Therapeutic vaccination against chronic hepatitis C virus infection

Recent Insights into the Role of B Cells in Chronic Hepatitis B and C Infections

Chronic viral hepatitis infections, caused by the hepatitis B or C virus, are a major global health problem causing an estimated one million deaths each year. Immunological studies have classically focused on T cells, while B cells have largely been neglected. Emerging evidence, however, highlights a role for B cells in the immunopathogenesis of chronic hepatitis B and C infections. B cell responses appear to be altered across different clinical phases of chronic HBV infection and across stages of disease in chronic HCV infection. These B cell responses show signs of a more activated state with a simultaneous enrichment of phenotypically exhausted atypical memory B cells. Despite the fact that studies show an activating B cell signature in chronic viral hepatitis infection, antibody responses to HBsAg remain impaired in chronic HBV infection, and glycoprotein E2-specific neutralizing antibody responses remain delayed in the acute phase of HCV infection. At the same time, studies have reported that a subset of HBV- and HCV-specific B cells exhibit an exhausted phenotype. This may, at least in part, explain why antibody responses in chronic HBV and HCV patients are suboptimal. Here, we summarize recent findings and discuss upcoming research questions while looking forward to how new single-cell technologies could provide novel insights into the role of B cells in chronic viral hepatitis infections.

Development of therapeutic vaccines for the treatment of diseases

Vaccines are one of the most effective medical interventions to combat newly emerging and re-emerging diseases. Prophylactic vaccines against rabies, measles, etc., have excellent effectiveness in preventing viral infection and associated diseases. However, the host immune response is unable to inhibit virus replication or eradicate established diseases in most infected people. Therapeutic vaccines, expressing specific endogenous or exogenous antigens, mainly induce or boost cell-mediated immunity via provoking cytotoxic T cells or elicit humoral immunity via activating B cells to produce specific antibodies. The ultimate aim of a therapeutic vaccine is to reshape the host immunity for eradicating a disease and establishing lasting memory. Therefore, therapeutic vaccines have been developed for the treatment of some infectious diseases and chronic noncommunicable diseases. Various technological strategies have been implemented for the development of therapeutic vaccines, including molecular-based vaccines (peptide/protein, DNA and mRNA vaccines), vector-based vaccines (bacterial vector vaccines, viral vector vaccines and yeast-based vaccines) and cell-based vaccines (dendritic cell vaccines and genetically modified cell vaccines) as well as combinatorial approaches. This review mainly summarizes therapeutic vaccine-induced immunity and describes the development and status of multiple types of therapeutic vaccines against infectious diseases, such as those caused by HPV, HBV, HIV, HCV, and SARS-CoV-2, and chronic noncommunicable diseases, including cancer, hypertension, Alzheimer's disease, amyotrophic lateral sclerosis, diabetes, and dyslipidemia, that have been evaluated in recent preclinical and clinical studies.

The Relationship Between HCV-NS5A Gene Mutations and Resistance to Combination Therapy in Patients with HCV- Genotype 1-B

Background

Hepatitis C virus (HCV) is one of the major causes of chronic liver disease, as it holds a significant role in developing liver cirrhosis and hepatocellular carcinoma. Combination therapy with Pegaferon and Ribavirin leads to viral clearance of only 50% of patients. During the host antiviral response, protein kinase R (PKR) interacts with eukaryotic translation initiation factor 2 alpha (eIF2α), that leads to the inhibition of viral protein synthesis. The viral NS5A protein appears to interfere with this antiviral action, evading the host immune response. However, mutations in the NS5A gene have been observed to render HCV more susceptible to treatment. The aim of this study was to determine the mutations present in the IFN Sensitivity Determining Region (ISDR) and NS5A-PKRbinding domain regions in chronic HCV infected patients before and after therapy.

Methods

Viral RNA was isolated from the plasma of 52 chronic HCV infected patients before and after treatment. RT-Nested PCR reaction was used to reverse transcription and amplification of target fragment using the specific primers.

