MEDICINE. Global control of hepatitis C virus

Glycoengineering of the hepatitis C virus E2 glycoprotein leads to improved biochemical properties and enhanced immunogenicity

An effective vaccine against hepatitis C virus (HCV) must elicit the production of broadly neutralizing antibodies (bnAbs) reproducibly against the E1E2 glycoprotein complex. Little is known about how glycan content affects this process. Ideally, glycans would maximize epitope exposure without compromising antigen stability or exposing new epitopes. However, typical recombinant vaccines contain considerable heterogeneity in glycan content, which can affect the antibody response and neutralization potency. Here we employed glycoengineered Chinese hamster ovary (geCHO) cell lines that impart nearly homogeneous glycosylation as a means to test how specific glycan features influence antigenicity and immunogenicity for the secreted HCV E2 ectodomain (sE2). Specific geCHO antigens exhibited a modest but reproducible increase in affinity for some mAbs relative to CHO- and HEK293-produced sE2. Surprisingly, one geCHO sE2 antigen failed to bind the CD81 receptor, indicating the potential for significant glycan effects on biochemical properties. We immunized mice with the four antigens and found the total antibody response to be the same for all groups. However, sera from one geCHO group exhibited a 7-fold improvement in neutralization against the homologous HCV pseudovirus and had the most mice whose sera exhibited neutralization activity against genotypes 1b, 2a, 2b, and 3. Further analysis identified beneficial and deleterious glycan features, and the glycan that correlated the most with decreased potency was relatively small. However, size was not the sole determinant of glycan-driven effects on the antibody response. In summary, glycan content impacts biochemical properties of antigens to varying degrees and such effects can influence immune response quality and uniformity.

Targeting cGAS-STING: modulating the immune landscape of hepatic diseases

Liver diseases, including viral hepatitis, alcoholic liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and hepatocellular carcinoma (HCC), represent a significant threat to global health due to their high mortality rates. The cGAS-STING pathway, a critical part of the innate immune system, plays a crucial role in detecting cytoplasmic DNA and initiating immune responses, including autoimmune inflammation and antitumor immunity. Genomic instability during cancer progression can trigger this pathway by releasing DNA into the cytoplasm. Emerging research indicates that cGAS-STING signaling is intricately involved in maintaining liver homeostasis and contributes to the pathogenesis of various liver diseases. This review outlines the cGAS-STING pathway, with a particular focus on its activation mechanism and its roles in several notable liver conditions. Specifically, we explore the complex interplay of cGAS-STING signaling in viral hepatitis, ALD, MASLD, and HCC, and discuss its potential as a therapeutic target. For example, in HCC, strategies targeting cGAS-STING include using nanomaterials to deliver STING agonists, combining radiofrequency ablation (RFA) with cGAS-STING activation, and leveraging radiotherapy to enhance pathway activation. Furthermore, modulating cGAS-STING activity may offer therapeutic avenues for viral hepatitis and chronic liver diseases like MASLD and ALD, either by boosting antiviral responses or mitigating inflammation. This review highlights the complex role of cGAS-STING signaling in these specific liver diseases and underscores the need for further research to fully realize its therapeutic potential.

Hepatitis C Virus E1E2 Structure, Diversity, and Implications for Vaccine Development

Hepatitis C virus (HCV) is a major medical health burden and the leading cause of chronic liver disease and cancer worldwide. More than 58 million people are chronically infected with HCV, with 1.5 million new infections occurring each year. An effective HCV vaccine is a major public health and medical need as recognized by the World Health Organization. However, due to the high variability of the virus and its ability to escape the immune response, HCV rapidly accumulates mutations, making vaccine development a formidable challenge. An effective vaccine must elicit broadly neutralizing antibodies (bnAbs) in a consistent fashion. After decades of studies from basic research through clinical development, the antigen of choice is considered the E1E2 envelope glycoprotein due to conserved, broadly neutralizing antigenic domains located in the constituent subunits of E1, E2, and the E1E2 heterodimeric complex itself. The challenge has been elicitation of robust humoral and cellular responses leading to broad virus neutralization due to the relatively low immunogenicity of this antigen. In view of this challenge, structure-based vaccine design approaches to stabilize key antigenic domains have been hampered due to the lack of E1E2 atomic-level resolution structures to guide them. Another challenge has been the development of a delivery platform in which a multivalent form of the antigen can be presented in order to elicit a more robust anti-HCV immune response. Recent nanoparticle vaccines are gaining prominence in the field due to their ability to facilitate a controlled multivalent presentation and trafficking to lymph nodes, where they can interact with both the cellular and humoral components of the immune system. This review focuses on recent advances in understanding the E1E2 heterodimeric structure to facilitate a rational design approach and the potential for development of a multivalent nanoparticle-based HCV E1E2 vaccine. Both aspects are considered important in the development of an effective HCV vaccine that can effectively address viral diversity and escape.

Prospects for developing an Hepatitis C virus E1E2-based nanoparticle vaccine

Globally, more than 58 million people are chronically infected with Hepatitis C virus (HCV) with 1.5 million new infections occurring each year. An effective vaccine for HCV is therefore a major unmet medical and public health need. Since HCV rapidly accumulates mutations, vaccines must elicit the production of broadly neutralising antibodies (bnAbs) in a reproducible fashion. Decades of research have generated a number of HCV vaccine candidates. Based on the available data and research through clinical development, a vaccine antigen based on the E1E2 glycoprotein complex appears to be the best choice, but robust induction of humoral and cellular responses leading to virus neutralisation has not yet been achieved. One issue that has arisen in developing an HCV vaccine (and many other vaccines as well) is the platform used for antigen delivery. The majority of viral vaccine trials have employed subunit vaccines. However, subunit vaccines often have limited immunogenicity, as seen for HCV, and thus multiple formats must be examined in order to elicit a robust anti-HCV immune response. Nanoparticle vaccines are gaining prominence in the field due to their ability to facilitate a controlled multivalent presentation and trafficking to lymph nodes, where they can interact with both arms of the immune system. This review discusses the potential for development of a nanoparticle-based HCV E1E2 vaccine, with an emphasis on the potential benefits of such an approach along with the major challenges facing the incorporation of E1E2 into nanoparticulate delivery systems and how those challenges can be addressed.

Signatures of VH1-69-derived hepatitis C virus neutralizing antibody precursors defined by binding to envelope glycoproteins

An effective preventive vaccine for hepatitis C virus (HCV) remains a major unmet need. Antigenic region 3 (AR3) on the E1E2 envelope glycoprotein complex overlaps with the CD81 receptor binding site and represents an important epitope for broadly neutralizing antibodies (bNAbs) and is therefore important for HCV vaccine design. Most AR3 bNAbs utilize the VH1-69 gene and share structural features that define the AR3C-class of HCV bNAbs. In this work, we identify recombinant HCV glycoproteins based on a permuted E2E1 trimer design that bind to the inferred VH1-69 germline precursors of AR3C-class bNAbs. When presented on nanoparticles, these recombinant E2E1 glycoproteins efficiently activate B cells expressing inferred germline AR3C-class bNAb precursors as B cell receptors. Furthermore, we identify critical signatures in three AR3C-class bNAbs that represent two subclasses of AR3C-class bNAbs that will allow refined protein design. These results provide a framework for germline-targeting vaccine design strategies against HCV.

Identification of novel neutralizing determinants for protection against HCV

BACKGROUND AND AIMS

HCV evasion of neutralizing antibodies (nAb) results in viral persistence and poses challenges to the development of an urgently needed vaccine. N-linked glycosylation of viral envelope proteins is a key mechanism for such evasion. To facilitate rational vaccine design, we aimed to identify determinants of protection of conserved neutralizing epitopes.

APPROACH AND RESULTS

Using a reverse evolutionary approach, we passaged genotype 1a, 1b, 2a, 3a, and 4a HCV with envelope proteins (E1 and E2) derived from chronically infected patients without selective pressure by nAb in cell culture. Compared with the original viruses, HCV recombinants, engineered to harbor substitutions identified in polyclonal cell culture-passaged viruses, showed highly increased fitness and exposure of conserved neutralizing epitopes in antigenic regions 3 and 4, associated with protection from chronic infection. Further reverse genetic studies of acquired E1/E2 substitutions identified positions 418 and 532 in the N1 and N6 glycosylation motifs, localizing to adjacent E2 areas, as key regulators of changes of the E1/E2 conformational state, which governed viral sensitivity to nAb. These effects were independent of predicted glycan occupancy.

CONCLUSIONS

We show how N-linked glycosylation motifs can trigger dramatic changes in HCV sensitivity to nAb, independent of glycan occupancy. These findings aid in the understanding of HCV nAb evasion and rational vaccine design, as they can be exploited to stabilize the structurally flexible envelope proteins in an open conformation, exposing important neutralizing epitopes. Finally, this work resulted in a panel of highly fit cell culture infectious HCV recombinants.

