Hepatitis C virus (HCV) is a positive sense, single-stranded RNA virus in the Flaviviridae family. It causes acute hepatitis with a high propensity for chronic infection. Chronic HCV infection can progress to severe liver disease including cirrhosis and hepatocellular carcinoma. In the last decade, our basic understanding of HCV virology and life cycle has advanced greatly with the development of HCV cell culture and replication systems. Our ability to treat HCV infection has also been improved with the combined use of interferon, ribavirin and small molecule inhibitors of the virally encoded NS3/4A protease, although better therapeutic options are needed with greater antiviral efficacy and less toxicity. In this article, we review various aspects of HCV life cycle including viral attachment, entry, fusion, viral RNA translation, posttranslational processing, HCV replication, viral assembly and release. Each of these steps provides potential targets for novel antiviral therapeutics to cure HCV infection and prevent the adverse consequences of progressive liver disease.
Antigens, CD81/metabolism ; Genome, Viral ; Hepacivirus/genetics/*physiology ; Humans ; RNA, Viral/metabolism ; Scavenger Receptors, Class B/metabolism ; Viral Envelope Proteins/chemistry/metabolism ; Viral Nonstructural Proteins/chemistry/metabolism ; Virus Assembly ; Virus Internalization ; Virus Replication

The receptor-binding domain(RBD) protein of HCoV-NL63 is a major target in the development of diagnostic assay and vaccine, it has a pivotal role in receptor attachment, viral entry and membrane fusion. In this study, we prepared 2 purified recombinant HCoV-NL63 RBD proteins using in E. coli system and identified the proteins by Western blotting. We first optimized codon and synthesized the RL (232-684aa)coding gene, then amplified the RL or RS(476-616aa) coding gene via PCR using different primers . The RL or RS coding gene was cloned into the pM48 expression vector fused with TrxA tag. The RBD (RL and RS) of HCoV-NL63 were expressed majorly as inclusion body when expressed in E. coli BL21pLys S under different conditions. The expressed products were purified by affinity chromatography then analyzed by SDS-PAGE and Western blotting. Our results showed that the recombinant RBD proteins were maximally expressed at 37 degrees C with 0. 8mM IPTG induction for 4h. RL or RS protein with 95 % purity was obtained and reacted positively with anti-sera from mice immunized with the recombinant vaccinia virus (Tiantan strain) in which HCoV-NL63 RL or RS protein was expressed. In conclusion, the purified recombinant RBD proteins(RL and RS)derived from E. coli were first prepared in China and they might provide a basis for further exploring biological role and vaccine development of HCoV-NL63.
Animals ; Coronavirus Infections ; metabolism ; virology ; Coronavirus NL63, Human ; chemistry ; genetics ; metabolism ; Escherichia coli ; genetics ; metabolism ; Gene Expression ; Humans ; Mice ; Mice, Inbred BALB C ; Protein Engineering ; Protein Structure, Tertiary ; Receptors, Virus ; metabolism ; Viral Envelope Proteins ; chemistry ; genetics ; metabolism

In this study, Recombinant baculoviruses rBac-NF and rBac-NG were generated for expressing F and G proteins Nipah virus (NiV) . The expression of recommbinant G (rNG) and F (rNF) protein in rBac-NF and rBac-NG infected cells were confirmed by western-blot. Both rNG and rNF showed sensitive and specific antigenic reaction to rabbit serum anti-Nipah virus in indirect immunofluorescence detection and indirect ELISA. Immunization with rBac-NF and rBac-NG infected insect cells elicited G ad F protein specific antibody responses in mice. Furthermore, the G ad F specific antibodies could neutralize the infectivity of the VSVdeltaG* F/G, the NiV F and G envelope glycoproteins psudotyped recombinant Vesicular Stomatitis Virus expressing green fluorescence protein. The results demonstrated F and G protein expressed by the recombinant baculoviruses could be safe economic diagnostic antigens for the surveillance and monitoring of NiV and promising subunit vaccines for the prevention of NiV.
Animals ; Antigens, Viral ; immunology ; Baculoviridae ; genetics ; metabolism ; Mice ; Mice, Inbred BALB C ; Nipah Virus ; chemistry ; genetics ; Rabbits ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology ; Recombination, Genetic ; Viral Envelope Proteins ; biosynthesis ; genetics ; immunology