Results

Sequence analysis revealed no relationship between NS5A mutations and response to treatment. No significant difference was found between the mutations before and 3 months after treatment among responders and non-responders.

Conclusion

This study showed that the number of mutations in NS5A did not significantly differ between the patients who responded to treatment and the patients that did not. Therefore, sequencing of these regions does not appear to be a suitable tool for predicting treatment outcomes.

Hepatitis C: looking into the future

INTRODUCTION

The recent availability of highly effective hepatitis C medications, with a cure rate approaching 100%, has created a wide range of questions and uncertainties.

AREAS COVERED

The most recent data around hepatitis C virus (HCV) elimination will be reviewed. In addition, the impact of HCV cure or sustained virologic response (SVR) on the risk for hepatocellular carcinoma (HCC) development will be discussed. Although the terms 'SVR' and 'cure' are used interchangeably, there are little data to support that they are actually the same. In this review, we will shed some light on the status of HCV vaccine development, obstacles, and published experience. Finally, in the face of decreasing HCV patients needing transplantation, and increasing available organs from donors infected with HCV, the question is that, is it possible to transplant an organ infected with HCV to a patient who is not infected? The pros and cons of transplanting HCV-positive organs to HCV-negative recipients will be discussed.

EXPERT OPINION

Although the new advances in HCV treatment have solved many problems, it created several new issues which the medical community has to deal with and which will likely remain in the near future.

Alphavirus-based hepatitis C virus therapeutic vaccines: can universal helper epitopes enhance HCV-specific cytotoxic T lymphocyte responses?

Background:

Antigen-specific T cell immune responses play a pivotal role in resolving acute and chronic hepatitis C virus (HCV) infections. Currently, no prophylactic or therapeutic vaccines against HCV are available. We previously demonstrated the preclinical potency of therapeutic HCV vaccines based on recombinant Semliki Forest virus (SFV) replicon particles. However, clinical trials do not always meet the high expectations of preclinical studies, thus, optimization of vaccine strategies is crucial. In efforts to further increase the frequency of HCV-specific immune responses in the candidate SFV-based vaccines, the authors assessed whether inclusion of three strong, so-called universal helper T cell epitopes, and an endoplasmic reticulum localization, and retention signal (collectively termed sigHELP-KDEL cassette) could enhance HCV-specific immune responses.

Methods:

We included the sigHELP-KDEL cassette in two of the candidate SFV-based HCV vaccines, targeting NS3/4A and NS5A/B proteins. We characterized the new constructs in vitro for the expression and stability of the transgene-encoded proteins. Their immune efficacy with respect to HCV-specific immune responses in vivo was compared with the parental SFV vaccine expressing the corresponding HCV antigen. Further characterization of the functionality of the HCV-specific CD8⁺ T cells was assessed by surface and intracellular cytokine staining and flow cytometry analysis.

Results:

Moderate, but significantly, enhanced frequencies of antigen-specific immune responses were achieved upon lower/suboptimal dosage immunization. In optimal dosage immunization, the inclusion of the cassette did not further increase the frequencies of HCV-specific CD8⁺ T cells when compared with the parental vaccines and the frequencies of effector and memory populations were identical.

Conclusion:

We hypothesize that the additional effect of the sigHELP-KDEL cassette in SFV-based vaccines depends on the immunogenicity, nature, and stability of the target antigen expressed by the vaccine.

Nucleic acid vaccines for hepatitis B and C virus

Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections accounts for an important global health problem affecting over 250 million people all around the world. They can cause acute, transient and chronic infections in the human liver. Chronic infection of liver can lead to its failure or cancer. To deal with this problem, alternative approaches or strategies to inhibit these infections have already been started. DNA and mRNA-based vaccination will increase the efficacy and reduce toxicity in patients with Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections. Gene vaccines represent a promising alternative to conventional vaccine approaches because of their high potency, capacity for rapid development, low-cost manufacture and safe administration. MRNA-based vaccination is a method to elicit potent antigen-specific humoral and cell-mediated immune responses with a superior safety profile compared with DNA vaccines. Exploring the intricacies of these pathways can potentially help the researchers to explore newer vaccines. In this study, DNA and mRNA-based vaccination are introduced as an approach to treat Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections. DNA and mRNA-based vaccines as one of the most successful therapeutics are introduced and the clinical outcomes of their exploitation are explained.

