Hepatitis C virus vaccines--progress and perspectives

An Insight into Hepatitis C Virus: In Search of Promising Drug Targets

Hepatitis C Virus (HCV) is a global health concern, chronically infecting over 70 million people worldwide. HCV is a bloodborne pathogen that primarily affects the liver, and chronic HCV infection can lead to cirrhosis, liver cancer, and liver failure over time. There is an urgent need for more effective approaches to prevent and treat HCV. This review summarizes current knowledge on the virology, transmission, diagnosis, and management of HCV infection. It also provides an in-depth analysis of HCV proteins as promising targets for antiviral drug and vaccine development. Specific HCV proteins discussed as potential drug targets include the NS5B polymerase, NS3/4A protease, entry receptors like CD81, and core proteins. The implications of HCV proteins as diagnostic and prognostic biomarkers are also explored. Current direct-acting antiviral therapies are effective but have cost, genotype specificity, and resistance limitations. This review aims to synthesize essential information on HCV biology and pathogenesis to inform future research on improved preventive, diagnostic, and therapeutic strategies against this global infectious disease threat.

Small molecule NS5B RdRp non-nucleoside inhibitors for the treatment of HCV infection: A medicinal chemistry perspective

Hepatitis C virus (HCV) infection has become a global health problem with enormous risks. Nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase (RdRp) is a component of HCV, which can promote the formation of the viral RNA replication complex and is also an essential part of the replication complex itself. It plays a vital role in the synthesis of the positive and negative strands of HCV RNA. Therefore, the development of small-molecule inhibitors targeting NS5B RdRp is of great value for treating HCV infection-related diseases. Compared with NS5B RdRp nucleoside inhibitors, non-nucleoside inhibitors have more flexible structures, simpler mechanisms of action, and more predictable efficacy and safety of drugs in humans. Technological advances over the past decade have led to remarkable achievements in developing NS5B RdRp inhibitors. This review will summarize the non-nucleoside inhibitors targeting NS5B RdRp developed in the past decade and describe their structure optimization process and structure-activity relationship.

Combating Human Viral Diseases: Will Plant-Based Vaccines Be the Answer?

Molecular pharming or the technology of application of plants and plant cell culture to manufacture high-value recombinant proteins has progressed a long way over the last three decades. Whether generated in transgenic plants by stable expression or in plant virus-based transient expression systems, biopharmaceuticals have been produced to combat several human viral diseases that have impacted the world in pandemic proportions. Plants have been variously employed in expressing a host of viral antigens as well as monoclonal antibodies. Many of these biopharmaceuticals have shown great promise in animal models and several of them have performed successfully in clinical trials. The current review elaborates the strategies and successes achieved in generating plant-derived vaccines to target several virus-induced health concerns including highly communicable infectious viral diseases. Importantly, plant-made biopharmaceuticals against hepatitis B virus (HBV), hepatitis C virus (HCV), the cancer-causing virus human papillomavirus (HPV), human immunodeficiency virus (HIV), influenza virus, zika virus, and the emerging respiratory virus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been discussed. The use of plant virus-derived nanoparticles (VNPs) and virus-like particles (VLPs) in generating plant-based vaccines are extensively addressed. The review closes with a critical look at the caveats of plant-based molecular pharming and future prospects towards further advancements in this technology. The use of biopharmed viral vaccines in human medicine and as part of emergency response vaccines and therapeutics in humans looks promising for the near future.

Indole - a promising pharmacophore in recent antiviral drug discovery

The bicyclic molecule indole has been in the limelight because of its numerous pharmacological potencies. It is used as an excellent scaffold in drug discovery of medicinal drugs such as antimicrobials, anticancer agents, antihypertensives, anti-proliferative agents and anti-inflammatory agents. In spite of its diverse therapeutic activity, it is used as a key pharmacophore in synthesizing the most potent biological agents. Besides, viral infections are ubiquitous and their prevention and cure have become a great challenge. In this regard, the design of indole-containing antiviral drugs is accomplished to combat viral infections. A lot of research is being carried out towards antiviral drug discovery by many researchers round the clock. Herein, the antiviral activity of recently discovered indole scaffolds is compiled and critically evaluated to give a meaningful summary. In addition, the structure-activity relationship of remarkable antiviral agents is discussed. Also, the structural motifs attributed to noteworthy antiviral properties are highlighted to guide future antiviral research.

Cancer Prevention: Lessons Learned and Future Directions

In this review, we address selected areas that are central to the state-of-the-art of cancer prevention science. The emphasis on prevention as a viable and critical approach to decreasing cancer mortality has gained traction in recent years, evidenced by its inclusion in the US Vice President's Cancer Initiative (also termed 'Moonshot'). Cancer prevention occurs by arresting, slowing down, or reversing the carcinogenic process before invasion into surrounding tissue or by avoiding or blocking causative exposure. An important challenge is to identify individuals who will benefit most from preventive interventions with the least possible harm. Preventive interventions range from avoiding known carcinogens (e.g., tobacco or asbestos) to intervening with anticarcinogenic strategies (behavioral modifications , such as diet and exercise; medications; nutritional agents; and vaccination against causative agents). Here, we focus on active intervention with measures involving pharmaceutical and immunological agents.