Hepatitis C virus: A critical approach to who really needs treatment

Introduction of effective drugs in the treatment of hepatitis C virus (HCV) infection has prompted the World Health Organization to declare a global eradication target by 2030. Propositions have been made to screen the general population and treat all HCV carriers irrespective of the disease status. A year ago the new severe acute respiratory syndrome coronavirus 2 virus appeared causing a worldwide pandemic of coronavirus disease 2019 disease. Huge financial resources were redirected, and the pandemic became the first priority in every country. In this review, we examined the feasibility of the World Health Organization elimination program and the actual natural course of HCV infection. We also identified and analyzed certain comorbidity factors that may aggravate the progress of HCV and some marginalized subpopulations with characteristics favoring HCV dissemination. Alcohol consumption, HIV coinfection and the presence of components of metabolic syndrome including obesity, hyperuricemia and overt diabetes were comorbidities mostly responsible for increased liver-related morbidity and mortality of HCV. We also examined the significance of special subpopulations like people who inject drugs and males having sex with males. Finally, we proposed a different micro-elimination screening and treatment program that can be implemented in all countries irrespective of income. We suggest that screening and treatment of HCV carriers should be limited only in these particular groups.

Eliminating viral hepatitis in children after liver transplants: How to reach the goal by 2030

Viral hepatitis infections are a great burden in children who have received liver transplant. Hepatotropic viruses can cause liver inflammation that can develop into liver graft fibrosis and cirrhosis over the long term. Immunological reactions due to viral hepatitis infections are associated with or can mimic graft rejection, rendering the condition difficult to manage. Prevention strategies using vaccinations are agreeable to patients, safe, cost-effective and practical. Hence, strategies to eliminate viral hepatitis A and B focus mainly on immunization programmes for children who have received a liver transplant. Although a vaccine has been developed to prevent hepatitis C and E viruses, its use is not licensed worldwide. Consequently, eliminating hepatitis C and E viruses mainly involves early detection in children with suspected cases and effective treatment with antiviral therapy. Good hygiene and sanitation are also important to prevent hepatitis A and E infections. Donor blood products and liver grafts should be screened for hepatitis B, C and E in children who are undergoing liver transplantation. Future research on early detection of viral hepatitis infections should include molecular techniques for detecting hepatitis B and E. Moreover, novel antiviral drugs for eradicating viral hepatitis that are highly effective and safe are needed for children who have undergone liver transplantation.

Virus-Like Particles Containing the E2 Core Domain of Hepatitis C Virus Generate Broadly Neutralizing Antibodies in Guinea Pigs

A vaccine to prevent hepatitis C virus (HCV) infection is urgently needed for use alongside direct-acting antiviral drugs to achieve elimination targets. We have previously shown that a soluble recombinant form of the glycoprotein E2 ectodomain (residues 384 to 661) that lacks three variable regions (Δ123) is able to elicit a higher titer of broadly neutralizing antibodies (bNAbs) than the parental form (receptor-binding domain [RBD]). In this study, we engineered a viral nanoparticle that displays HCV glycoprotein E2 on a duck hepatitis B virus (DHBV) small surface antigen (S) scaffold. Four variants of E2-S virus-like particles (VLPs) were constructed: Δ123-S, RBD-S, Δ123A7-S, and RBDA7-S; in the last two, 7 cysteines were replaced with alanines. While all four E2-S variant VLPs display E2 as a surface antigen, the Δ123A7-S and RBDA7-S VLPs were the most efficiently secreted from transfected mammalian cells and displayed epitopes recognized by cross-genotype broadly neutralizing monoclonal antibodies (bNMAbs). Both Δ123A7-S and RBDA7-S VLPs were immunogenic in guinea pigs, generating high titers of antibodies reactive to native E2 and able to prevent the interaction between E2 and the cellular receptor CD81. Four out of eight animals immunized with Δ123A7-S elicited neutralizing antibodies (NAbs), with three of those animals generating bNAbs against 7 genotypes. Immune serum generated by animals with NAbs mapped to major neutralization epitopes located at residues 412 to 420 (epitope I) and antigenic region 3. VLPs that display E2 glycoproteins represent a promising vaccine platform for HCV and could be adapted to large-scale manufacturing in yeast systems.

IMPORTANCE There is currently no vaccine to prevent hepatitis C virus infection, which affects more than 71 million people globally and is a leading cause of progressive liver disease, including cirrhosis and cancer. Broadly neutralizing antibodies that recognize the E2 envelope glycoprotein can protect against heterologous viral infection and correlate with viral clearance in humans. However, broadly neutralizing antibodies are difficult to generate due to conformational flexibility of the E2 protein and epitope occlusion. Here, we show that a VLP vaccine using the duck hepatitis B virus S antigen fused to HCV glycoprotein E2 assembles into virus-like particles that display epitopes recognized by broadly neutralizing antibodies and elicit such antibodies in guinea pigs. This platform represents a novel HCV vaccine candidate amenable to large-scale manufacture at low cost.

Profiling the HCV Immune Response in Patients with Chronic Liver Diseases and Hepatocellular Carcinoma by Peptide Microarray Analysis

BACKGROUND

Chronic infection with hepatitis C virus (HCV) is among the major causes of hepatic fibrosis, cirrhosis, as well as hepatocellular carcinoma (HCC), and it is associated with a significant risk of developing lymphoproliferative disorders. The rate of clinical disease progression is variable depending on multiple host and viral factors, including immune response.

METHODS

To perform a comprehensive epitope mapping of anti-HCV antibodies in patients suffering from HCV-related liver or lymphoproliferative diseases, we analyzed clinical samples on a peptide microarray platform made of 5952 overlapping 15-mer synthetic peptides derived from the whole HCV proteome. We evaluated the antibody profile of 71 HCV-positive patients diagnosed with HCC, mixed cryoglobulinemia (MC), and HCV chronic infection. Antibody reactivity against virus peptides was detected in all HCVpositive patients. Importantly, the signal amplitude varied significantly within and between diverse patient groups.

RESULTS

Antibody reactivity against C peptides were found generally low in HCV chronically infected asymptomatic subjects and increasingly high in HCC and MC patients. Moreover, we found a statistically significant higher IgG response in HCC and MC patients against specific domains of HCV C, E2, NS3, NS4A, NS4B, NS5A, and p7 compared to HCV-positive subjects.

CONCLUSION

In conclusion, our data suggest that immune response against specific HCV protein domains may represent useful biomarkers of disease progression among HCVpositive patients and suggest that peptide microarrays are good tools for the screening of immunotherapy targets in preclinical HCV research.

Structural and Biophysical Characterization of the HCV E1E2 Heterodimer for Vaccine Development

An effective vaccine for the hepatitis C virus (HCV) is a major unmet medical and public health need, and it requires an antigen that elicits immune responses to multiple key conserved epitopes. Decades of research have generated a number of vaccine candidates; based on these data and research through clinical development, a vaccine antigen based on the E1E2 glycoprotein complex appears to be the best choice. One bottleneck in the development of an E1E2-based vaccine is that the antigen is challenging to produce in large quantities and at high levels of purity and antigenic/functional integrity. This review describes the production and characterization of E1E2-based vaccine antigens, both membrane-associated and a novel secreted form of E1E2, with a particular emphasis on the major challenges facing the field and how those challenges can be addressed.

Immunopotentiating and Delivery Systems for HCV Vaccines

Development of preventive vaccines against hepatitis C virus (HCV) remains one of the main strategies in achieving global elimination of the disease. The effort is focused on the quest for vaccines capable of inducing protective cross-neutralizing humoral and cellular immune responses, which in turn dictate the need for rationally designed cross-genotype vaccine antigens and potent immunoadjuvants systems. This review provides an assessment of the current state of knowledge on immunopotentiating compounds and vaccine delivery systems capable of enhancing HCV antigen-specific immune responses, while focusing on the synergy and interplay of two modalities. Structural, physico-chemical, and biophysical features of these systems are discussed in conjunction with the analysis of their in vivo performance. Extreme genetic diversity of HCV-a well-known hurdle in the development of an HCV vaccine, may also present a challenge in a search for an effective immunoadjuvant, as the effort necessitates systematic and comparative screening of rationally designed antigenic constructs. The progress may be accelerated if the preference is given to well-defined molecular immunoadjuvants with greater formulation flexibility and adaptability, including those capable of spontaneous self-assembly behavior, while maintaining their robust immunopotentiating and delivery capabilities.