TLR9-Mediated Conditioning of Liver Environment Is Essential for Successful Intrahepatic Immunotherapy and Effective Memory Recall

Immune defense against hepatotropic viruses such as hepatitis B (HBV) and hepatitis C (HCV) poses a major challenge for therapeutic approaches. Intrahepatic cytotoxic CD8 T cells that are crucial for an immune response against these viruses often become exhausted resulting in chronic infection. We elucidated the T cell response upon therapeutic vaccination in inducible transgenic mouse models in which variable percentages of antigen-expressing hepatocytes can be adjusted, providing mosaic antigen distribution and reflecting the varying viral antigen loads observed in patients. Vaccination-induced endogenous CD8 T cells could eliminate low antigen loads in liver but were functionally impaired if confronted with elevated antigen loads. Strikingly, only by conditioning the liver environment with TLR9 ligand prior and early after peripheral vaccination, successful immunization against high intrahepatic antigen density with its elimination was achieved. Moreover, TLR9 immunomodulation was also indispensable for functional memory recall after high frequency antigen challenge. Together, the results indicate that TLR9-mediated conditioning of liver environment during therapeutic vaccination or antigen reoccurrence is crucial for an efficacious intrahepatic T cell response.

Oral Combination Vaccine, Comprising Bifidobacterium Displaying Hepatitis C Virus Nonstructural Protein 3 and Interferon-α, Induces Strong Cellular Immunity Specific to Nonstructural Protein 3 in Mice

We previously generated an oral hepatitis C virus (HCV) vaccine using Bifidobacterium displaying the HCV nonstructural protein 3 (NS3) polypeptide. NS3-specific cellular immunity is important for viral clearance and recovery from HCV infection. In this study, we enhanced the cellular immune responses induced by our oral HCV vaccine, Bifidobacterium longum 2165 (B. longum 2165), by combining interferon-α (IFN-α) as an adjuvant with the vaccine in a mouse experimental model. IFN-α is a widely used cytokine meeting the standard of care (SOC) for HCV infection and plays various immunoregulatory roles. We treated C57BL/6N mice with B. longum 2165 every other day and/or IFN-α twice a week for a month and then analyzed the immune responses using spleen cells. We determined the induction of NS3-specific cellular immunity by cytokine quantification, intracellular cytokine staining, and a cytotoxic T lymphocyte (CTL) assay targeting EL4 tumor cells expressing NS3/4A protein (EL4-NS3/4A). We also treated mice bearing EL4-NS3/4A tumor with the combination therapy in vivo. The results confirmed that the combination therapy of B. longum 2165 and IFN-α induced significantly higher IFN-γ secretion, higher population of CD4⁺T and CD8⁺T cells secreting IFN-γ, and higher CTL activity against EL4-NS3/4A cells compared with the control groups of phosphate-buffered saline, B. longum 2165 alone, and IFN-α alone (p < 0.05). We also confirmed that the combination therapy strongly enhanced tumor growth inhibitory effects in vivo with no serious adverse effects (p < 0.05). These results suggest that the combination of B. longum 2165 and IFN-α could induce a strong cellular immunity specific to NS3 protein as a combination therapy augmenting the current SOC immunotherapy against chronic HCV infection.

Immunologic approaches to cancer prevention-current status, challenges, and future perspectives

The potential of the immune system to recognize and reject tumors has been investigated for more than a century. However, only recently impressive breakthroughs in cancer immunotherapy have been seen with the use of checkpoint inhibitors. The experience with various immune-based strategies in the treatment of late cancer highlighted the importance of negative impact advanced disease has on immunity. Consequently, use of immune modulation for cancer prevention rather than therapy has gained considerable attention, with many promising results seen already in preclinical and early clinical studies. Although not without challenges, these results provide much excitement and optimism that successful cancer immunoprevention could be within our reach. In this review we will discuss the current state of predominantly primary and secondary cancer immunoprevention, relevant research, potential barriers, and future directions.