Probing the antigenicity of hepatitis C virus envelope glycoprotein complex by high-throughput mutagenesis

The hepatitis C virus (HCV) envelope glycoproteins E1 and E2 form a non-covalently linked heterodimer on the viral surface that mediates viral entry. E1, E2 and the heterodimer complex E1E2 are candidate vaccine antigens, but are technically challenging to study because of difficulties in producing natively folded proteins by standard protein expression and purification methods. To better comprehend the antigenicity of these proteins, a library of alanine scanning mutants comprising the entirety of E1E2 (555 residues) was created for evaluating the role of each residue in the glycoproteins. The mutant library was probed, by a high-throughput flow cytometry-based assay, for binding with the co-receptor CD81, and a panel of 13 human and mouse monoclonal antibodies (mAbs) that target continuous and discontinuous epitopes of E1, E2, and the E1E2 complex. Together with the recently determined crystal structure of E2 core domain (E2c), we found that several residues in the E2 back layer region indirectly impact binding of CD81 and mAbs that target the conserved neutralizing face of E2. These findings highlight an unexpected role for the E2 back layer in interacting with the E2 front layer for its biological function. We also identified regions of E1 and E2 that likely located at or near the interface of the E1E2 complex, and determined that the E2 back layer also plays an important role in E1E2 complex formation. The conformation-dependent reactivity of CD81 and the antibody panel to the E1E2 mutant library provides a global view of the influence of each amino acid (aa) on E1E2 expression and folding. This information is valuable for guiding protein engineering efforts to enhance the antigenic properties and stability of E1E2 for vaccine antigen development and structural studies.

Both Hepatitis C Virus-Specific T Cell Responses and IL28B rs12979860 Single-Nucleotide Polymorphism Genotype Influence Antihepatitis C Virus Treatment Outcome in Patients with Chronic Hepatitis C

Despite new treatments for hepatitis C virus (HCV) infection, IFNα-based regimens still have clinical relevance in special populations of patients and remain the only therapeutic option for many patients. We sought to elucidate the interplay between two relevant factors (IL28B polymorphism and T cell immune responses) involved in the outcome of this therapy in HCV-infected patients. We evaluated 38 patients infected with HCV genotype 1-17 coinfected with HIV-who were undergoing a full course of pegIFNα/RBV therapy. The interdependence and roles of T cell-mediated immune responses and IL28B rs12979860 single-nucleotide polymorphism genotype as predictors of virological response to anti-HCV treatment in patients with chronic hepatitis C were evaluated using nonparametric tests. Factors associated with rapid virological response (RVR) in univariate analysis were presence of CD4 T cell response against NS3 HCV protein, low baseline HCV-RNA, and IL28B CC genotype. Factors associated with sustained virological response (SVR) in univariate analysis were IL28B CC genotype, low baseline HCV-RNA, and presence of CD4 response against NS2. In the multivariate analysis, low baseline HCV-RNA and NS3-specific CD4 response showed a clear trend toward association with RVR (P = 0.09 and P = 0.07, respectively). Regarding SVR, IL28B CC genotype was the strongest predictor (P = 0.02), with presence of NS2-specific CD4 response showing a clear trend (P = 0.09). HCV-specific T cell response influences the outcome of pegIFNα/RBV therapy regardless of IL28B genotype. HCV-specific T cell responses (adaptive immunity) seem to influence viral clearance both in the short and long term during therapy (RVR and SVR), whereas the influence of the IL28B genotype (innate immunity) may be more relevant to the long-lasting therapeutic effect (SVR).

A Sequence in the loop domain of hepatitis C virus E2 protein identified in silico as crucial for the selective binding to human CD81

Hepatitis C virus (HCV) is a species-specific pathogenic virus that infects only humans and chimpanzees. Previous studies have indicated that interactions between the HCV E2 protein and CD81 on host cells are required for HCV infection. To determine the crucial factors for species-specific interactions at the molecular level, this study employed in silico molecular docking involving molecular dynamic simulations of the binding of HCV E2 onto human and rat CD81s. In vitro experiments including surface plasmon resonance measurements and cellular binding assays were applied for simple validations of the in silico results. The in silico studies identified two binding regions on the HCV E2 loop domain, namely E2-site1 and E2-site2, as being crucial for the interactions with CD81s, with the E2-site2 as the determinant factor for human-specific binding. Free energy calculations indicated that the E2/CD81 binding process might follow a two-step model involving (i) the electrostatic interaction-driven initial binding of human-specific E2-site2, followed by (ii) changes in the E2 orientation to facilitate the hydrophobic and van der Waals interaction-driven binding of E2-site1. The sequence of the human-specific, stronger-binding E2-site2 could serve as a candidate template for the future development of HCV-inhibiting peptide drugs.