From Structural Studies to HCV Vaccine Design

Hepatitis C virus (HCV) is a serious and growing public health problem despite recent developments of antiviral therapeutics. To achieve global elimination of HCV, an effective cross-genotype vaccine is needed. The failure of previous vaccination trials to elicit an effective cross-reactive immune response demands better vaccine antigens to induce a potent cross-neutralizing response to improve vaccine efficacy. HCV E1 and E2 envelope (Env) glycoproteins are the main targets for neutralizing antibodies (nAbs), which aid in HCV clearance and protection. Therefore, a molecular-level understanding of the nAb responses against HCV is imperative for the rational design of cross-genotype vaccine antigens. Here we summarize the recent advances in structural studies of HCV Env and Env-nAb complexes and how they improve our understanding of immune recognition of HCV. We review the structural data defining HCV neutralization epitopes and conformational plasticity of the Env proteins, and the knowledge applicable to rational vaccine design.

HCV Core/NS3 Protein Immunization with "N-Terminal Heat Shock gp96 Protein (rNT (gp96))" Induced Strong and Sustained Th1-Type Cytokines in Immunized Mice

Feeble cellular responses induced by T cell-based vaccines are a major challenge for the development of an effective vaccine against Hepatitis C virus (HCV) infection. To address this challenge, the potential of N-terminal fragment of gp96 heat shock protein (rNT (gp96) as an adjuvant was evaluated and compared to that of the CpG (as a recognized Th1-type adjuvant) in the formulation of HCV core/NS3 antigens in three immunization strategies of protein/protein, DNA/DNA, and DNA/protein. Immunized mice were evaluated for elicited immune responses in week 3 (W3) and 11 post-immunizations. Our results demonstrated that the protein (subunit) vaccine formulated with rNT (gp96) in protein/protein strategy (core/NS3 + gp96) was significantly more efficient than CpG oligodeoxynucleotides (CpG ODN) formulation and all other immunization strategies in the induction of Th1-type cytokines. This group of mice (core/NS3 + gp96) also elicited a high level of anti-Core-NS3 total immunoglobulin G (IgG) with dominant IgG2a isotype at W3. Thus, the co-administration of recombinant NT (gp96) protein with rHCV proteins might be a promising approach in the formulation of HCV subunit vaccine candidates for induction of high levels of Th1 cytokines and humoral responses.

In Vivo and In Vitro Potency of Polyphosphazene Immunoadjuvants with Hepatitis C Virus Antigen and the Role of Their Supramolecular Assembly

Two well-defined synthetic polyphosphazene immunoadjuvants, PCPP and PCEP, were studied for their ability to potentiate the immune response to the hepatitis C virus (HCV) E2 glycoprotein antigen in vivo. We report that PCEP induced significantly higher serum neutralization and HCV-specific IgG titers in mice compared to other adjuvants used in the study: PCPP, Alum, and Addavax. PCEP also shifted the response toward the desirable balanced Th1/Th2 immunity, as evaluated by the antibody isotype ratio (IgG2a/IgG1). The in vivo results were analyzed in the context of antigen-adjuvant molecular interactions in the system and in vitro immunostimulatory activity of formulations. Asymmetric flow field flow fractionation (AF4) and dynamic light scattering (DLS) analysis showed that both PCPP and PCEP spontaneously self-assemble with the E2 glycoprotein with the formation of multimeric water-soluble complexes, which demonstrates the role of polyphosphazene macromolecules as vaccine delivery vehicles. Intrinsic in vitro immunostimulatory activity of polyphosphazene adjuvants, which was assessed using a mouse macrophage cell line, revealed comparable activities of both polymers and did not provide an explanation of their in vivo performance. However, PCEP complexes with E2 displayed greater stability against agglomeration and improved in vitro immunostimulatory activity compared to those of PCPP, which is in line with superior in vivo performance of PCEP. The results emphasize the importance of often neglected antigen-polyphosphazene self-assembly mechanisms in formulations, which can provide important insights on their in vivo behavior and facilitate the establishment of a structure-activity relationship for this important class of immunoadjuvants.

Hepatitis C virus core protein: Not just a nucleocapsid building block, but an immunity and inflammation modulator

Coevolution occurs between viruses and their hosts. The hosts need to evolve means to eliminate pathogenic virus infections, and the viruses, for their own survival and multiplication, have to develop mechanisms to escape clearance by hosts. Hepatitis C virus (HCV) of Flaviviridae is a pathogen which infects human liver and causes hepatitis, a condition of liver inflammation. Unlike most of the other flaviviruses, HCV has an excellent ability to evade host immunity to establish chronic infection. The persistent liver infection leads to chronic hepatitis, liver cirrhosis, hepatocellular carcinoma (HCC), as well as extrahepatic HCV-related diseases. HCV genomic RNA only expresses 10 proteins, many of which bear functions, in addition to those involved in HCV life cycle, for assisting the virus to develop its persistency. HCV core protein is a structural protein which encapsulates HCV genomic RNA and assembles into nucleocapsids. The core protein is also found to exert functions to affect host inflammation and immune responses by altering a variety of host pathways. This paper reviews the studies regarding the HCV core protein-induced alterations of host immunity and inflammatory responses, as well as the involvements of the HCV core protein in pro- and anti-inflammatory cytokine stimulations, host cellular transcription, lipid metabolism, cell apoptosis, cell proliferations, immune cell differentiations, oxidative stress, and hepatocyte steatosis, which leads to liver fibrosis, cirrhosis, and HCC. Implications of roles played by the HCV core protein in therapeutic resistance are also discussed.

In silico design and analysis of NS4B inhibitors against hepatitis C virus

The hepatitis C virus is a communicable disease that gradually harms the liver leading to cirrhosis and hepatocellular carcinoma. Important therapeutic interventions have been reached since the discovery of the disease. However, its resurgence urges the need for new approaches against this malady. The NS4B receptor is one of the important proteins for Hepatitis C Virus RNA replication that acts by mediating different viral properties. In this work, we opt to explore the relationships between the molecular structures of biologically tested NS4B inhibitors and their corresponding inhibitory activities to assist the design of novel and potent NS4B inhibitors. For that, a set of 115 indol-2-ylpyridine-3-sulfonamides (IPSA) compounds with inhibitory activity against NS4B is used. A hybrid genetic algorithm combined with multiple linear regressions (GA-MLR) was implemented to construct a predictive model. This model was further used and applied to a set of compounds that were generated based on a pharmacophore modeling study combined with virtual screening to identify structurally similar lead compounds. Multiple filtrations were implemented for selecting potent hits. The selected hits exhibited advantageous molecular features, allowing for favorable inhibitory activity against HCV. The results showed that 7 out of 1285 screened compounds, were selected as potent candidate hits where Zinc14822482 exhibits the best predicted potency and pharmacophore features. The predictive pharmacokinetic analysis further justified the compounds as potential hit molecules, prompting their recommendation for a confirmatory biological evaluation. We believe that our strategy could help in the design and screening of potential inhibitors in drug discovery.Communicated by Ramaswamy H. Sarma.

Structure-Based Design of Hepatitis C Virus E2 Glycoprotein Improves Serum Binding and Cross-Neutralization

An effective vaccine for hepatitis C virus (HCV) is a major unmet need, and it requires an antigen that elicits immune responses to key conserved epitopes. Based on structures of antibodies targeting HCV envelope glycoprotein E2, we designed immunogens to modulate the structure and dynamics of E2 and favor induction of broadly neutralizing antibodies (bNAbs) in the context of a vaccine. These designs include a point mutation in a key conserved antigenic site to stabilize its conformation, as well as redesigns of an immunogenic region to add a new N-glycosylation site and mask it from antibody binding. Designs were experimentally characterized for binding to a panel of human monoclonal antibodies (HMAbs) and the coreceptor CD81 to confirm preservation of epitope structure and preferred antigenicity profile. Selected E2 designs were tested for immunogenicity in mice, with and without hypervariable region 1, which is an immunogenic region associated with viral escape. One of these designs showed improvement in polyclonal immune serum binding to HCV pseudoparticles and neutralization of isolates associated with antibody resistance. These results indicate that antigen optimization through structure-based design of the envelope glycoproteins is a promising route to an effective vaccine for HCV.IMPORTANCE Hepatitis C virus infects approximately 1% of the world's population, and no vaccine is currently available. Due to the high variability of HCV and its ability to actively escape the immune response, a goal of HCV vaccine design is to induce neutralizing antibodies that target conserved epitopes. Here, we performed structure-based design of several epitopes of the HCV E2 envelope glycoprotein to engineer its antigenic properties. Designs were tested in vitro and in vivo, demonstrating alteration of the E2 antigenic profile in several cases, and one design led to improvement of cross-neutralization of heterologous viruses. This represents a proof of concept that rational engineering of HCV envelope glycoproteins can be used to modulate E2 antigenicity and optimize a vaccine for this challenging viral target.