Oral anti-CD3 immunotherapy for HCV-nonresponders is safe, promotes regulatory T cells and decreases viral load and liver enzyme levels: results of a phase-2a placebo-controlled trial

Orally administered anti-CD3 antibodies are biologically active in the gut through induction of regulatory T cells, exert an immune-modulatory effect, and alleviate insulin resistance and liver damage in patients with NASH.

AIMS

To determine the safety of oral anti-CD3 monoclonal antibody (MAb) immunotherapy in chronic HCV patients with associated immune dysfunction.

METHODS

Four groups (n = 9) of chronic HCV patients who were nonresponders to interferon plus ribavirin therapy received oral placebo (group A) or anti-CD3 MAb at one of three dosage levels for 30 days. Patients were followed for safety parameters and serum levels of liver enzymes, virus, cytokines and regulatory T cells.

RESULTS

Oral anti-CD3 immunotherapy was safe and well tolerated; no treatment-related adverse events were noted. The following improvements were noted relative to pretreatment levels: HCV viral load and AST and ALT levels decreased in the low- and high-dose groups following 30 days of therapy. In two of the treated groups, an increase in regulatory T cells (CD4(+) CD25(+) ) was noted. The positive effects were somewhat more apparent in subjects with initially elevated liver enzyme levels.

CONCLUSIONS

Oral anti-CD3 MAb immunotherapy for nonresponder HCV patients was safe and well tolerated. Trends and statistically significant improvements were observed as reductions in viral load and liver enzyme levels, along with an increase in regulatory T-cell levels. These data support a role for the immune system in the pathogenesis of HCV infection and suggest that this immunotherapy is worthy of evaluation in combination with HCV antiviral drugs.

Encapsulated cellular implants for recombinant protein delivery and therapeutic modulation of the immune system

Ex vivo gene therapy using retrievable encapsulated cellular implants is an effective strategy for the local and/or chronic delivery of therapeutic proteins. In particular, it is considered an innovative approach to modulate the activity of the immune system. Two recently proposed therapeutic schemes using genetically engineered encapsulated cells are discussed here: the chronic administration of monoclonal antibodies for passive immunization against neurodegenerative diseases and the local delivery of a cytokine as an adjuvant for anti-cancer vaccines.

The roles of endoplasmic reticulum overload response induced by HCV and NS4B protein in human hepatocyte viability and virus replication

Hepatitis C virus (HCV) replication is associated with endoplasmic reticulum (ER) and its infection triggers ER stress. In response to ER stress, ER overload response (EOR) can be activated, which involves the release of Ca²⁺ from ER, production of reactive oxygen species (ROS) and activation of nuclear factor κB (NF-κB). We have previously reported that HCV NS4B expression activates NF-κB via EOR-Ca²⁺-ROS pathway. Here, we showed that NS4B expression and HCV infection activated cancer-related NF-κB signaling pathway and induced the expression of cancer-related NF-κB target genes via EOR-Ca²⁺-ROS pathway. Moreover, we found that HCV-activated EOR-Ca²⁺-ROS pathway had profound effects on host cell viability and HCV replication. HCV infection induced human hepatocyte death by EOR-Ca²⁺-ROS pathway, whereas activation of EOR-Ca²⁺-ROS-NF-κB pathway increased the cell viability. Meanwhile, EOR-Ca²⁺-ROS-NF-κB pathway inhibited acute HCV replication, which could alleviate the detrimental effect of HCV on cell viability and enhance chronic HCV infection. Together, our findings provide new insights into the functions of EOR-Ca²⁺-ROS-NF-κB pathway in natural HCV replication and pathogenesis.