T- and B-cell responses to multivalent prime-boost DNA and viral vectored vaccine combinations against hepatitis C virus in non-human primates

Immune responses against multiple epitopes are required for the prevention of hepatitis C virus (HCV) infection, and the progression to phase I trials of candidates may be guided by comparative immunogenicity studies in non-human primates. Four vectors, DNA, SFV, human serotype 5 adenovirus (HuAd5) and Modified Vaccinia Ankara (MVA) poxvirus, all expressing hepatitis C virus Core, E1, E2 and NS3, were combined in three prime-boost regimen, and their ability to elicit immune responses against HCV antigens in rhesus macaques was explored and compared. All combinations induced specific T-cell immune responses, including high IFN-γ production. The group immunized with the SFV+MVA regimen elicited higher E2-specific responses as compared with the two other modalities, while animals receiving HuAd5 injections elicited lower IL-4 responses as compared with those receiving MVA. The IFN-γ responses to NS3 were remarkably similar between groups. Only the adenovirus induced envelope-specific antibody responses, but these failed to show neutralizing activity. Therefore, the two novel regimens failed to induce superior responses as compared with already existing HCV vaccine candidates. Differences were found in response to envelope proteins, but the relevance of these remain uncertain given the surprisingly poor correlation with immunogenicity data in chimpanzees, underlining the difficulty to predict efficacy from immunology studies.

Wide variation in estimates of global prevalence and burden of chronic hepatitis B and C infection cited in published literature

To evaluate the extent of heterogeneity in global estimates of chronic hepatitis B (HBV) and C (HCV) cited in the published literature, we undertook a systematic review of the published literature. We identified articles from 2010 to 2014 that had cited global estimates for at least one of ten indicators [prevalence and numbers infected with HBV, HCV, HIV-HBV or HIV-HCV co-infection, and mortality (number of deaths annually) for HBV and HCV]. Overall, 488 articles were retrieved: 239 articles cited a HBV-related global estimate [prevalence (n = 12), number infected (n = 193) and number of annual deaths (n = 82)]; 280 articles had HCV-related global estimates [prevalence (n = 86), number infected (n = 203) and number of annual deaths (n = 31)]; 31 had estimates on both HBV and HCV; 54 had HIV-HBV co-infection estimates [prevalence (n = 42) and number co-infected (n = 12)]; and 68 had estimates for HIV-HCV co-infection [prevalence (n = 40) and number co-infected (n = 28)]. There was considerable heterogeneity in the estimates cited and also a lack of consistency in the terminology used. Although 40% of 488 articles cited WHO as the source of the estimate, many of these were from outdated or secondary sources. Our findings highlight the importance of clear and consistent communication from WHO and other global health agencies on current consensus estimates of hepatitis B and C burden and prevalence, the need for standardisation in their citation, and for regular updates.

New Mechanism of Hepatic Fibrogenesis: Hepatitis C Virus Infection Induces Transforming Growth Factor β1 Production through Glucose-Regulated Protein 94

Hepatitis C virus (HCV) is one of the leading causes of chronic liver inflammatory disease (hepatitis), which often leads to more severe diseases, such as liver fibrosis, cirrhosis, and hepatocellular carcinoma. Liver fibrosis, in particular, is a major pathogenic consequence of HCV infection, and transforming growth factor β1 (TGF-β1) plays a key role in its pathogenesis. Several HCV proteins have been suggested to either augment or suppress the expression of TGF-β1 by HCV-infected cells. Here, we report that TGF-β1 levels are elevated in HCV-infected hepatocytes cultured in vitro and in liver tissue of HCV patients. Notably, the level of TGF-β1 in media from in vitro-cultured HCV-infected hepatocytes was high enough to activate primary hepatic stellate cells isolated from rats. This indicates that TGF-β1 secreted by HCV-infected hepatocytes is likely to play a key role in the liver fibrosis observed in HCV patients. Moreover, we showed that HCV E2 protein triggers the production of TGF-β1 by HCV-infected cells through overproduction of glucose-regulated protein 94 (GRP94).

IMPORTANCE

Hepatic fibrosis is a critical step in liver cirrhosis caused by hepatitis C virus infection. It is already known that immune cells, including Kupffer cells, mediate liver fibrosis. Recently, several papers have suggested that HCV-infected hepatocytes also significantly produce TGF-β1. Here, we provide the first examination of TGF-β1 levels in the hepatocytes of HCV patients. Using an HCV culture system, we showed that HCV infection increases TGF-β1 production in hepatocytes. Furthermore, we confirmed that the amount of TGF-β1 secreted by HCV-infected hepatocytes was sufficient to activate primary hepatic stellate cells. To understand the molecular basis of TGF-β1 production in HCV-infected hepatocytes, we used HCV replicons and various stable cell lines. Finally, we elucidated that HCV E2 triggered TGF-β1 secretion via GRP94 mediated NF-κB activation. This study contributes to the understanding of liver fibrosis by HCV and suggests a new potential target (GRP94) for blocking liver cirrhosis in HCV patients.