SARS-CoV-2 will constantly sweep its tracks: a vaccine containing CpG motifs in 'lasso' for the multi-faced virus

During the current COVID-19 pandemic, the global ratio between the dead and the survivors is approximately 1 to 10, which has put humanity on high alert and provided strong motivation for the intensive search for vaccines and drugs. It is already clear that if we follow the most likely scenario, which is similar to that used to create seasonal influenza vaccines, then we will need to develop improved vaccine formulas every year to control the spread of the new, highly mutable coronavirus SARS-CoV-2. In this article, using well-known RNA viruses (HIV, influenza viruses, HCV) as examples, we consider the main successes and failures in creating primarily highly effective vaccines. The experience accumulated dealing with the biology of zoonotic RNA viruses suggests that the fight against COVID-19 will be difficult and lengthy. The most effective vaccines against SARS-CoV-2 will be those able to form highly effective memory cells for both humoral (memory B cells) and cellular (cross-reactive antiviral memory T cells) immunity. Unfortunately, RNA viruses constantly sweep their tracks and perhaps one of the most promising solutions in the fight against the COVID-19 pandemic is the creation of 'universal' vaccines based on conservative SARS-CoV-2 genome sequences (antigen-presenting) and unmethylated CpG dinucleotides (adjuvant) in the composition of the phosphorothioate backbone of single-stranded DNA oligonucleotides (ODN), which can be effective for long periods of use. Here, we propose a SARS-CoV-2 vaccine based on a lasso-like phosphorothioate oligonucleotide construction containing CpG motifs and the antigen-presenting unique ACG-containing genome sequence of SARS-CoV-2. We found that CpG dinucleotides are the most rare dinucleotides in the genomes of SARS-CoV-2 and other known human coronaviruses, and hypothesized that their higher frequency could be responsible for the unwanted increased lethality to the host, causing a ‘cytokine storm’ in people who overexpress cytokines through the activation of specific Toll-like receptors in a manner similar to TLR9-CpG ODN interactions. Interestingly, the virus strains sequenced in China (Wuhan) in February 2020 contained on average one CpG dinucleotide more in their genome than the later strains from the USA (New York) sequenced in May 2020. Obviously, during the first steps of the microevolution of SARS-CoV-2 in the human population, natural selection tends to select viral genomes containing fewer CpG motifs that do not trigger a strong innate immune response, so the infected person has moderate symptoms and spreads SARS-CoV-2 more readily. However, in our opinion, unmethylated CpG dinucleotides are also capable of preparing the host immune system for the coronavirus infection and should be present in SARS-CoV-2 vaccines as strong adjuvants.

Hepatitis C virus vaccine design: focus on the humoral immune response

Despite the recent development of safe and highly effective direct-acting antivirals, hepatitis C virus (HCV) infection remains a significant health problem. In 2016, the World Health Organization set out to reduce the rate of new HCV infections by 90% by 2030. Still, global control of the virus does not seem to be achievable in the absence of an effective vaccine. Current approaches to the development of a vaccine against HCV include the production of recombinant proteins, synthetic peptides, DNA vaccines, virus-like particles, and viral vectors expressing various antigens. In this review, we focus on the development of vaccines targeting the humoral immune response against HCV based on the cumulative evidence supporting the important role of neutralizing antibodies in protection against HCV infection. The main targets of HCV-specific neutralizing antibodies are the glycoproteins E1 and E2. Recent advances in the knowledge of HCV glycoprotein structure and their epitopes, as well as the possibility of getting detailed information on the human antibody repertoire generated by the infection, will allow rational structure-based antigen design to target specific germline antibodies. Although obtaining a vaccine capable of inducing sterilizing immunity will be a difficult task, a vaccine that prevents chronic hepatitis C infections, a more realistic goal in the short term, would have a considerable health impact.

High success rates for the use of sofosbuvir/ombitasvir/paritaprevir/ritonavir + ribavirin and sofosbuvir/simeprevir/daclatasvir + ribavirin in retreatment of chronic hepatitis C infection after unsuccessful sofosbuvir/daclatasvir therapy: a real-life experience

The aim of this work was assessment of the efficacy and tolerability of two different regimens for retreatment of hepatitis C virus (HCV) patients who failed to respond to SOF/DCV-based therapy. This prospective study included 104 HCV patients who failed to respond to SOF/DCV-based therapy. Patients were randomly allocated to two groups. Efficacy and tolerability were assessed. The 12-week sustained virological response (SVR12) rates were 96% and 94.4% in groups B and A, respectively, with no significant difference (p = 1.000). Most adverse events reported were mild to moderate, with no deaths during the study. Multi-target direct-acting antiviral (DAA) combinations are efficient for retreatment of HCV patients after failure of SOF/DCV-based therapy in real-world management.ClinicalTrials.gov identifier: NCT02992457.

Innate Immune Response against Hepatitis C Virus: Targets for Vaccine Adjuvants

Despite successful treatments, hepatitis C virus (HCV) infections continue to be a significant world health problem. High treatment costs, the high number of undiagnosed individuals, and the difficulty to access to treatment, particularly in marginalized susceptible populations, make it improbable to achieve the global control of the virus in the absence of an effective preventive vaccine. Current vaccine development is mostly focused on weakly immunogenic subunits, such as surface glycoproteins or non-structural proteins, in the case of HCV. Adjuvants are critical components of vaccine formulations that increase immunogenic performance. As we learn more information about how adjuvants work, it is becoming clear that proper stimulation of innate immunity is crucial to achieving a successful immunization. Several hepatic cell types participate in the early innate immune response and the subsequent inflammation and activation of the adaptive response, principally hepatocytes, and antigen-presenting cells (Kupffer cells, and dendritic cells). Innate pattern recognition receptors on these cells, mainly toll-like receptors, are targets for new promising adjuvants. Moreover, complex adjuvants that stimulate different components of the innate immunity are showing encouraging results and are being incorporated in current vaccines. Recent studies on HCV-vaccine adjuvants have shown that the induction of a strong T- and B-cell immune response might be enhanced by choosing the right adjuvant.

Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment

Hepatitis C virus (HCV) infection is the major risk factor for liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of HCC initiation, growth, and metastasis appear to be highly complex due to the decade-long interactions between the virus, immune system, and overlapping bystander effects of host metabolic liver disease. The lack of a readily accessible animal model system for HCV is a significant obstacle to understand the mechanisms of viral carcinogenesis. Traditionally, the primary prevention strategy of HCC has been to eliminate infection by antiviral therapy. The success of virus elimination by antiviral treatment is determined by the SVR when the HCV is no longer detectable in serum. Interferon-alpha (IFN-α) and its analogs, pegylated IFN-α (PEG-IFN-α) alone with ribavirin (RBV), have been the primary antiviral treatment of HCV for many years with a low cure rate. The cloning and sequencing of HCV have allowed the development of cell culture models, which accelerated antiviral drug discovery. It resulted in the selection of highly effective direct-acting antiviral (DAA)-based combination therapy that now offers incredible success in curing HCV infection in more than 95% of all patients, including those with cirrhosis. However, several emerging recent publications claim that patients who have liver cirrhosis at the time of DAAs treatment face the risk of HCC occurrence and recurrence after viral cure. This remains a substantial challenge while addressing the long-term benefit of antiviral medicine. The host-related mechanisms that drive the risk of HCC in the absence of the virus are unknown. This review describes the multifaceted mechanisms that create a tumorigenic environment during chronic HCV infection. In addition to the potential oncogenic programming that drives HCC after viral clearance by DAAs, the current status of a biomarker development for early prediction of cirrhosis regression and HCC detection post viral treatment is discussed. Since DAAs treatment does not provide full protection against reinfection or viral transmission to other individuals, the recent studies for a vaccine development are also reviewed.

Prolactin Induces IL-2 Associated TRAIL Expression on Natural Killer Cells from Chronic Hepatitis C Patients In vivo and In vitro

BACKGROUND

Natural killer cells (NKC) are a major component of the innate immune response to HCV, mediating their effects through TRAIL and IFN-γ. However, their function is diminished in chronic HCV patients (HCVp). Prolactin is an immunomodulatory hormone capable of activating NKC.

OBJECTIVE

The study aims to explore if hyperprolactinemia can activate NKC in HCVp.

METHODS

We treated twelve chronic HCVp (confidence level =95%, power =80%) for 15 days with Levosulpiride plus Cimetidine to induce mild hyperprolactinemia. Before and after treatment, we determined TRAIL and NKG2D expression on peripheral blood NKC, along with cytokine profiles, viral loads and liver function. We also evaluated in vitro effects of prolactin and/or IL-2 on NKC TRAIL or NKG2D expression and IFN-γ levels on cultured blood mononuclear cells from 8 HCVp and 7 healthy controls.

RESULTS

The treatment induced mild hyperprolactinemia and increased TRAIL expression on NKC as well as the secretion of IL-1ra, IL-2, PDGF and IFN-γ. Viral loads decreased in six HCVp. IL-2 and TRAIL together explained the viral load decrease. In vitro, prolactin plus IL-2 synergized to increase TRAIL and NKG2D expression on NKC from HCVp but not in controls.