The advances in research on the pharmacological effects of Fructus Ligustri Lucidi

Fructus Ligustri Lucidi is a well-known invigorator in Chinese materia medica with hepatoprotective effect, anticancer activity, antioxidant activity, and so on. And oleanolic acids are the major pharmacologically active components in Fructus Ligustri Lucidi. So it has great value in medical health, and may be developed to a complementary and alternative medicine through further research. In this paper, the advances in research on pharmacological effects of Fructus Ligustri Lucidi were summarized by reviewing the recent related literature.

Prediction of T-cell epitopes of hepatitis C virus genotype 5a

Background

Hepatitis C virus (HCV) is a public health problem with almost 185 million people estimated to be infected worldwide and is one of the leading causes of hepatocellular carcinoma. Currently, there is no vaccine for HCV infection and the current treatment does not clear the infection in all patients. Because of the high diversity of HCV, protective vaccines will have to overcome significant viral antigenic diversities. The objective of this study was to predict T-cell epitopes from HCV genotype 5a sequences.

Methods

HCV near full-length protein sequences were analyzed to predict T-cell epitopes that bind human leukocyte antigen (HLA) class I and HLA class II in HCV genotype 5a using Propred I and Propred, respectively. The Antigenicity score of all the predicted epitopes were analysed using VaxiJen v2.0. All antigenic predicted epitopes were analysed for conservation using the IEDB database in comparison with 406, 221, 98, 33, 45, 45 randomly selected sequences from each of the HCV genotypes 1a, 1b, 2, 3, 4 and 6 respectively, downloaded from the GenBank. For epitope prediction binding to common HLA alleles found in South Africa, the IEDB epitope analysis tool was used.

Results

A total of 24 and 77 antigenic epitopes that bind HLA class I and HLA class II respectively were predicted. The highest number of HLA class I binding epitopes were predicted within the NS3 (63%), followed by NS5B (21%). For the HLA class II, the highest number of epitopes were predicted in the NS3 (30%) followed by the NS4B (23%) proteins. For conservation analysis, 8 and 31 predicted epitopes were conserved in different genotypes for HLA class I and HLA class II alleles respectively. Several epitopes bind with high affinity for both HLA class I alleles and HLA class II common in South Africa.

Conclusion

The predicted conserved T-cell epitopes analysed in this study will contribute towards the future design of HCV vaccine candidates which will avoid variation in genotypes, which in turn will be capable of inducing broad HCV specific immune responses.

Efficacy of immunotherapy with TG4040, peg-interferon, and ribavirin in a Phase 2 study of patients with chronic HCV infection

BACKGROUND & AIMS

TG4040 is a modified vaccinia Ankara (MVA) virus that expresses the hepatitis C virus (HCV) proteins NS3, NS4, and NS5B. We performed a phase II open-label study to determine the efficacy, safety, and immunotherapeutic properties of TG4040 in combination with pegylated interferon α-2a and ribavirin (PEG-IFNα/RBV) in patients with chronic HCV infection.

METHODS

Treatment-naive patients with HCV genotype 1 infection were assigned randomly to 1 of the following groups: PEG-IFNα/RBV for 48 weeks (group A, n = 31), PEG-IFNα/RBV for 4 weeks followed by PEG-IFNα/RBV for 44 weeks with 6 injections of TG4040 (group B, n = 63), or TG4040 for 12 weeks (7 injections) followed by PEG-IFNα/RBV for 48 weeks with 6 injections of TG4040 (group C, n = 59). The primary end point was complete early virologic response (cEVR), defined as HCV-RNA level less than 10 IU/mL after 12 weeks of PEG-IFNα/RBV treatment.

RESULTS

In group C, 64.2% of evaluable patients achieved cEVR, compared with 30.0% in group A and 45.9% in group B (P = .0003 for group C vs A). A higher percentage of patients achieved a sustained virologic response 24 weeks after therapy ended in group C (58.2%) than in groups A (48.4%) or B (50.8%). HCV- and MVA-specific T-cell responses were observed predominantly in group C. As expected, most patients given injections of TG4040 developed anti-MVA antibodies. The combination of TG4040 and PEG-IFNα/RBV was reasonably well tolerated. However, PEG-IFNα-associated thrombocytopenia developed in 3 patients who carried the class II HLA allele DRB01*04.

