HCV envelope protein function is dependent on the peptides preceding the glycoproteins

Recombinant hepatitis C virus-envelope protein 2 interactions with low-density lipoprotein/CD81 receptors

Hepatitis C virus (HCV) envelope protein 2 (E2) is involved in viral binding to host cells. The aim of this work was to produce recombinant E2B and E2Y HCV proteins in Escherichia coli and Pichia pastoris, respectively, and to study their interactions with low-density lipoprotein receptor (LDLr) and CD81 in human umbilical vein endothelial cells (HUVEC) and the ECV304 bladder carcinoma cell line. To investigate the effects of human LDL and differences in protein structure (glycosylated or not) on binding efficiency, the recombinant proteins were either associated or not associated with lipoproteins before being assayed. The immunoreactivity of the recombinant proteins was analysed using pooled serum samples that were either positive or negative for hepatitis C. The cells were immunophenotyped by LDLr and CD81 using flow cytometry. Binding and binding inhibition assays were performed in the presence of LDL, foetal bovine serum (FCS) and specific antibodies. The results revealed that binding was reduced in the absence of FCS, but that the addition of human LDL rescued and increased binding capacity. In HUVEC cells, the use of antibodies to block LDLr led to a significant reduction in the binding of E2B and E2Y. CD81 antibodies did not affect E2B and E2Y binding. In ECV304 cells, blocking LDLr and CD81 produced similar effects, but they were not as marked as those that were observed in HUVEC cells. In conclusion, recombinant HCV E2 is dependent on LDL for its ability to bind to LDLr in HUVEC and ECV304 cells. These findings are relevant because E2 acts to anchor HCV to host cells; therefore, high blood levels of LDL could enhance viral infectivity in chronic hepatitis C patients.

Inflammatory response of endothelial cells to hepatitis C virus recombinant envelope glycoprotein 2 protein exposure

The hepatitis C virus (HCV) encodes approximately 10 different structural and non-structural proteins, including the envelope glycoprotein 2 (E2). HCV proteins, especially the envelope proteins, bind to cell receptors and can damage tissues. Endothelial inflammation is the most important determinant of fibrosis progression and, consequently, cirrhosis. The aim of this study was to evaluate and compare the inflammatory response of endothelial cells to two recombinant forms of the HCV E2 protein produced in different expression systems (Escherichia coli and Pichia pastoris). We observed the induction of cell death and the production of nitric oxide, hydrogen peroxide, interleukin-8 and vascular endothelial growth factor A in human umbilical vein endothelial cells (HUVECs) stimulated by the two recombinant E2 proteins. The E2-induced apoptosis of HUVECs was confirmed using the molecular marker PARP. The apoptosis rescue observed when the antioxidant N-acetylcysteine was used suggests that reactive oxygen species are involved in E2-induced apoptosis. We propose that these proteins are involved in the chronic inflammation caused by HCV.

Scotomas in molecular virology and epidemiology of hepatitis C virus

In the 1970s, scientists learned of a new pathogen causing non-A, non-B hepatitis. Classical approaches were used to isolate and characterize this new pathogen, but it could be transmitted experimentally only to chimpanzees and progress was slow until the pathogen was identified as hepatitis C virus (HCV) in 1989. Since then, research and treatment of HCV have expanded with the development of modern biological medicine: HCV genome organization and polyprotein processing were delineated in 1993; the first three-dimensional structure of HCV nonstructural protein (NS3 serine protease) was revealed in 1996; an infectious clone of HCV complementary DNA was first constructed in 1997; interferon and ribavirin combination therapy was established in 1998 and the therapeutic strategy gradually optimized; the HCV replicon system was produced in 1999; functional HCV pseudotyped viral particles were described in 2003; and recombinant infectious HCV in tissue culture was produced successfully in 2005. Recently, tremendous advances in HCV receptor discovery, understanding the HCV lifecycle, decryption of the HCV genome and proteins, as well as new anti-HCV compounds have been reported. Because HCV is difficult to isolate and culture, researchers have had to avail themselves to the best of modern biomedical technology; some of the major achievements in HCV research have not only advanced the understanding of HCV but also promoted knowledge of virology and cellular physiology. In this review, we summarize the advancements and remaining scotomas in the molecular virology and epidemiology of HCV.