CONCLUSION

Levosulpiride/Cimetidine treatment induced mild hyperprolactinaemia that was associated with NKC activation and Th1-type cytokine profile. Also, an increase in TRAIL and IL-2 was associated with viral load decrease. This treatment could potentially be used to reactivate NKC in HCVp.

Protective cellular immune response against hepatitis C virus elicited by chimeric protein formulations in BALB/c mice

The eradication of hepatitis C virus (HCV) infection is a public health priority. Despite the efficiency of treatment with direct-acting antivirals, the high cost of the therapy and the lack of accurate data about the HCV-infected population worldwide constitute important factors hampering this task. Hence, an affordable preventive vaccine is still necessary for reducing transmission and the future disease burden globally. In this work, chimeric proteins (EnvCNS3 and NS3EnvCo) encompassing conserved and immunogenic epitopes from the HCV core, E1, E2 and NS3 proteins were produced in Escherichia coli, and their immunogenicity was evaluated in BALB/c mice. The impact of recombinant HCV E2.680 protein and oligodeoxynucleotide 39M (ODN39M) on the immune response to chimeric proteins was also assessed. Immunization with chimeric proteins mixed with E2.680 enhanced the antibody and cellular response against HCV antigens and chimeric proteins. Interestingly, the combination of NS3EnvCo with E2.680 and ODN39M as adjuvant elicited a potent antibody response characterized by an increase in antibodies of the IgG2a subclass against E2.680, NS3 and chimeric proteins, suggesting the induction of a Th1-type response. Moreover, a cytotoxic T lymphocyte response and a broad response of IFN-γ-secreting cells against HCV antigens were induced with this formulation as well. This T cell response was able to protect vaccinated mice against challenge with a surrogate model based on HCV recombinant vaccinia virus. Overall, the vaccine candidate NS3EnvCo/E2.680/ODN39M might constitute an effective immunogen against HCV with potential for reducing the likelihood of viral persistence.

Progress towards elimination goals for viral hepatitis

The global burden of viral hepatitis is substantial; in terms of mortality, hepatitis B virus and hepatitis C virus infections are on a par with HIV, malaria and tuberculosis, among the top four global infectious diseases. In 2016, the 194 Member States of the World Health Organization committed to eliminating viral hepatitis as a public health threat by 2030, with a particular focus on hepatitis B virus and hepatitis C virus infection. With only 10 years to go until the 2030 deadline is reached, and although much progress has been made towards elimination, there are still some important gaps in terms of policy and progress. In this Viewpoint, we asked a selection of scientists and clinicians working in the viral hepatitis field for their opinions on whether elimination of viral hepatitis by 2030 is feasible, what the key areas of progress are and what the focus for the next 10 years and beyond should be for viral hepatitis elimination.

HCV p7 as a novel vaccine-target inducing multifunctional CD4+ and CD8+ T-cells targeting liver cells expressing the viral antigen

Despite recent treatment advances for chronic hepatitis C virus (HCV) infection, a vaccine is urgently needed for global control of this important liver pathogen. The lack of robust immunocompetent HCV infection models makes it challenging to identify correlates of protection and test vaccine efficacy. However, vigorous CD4⁺ and CD8⁺ T-cell responses are detected in patients that spontaneously resolve acute infection, whereas dysfunctional T-cell responses are a hallmark of chronic infection. The HCV p7 protein, forming ion-channels essential for viral assembly and release, has not previously been pursued as a vaccine antigen. Herein, we demonstrated that HCV p7 derived from genotype 1a and 1b sequences are highly immunogenic in mice when employed as overlapping peptides formulated as nanoparticles with the cross-priming adjuvant, CAF09. This approach induced multifunctional cytokine producing CD4⁺ and CD8⁺ T-cells targeting regions of p7 that are subject to immune pressure during HCV infection in chimpanzees and humans. Employing a surrogate in vivo challenge model of liver cells co-expressing HCV-p7 and GFP, we found that vaccinated mice cleared transgene expressing cells. This study affirms the potential of a T-cell inducing nanoparticle vaccine platform to target the liver and introduces HCV p7 as a potential target for HCV vaccine explorations.

Rapid decrease in titer and breadth of neutralizing anti-HCV antibodies in HIV/HCV-coinfected patients who achieved SVR

The main targets for neutralizing anti-hepatitis C virus (HCV) antibodies (HCV-nAbs) are the E1 and E2 envelope glycoproteins. We have studied the characteristics of HCV-nAbs through a retrospective study involving 29 HIV/HCV-coinfected patients who achieved sustained virological response (SVR) with peg-IFNα + ribavirin anti-HCV therapy. Plasma samples at baseline and week 24 after SVR were used to perform neutralization assays against five JFH1-based HCV recombinant viruses coding for E1 and E2 from genotypes 1a (H77), 1b (J4), 2a (JFH1), 3a (S52) and 4a (ED43). At baseline, the majority of plasma samples neutralized 1a, 1b, 2a, and 4a, but not 3a, genotypes. Twenty-four weeks following SVR, most neutralizing titers declined substantially. Furthermore, titers against 3a and 2a were not detected in many patients. Plasma samples with high HCV-nAb titers neutralized all genotypes, and the highest titers at the starting point correlated with the highest titers at week 24 after SVR. In conclusion, high titers of broad-spectrum HCV-nAbs were detected in HIV/HCV-coinfected individuals, however, those titers declined soon after SVR.

A dynamic model and some strategies on how to prevent and control hepatitis c in mainland China

Background

Hepatitis C virus (HCV) is a leading cause of chronic liver disease. As yet there is no approved vaccine protects against contracting hepatitis C. HCV seriously affects many people’s health in the world.

Methods

In this article, an epidemiological model is proposed and discussed to understand the transmission and prevalence of hepatitis C in mainland China. This research concentrates on hepatitis C data from Chinese Center for Disease Control and Prevention (China’s CDC). The optimal parameters of the model are obtained by calculating the minimum chi-square value. Sensitivity analyses of the basic reproduction number and the endemic equilibrium are conducted to evaluate the effectiveness of control measures.

Results

Vertical infection is not the most important factor that causes hepatitis C epidemic, but contact transmission is. The proportion of acute patients who are transformed into chronic patients is about 82.62%. The possibility of the hospitalized patients who are restored to health is about 76.24%. There are about 92.32% of acute infected are not treated. The reproduction number of hepatitis C in mainland China is estimated as approximately 1.6592.

Conclusion

We find that small changes of transmission infection rate of acutely infected population, transmission infection rate of exposed population, transition rate for the acutely infected, and rate of progression to acute stage from the exposed can achieve the purpose of controlling HCV through sensitivity analysis. Finally, based on the results of sensitivity analysis, we find out several preventions and control strategies to control the Hepatitis C.

Genetic mutations in NF-κB pathway genes were associated with the protection from hepatitis C virus infection among Chinese Han population

Host genetic polymorphism is one of major unalterable major factors for HCV infection. NF-κB proteins play multiple roles in immune response and involve in HCV infection and progression. This study was conducted to explore the relationship between single nucleotide polymorphisms (SNPs) in NF-κB pathway and the susceptibility as well as resolution of HCV infection. A total of 1642 Chinese subjects were enrolled in the study, including 963 uninfected control cases, 231 cases with spontaneous viral clearance and 448 cases with persistent HCV infection, and four SNPs (Rel rs842647, NF-κB2 rs12769316, RelA rs7101916, RelB rs28372683) were genotyped by TaqMan assay among them. Potentially functional polymorphisms were analyzed using online bioinformatics tools. The logistic analyses results indicated that RelA rs7101916 T allele (PBonferroni = 0.016) and RelB rs28372683 A allele (PBonferroni = 4.8e-5) were associated with an decreased risk of the susceptibility to HCV infection among Chinese Han population, which were consistent with the results of cumulative effects and haplotype analysis. The silico analysis of SNPs function suggested that the genetic variation of rs7101916 and rs28372683 could influence gene transcriptional regulation and expression, subsequently affecting NF-κB pathway activation and the susceptibility to HCV infection. This study firstly reported that the carriage of RelA rs7101916 T or RelB rs28372683 A was the potential protective factor against HCV infection among the Chinese population.