Peripheral lymphocyte subsets in chronic hepatitis C: Effects of 12 weeks of antiviral treatment with interferon-alpha plus ribavirin

Chronic infection with hepatitis C virus (HCV) causes a quantitative and functional alteration in innate and adaptative immunity. In the present work, we determined by flow-cytometry the profile of blood lymphocyte of untreated HCV patients and in subjects of this group that achieved or not an early virologic response at 12-weeks of treatment with interferon-α plus ribavirin. Twenty-six untreated HCV patients and 20 control healthy individuals were enrolled in the study. Untreated HCV patients had a higher proportion of B cell and a lower proportion of CD8(+) T cell and NK cells than healthy individuals did, but the proportions of CD4(+) T cells and Treg cells (CD4(+)CD25(+)Foxp3(+)) were similar in these patients and controls. Untreated HCV patients presenting cryoglobulinemia had a lower proportion of Treg cells and a lower Treg/NK cell ratio when compared with those without cryoglobulins. Nineteen out of 26 untreated HCV patients remained in the study and were treated with Interferon-α plus ribavirin. At 12-weeks of treatment, 10 of them achieved early virologic response (EVR), whereas 9 were non-responders (NR). EVR patients differed from NR patients in the increase of their proportion of NK cells at 12 weeks of treatment. In conclusion, untreated HCV patients exhibit an altered profile of blood lymphocyte subsets, including a reduction in the proportion of CD4(+)CD25(+)FoxP3(+)T regulatory cells in patients that present cryoglobulinemia. An early virological response at 12-weeks of treatment with IFN-α plus ribavirin seems to be associated a significant improvement in the proportion of NK cells of HCV treated patients.

Heterologous Expression of Hepatitis C Virus Core Protein in Oil Seeds of Brassica napus L

Background:

Hepatitis c virus (HCV), prevalent among 3% of the world population, is a major worldwide public health concern and an effective vaccination could help to overcome this problem. Plant seeds as low-cost vaccine expression platforms are highly desirable to produce antigens.

Objectives:

The present study was aimed at investigating the possible expression of recombinant HCV core protein, as a leading HCV vaccine candidate, in canola (Brassica napus) plant seeds in order to be used as an effective immunogen for vaccine researches.

Materials and Methods:

A codon-optimized gene harboring the Kozak sequence, 6 × His-tag, HCVcp (1 - 122 residues) and KDEL (Lys-Asp-Glu-Leu) peptide in tandem was designed and expressed under the control of the seed specific promoter, fatty acid elongase 1 (FAE1), to accumulate the recombinant protein in canola (B. napus L.) seeds. Transgenic lines were screened and the presence of the transgene was confirmed in the T0 plants by polymerase chain reaction (PCR). The quantity and quality of the HCV core protein (HCVcp) in transgenic seeds were evaluated by enzyme-linked immunosorbent assay (ELISA) and western blot, respectively.

Results:

Western blot analysis using anti-His antibody confirmed the presence of a 15 kDa protein in the seeds of T1 transgenic lines. The amount of antigenic protein accumulated in the seeds of these transgenic lines was up to 0.05% of the total soluble protein (TSP).

Conclusions:

The canola oilseeds could provide a useful expression system to produce HCV core protein as a vaccine candidate.

Distinct Escape Pathway by Hepatitis C Virus Genotype 1a from a Dominant CD8+ T Cell Response by Selection of Altered Epitope Processing

Antiviral CD8(+) T cells are a key component of the adaptive immune response against HCV, but their impact on viral control is influenced by preexisting viral variants in important target epitopes and the development of viral escape mutations. Immunodominant epitopes highly conserved across genotypes therefore are attractive for T cell based prophylactic vaccines. Here, we characterized the CD8(+) T cell response against the highly conserved HLA-B*51-restricted epitope IPFYGKAI1373-1380 located in the helicase domain of NS3 in people who inject drugs (PWID) exposed predominantly to HCV genotypes 1a and 3a. Despite this epitope being conserved in both genotypes, the corresponding CD8(+) T cell response was detected only in PWID infected with genotype 3a and HCV-RNA negative PWID, but not in PWID infected with genotype 1a. In genotype 3a, the detection of strong CD8(+) T cell responses was associated with epitope variants in the autologous virus consistent with immune escape. Analysis of viral sequences from multiple cohorts confirmed HLA-B*51-associated escape mutations inside the epitope in genotype 3a, but not in genotype 1a. Here, a distinct substitution in the N-terminal flanking region located 5 residues upstream of the epitope (S1368P; P = 0.00002) was selected in HLA-B*51-positive individuals. Functional assays revealed that the S1368P substitution impaired recognition of target cells presenting the endogenously processed epitope. The results highlight that, despite an epitope being highly conserved between two genotypes, there are major differences in the selected viral escape pathways and the corresponding T cell responses.