The novel replication-defective vaccinia virus (Tiantan strain)-based hepatitis C virus vaccine induces robust immunity in macaques

The induction of a robust neutralizing antibody (nAb) response is likely to be as essential as specific cell-mediated immunity (CMI) against multiple antigens for the development of effective preventive and therapeutic vaccines against hepatitis C virus (HCV) infection in humans. To date, no data on the immunogenicity of the replication-defective vaccinia virus (derived from the Tiantan strain) (rNTV)-based HCV vaccine in primates have been reported. This study describes in detail the immunogenicity of various vaccine candidates in rhesus macaques, including rNTV-based and replication-defective recombinant adenoviral (rAd)-based HCV vaccines, as well as HCV pseudotyped virus-like particles (HCVpp). Our data showed that rAd-HCV vaccine boosting induced robust CMI, while priming or boosting with HCVpp enhanced the antigen-specific nAb response after rAd-HCV vaccination; however, CMI was not enhanced. Vaccination includes rNTV-HCV priming induced robust antigen-specific antibody, particularly nAbs, and CMI responses. Furthermore, more robust and longer-lasting CMI and higher cytokine levels (both Th1 and Th2 types, especially IFN-γ) resulted from boosting with rAd-HCV. We conclude that the rNTV-based HCV vaccine induces robust nAbs and CMI when combined with a heterogeneous primer-booster strategy, which shows promise for development of a human HCV vaccine.

Induction of broadly neutralising HCV antibodies in mice by integration-deficient lentiviral vector-based pseudotyped particles

Introduction

Integration-deficient lentiviral vectors (IDLVs) are a promising platform for immunisation to elicit both humoral immunity and cellular mediated immunity (CMI). Here, we compared the specific immunity in mice immunised via different regimens (homologous and cocktail) with IDLV-based HCV pseudoparticles (HCVpps) carrying pseudotyped glycoproteins E1E2 and bearing the HCV NS3 gene. Humoral and cell-mediated immune responses were also evaluated after IDLV-HCVpp immunisation combined with heterologous rAd5-CE1E2 priming protocols. Sera from the mice effectively elicited anti-E1, -E2, and -NS3 antibody responses, and neutralised various HCVpp subtypes (1a, 1b, 2a, 3a and 5a). No significant CMI was detected in the groups immunised with IDLV-based HCVpps. In contrast, the combination of rAd5-CE1E2 priming and IDLV-based HCVpp boosting induced significant CMI against multiple antigens (E1, E2, and NS3).

Conclusion

IDLV-based HCVpps are a promising vaccination platform and the combination of rAd5-CE1E2 and IDLV-based HCVpp prime-boost strategy should be further explored for the development of a cross-protective HCV vaccine.

Down-regulation of IRES containing 5'UTR of HCV genotype 3a using siRNAs

Background

Hepatitis C virus (HCV) is a major causative agent of liver associated diseases leading to the development of hepatocellular carcinoma (HCC) all over the world and genotype-3a responsible for most of the cases in Pakistan. Due to the limited efficiency of current chemotherapy of interferon-α (IFN-α) and ribavirin against HCV infection alternative options are desperately needed out of which the recently discovered RNAi represent a powerful silencing approach for molecular therapeutics through a sequence-specific RNA degradation process to silence virus infection or replication. HCV translation is mediated by a highly conserved internal ribosome entry site (IRES) within the 5'UTR region making it a relevant target for new drug development.

Materials and methods

The present study was proposed to assess and explore the possibility of HCV silencing using siRNA targeting 5'UTR. For this analysis full length HCV 5'UTR of HCV-3a (pCR3.1/5'UTR) was tagged with GFP protein for in vitro analysis in Huh-7 cells. siRNA targeting 5'UTR were designed, and tested against constructed vector in Huh-7 cell line both at RNA and Protein levels. Furthermore, the effect of these siRNAs was confirmed in HCV-3a serum infected Huh-7 cell line.

Results

The expression of 5'UTR-GFP was dramatically reduced both at mRNA and protein levels as compared with Mock transfected and control siRNAs treated cells using siRNAs against IRES of HCV-3a genotype. The potential of siRNAs specificity to inhibit HCV-3a replication in serum-infected Huh-7 cells was also investigated; upon treatment with siRNAs a significant decrease in HCV viral copy number and protein expression was observed.