Functional expression and characterization of the envelope glycoprotein E1E2 heterodimer of hepatitis C virus

Hepatitis C virus (HCV) is a member of Hepacivirus and belongs to the family of Flaviviridae. HCV infects millions of people worldwide and may lead to cirrhosis and hepatocellular carcinoma. HCV envelope proteins, E1 and E2, play critical roles in viral cell entry and act as major epitopes for neutralizing antibodies. However, unlike other known flaviviruses, it has been challenging to study HCV envelope proteins E1E2 in the past decades as the in vitro expressed E1E2 heterodimers are usually of poor quality, making the structural and functional characterization difficult. Here we express the ectodomains of HCV E1E2 heterodimer with either an Fc-tag or a de novo designed heterodimeric tag and are able to isolate soluble E1E2 heterodimer suitable for functional and structural studies. Then we characterize the E1E2 heterodimer by electron microscopy and model the structure by the coevolution based modeling strategy with Rosetta, revealing the potential interactions between E1 and E2. Moreover, the E1E2 heterodimer is applied to examine the interactions with the known HCV receptors, neutralizing antibodies as well as the inhibition of HCV infection, confirming the functionality of the E1E2 heterodimer and the binding profiles of E1E2 with the cellular receptors. Therefore, the expressed E1E2 heterodimer would be a valuable target for both viral studies and vaccination against HCV.

Hepatitis C virus (HCV) is an enveloped virus that infects millions of people worldwide and may lead to cirrhosis and hepatocellular carcinoma. HCV has two envelope proteins, E1 and E2, which form heterodimers on viral surface and are critical for HCV cell entry. However, current studies of HCV E1E2 are often limited by the poor quality of the in vitro expressed E1E2 heterodimers. Here we express the ectodomains of HCV E1E2 with different tags, and are able to isolate soluble E1E2 ectodomains suitable for structural and functional studies. Then we generate the 3D reconstruction of E1E2 heterodimer by electron microscopy and also model the E1E2 structure by the coevolution based strategy with Rosetta, showing the potential interactions between E1 and E2. Moreover, the E1E2 heterodimer is applied to examine the interactions with the HCV cellular receptors, neutralizing antibodies as well as the inhibition of HCV infection. These results suggest that the expressed E1E2 heterodimer would be a promising target for both viral studies and vaccination against HCV.

Hepatitis C Virus E2 Envelope Glycoprotein Induces an Immunoregulatory Phenotype in Macrophages

A comprehensive strategy to control hepatitis C virus (HCV) infection needs a vaccine. Our phase I study with recombinant HCV E1/E2 envelope glycoprotein (EnvGPs) as a candidate vaccine did not induce a strong immune response in volunteers. We analyzed the interactions of HCV EnvGPs with human monocyte-derived macrophages as antigen-presenting cells. HCV E2 induced immune regulatory cytokine interleukin (IL)-10 and soluble CD163 (sCD163) protein expression in macrophages from 7 of 9 blood donors tested. Furthermore, HCV E2 enhanced Stat3 and suppressed Stat1 activation, reflecting macrophage polarization toward M2 phenotype. E2-associated macrophage polarization appeared to be dependent of its interaction with CD81 leading endothelial growth factor receptor (EGFR) activation. Additionally, E2 suppressed the expression of C3 complement, similar to HCV-exposed dendritic cells (DCs), implying potential impairment of immune cell priming. Conclusion: Our results suggest that E2 EnvGP may not be an ideal candidate for HCV vaccine development, and discrete domains within E2 may prove to be more capable of elliciting a protective immune response. (Hepatology 2018).

Structural Vaccinology for Viral Vaccine Design

Although vaccines have proven pivotal against arrays of infectious viral diseases, there are still no effective vaccines against many viruses. New structural insights into the viral envelope, protein conformation, and antigenic epitopes can guide the design of novel vaccines against challenging viruses such as human immunodeficiency virus (HIV), hepatitis C virus, enterovirus A71, and dengue virus. Recent studies demonstrated that applications of this structural information can solve some of the vaccine conundrums. This review focuses on recent advances in structure-based vaccine design, or structural vaccinology, for novel and innovative viral vaccine design.

Antigenicity and Immunogenicity of Differentially Glycosylated Hepatitis C Virus E2 Envelope Proteins Expressed in Mammalian and Insect Cells

The development of a prophylactic vaccine for hepatitis C virus (HCV) remains a global health challenge. Cumulative evidence supports the importance of antibodies targeting the HCV E2 envelope glycoprotein to facilitate viral clearance. However, a significant challenge for a B cell-based vaccine is focusing the immune response on conserved E2 epitopes capable of eliciting neutralizing antibodies not associated with viral escape. We hypothesized that glycosylation might influence the antigenicity and immunogenicity of E2. Accordingly, we performed head-to-head molecular, antigenic, and immunogenic comparisons of soluble E2 (sE2) produced in (i) mammalian (HEK293) cells, which confer mostly complex- and high-mannose-type glycans; and (ii) insect (Sf9) cells, which impart mainly paucimannose-type glycans. Mass spectrometry demonstrated that all 11 predicted N-glycosylation sites were utilized in both HEK293- and Sf9-derived sE2, but that N-glycans in insect sE2 were on average smaller and less complex. Both proteins bound CD81 and were recognized by conformation-dependent antibodies. Mouse immunogenicity studies revealed that similar polyclonal antibody responses were generated against antigenic domains A to E of E2. Although neutralizing antibody titers showed that Sf9-derived sE2 induced moderately stronger responses than did HEK293-derived sE2 against the homologous HCV H77c isolate, the two proteins elicited comparable neutralization titers against heterologous isolates. Given that global alteration of HCV E2 glycosylation by expression in different hosts did not appreciably affect antigenicity or overall immunogenicity, a more productive approach to increasing the antibody response to neutralizing epitopes may be complete deletion, rather than just modification, of specific N-glycans proximal to these epitopes.IMPORTANCE The development of a vaccine for hepatitis C virus (HCV) remains a global health challenge. A major challenge for vaccine development is focusing the immune response on conserved regions of the HCV envelope protein, E2, capable of eliciting neutralizing antibodies. Modification of E2 by glycosylation might influence the immunogenicity of E2. Accordingly, we performed molecular and immunogenic comparisons of E2 produced in mammalian and insect cells. Mass spectrometry demonstrated that the predicted glycosylation sites were utilized in both mammalian and insect cell E2, although the glycan types in insect cell E2 were smaller and less complex. Mouse immunogenicity studies revealed similar polyclonal antibody responses. However, insect cell E2 induced stronger neutralizing antibody responses against the homologous isolate used in the vaccine, albeit the two proteins elicited comparable neutralization titers against heterologous isolates. A more productive approach for vaccine development may be complete deletion of specific glycans in the E2 protein.

Binding of cellular nucleolin with the viral core RNA G-quadruplex structure suppresses HCV replication

Hepatitis C virus (HCV) infection is a major cause of human chronic liver disease and hepatocellular carcinoma. G-quadruplex (G4) is an important four-stranded secondary structure of nucleic acids. Recently, we discovered that the core gene of HCV contains a G4 RNA structure; however, the interaction between the HCV core RNA G4 and host cellular proteins, and the roles of the HCV core RNA G4 in HCV infection and pathogenesis remain elusive. Here, we identified a cellular protein, nucleolin (NCL), which bound and stabilized the HCV core RNA G4 structure. We demonstrated the direct interaction and colocalization between NCL and wild-type core RNA G4 at both in vitro and in cell physiological conditions of the alive virus; however no significant interaction was found between NCL and G4-modified core RNA. NCL is also associated with HCV particles. HCV infection induced NCL mRNA and protein expression, while NCL suppressed wild-type viral replication and expression, but not G4-modified virus. Silencing of NCL greatly enhanced viral RNA replication. Our findings provide new insights that NCL may act as a host factor for anti-viral innate immunity, and binding of cellular NCL with the viral core RNA G4 structure is involved in suppressing HCV replication.

Sustained Viral Response in Genotype 4 Chronic Hepatitis C Virus-infected Children and Adolescents Treated With Sofosbuvir/Ledipasvir

OBJECTIVES

Recently, direct acting antivirals (DAAs), sofosbuvir (SOF) combined with ledipasvir (LED), were approved for treatment of hepatitis C virus (HCV)-infected children 12 years of age and older or weighting at least 35 kg for all HCV genotypes. The aim of this study was to assess the safety and efficacy of SOF/LED in genotype 4 HCV-infected Egyptian children and adolescents.

METHODS

This observational study included 40 consecutive HCV-infected children of age 12 to <18 years old or weighing >35 kg, both treatment-naive and treatment-experienced. All of the children were hepatitis B virus-negative and had normal renal functions and heart rate. Patients received oral, fixed-dose combination tablet of SOF/LED (400 mg SOF, 90 mg LED [Harvoni]) once daily for 12 weeks. Potential side effects were recorded at weeks 4, 8, and 12 weeks of treatment. The study primary outcome was sustained virological response 12 weeks (SVR12) after end-of-treatment.

RESULTS

The study included 40 children and adolescents, 24 were boys (60%); their age ranged between 11.5 and 17.5 years (mean 13.9 ± 1.5). Baseline viral load ranged between 9630 and 24,600,000 IU/mL. HCV RNA became negative in 39 patients (97.5%) at 4 weeks and in all patients (100%) at weeks 8, 12, and SVR12. Asthenia was the commonest side effect, reported in 52.5% followed by headache in 47.5%.