CONCLUSIONS

A higher percentage of patients with chronic HCV infection who received immunotherapy with TG4040 followed by TG4040 and PEG-IFNα/RBV achieved a cEVR compared with patients who received only PEG-IFNα/RBV therapy. These findings show that immunotherapies that activate T cells are effective in patients with chronic HCV infection. ClinicalTrials.gov number, NCT01055821.

Alphavirus-based vaccines encoding nonstructural proteins of hepatitis C virus induce robust and protective T-cell responses

An absolute prerequisite for a therapeutic vaccine against hepatitis C virus (HCV) infection is the potency to induce HCV-specific vigorous and broad-spectrum T-cell responses. Here, we generated three HCV vaccines based on a recombinant Semliki Forest virus (rSFV) vector expressing all- or a part of the conserved nonstructural proteins (nsPs) of HCV. We demonstrated that an rSFV vector was able to encode a transgene as large as 6.1 kb without affecting its vaccine immunogenicity. Prime-boost immunizations of mice with rSFV expressing all nsPs induced strong and long-lasting NS3-specific CD8(+) T-cell responses. The strength and functional heterogeneity of the T-cell response was similar to that induced with rSFV expressing only NS3/4A. Furthermore this leads to a significant growth delay and negative selection of HCV-expressing EL4 tumors in an in vivo mouse model. In general, as broad-spectrum T-cell responses are only seen in patients with resolved HCV infection, this rSFV-based vector, which expresses all nsPs, inducing robust T-cell activity has a potential for the treatment of HCV infections.

Treatment as prevention and cure towards global eradication of hepatitis C virus

The availability of curative, direct-acting antiviral drugs against hepatitis C virus (HCV) sparks an ethical call for HCV eradication and provides essential tools to spearhead the effort. Challenges include increasing awareness of the chronic hepatitis C epidemic, garnering sufficient public, private, and governmental financial will to invest in the necessary resources, developing pangenotypic drug regimens for global application, and mitigating ethical concerns. To achieve these goals, stakeholders including clinicians, public health professionals, legislators, advocates, and industry can employ a variety of strategies such as increasing HCV screening, implementing treatment as prevention, and improving linkage to care, as well as developing innovative pricing and payment solutions, stimulating innovation through local drug development in high-prevalence regions, continuing vaccine development, and creating efficiencies in the marketing and distribution of educational materials and drug treatments.

Development of chimpanzee adenoviruses as vaccine vectors: challenges and successes emerging from clinical trials

Replication-defective chimpanzee adenovirus vectors are emerging as a promising new class of genetic vaccine carriers. Chimpanzee adenovirus vectors have now reached the clinical stage and appear to be endowed with all the properties needed for human vaccine development, including high quality and magnitude of the immune response induced against the encoded antigens, good safety and ease of manufacturing on a large-scale basis. Here the authors review the recent findings of this novel class of adenovirus vectors and compare their properties to other clinical stage vaccine vectors derived from poxvirus, alphavirus and human adenovirus.

Immunotherapy in preneoplastic disease: targeting early procarcinogenic inflammatory changes that lead to immune suppression and tumor tolerance

Recent advances in immunotherapy have demonstrated that single agent vaccines can be effective when given as primary prevention before exposure to the causative agent, and partially effective in some patients with existing cancer. However, as tumors develop and progress, tumor-induced immune suppression and tolerance present the greatest barrier to therapeutic success. Preneoplastic disease represents an important opportunity to intervene with tumor antigen-targeted vaccines before these mechanisms of immune evasion outpace efforts by the immune system to destroy precancerous cells. However, as we discuss in this review, emerging evidence suggests that procarcinogenic inflammatory changes occur early in cancer development, in both patients and mouse models of cancer progression. Defining early inhibitory signals within tumor microenvironments will yield insights that can eventually be used in the clinic to target these events and deliver treatments that can be used in addition to cancer vaccines to prevent premalignant and early invasive cancers.