IMPORTANCE

HCV is able to evolutionary adapt to CD8(+) T cell immune pressure in multiple ways. Beyond selection of mutations inside targeted epitopes, this study demonstrates that HCV inhibits epitope processing by modification of the epitope flanking region under T cell immune pressure. Selection of a substitution five amino acids upstream of the epitope underlines that efficient antigen presentation strongly depends on its larger sequence context and that blocking of the multistep process of antigen processing by mutation is exploited also by HCV. The pathways to mutational escape of HCV are to some extent predictable but are distinct in different genotypes. Importantly, the selected escape pathway of HCV may have consequences for the destiny of antigen-specific CD8(+) T cells.

Recent advances on the synthesis of hepatitis C virus NS5B RNA-dependent RNA-polymerase inhibitors

Hepatitis C is a viral liver infection considered as the major cause of cirrhosis and hepatocellular carcinoma (HCC). The HCV NS5B polymerase, an RNA-dependent RNA polymerase, is essential for HCV replication, which is able to catalyze the synthesis of positive (genomic) and negative (template) strand HCV RNA, but has no functional equivalent in mammalian cells. Therefore, the NS5B polymerase has emerged as an attractive target for the development of specifically targeted antiviral therapy for HCV (DAA, for direct-acting antivirals). Recently, a growing number of compounds have been reported as the NS5B polymerase inhibitors, some of which especially have been licensed in clinical trials. This review describes recent advances on the synthesis of the NS5B polymerase inhibitors, focusing on the merits and demerits of their synthetic methods. In particular, inspiration from the synthesis and the future direction of the NS5B polymerase inhibitors are highlighted.

Co-expression of hepatitis C virus polytope-HBsAg and p19-silencing suppressor protein in tobacco leaves

CONTEXT

Plants transformed by virus-based vectors have emerged as promising tools to rapidly express large amounts and inexpensive antigens in transient condition.

OBJECTIVE

We studied the possibility of transient-expression of an HBsAg-fused polytopic construct (HCVpc) [containing H-2d and HLA-A2-restricted CD8+CTL-epitopic peptides of C (Core; aa 132-142), E6 (Envelope2; aa 614-622), N (NS3; aa 1406-1415), and E4 (Envelope2; aa 405-414) in tandem of CE6NE4] in tobacco (Nicotiana tabacum) leaves for the development of a plant-based HCV vaccine.

MATERIALS AND METHODS

A codon-optimized gene encoding the Kozak sequence, hexahistidine (6×His)-tag peptide, and HCVpc in tandem was designed, chemically synthesized, fused to HBsAg gene, and inserted into Potato virus X (PVX-GW) vector under the control of duplicated PVX coat protein promoter (CPP). The resulted recombinant plasmids (after confirmation by restriction and sequencing analyses) were transferred into Agrobacterium tumefaciens strain GV3101 and vacuum infiltrated into tobacco leaves. The effect of gene-silencing suppressor, p19 protein from tomato bushy stunt virus, on the expression yield of HCVpc-HBsAg was also evaluated by co-infiltration of a p19 expression vector.

RESULTS

Codon-optimized gene increased adaptation index (CAI) value (from 0.61 to 0.92) in tobacco. The expression of the HCVpc-HBsAg was confirmed by western blot and HBsAg-based detection ELISA on total extractable proteins of tobacco leaves. The expression level of the fusion protein was significantly higher in p19 co-agroinfiltrated plants.

DISCUSSION AND CONCLUSION

The results indicated the possibility of expression of HCVpc-HBsAg constructs with proper protein conformations in tobacco for final application as a plant-derived HCV vaccine.

Prophylactic vaccinations in chronic kidney disease: Current status

In this review, recent data on results concerning prophylactic vaccinations against hepatitis B virus, influenza viruses, and pneumococci are presented. Effects of active immunization in chronic kidney disease depend on category of glomerular filtration rate (GFR). The lower GFR category the better results of response to vaccination. Abnormalities in toll-like receptors and down-regulation of B-cell activating factor receptor in transitional B cells were recently included into uremia-associated deficits in immunocompetence. Development of novel, more potent vaccines containing toll-like receptor agonists as adjuvants may help to achieve more effective immunization against hepatitis B virus in immunocompromised patients. Experimental studies announce further vaccine adjuvants. A vaccine against hepatitis C virus is not available yet, but promising results were already obtained in the experimental and preliminary clinical studies. Prophylactic vaccinations against influenza viruses and pneumococci become increasingly popular in dialysis facilities due to their proved benefits.

Trans-splicing group I intron targeting hepatitis C virus IRES mediates cell death upon viral infection in Huh7.5 cells