The highly virulent PRRSV isolate strain HN-1/06 was cultivated on Marc-145. To study the viral entry mechanisms, the GP5 gene of PRRSV isolate was amplified by RT-PCR and cloned into pcDNA3.0 to generate the expressing plasmid pcDNA-GP5. pcDNA-GP5 was transfected into 293T by the calcium phosphate precipitation method. Analysis of flow cytometry confirmed that the GP5 proteins were expressed in surface of the 293T cells. Then 293T cells were transfected with pcDNA-GP5, pHIT60 and pHIT111 plasmids to generate pseudotyping virus. The pseudotyping virus supernatant was harvested 48 hours post-transfection and was detected by Western blotting and infection assay. Western blotting indicated that the GP5 glycoproteins were incorporated into the retroviral pseudotyped virus. Infection assay showed that the pseudotyped virus infected 293T and Mark-145 cell. The pseudotyped virus could be used to further study infectious mechanism of PRRSV.
Animals ; Cell Line ; Cloning, Molecular ; Endothelial Cells ; cytology ; metabolism ; virology ; Leukemia Virus, Murine ; genetics ; metabolism ; Mice ; Porcine respiratory and reproductive syndrome virus ; chemistry ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; Swine ; Transfection ; Viral Envelope Proteins ; biosynthesis ; genetics ; Virion ; genetics ; metabolism

The glycoprotein 3 (GP3) of type II porcine reproductive and respiratory syndrome virus has the characteristic domains of a membrane protein. However, this protein has been reported to be retained in the endoplasmic reticulum (ER) rather than transported to the plasma membrane of the cell. In this study, we performed confocal laser scanning microscopy analysis of variants of GP3 and foundthat the signal sequence of the GP3 led to confinement of GP3 in the ER, while the functional ortransmembrane domain did not affect its localization. Based on these results, we concludedthat the signal sequence of GP3 contains the ER retention signal, which might play an important role in assembly of viral proteins.
Animals ; Cell Line ; Cell Membrane/*metabolism/virology ; Cricetinae ; Endoplasmic Reticulum/*metabolism/virology ; Microscopy, Confocal/veterinary ; Plasmids/genetics/metabolism ; Porcine respiratory and reproductive syndrome virus/*genetics/metabolism ; *Protein Sorting Signals ; Sequence Analysis, Protein/veterinary ; Viral Envelope Proteins/chemistry/*genetics/metabolism

OBJECTIVETo study anti-HIV activity and mechanism of Cynanchum otophyllum glucan sulfate in vitro.

METHODAnti-HIV-1 activity was detected with syncytial formation assay and quantitative P24 enzyme-linked immunosorbent assay (ELISA); cytotoxicity was tested with MTT colorimetric assay. Antiviral mechanism was investigated by fusion inhibition, time of addition and pre-treatment experiments.

RESULTThe 50% inhibition concentrations (IC50) of PS20 for HIV-1(IIIB), HIV-1(Ada-M), and HIV-1(Bal), were 0.26, 0.46, 0.90 micromol x L(-1), respectively. Studies on antiviral mechanism of PS20 showed that target molecule may be viral envelope protein.

CONCLUSIONThe results suggested that PS20 had high anti-HIV activity and was worth to be studied further.

Anti-HIV Agents ; pharmacology ; Cell Fusion ; Cell Line ; Cell Proliferation ; drug effects ; Cynanchum ; chemistry ; Glucans ; isolation & purification ; pharmacology ; HIV-1 ; drug effects ; Humans ; Inhibitory Concentration 50 ; Plant Extracts ; pharmacology ; Plant Roots ; chemistry ; metabolism ; Viral Envelope Proteins ; drug effects

BACKGROUNDTo investigate the interaction between the host cell and the truncated S fragments to identify the receptor-binding domain of the spike (S) protein of SARS-associated coronavirus (SARS-CoV).