CONCLUSIONS

Treatment with all-oral DAAs (SOF/LED) for 12 weeks was well tolerated in Egyptian children and adolescents infected with genotype 4 HCV, with 100% SVR12 and negligible side effects.

Reversing immune dysfunction and liver damage after direct-acting antiviral treatment for hepatitis C

The introduction of small molecules targeting viral functions has caused a paradigm shift in hepatitis C virus (HCV) treatment. Administration of these direct-acting antivirals (DAAs) achieves a complete cure in almost all treated patients with short-duration therapy and minimal side effects. Although this is a major improvement over the previous pegylated interferon plus ribavirin (PEG-IFNα/RBV) standard-of-care treatment for HCV, remaining questions address several aspects of the long-term benefits of DAA therapy. Interferon (IFN)-based treatment with successful outcome was associated with substantial reduction in liver disease–related mortality. However, emerging data suggest a complex picture and several confounding factors that influence the effect of both IFN-based and DAA therapies on immune restoration and limiting liver disease progression. We review current knowledge of restoration of innate and HCV-specific immune responses in DAA-mediated viral elimination in chronic HCV infection, and we identify future research directions to achieve long-term benefits in all cured patients and reduce HCV-related liver disease morbidity and mortality.

Hepatitis C Vaccines, Antibodies, and T Cells

The development of vaccines that protect against persistent hepatitis C virus (HCV) infection remain a public health priority. The broad use of highly effective direct-acting antivirals (DAAs) is unlikely to achieve HCV elimination without vaccines that can limit viral transmission. Two vaccines targeting either the antibody or the T cell response are currently in preclinical or clinical trials. Next-generation vaccines will likely involve a combination of these two strategies. This review summarizes the state of knowledge about the immune protective role of HCV-specific antibodies and T cells and the current vaccine strategies. In addition, it discusses the potential efficacy of vaccination in DAA-cured individuals. Finally, it summarizes the challenges to vaccine development and the collaborative efforts required to overcome them.

Healthcare Costs for Chronic Hepatitis C in South Korea from 2009 to 2013: An Analysis of the National Health Insurance Claims' Data

Background/Aims

The introduction of direct-acting antivirals (DAA) in 2013 revolutionized hepatitis C virus (HCV) treatment, offering a cure rate >90%. However, this therapy is expensive, and estimations of the number of chronic HCV-infected (CHC) patients and their treatment costs pre-2013 are therefore essential for creating policies and expanding drug access. Herein, we aimed to investigate the number of HCV-related liver disease patients, their healthcare utilization, their annual direct medical costs, and the interferon-based antiviral treatment rates and costs from 2009 to 2013 in South Korea.

Methods

The National Health Insurance database was reviewed, and patients diagnosed with CHC from 2009 to 2013 were extracted. Data regarding detailed healthcare utilization, prescribed drugs, and direct medical costs were obtained. For annual direct healthcare cost calculations, a prevalence-based approach was used.

Results

Overall, 181,768 CHC patients were identified. In 2013, the annual per-patient costs for chronic hepatitis, liver cirrhosis, hepatocellular carcinoma, and the first year post-liver transplant were 895, 1,873, 6,945, and 67,359 United States dollars, respectively. Interferon-based antiviral therapeutics were prescribed to 25,223 patients (13.9%).

Conclusions

Healthcare costs have increased remarkably with increasing liver disease severity. Thus, efforts to stop disease progression are needed. Moreover, the low rate of interferon-based therapy indicates an unmet need for DAA.

Alcohol attenuates anti-HCV function of IFN-λ1 through up-regulation of PLASy expression in human hepatic cells

Alcohol could compromise the anti-hepatitis C virus (HCV) function of interferon-alpha (IFN-α). However, little information is available about the effect of alcohol on interferon-lambda (IFN-λ, type III IFN), a novel candidate for development of therapy for HCV infection. Huh7 cells were infected with HCV JFH-1 virus, then treated with alcohol, and/or IFN-λ1. RT-PCR and Western blot were used to detect the levels of HCV and key cellular factors. Overexpression or silencing expression was performed to verify the role of key factors in alcohol-attenuated anti-HCV function of IFN-λ1. Alcohol treatment compromised anti-HCV effect of IFN-λ1 in HCV JFH-1-infected Huh7 cells, evidenced by the significantly increased levels of HCV RNA, and HCV core protein in alcohol-/IFN-λ1-treated cells compared to cells with IFN-λ1 treatment alone. Investigation of the mechanisms responsible for the alcohol action revealed that alcohol enhanced the expression of protein inhibitor of activated STAT (PIASy). Overexpression of PIASy compromised anti-HCV ability of IFN-λ1, whereas silencing expression of PIASy partly restored the alcohol-attenuated anti-HCV effect of IFN-λ1. More importantly, overexpression of PIASy significantly down-regulated the level of IFN-λ1-indcued phosphorylation of STAT1 (p-STAT1), an important adaptor in IFN-λ pathway, as well as reduced the expression of IFN-λ1-induced IFN-stimulated genes 56 (ISG56), and myxovirus resistance 1 (Mx1), two antiviral effectors in in IFN-λ pathway. These findings indicate that alcohol, through inducing the expression of negative regulator in IFN-λ pathway, inhibits IFN-λ-mediated anti-HCV action in human hepatic cells, which may lead to the poor efficacy of IFN-λ-based therapy against HCV infection.

Computational Modeling of Hepatitis C Virus Envelope Glycoprotein Structure and Recognition

Hepatitis C virus (HCV) is a major global health concern, and though therapeutic options have improved, no vaccine is available despite decades of research. As HCV can rapidly mutate to evade the immune response, an effective HCV vaccine must rely on identification and characterization of sites critical for broad immune protection and viral neutralization. This knowledge depends on structural and mechanistic insights of the E1 and E2 envelope glycoproteins, which assemble as a heterodimer on the surface of the virion, engage coreceptors during host cell entry, and are the primary targets of antibodies. Due to the challenges in determining experimental structures, structural information on E1 and E2 and their interaction is relatively limited, providing opportunities to model the structures, interactions, and dynamics of these proteins. This review highlights efforts to model the E2 glycoprotein structure, the assembly of the functional E1E2 heterodimer, the structure and binding of human coreceptors, and recognition by key neutralizing antibodies. We also discuss a comparison of recently described models of full E1E2 heterodimer structures, a simulation of the dynamics of key epitope sites, and modeling glycosylation. These modeling efforts provide useful mechanistic hypotheses for further experimental studies of HCV envelope assembly, recognition, and viral fitness, and underscore the benefit of combining experimental and computational modeling approaches to reveal new insights. Additionally, computational design approaches have produced promising candidates for epitope-based vaccine immunogens that specifically target key epitopes, providing a possible avenue to optimize HCV vaccines versus using native glycoproteins. Advancing knowledge of HCV envelope structure and immune recognition is highly applicable toward the development of an effective vaccine for HCV and can provide lessons and insights relevant to modeling and characterizing other viruses.

[Personalized treatment of viral hepatitis of the present and the future : Hepatitis B, C, delta, and E]

Precision medicine is also possible for infectious diseases as shown for the treatment of chronic viral hepatitis, especially if different options are available. In hepatitis B virus (HBV) infection, treatment indication as well as the choice of treatment and the decisions to stop treatment are based on viral markers and alanine aminotransferase (ALT) level. Future therapies for HBV infection aiming for functional cure or even virus elimination may be even more personalized and have to take into account the immune status of a given patient. Such treatment modalities might also increase the chance for successful treatment of chronic hepatitis delta where treatment options are still very limited. Some new therapeutic concepts targeting host receptors or host enzymes are promising, but may require individualized approaches. Chronic hepatitis C is a good example for precision medicine based on viral and host factors. However, the main reason for individualized direct-acting antiviral (DAA) treatment is to save costs. As DAAs are effective in more than 95% of patients, elimination of HCV seems to be possible at the level of a given country or even on a global scale. However, owing to high reinfection rates in high-risk groups and limited availability of antiviral therapy in many high endemic countries, it must still be decided whether an HCV vaccine or pre-exposure prophylaxis is required to achieve this goal. Hepatitis E is an emerging topic as this is the most frequent acute hepatitis virus infection. It can result in a chronic infection in immunosuppressed individuals. Treatment options are still limited and individualized management is based on tailoring immunosuppressive therapy and therapy with ribavirin. Thus, personalized therapy of hepatitis E virus infection is still limited.