The HCV-IRES sequence is vital for both protein translation and genome replication and serves as a potential target for anti-HCV therapy. We constructed a series of anti-HCV group I introns (αHCV-GrpIs) to attack conserved target sites within the HCV IRES. These αHCV-GrpIs were designed to mediate a trans-splicing reaction that replaces the viral RNA genome downstream of the 5' splice site with a 3' exon that encodes an apoptosis-inducing gene. Pro-active forms of the apoptosis inducing genes BID, Caspase 3, Caspase 8, or tBax were modified by incorporation of the HCV NS5A/5B cleavage sequence in place of their respective endogenous cleavage sites to ensure that only HCV infected cells would undergo apoptosis following splicing and expression. Huh7.5 cells transfected with each intron were challenged at MOI 0.1 with HCV-Jc1FLAG2 which expresses a Gaussia Luciferase (GLuc) marker. Virus-containing supernatants were then assayed for GLuc expression as a measure of viral replication inhibition. Cellular extracts were analyzed for the presence of correct splice products by RT-PCR and DNA sequencing. We also measured levels of Caspase 3 activity as a means of quantifying apoptotic cell death. Each of these αHCV-GrpI introns was able to correctly splice their 3' apoptotic exons onto the virus RNA genome at the targeted Uracil, and resulted in greater than 80% suppression of the GLuc marker. A more pronounced suppression effect was observed with TCID₅₀ virus titrations, which demonstrated that these αHCV-GrpIs were able to suppress viral replication by more than 2 logs, or greater than 99%. Robust activation of the apoptotic factor within the challenged cells was evidenced by a significant increase of Caspase 3 activity upon viral infection compared to non-challenged cells. This novel genetic intervention tool may prove beneficial in certain HCV subjects.

Hepatitis C vaccine clinical trials among people who use drugs: potential for participation and involvement in recruitment

Candidate prophylactic HCV vaccines are approaching phase III clinical trial readiness, yet little is known about the potential for participation among target groups or innovative ways to promote enrollment within 'hard-to-reach' populations. This study describes HCV vaccine trial participation willingness among a high-risk sample of people who use drugs and their willingness to assist researchers by promoting the trial among peers. Willingness to participate in and encourage peers' participation in an HCV vaccine trial was assessed among injection and non-injection drug users enrolled in a cohort study in Kentucky using interviewer-administered questionnaires (n=165 and 415, respectively, with willingness to participate assessed among HCV-seronegative participants only). Generalized linear mixed models were used to determine correlates to being "very likely" to participate or encourage participation in a trial. Most reported being likely to participate or encourage participation in a vaccine trial (63% and 87%, respectively). Men were significantly less likely to report willingness to encourage others' participation, while willingness to encourage was higher among lower income, HCV-seropositive, heroin-using, and methamphetamine-using participants. Unemployment, lesser education, receipt of financial support from more peers, and nonmedical prescription drug use were positively associated with willingness to participate. Differential enrollment in HCV vaccine clinical trials by socioeconomic status may occur, underscoring ethical considerations and need for avoiding coercion. Notably, the data suggest that a peer-driven approach to promoting trial participation among people who use drugs could be feasible in this population and that HCV-seropositive individuals and women could be especially instrumental in these efforts.

Enhanced-Transient Expression of Hepatitis C Virus Core Protein in Nicotiana tabacum, a Protein With Potential Clinical Applications

BACKGROUND

Hepatitis C virus (HCV) is major cause of liver cirrhosis in humans. HCV capsid (core) protein (HCVcp) is a highly demanded antigen for various diagnostic, immunization and pathogenesis studies. Plants are considered as an expression system for producing safe and inexpensive biopharmaceutical proteins. Although invention of transgenic (stable) tobacco plants expressing HCVcp with proper antigenic properties was recently reported, no data for "transient-expression" that is currently the method of choice for rapid, simple and lower-priced protein expression in plants is available for HCVcp.

OBJECTIVES

The purpose of this study was to design a highly codon-optimized HCVcp gene for construction of an efficient transient-plant expression system for production of HCVcp with proper antigenic properties in a regional tobacco plant (Iranian Jafarabadi-cultivar) by evaluation of different classes of vectors and suppression of gene-silencing in tobacco.

MATERIALS AND METHODS

A codon-optimized gene encoding the Kozak sequence, 6xHis-tag, HCVcp (1-122) and KDEL peptide in tandem (from N- to C-terminal) was designed and inserted into potato virus-X (PVX) and classic pBI121 binary vectors in separate cloning reactions. The resulted recombinant plasmids were transferred into Agrobacterium tumefaciens and vacuum infiltrated into tobacco leaves. The effect of gene silencing suppressor P19 protein derived from tomato bushy stunt virus on the expression yield of HCVcp by each construct was also evaluated by co-infiltration in separate groups. The expressed HCVcp was evaluated by dot and western blotting and ELISA assays.

RESULTS

The codon-optimized gene had an increased adaptation index value (from 0.65 to 0.85) and reduced GC content (from 62.62 to 51.05) in tobacco and removed the possible deleterious effect of "GGTAAG" splice site in native HCVcp. Blotting assays via specific antibodies confirmed the expression of the 15 kDa HCVcp. The expression level of HCVcp was enhanced by 4-5 times in P19 co-agroinfiltrated plants with better outcomes for PVX, compared to pBI121 vector (0.022% versus 0.019% of the total soluble protein). The plant-derived HCVcp (pHCVcp) could properly identify the HCVcp antibody in HCV-infected human sera compared to Escherichia coli-derived HCVcp (eHCVcp), indicating its potential for diagnostic/immunization applications.

CONCLUSIONS

By employment of gene optimization strategies, use of viral-based vectors and suppression of plant-derived gene silencing effect, efficient transient expression of HCVcp in tobacco with proper antigenic properties could be possible.