Conclusions

Overall, the present work of siRNAs against HCV 5'UTR inhibits HCV-3a expression and represents effective future therapeutic opportunities against HCV-3a genotype.

Signal peptide replacements enhance expression and secretion of hepatitis C virus envelope glycoproteins

A large number of researches focused on glycoproteins E1 and E2 of hepatitis C virus (HCV) aimed at the development of anti-HCV vaccines and inhibitors. Enhancement of E1/E2 expression and secretion is critical for the characterization of these glycoproteins and thus for subunit vaccine development. In this study, we designed and synthesized three signal peptide sequences based on online programs SignalP, TargetP, and PSORT, then removed and replaced the signal peptide preceding E1/E2 by overlapping the polymerase chain reaction method. We assessed the effect of this alteration on E1/E2 expression and secretion in mammalian cells, using western blot analysis, dot blot, and Galanthus nivalis agglutinin lectin capture enzyme immunoassay. Replacing the peptides preceding E1 and E2 with the signal peptides of the tissue plasminogen activator and Gaussia luciferase resulted in maximum enhancement of E1/E2 expression and secretion of E1 in mammalian cells, without altering glycosylation. Such an advance would help to facilitate both the research of E1/E2 biology and the development of an effective HCV subunit vaccine. The strategy used in this study could be applied to the expression and production of other glycoproteins in mammalian cell line-based systems.

Characterization of neuraminidases from the highly pathogenic avian H5N1 and 2009 pandemic H1N1 influenza A viruses

To study the precise role of the neuraminidase (NA), and its stalk region in particular, in the assembly, release, and entry of influenza virus, we deleted the 20-aa stalk segment from 2009 pandemic H1N1 NA (09N1) and inserted this segment, now designated 09s60, into the stalk region of a highly pathogenic avian influenza (HPAI) virus H5N1 NA (AH N1). The biological characterization of these wild-type and mutant NAs was analyzed by pseudotyped particles (pseudoparticles) system. Compared with the wild-type AH N1, the wild-type 09N1 exhibited higher NA activity and released more pseudoparticles. Deletion/insertion of the 09s60 segment did not alter this relationship. The infectivity of pseudoparticles harboring NA in combination with the hemagglutinin from HPAI H5N1 (AH H5) was decreased by insertion of 09s60 into AH N1 and was increased by deletion of 09s60 from 09N1. When isolated from the wild-type 2009H1N1 virus, 09N1 existed in the forms (in order of abundance) dimer>>tetramer>monomer, but when isolated from pseudoparticles, 09N1 existed in the forms dimer>monomer>>>tetramer. After deletion of 09s60, 09N1 existed in the forms monomer>>>dimer. AH N1 from pseudoparticles existed in the forms monomer>>dimer, but after insertion of 09s60, it existed in the forms dimer>>monomer. Deletion/insertion of 09s60 did not alter the NA glycosylation pattern of 09N1 or AH N1. The 09N1 was more sensitive than the AH N1 to the NA inhibitor oseltamivir, suggesting that the infectivity-enhancing effect of oseltamivir correlates with robust NA activity.

Inhibition of hepatitis C virus genotype 3a by siRNAs targeting envelope genes

Hepatitis C virus (HCV) genotype 3a is considered a significant risk factor for the development of liver diseases and hepatocellular carcinoma for most of the cases in Pakistan. Because of the limited efficiency of the current therapy, RNA interference (RNAi), which results in sequence-specific degradation of HCV RNA, has potential as a powerful alternative molecular therapeutic approach. The envelope genes (E1 and E2) of HCV come in immediate contact with cells during infection and therefore might be a relevant target for new drug development. In the present study, the expression of E1 and E2 genes of HCV genotype 3a was dramatically reduced at both the mRNA and protein level using gene-specific small interfering RNAs (siRNA) when compared to mock-transfected and cells treated with control siRNAs. The potential of siRNAs to inhibit HCV-3a replication in serum-infected Huh-7 cells was also demonstrated by combined treatment of siRNAs against the E1 and E2 genes, which resulted in a significant decrease in HCV viral copy number. This clearly demonstrates that the RNAi-mediated silencing of HCV E1 and E2 is among the first of its type for the development of an effective siRNA-based therapeutic option against HCV-3a.

