotein receptor expression on the cell surfaces of the Huh7 clones differed among the clones. Interestingly, we found that all of the permissive cell clones expressed CD81 while the nonpermissive cell clones did not. To confirm the importance of CD81 expression for HCV permissiveness, CD81 was then transiently and stably expressed on a nonpermissive Huh7 cell clone, which was consequently restored to HCV infection permissiveness. Furthermore, permissiveness was down-regulated upon transfection of CD81 silencing RNA into a CD81-positive cell clone. In conclusion, CD81 expression is an important determinant of HCV permissiveness of Huh7 cell clones harboring different characteristics.

Atomic force microscopy dissects the hierarchy of genome architectures in eukaryote, prokaryote, and chloroplast

Because of its applicability to biological specimens (nonconductors), a single-molecule-imaging technique, atomic force microscopy (AFM), has been particularly powerful for visualizing and analyzing complex biological processes. Comparative analyses based on AFM observation revealed that the bacterial nucleoids and human chromatin were constituted by a detergent/salt-resistant 30-40-nm fiber that turned into thicker fibers with beads of 70-80 nm diameter. AFM observations of the 14-kbp plasmid and 110-kbp F plasmid purified from Escherichia coli demonstrated that the 70-80-nm fiber did not contain a eukaryotic nucleosome-like "beads-on-a-string" structure. Chloroplast nucleoid (that lacks bacterial-type nucleoid proteins and eukaryotic histones) also exhibited the 70-80-nm structural units. Interestingly, naked DNA appeared when the nucleoids from E. coli and chloroplast were treated with RNase, whereas only 30-nm chromatin fiber was released from the human nucleus with the same treatment. These observations suggest that the 30-40-nm nucleoid fiber is formed with a help of nucleoid proteins and RNA in E. coli and chroloplast, and that the eukaryotic 30-nm chromatin fiber is formed without RNA. On the other hand, the 70-80-nm beaded structures in both E. coli and human are dependent on RNA.

Translational enhancement of HCV RNA genotype 1b by 3'-untranslated and envelope 2 protein-coding sequences

HCV RNA has a unique regulatory mechanism for translation. The X region of 3'-UTR and core-coding sequence regulate HCV translation. In this study, we clarified that the entire 3'-UTR also enhances HCV translation, and the envelope-coding sequence of HCV genotype 1b increases degree of this enhancement. In the luciferase reporter assay using rabbit reticulocyte lysates, translational enhancement by 3'-UTR with core to E2 regions was 25-fold higher when compared with control RNA lacking the 3'-UTR. Presence of the entire E2 sequence was important for this enhancement. This phenomenon was not due to transcript stability, and envelope protein alone did not affect translation. E2-coding sequence of genotype 1a had no effect on translation. We observed the same results in animal cell culture systems using bicistronic RNA. Structural protein-coding sequences and 3'-UTR of HCV RNA regulate viral translation, and a target for antiviral agents may be present in these regions.