Cell-cell contact-mediated hepatitis C virus (HCV) transfer, productive infection, and replication and their requirement for HCV receptors

Hepatitis C virus (HCV) infection is believed to begin with interactions between cell-free HCV and cell receptors that include CD81, scavenger receptor B1 (SR-B1), claudin-1 (CLDN1), and occludin (OCLN). In this study, we have demonstrated that HCV spreading from infected hepatocytes to uninfected hepatocytes leads to the transfer of HCV and the formation of infection foci and is cell density dependent. This cell-cell contact-mediated (CCCM) HCV transfer occurs readily and requires all these known HCV receptors and an intact actin cytoskeleton. With a fluorescently labeled replication-competent HCV system, the CCCM transfer process was further dissected by live-cell imaging into four steps: donor cell-target cell contact, formation of viral puncta-target cell conjugation, transfer of viral puncta, and posttransfer. Importantly, the CCCM HCV transfer leads to productive infection of target cells. Taken together, these results show that CCCM HCV transfer constitutes an important and effective route for HCV infection and dissemination. These findings will aid in the development of new and novel strategies for preventing and treating HCV infection.

High, broad, polyfunctional, and durable T cell immune responses induced in mice by a novel hepatitis C virus (HCV) vaccine candidate (MVA-HCV) based on modified vaccinia virus Ankara expressing the nearly full-length HCV genome

A major goal in the control of hepatitis C infection is the development of a vaccine. Here, we have developed a novel HCV vaccine candidate based on the highly attenuated poxvirus vector MVA (referred to as MVA-HCV) expressing the nearly full-length (7.9-kbp) HCV sequence, with the aim to target almost all of the T and B cell determinants described for HCV. In infected cells, MVA-HCV produces a polyprotein that is subsequently processed into the structural and nonstructural HCV proteins, triggering the cytoplasmic accumulation of dense membrane aggregates. In both C57BL/6 and transgenic HLA-A2-vaccinated mice, MVA-HCV induced high, broad, polyfunctional, and long-lasting HCV-specific T cell immune responses. The vaccine-induced T cell response was mainly mediated by CD8 T cells; however, although lower in magnitude, the CD4(+) T cells were highly polyfunctional. In homologous protocol (MVA-HCV/MVA-HCV) the main CD8(+) T cell target was p7+NS2, whereas in heterologous combination (DNA-HCV/MVA-HCV) the main target was NS3. Antigenic responses were also detected against other HCV proteins (Core, E1-E2, and NS4), but the magnitude of the responses was dependent on the protocol used. The majority of the HCV-induced CD8(+) T cells were triple or quadruple cytokine producers. The MVA-HCV vaccine induced memory CD8(+) T cell responses with an effector memory phenotype. Overall, our data showed that MVA-HCV induced broad, highly polyfunctional, and durable T cell responses of a magnitude and quality that might be associated with protective immunity and open the path for future considerations of MVA-HCV as a prophylactic and/or therapeutic vaccine candidate against HCV.

Oleanolic acid and ursolic acid: novel hepatitis C virus antivirals that inhibit NS5B activity

Hepatitis C virus (HCV) infects up to 170 million people worldwide and causes significant morbidity and mortality. Unfortunately, current therapy is only curative in approximately 50% of HCV patients and has adverse side effects, which warrants the need to develop novel and effective antivirals against HCV. We have previously reported that the Chinese herb Fructus Ligustri Lucidi (FLL) directly inhibited HCV NS5B RNA-dependent RNA polymerase (RdRp) activity (Kong et al., 2007). In this study, we found that the FLL aqueous extract strongly suppressed HCV replication. Further high-performance liquid chromatography (HPLC) analysis combined with inhibitory assays indicates that oleanolic acid and ursolic acid are two antiviral components within FLL aqueous extract that significantly suppressed the replication of HCV genotype 1b replicon and HCV genotype 2a JFH1 virus. Moreover, oleanolic acid and ursolic acid exhibited anti-HCV activity at least partly through suppressing HCV NS5B RdRp activity as noncompetitive inhibitors. Therefore, our results for the first time demonstrated that natural products oleanolic acid and ursolic acid could be used as potential HCV antivirals that can be applied to clinic trials either as monotherapy or in combination with other HCV antivirals.