Activity of core-modified 10-23 DNAzymes against HCV

The highly conserved untranslated regions of the hepatitis C virus (HCV) play a fundamental role in viral translation and replication and are therefore attractive targets for drug development. A set of modified DNAzymes carrying (2'R)-, (2'S)-2'-deoxy-2'-C-methyl- and -2'-O-methylnucleosides at various positions of the catalytic core were assayed against the 5'-internal ribosome entry site element (5'-IRES) region of HCV. Intracellular stability studies showed that the highest stabilization effects were obtained when the DNAzymes' cores were jointly modified with 2'-C-methyl- and 2'-O-methylnucleosides, yielding an increase by up to fivefold in the total DNAzyme accumulation within the cell milieu within 48 h of transfection. Different regions of the HCV IRES were explored with unmodified 10-23 DNAzymes for accessibility. A subset of these positions was tested for DNAzyme activity using an HCV IRES-firefly luciferase translation-dependent RNA (IRES-FLuc) transcript, in the rabbit reticulocyte lysate system and in the Huh-7 human hepatocarcinoma cell line. Inhibition of IRES-dependent translation by up to 65 % was observed for DNAzymes targeting its 285 position, and it was also shown that the modified DNAzymes are as active as the unmodified one.

Production and characterization of high-titer serum-free cell culture grown hepatitis C virus particles of genotype 1-6

Recently, cell culture systems producing hepatitis C virus particles (HCVcc) were developed. Establishment of serum-free culture conditions is expected to facilitate development of a whole-virus inactivated HCV vaccine. We describe generation of genotype 1-6 serum-free HCVcc (sf-HCVcc) from Huh7.5 hepatoma cells cultured in adenovirus expression medium. Compared to HCVcc, sf-HCVcc showed 0.6-2.1 log10 higher infectivity titers (4.7-6.2 log10 Focus Forming Units/mL), possibly due to increased release and specific infectivity of sf-HCVcc. In contrast to HCVcc, sf-HCVcc had a homogeneous single-peak density profile. Entry of sf-HCVcc depended on HCV co-receptors CD81, LDLr, and SR-BI, and clathrin-mediated endocytosis. HCVcc and sf-HCVcc were neutralized similarly by chronic-phase patient sera and by human monoclonal antibodies targeting conformational epitopes. Thus, we developed serum-free culture systems producing high-titer single-density sf-HCVcc, showing similar biological properties as HCVcc. This methodology has the potential to advance HCV vaccine development and to facilitate biophysical studies of HCV.

New pyrazolobenzothiazine derivatives as hepatitis C virus NS5B polymerase palm site I inhibitors

We have previously identified the pyrazolobenzothiazine scaffold as a promising chemotype against hepatitis C virus (HCV) NS5B polymerase, a validated and promising anti-HCV target. Herein we describe the design, synthesis, enzymatic, and cellular characterization of new pyrazolobenzothiazines as anti-HCV inhibitors. The binding site for a representative derivative was mapped to NS5B palm site I employing a mutant counterscreen assay, thus validating our previous in silico predictions. Derivative 2b proved to be the best selective anti-HCV derivative within the new series, exhibiting a IC50 of 7.9 μM against NS5B polymerase and antiviral effect (EC50 = 8.1 μM; EC90 = 23.3 μM) coupled with the absence of any antimetabolic effect (CC50 > 224 μM; SI > 28) in a cell based HCV replicon system assay. Significantly, microscopic analysis showed that, unlike the parent compounds, derivative 2b did not show any significant cell morphological alterations. Furthermore, since most of the pyrazolobenzothiazines tested altered cell morphology, this undesired aspect was further investigated by exploring possible perturbation of lipid metabolism during compound treatment.

Recombinant adenoviral vector expressing HCV NS4 induces protective immune responses in a mouse model of Vaccinia-HCV virus infection: a dose and route conundrum

Hepatitis C virus (HCV) leads to chronic infection in the majority of infected patients presumably due to failure or inefficiency of the immune responses generated. Both antibody and cellular immune responses have been suggested to be important in viral clearance. Non-replicative adenoviral vectors expressing antigens of interest are considered as attractive vaccine vectors for a number of pathogens. In this study, we sought to evaluate cellular and humoral immune responses against HCV NS4 protein using recombinant adenovirus as a vaccine vector expressing NS4 antigen. We have also measured the effect of antigen doses and routes of immunization on the quality and extent of the immune responses, especially their role in viral load reduction, in a recombinant Vaccinia-HCV (Vac-HCV) infection mouse model. Our results show that an optimum dose of adenovirus vector (2×10(7)pfu/mouse) administered intramuscularly (i.m.) induces high T cell proliferation, granzyme B-expressing CD8(+) T cells, pro-inflammatory cytokines such as IFN-γ, TNF-α, IL-2 and IL-6, and antibody responses that can significantly reduce the Vac-HCV viral load in the ovaries of female C57BL/6 mice. Our results demonstrate that recombinant adenovirus vector can induce both humoral and cellular protective immunity against HCV-NS4 antigen, and that immunity is intricately controlled by route and dose of immunizing vector.