METHODSTwo different fragments S260-600 and S397-796 of the SARS-CoV S protein were expressed in Escherichia coli (E.coli) using a pET expression vector, respectively. The two recombinant proteins were separately verified by Western blot, purified by nickel-affinity chromatography, and incubated with Vero cells, a susceptible cell line of SARS-CoV infection, for cell binding assay. After the sequential probing with sera from convalescent SARS-patients and FITC-labeled anti-human IgG, the cells were analyzed by flow cytometry. The NIH 3T3 cell, a non-permissive cell line of SARS-CoV infection, was used as controls.

RESULTSThe recombinant proteins S260-600 and S397-796 were efficiently expressed in an insoluble form in E.coli. The appropriate expression of the proteins was confirmed by Western blotting using both SARS patients' sera and anti-6 x histidine antibody. The flow cytometry results showed that the both proteins were able to bind Vero cells, but the binding ability of S260-600 was somewhat stronger than that of S397-796. In contrast, the S260-600 protein did not bind NIH3T3 cells.

CONCLUSIONBoth S260-600 and S397-796 exhibited different receptor binding activity. The S260-600 fragment probably contains the important receptor binding domain and could be a potential candidate for the development of SARS vaccine and anti-SARS therapeutics.

Animals ; Binding, Competitive ; Blotting, Western ; Cercopithecus aethiops ; Escherichia coli ; genetics ; metabolism ; Membrane Glycoproteins ; chemistry ; genetics ; metabolism ; Mice ; NIH 3T3 Cells ; Peptide Fragments ; chemistry ; genetics ; metabolism ; Protein Binding ; Receptors, Cell Surface ; metabolism ; Recombinant Proteins ; isolation & purification ; metabolism ; SARS Virus ; genetics ; metabolism ; Spike Glycoprotein, Coronavirus ; Vero Cells ; Viral Envelope Proteins ; chemistry ; genetics ; metabolism

During July to November in 2007, several outbreaks of Hemangiomas in Hy-line Brown laying hens were observed in China. The virus that infected these flocks was identified in cultured DF-1 cells by PCR and indirect fluorescent assay (IFA) with ALV-J specific monoclonal antibody JE-9. The gp85 gene of one strain named WS0705 of ALV-J was cloned and expressed. Phylogenetic analysis showed that gp85 amino sequences of WS0705 strain had the highest homology with that of the prototype HPRS-103. The gp85 gene from a constructed plasmid pMD18-T-WS0705gp85 was cloned into baculovirus transfer vector. rBac-WS0705gp85 was obtained by the Bac-to-Bac baculovirus expression system. The rBac-WS0705gp85 protein was analyzed by indirect immunofluor escence assay and Western blot. The results showed that positive green fluorescent was present in Sf9 cells infected with the recombinant virus and a 35 kD band was present in western blot. It is concluded that WS0705 gp85 gene was expressed in Sf9 cells infected with the recombinant virus and the SU protein of WS0705 can bind specifically to JE9 MAb of ALV-J. The expressed protein can be used to detect hemangiomas induced by ALV-J.
Amino Acid Sequence ; Animals ; Avian Leukosis Virus ; classification ; genetics ; Blotting, Western ; Cell Line ; Cloning, Molecular ; Electrophoresis, Polyacrylamide Gel ; Gene Expression ; Hemangioma ; virology ; Phylogeny ; Polymerase Chain Reaction ; Sequence Alignment ; Viral Envelope Proteins ; chemistry ; genetics ; isolation & purification ; metabolism