Best strategies for global HCV eradication

Worldwide eradication of hepatitis C virus (HCV) is possible through a combination of prevention education, universal clinical and targeted community screening, effective linkage to care and treatment with promising new direct-acting antiviral drug regimens. Universal screening should be offered in all healthcare visits, and parallel community screening efforts should prioritize high-prevalence, high-transmission populations including injection drug users, prison inmates and those with HIV/HCV co-infection. Increasing awareness of HCV infection through screening, improving treatment uptake and cure rates by providing linkage to care and more effective treatment, and ultimately combining education efforts with vaccination campaigns to prevent transmission and reinfection can slow and eventually stop the 'silent epidemic'.

Hepatitis C virus vaccines in the era of new direct-acting antivirals

Hepatitis C virus (HCV) infection is a major global health problem as it has a high propensity for establishing chronicity. Chronic HCV carriers are at risk of developing severe liver disease including fibrosis, cirrhosis and liver cancer. While treatment has considerably improved over the years, therapy is still only partially effective, and is plagued by side effects, which contribute to treatment failure and is expensive to manage. The drug development pipeline contains several compounds that hold promise to achieve the goal of a short and more tolerable therapy, and are also likely to improve treatment response rates. It remains to be seen, however, how potent antiviral drug cocktails will affect the hepatitis C burden worldwide. In resource-poor environments, considerable costs, inadequate infrastructure for medical supervision and distribution may diminish the impact of future therapies. Consequently, development of novel therapeutic and prophylactic strategies is imperative to contain HCV infection globally.

Granulocyte-macrophage colony-stimulating factor genetic adjuvant enhances the immune stimulatory effects of plasmid DNA encoding the hepatitis C virus core protein

AIM: To study the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) genetic adjuvant on immune response induced by plasmid DNA encoding the hepatitis C virus (HCV) core (C) protein.

METHODS: The gene encoding the HCV C protein was amplified by PCR from HCV 1b genotype and inserted into the pUC119 vector. The HCV C gene was then subcloned into the pCMH6K eukaryotic vector, and the resulting plasmid was named pCMH6K/HCV-C. The recombinant vector was confirmed by restriction enzyme analysis and DNA sequencing, and transfected into China hamster ovary (CHO) cells with Lipofectamine 2000. Distribution of the HCV C protein in transfected CHO cells was detected by immunofluorescence. Balb/c mice were vaccinated with the recombinant plasmid with or without the GM-CSF gene. HCV C-specific antibody in serum was measured by ELISA. The changes in T lymphocyte subsets and levels of Th cell intracellular cytokines interferon-γ (IFN-γ) and interleukin-4 (IL-4) in splenic cell suspension from immunized mice were evaluated by flow cytometric analysis. CTL activity was assessed by LDH assay.

RESULTS: Restrict enzyme digestion and DNA sequencing indicated that the recombinant pCMH6K/HCV-C was successfully constructed. The expression of plasmid-encoded protein was mainly distributed in membrane and scarcely in cytoplasm of transfected CHO cells. The percentage of CD4⁺ T cells in spleen cells in the pCMH6K/HCV-C+pGM-CSF co-vaccination group was significantly higher than those in other groups (all P < 0.05). The percentage of CD8⁺ T cells showed no significant differences among each group (P > 0.05). CTL activity induced by GM-CSF DNA co-vaccination was significantly higher than that immunized with the same amount of other naked DNA (P < 0.05). The ratio of IFN-γ to IL-4 in spleen cells from GM-CSF DNA co-vaccination group was significantly higher than those in other groups (all P < 0.05).

CONCLUSION: GM-CSF DNA could enhance the immune stimulatory effects of HCV DNA vaccine and induce Th1-type immune response.