Why is it so difficult to develop a hepatitis C virus preventive vaccine?

With an estimated 3% of the world's population chronically infected, hepatitis C virus (HCV) represents a major health problem for which an efficient vaccination strategy would be highly desirable. Indeed, chronic hepatitis C is recognized as one of the major causes of cirrhosis, hepatocarcinoma and liver failure worldwide and it is the most common indication for liver transplantation, accounting for 40-50% of liver transplants. Much progress has been made in the prevention of HCV transmission and in therapeutic intervention. However, even if a new wave of directly acting antivirals promise to overcome the problems of low efficacy and adverse effects observed for the current standard of care, which include interferon-α and ribavirin, an effective vaccine would be the only means to definitively eradicate infection and to diminish the burden of HCV-related diseases at affordable costs. Although there is strong evidence that the goal of a prophylactic vaccine could be achieved, there are huge development issues that have impeded reaching this goal and that still have to be addressed. In this article we address the question of whether an HCV vaccine is needed, whether it will eventually be feasible, and why it is so difficult to produce.

The versatile nature of the 6-aminoquinolone scaffold: identification of submicromolar hepatitis C virus NS5B inhibitors

We have previously reported that the 6-aminoquinolone chemotype is a privileged scaffold to obtain antibacterial and antiviral agents. Herein we describe the design, synthesis, and enzymatic and cellular characterization of new 6-aminoquinolone derivatives as potent inhibitors of NS5B polymerase, an attractive and viable therapeutic target to develop safe anti-HCV agents. The 6-amino-7-[4-(2-pyridinyl)-1-piperazinyl]quinolone derivative 8 proved to be the best compound of this series, exhibiting an IC50 value of 0.069 μM against NS5B polymerase and selective antiviral effect (EC50 = 3.03 μM) coupled with the absence of any cytostatic effect (CC50 > 163 μM; SI > 54) in Huh 9-13 cells carrying a HCV genotype 1b, as measured by MTS assay. These results indicate that the 6-aminoquinolone scaffold is worthy of further investigation in the context of NS5B-targeted HCV drug discovery programs.

Immunization of Mice by BCG Formulated HCV Core Protein Elicited Higher Th1-Oriented Responses Compared to Pluronic-F127 Copolymer

BACKGROUND

A supreme vaccine for Hepatitis C virus (HCV) infection should elicit strong Th1-oriented cellular responses. In the absence of a Th1-specific adjuvant, immunizations by protein antigens generally induce Th2-type and weak cellular responses.

OBJECTIVES

To evaluate the adjuvant effect of BCG in comparison with nonionic copolymer-Pluronic F127 (F127) as a classic adjuvant in the formulation of HCV core protein (HCVcp) as a candidate vaccine for induction of Th1 immune responses.

MATERIALS AND METHODS

Expression of N-terminally His-Tagged HCVcp (1-122) by pIVEX2.4a-core vector harboring the corresponding gene under the control of arabinose-inducible (araBAD) promoter was achieved in BL21-AI strain of E.coli and purified through application of nitrilotriacetic acid (Ni-NTA) chromatography. Mice were immunized subcutaneously (s.c.) in base of the tail with 100 μl of immunogen (F127+HCVcp or BCG+HCVcp; 5 μgHCVcp/mouse/dose) or control formulations (PBS, BCG, F127) at weeks 0, 3, 6. Total and subtypes of IgG, as well as cellular immune responses (Proliferation, In vivo CTL and IFN-γ/IL-4 ELISpot assays against a strong and dominant H2-d restricted, CD8+-epitopic peptide, core 39-48; RRGPRLGVRA of HCVcp) were compared in each group of immunized animals.

RESULTS

Expression and purification of core protein around the expected size (21 kDa) was confirmed by Western blotting. The HCVcp + BCG vaccinated mice showed significantly higher lymphocyte proliferation and IFN-γ production but lower levels of cell lysis (45% versus 62% in CTL assay) than the HCVcp+F127 immunized animals. "Besides, total anti-core IgG and IgG1 levels were significantly higher in HCVcp + F127 immunized mice as compared to HCVcp + BCG vaccinated animals, indicating relatively higher efficacy of F127 for the stimulation of humoral and Th2-oriented immune responses".

CONCLUSIONS

Results showed that HCVcp + BCG induced a moderate CTL and mixed Th1/Th2 immune responses with higher levels of cell proliferation and IFN-γ secretion, indicating that BCG may have a better outcome when formulated in HCVcp-based subunit vaccines.

Viral hepatitis: Cell-culture-derived HCV--a promising vaccine antigen

With millions of humans infected yearly with HCV, leading to cirrhosis and cancer, a vaccine is urgently needed. Cultured virus particles constitute the antigen in most antiviral vaccines. A study in mice demonstrated induction of neutralizing antibodies by immunization with cell-culture-derived HCV, providing new possibilities for vaccine development.