Avian leukosis virus subgroup J (ALV-J) is an avian retrovirus that can induce myelocytomas. A high-frequency mutation in gene envelope endows ALV-J with the potential for cross-species transmission. We wished to ascertain if the ALV-J can spread across species under selection pressure in susceptible and resistant hosts. First, we inoculated (in turn) two susceptible host birds (specific pathogen-free (SPF) chickens and turkeys). Then, we inoculated three resistant hosts (pheasants, quails and ducks) to detect the viral shedding, pathologic changes, and genetic evolution of different isolates. We found that pheasants and quails were infected under the selective pressure that accumulates stepwise in different hosts, and that ducks were not infected. Infection rates for SPF chickens and turkeys were 100% (16/16), whereas those for pheasants and quails were 37.5% (6/16) and 11.1% (3/27). Infected hosts showed immune tolerance, and inflammation and tissue damage could be seen in the liver, spleen, kidneys and cardiovascular system. Non-synonymous mutation and synonymous ratio (NS/S) analyses revealed the NS/S in hypervariable region (hr) 2 of pheasants and quails was 2.5. That finding suggested that mutation of isolates in pheasants and quails was induced by selective pressure from the resistant host, and that the hr2 region is a critical domain in cross-species transmission of ALV-J. Sequencing showed that ALV-J isolates from turkeys, pheasants and quails had moved away from the original virus, and were closer to the ALV-J prototype strain HPRS-103. However, the HPRS-103 strain cannot infect pheasants and quails, so further studies are needed.
Amino Acid Sequence ; Animals ; Avian Leukosis ; transmission ; virology ; Avian Leukosis Virus ; classification ; genetics ; physiology ; Chickens ; Ducks ; virology ; Galliformes ; virology ; Host Specificity ; Molecular Sequence Data ; Poultry Diseases ; transmission ; virology ; Quail ; virology ; Sequence Alignment ; Turkeys ; virology ; Viral Envelope Proteins ; chemistry ; genetics ; metabolism

This study aims to construct a eukaryotic expression system for envelope gene of Jaagsiekte sheep retrovirus, observes its localization in 293T cells, and investigates the potential in inducing malignant transformation of NIH3T3 cells. By RT-PCR, the full-length cDNA of envelope gene of Jaagsiekte sheep retrovirus (exJSRV-env) was amplified from the extract of naturally infected sheep lung. The clone of target gene was sub-cloned into eukaryotic expression system pEGFP-C1, and validated by PCR, restriction endonuclease, and sequencing. Bioinformatic analysis concerning biological function and cellular localiza tion of exJSRV-env was also performed. The recombinant clone of exJSRV-env was transfected into 293T cells and NIH3T3 cells by Lipofectamine LTX. The expression and celluar localization in 293T cells were validated by confocal microscopy. Soft agar colony formation assay was employed to test the anchorage-independent growth of NIH3T3. DNA sequencing and restriction enzyme digestion with Kpn I and Hind III indicated the correct construction of the recombinant plasmid, which was named pEGFP-C1/exJSRV-env. Amino acid sequence alignment of exJSRV-env with reference sequences found 85%-100% homogeneity. A YRNM motif was discovered at the cytoplasmic tail of envelope gene, which is exclusively found in exogenous viruses. Phylogenetic tree analysis showed that our clone of exJSRV-env clustered closely with pathogenic exogenous Jaagsiekte sheep retroviruses. Fluorescence microscopy indicated typical membrane localization of exJSRV-env protein. NIH3T3 cells transfected with exJSRV-env lost contact inhibition, and acquired colony forming ability in soft agar. This study indicated that envelope protein of Jaagsiekte sheep retrovirus can induce malignant transformation of mouse fibroblast cell NIH3T3. Discoveries of this study provide a basis for further structural and functional research on Jaagsiekte sheep retrovirus envelope protein.
Amino Acid Sequence ; Animals ; Betaretrovirus ; chemistry ; classification ; genetics ; physiology ; Cell Transformation, Viral ; Green Fluorescent Proteins ; genetics ; metabolism ; Mice ; Molecular Sequence Data ; NIH 3T3 Cells ; Phylogeny ; Retroviridae Infections ; veterinary ; virology ; Sequence Alignment ; Sheep ; Sheep Diseases ; virology ; Transformation, Genetic ; Tumor Virus Infections ; veterinary ; virology ; Viral Envelope Proteins ; chemistry ; genetics ; metabolism