Understanding and addressing hepatitis C reinfection in the oral direct-acting antiviral era

The availability of effective, simple, well-tolerated oral direct-acting antiviral (DAA) hepatitis C regimens has raised optimism for hepatitis C virus (HCV) elimination at the population level. HCV reinfection in key populations such as people who inject drugs (PWID) and HIV-infected men who have sex with men (MSM) however threatens the achievement of this goal from a patient, provider and population perspective. The goal of this review was to synthesize our current understanding of estimated rates and factors associated with HCV reinfection. This review also proposes interventions to aid understanding of and reduce hepatitis C reinfection among PWID and HIV-infected MSM in the oral direct-acting antiviral era.

Dysregulation of cellular microRNAs by human oncogenic viruses - Implications for tumorigenesis

Infection with certain animal and human viruses, often referred to as tumor viruses, induces oncogenic processes in their host. These viruses can induce tumorigenesis through direct and/or indirect mechanisms, and the regulation of microRNAs expression has been shown to play a key role in this process. Some human oncogenic viruses can express their own microRNAs; however, they all can dysregulate the expression of cellular microRNAs, facilitating their respective life cycles. The modulation of cellular microRNAs expression brings consequences to the host cells that may lead to malignant transformation, since microRNAs regulate the expression of genes involved in oncogenic pathways. This review focus on the mechanisms used by each human oncogenic virus to dysregulate the expression of cellular microRNAs, and their impact on tumorigenesis.

Genetic variations in NF-κB were associated with the susceptibility to hepatitis C virus infection among Chinese high-risk population

Polymorphisms within NF-κB pathway genes may be linked to hepatitis C virus (HCV) infection susceptibility and outcomes. We investigated the associations between single nucleotide polymorphisms (SNPs) in NF-κB and the susceptibility as well as resolution of HCV infection. A Chinese population, including 1125 uninfected control cases, 558 cases with spontaneous viral clearance and 898 cases with persistent HCV infection, was genotyped for four SNPs (rs11820062, rs230530, rs1056890 and rs3774963) using a TaqMan assay. Our logistic analyses indicate that the subjects carrying RelA rs11820062 A allele had a significantly increased risk of HCV susceptibility (P Bonferroni  < 0.003125 in a dominant or additive model). In stratified analysis, the increased risk associated with rs11820062 A allele on HCV susceptibility remained in some case subgroups. This study demonstrates that a genetic variant involved in the NF-κB pathway gene (rs11820062 A allele) is associated with an increased HCV susceptibility within a high-risk Chinese population.

Synergistic anti-HCV broadly neutralizing human monoclonal antibodies with independent mechanisms

There is an urgent need for a vaccine to combat the hepatitis C virus (HCV) pandemic, and induction of broadly neutralizing monoclonal antibodies (bNAbs) against HCV is a major goal of vaccine development. Even within HCV genotype 1, no single bNAb effectively neutralizes all viral strains, so induction of multiple neutralizing monoclonal antibodies (NAbs) targeting distinct epitopes may be necessary for protective immunity. Therefore, identification of optimal NAb combinations and characterization of NAb interactions can guide vaccine development. We analyzed neutralization profiles of 12 human NAbs across diverse HCV strains, assigning the NAbs to two functionally distinct clusters. We then measured neutralizing breadth of 35 NAb combinations against genotype 1 isolates, with each combination including one NAb from each neutralization cluster. Many NAbs displayed complementary neutralizing breadth, forming combinations with greater neutralization across diverse strains than any individual bNAb. Remarkably, one of the most broadly neutralizing combinations of two NAbs, designated HEPC74/HEPC98, also displayed enhanced potency, with interactions matching the Bliss independence model, suggesting that these NAbs inhibit HCV infection through independent mechanisms. Subsequent experiments showed that HEPC74 primarily blocks HCV envelope protein binding to CD81, while HEPC98 primarily blocks binding to scavenger receptor B1 and heparan sulfate. Together, these data identify a critical vulnerability resulting from the reliance of HCV on multiple cell surface receptors, suggesting that vaccine induction of multiple NAbs with distinct neutralization profiles is likely to enhance the breadth and potency of the humoral immune response against HCV.

HCV core antigen is an alternative marker to HCV RNA for evaluating active HCV infection: implications for improved diagnostic option in an era of affordable DAAs

The core antigen of the hepatitis C virus (HCV Ag) presents an alternative marker to HCV RNA when screening patients for HCV viremia. This study sought to evaluate the utility of HCV Ag as a marker to assess active HCV infection in individuals residing in an HCV-endemic area. From 298 HCV-seropositive individuals evaluated for the presence of anti-HCV antibody, HCV Ag and HCV RNA, anti-HCV antibody was detected in 252 individuals (signal-to-cutoff ratios ≥5), HCV RNA was detected in 222 individuals (88%), and HCV Ag was reactive (≥3 fmol/L) in 220 individuals (87%). HCV genotype 1, 3, and 6 were identified. HCV Ag significantly correlated with HCV RNA irrespective of HCV genotype and/or HBV co-infection (log HCV RNA = 2.67 + 0.95 [log HCV Ag], R2 = 0.890, p < 0.001). To predict HCV viremia (HCV Ag ≥ 3 fmol/L), the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 99%, 99%, 100%, 100% and 97%, respectively. We concluded that HCV Ag was a good surrogate marker for HCV RNA and could be used to diagnose active HCV infection in a resource-limited setting. As a result, a cost-effective strategy for screening and identifying active HCV carriers using HCV Ag detection would enable more patients access to efficacious and increasingly affordable direct-acting antivirals (DAAs) for the treatment of HCV infection.

Superior immunogenicity of HCV envelope glycoproteins when adjuvanted with cyclic-di-AMP, a STING activator or archaeosomes

Three decades after the discovery, hepatitis C virus (HCV) is still the leading cause of liver transplantation and poses a major threat to global health. In spite of recent advances in the development of direct acting antivirals, there is still a need for a prophylactic vaccine to limit the virus spread and protect at-risk populations, especially in developing countries, where the cost of the new treatments may severely limit access. The use of recombinant HCV glycoproteins E1E2 (rE1E2) in combination with the MF59, an oil-in-water emulsion-based adjuvant, has previously been shown to reduce the rate of chronicity in chimpanzees and to induce production of cross-neutralizing antibodies and cellular immune responses in human volunteers. To further improve neutralizing antibody responses in recipients along with robust T cell responses, we have explored the immunogenicity of different adjuvants when formulated with the HCV rE1E2 vaccine in mice. Our data show that cyclic di-adenosine monophosphate (c-di-AMP) and archaeosomes elicit strong neutralizing antibodies similar to those elicited using aluminum hydroxide/monophosphoryl lipid A (Alum/monophos. /MPLA) and MF59. However, both c-di-AMP and archaeosomes induced a more robust cellular immune response, which was confirmed by the detection of vaccine-specific poly-functional CD4⁺ T cells. We conclude that these adjuvants may substantially boost the immunogenicity of our E1E2 vaccine. In addition, our data also indicates that use of a partial or exclusive intranasal immunization regimen may also be feasible using c-di-AMP as adjuvant.

Structure-Based Design of Hepatitis C Virus Vaccines That Elicit Neutralizing Antibody Responses to a Conserved Epitope

Despite recent advances in therapeutic options, hepatitis C virus (HCV) remains a severe global disease burden, and a vaccine can substantially reduce its incidence. Due to its extremely high sequence variability, HCV can readily escape the immune response; thus, an effective vaccine must target conserved, functionally important epitopes. Using the structure of a broadly neutralizing antibody in complex with a conserved linear epitope from the HCV E2 envelope glycoprotein (residues 412 to 423; epitope I), we performed structure-based design of immunogens to induce antibody responses to this epitope. This resulted in epitope-based immunogens based on a cyclic defensin protein, as well as a bivalent immunogen with two copies of the epitope on the E2 surface. We solved the X-ray structure of a cyclic immunogen in complex with the HCV1 antibody and confirmed preservation of the epitope conformation and the HCV1 interface. Mice vaccinated with our designed immunogens produced robust antibody responses to epitope I, and their serum could neutralize HCV. Notably, the cyclic designs induced greater epitope-specific responses and neutralization than the native peptide epitope. Beyond successfully designing several novel HCV immunogens, this study demonstrates the principle that neutralizing anti-HCV antibodies can be induced by epitope-based, engineered vaccines and provides the basis for further efforts in structure-based design of HCV vaccines.IMPORTANCE Hepatitis C virus is a leading cause of liver disease and liver cancer, with approximately 3% of the world's population infected. To combat this virus, an effective vaccine would have distinct advantages over current therapeutic options, yet experimental vaccines have not been successful to date, due in part to the virus's high sequence variability leading to immune escape. In this study, we rationally designed several vaccine immunogens based on the structure of a conserved epitope that is the target of broadly neutralizing antibodies. In vivo results in mice indicated that these antigens elicited epitope-specific neutralizing antibodies, with various degrees of potency and breadth. These promising results suggest that a rational design approach can be used to generate an effective vaccine for this virus.