Inhibition of core gene of HCV 3a genotype using synthetic and vector derived siRNAs

Background

Hepatitis C virus (HCV) is a major causative agent of liver associated diseases throughout the world, with genotype 3a responsible for most of the cases in Pakistan. Due to the limited efficiency of current therapy, RNA interference (RNAi) a novel regulatory and powerful silencing approach for molecular therapeutics through a sequence-specific RNA degradation process represents an alternative option.

Results

The current study was purposed to assess and explore the possibility of RNAi to silence the HCV-3a Core gene expression, which play complex role in regulation of cell growth and host genes expression essential for infectivity and disease progression. To identify the potent siRNA target sites, 5 small interfering RNAs (siRNAs) against Core gene were designed and in vitro transcribed after consensus sequence analysis of different HCV-3a isolates. Antiviral effects of siRNAs showed upto 80% inhibition of Core gene expression by different siRNAs into Huh-7 cells as compared with Mock transfected and control siRNAs treated cells. For long lasting effect of siRNAs, vector based short hairpin siRNAs (shRNAs) were designed and tested against HCV-3a Core which resulted in a similar pattern of inhibition on RNA and protein expression of HCV Core as synthetic siRNAs. Furthermore, the efficacy of cell culture tested siRNA and shRNA, were evaluated for inhibition of HCV replication in HCV infected serum inoculated Huh-7 cells and a significant decrease in HCV viral copy number was observed.

Conclusions

Our results support the possibility of using consensus siRNA and shRNA-based molecular therapy as a promising strategy in effective inhibition of HCV-3a genotype.

Hemagglutinin and neuraminidase matching patterns of two influenza A virus strains related to the 1918 and 2009 global pandemics

The current pandemic influenza A (H1N1) virus has revealed a complicated reassortment of various influenza A viruses. The biological study of these viruses, especially of the viral envelope proteins hemagglutinin (HA) and neuraminidase (NA), is urgently needed for the control and prevention of H1N1 viruses. We have generated H1N1-2009 and H1N1-1918 pseudotyped particles (pp) with high infectivity. Combinations of HA1918 + NA2009 and HA2009 + NA1918 also formed infectious H1N1pps, among which the HA2009 + NA1918 combination resulted in the most highly infectious pp. Our study demonstrated that some reassortments of H1N1 viruses may hold the potential to produce higher infectivity than do their ancestors.

Cellular models for the screening and development of anti-hepatitis C virus agents

Investigations on the biology of hepatitis C virus (HCV) have been hampered by the lack of small animal models. Efforts have therefore been directed to designing practical and robust cellular models of human origin able to support HCV replication and production in a reproducible, reliable and consistent manner. Many different models based on different forms of virions and hepatoma or other cell types have been described including virus-like particles, pseudotyped particles, subgenomic and full length replicons, virion productive replicons, immortalised hepatocytes, fetal and adult primary human hepatocytes. This review focuses on these different cellular models, their advantages and disadvantages at the biological and experimental levels, and their respective use for evaluating the effect of antiviral molecules on different steps of HCV biology including virus entry, replication, particles generation and excretion, as well as on the modulation by the virus of the host cell response to infection.

Hepatitis C virus envelope glycoproteins complementation patterns and the role of the ecto- and transmembrane domains

We separated E1 and E2 of hepatitis C virus (HCV) genotypes 1a, 1b, and 2a into two individual expression plasmids and replaced the transmembrane domains of 1b and 2a E1 and E2 with that of genotype 1a. The complementation features of E1 and E2 as well as the contributions of both the ecto- and transmembrane domains to the formation of the E1E2 complex were evaluated using the HCV pseudoparticle(s) (HCVpp(s)) system. We demonstrated that 1aE2 could not only complement its native 1aE1, but could also complement 1bE1 as well; in genotype 1b, glycoprotein complex formation is primarily dependent on the overall biological characteristics of the intact native E1 and E2; in genotype 2a, although the interaction of intact native E1 and E2 is critical for the formation of the glycoprotein complex, the ectodomain made a greater contribution than that of the transmembrane domain. Our study provides valuable findings regarding HCV E1 and E2 biology and will be of use in both anti-HCV strategy and understanding on the mechanisms of coinfection of different HCV strains.