Immunogenicity and safety of different injection routes and schedules of IC41, a Hepatitis C virus (HCV) peptide vaccine

The bright side of chemistry: Exploring synthetic peptide-based anticancer vaccines

The present review focuses on synthetic peptide-based vaccine strategies in the context of anticancer intervention, paying attention to critical aspects such as peptide epitope selection, adjuvant integration, and nuanced classification of synthetic peptide cancer vaccines. Within this discussion, we delve into the diverse array of synthetic peptide-based anticancer vaccines, each derived from tumor-associated antigens (TAAs), including melanoma antigen recognized by T cells 1 (Melan-A or MART-1), mucin 1 (MUC1), human epidermal growth factor receptor 2 (HER-2), tumor protein 53 (p53), human telomerase reverse transcriptase (hTERT), survivin, folate receptor (FR), cancer-testis antigen 1 (NY-ESO-1), and prostate-specific antigen (PSA). We also describe the synthetic peptide-based vaccines developed for cancers triggered by oncovirus, such as human papillomavirus (HPV), and hepatitis C virus (HCV). Additionally, the potential synergy of peptide-based vaccines with common therapeutics in cancer was considered. The last part of our discussion deals with the realm of the peptide-based vaccines delivery, highlighting its role in translating the most promising candidates into effective clinical strategies. Although this discussion does not cover all the ongoing peptide vaccine investigations, it aims at offering valuable insights into the chemical modifications and the structural complexities of anticancer peptide-based vaccines.

Malignancy and viral infections in Sub-Saharan Africa: A review

The burden of malignancy related to viral infection is increasing in Sub-Saharan Africa (SSA). In 2018, approximately 2 million new cancer cases worldwide were attributable to infection. Prevention or treatment of these infections could reduce cancer cases by 23% in less developed regions and about 7% in developed regions. Contemporaneous increases in longevity and changes in lifestyle have contributed to the cancer burden in SSA. African hospitals are reporting more cases of cancer related to infection (e.g., cervical cancer in women and stomach and liver cancer in men). SSA populations also have elevated underlying prevalence of viral infections compared to other regions. Of 10 infectious agents identified as carcinogenic by the International Agency for Research on Cancer, six are viruses: hepatitis B and C viruses (HBV and HCV, respectively), Epstein-Barr virus (EBV), high-risk types of human papillomavirus (HPV), Human T-cell lymphotropic virus type 1 (HTLV-1), and Kaposi's sarcoma herpesvirus (KSHV, also known as human herpesvirus type 8, HHV-8). Human immunodeficiency virus type 1 (HIV) also facilitates oncogenesis. EBV is associated with lymphomas and nasopharyngeal carcinoma; HBV and HCV are associated with hepatocellular carcinoma; KSHV causes Kaposi's sarcoma; HTLV-1 causes T-cell leukemia and lymphoma; HPV causes carcinoma of the oropharynx and anogenital squamous cell cancer. HIV-1, for which SSA has the greatest global burden, has been linked to increasing risk of malignancy through immunologic dysregulation and clonal hematopoiesis. Public health approaches to prevent infection, such as vaccination, safer injection techniques, screening of blood products, antimicrobial treatments and safer sexual practices could reduce the burden of cancer in Africa. In SSA, inequalities in access to cancer screening and treatment are exacerbated by the perception of cancer as taboo. National level cancer registries, new screening strategies for detection of viral infection and public health messaging should be prioritized in SSA's battle against malignancy. In this review, we discuss the impact of carcinogenic viruses in SSA with a focus on regional epidemiology.

Recent Advances in Protective Vaccines against Hepatitis Viruses: A Narrative Review

Vaccination has been confirmed to be the safest and, sometimes, the only tool of defense against threats from infectious diseases. The successful history of vaccination is evident in the control of serious viral infections, such as smallpox and polio. Viruses that infect human livers are known as hepatitis viruses and are classified into five major types from A to E, alphabetically. Although infection with hepatitis A virus (HAV) is known to be self-resolving after rest and symptomatic treatment, there were 7134 deaths from HAV worldwide in 2016. In 2019, hepatitis B virus (HBV) and hepatitis C virus (HCV) resulted in an estimated 820,000 and 290,000 deaths, respectively. Hepatitis delta virus (HDV) is a satellite virus that depends on HBV for producing its infectious particles in order to spread. The combination of HDV and HBV infection is considered the most severe form of chronic viral hepatitis. Hepatitis E virus (HEV) is another orally transmitted virus, common in low- and middle-income countries. In 2015, it caused 44,000 deaths worldwide. Safe and effective vaccines are already available to prevent hepatitis A and B. Here, we review the recent advances in protective vaccines against the five major hepatitis viruses.

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.

Translational aspect in peptide drug discovery and development: An emerging therapeutic candidate

In the last two decades, protein-protein interactions (PPIs) have been used as the main target for drug development. However, with larger or superficial binding sites, it has been extremely difficult to disrupt PPIs with small molecules. On the other hand, intracellular PPIs cannot be targeted by antibodies that cannot penetrate the cell membrane. Peptides that have a combination of conformational rigidity and flexibility can be used to target difficult binding interfaces with appropriate binding affinity and specificity. Since the introduction of insulin nearly a century ago, more than 80 peptide drugs have been approved to treat a variety of diseases. These include deadly diseases such as cancer and human immunodeficiency virus infection. It is also useful against diabetes, chronic pain, and osteoporosis. Today, more research is being done on these drugs as lessons learned from earlier approaches, which are still valid today, complement newer approaches such as peptide display libraries. At the same time, integrated genomics and peptide display libraries are new strategies that open new avenues for peptide drug discovery. The purpose of this review is to examine the problems in elucidating the peptide-protein recognition mechanism. This is important to develop peptide-based interventions that interfere with endogenous protein interactions. New approaches are being developed to improve the binding affinity and specificity of existing approaches and to develop peptide agents as potentially useful drugs. We also highlight the key challenges that must be overcome in peptide drug development to realize their potential and provide an overview of recent trends in peptide drug development. In addition, we take an in-depth look at early efforts in human hormone discovery, smart medicinal chemistry and design, natural peptide drugs, and breakthrough advances in molecular biology and peptide chemistry.

Implementation of a controlled human infection model for evaluation of HCV vaccine candidates

Hepatitis C virus (HCV) remains a major global health concern. Directly acting antiviral (DAA) drugs have transformed the treatment of HCV. However, it has become clear that, without an effective HCV vaccine, it will not be possible to meet the World Health Organization targets of HCV viral elimination. Promising new vaccine technologies that generate high magnitude antiviral T and B cell immune responses and significant new funding have recently become available, stimulating the HCV vaccine pipeline. In the absence of an immune competent animal model for HCV, the major block in evaluating new HCV vaccine candidates will be the assessment of vaccine efficacy in humans. The development of a controlled human infection model (CHIM) for HCV could overcome this block, enabling the head-to-head assessment of vaccine candidates. The availability of highly effective DAA means that a CHIM for HCV is possible for the first time. In this review, we highlight the challenges and issues with currently available strategies to assess HCV vaccine efficacy including HCV "at-risk" cohorts and animal models. We describe the development of CHIM in other infections that are increasingly utilized by trialists and explore the ethical and safety concerns specific for an HCV CHIM. Finally, we propose an HCV CHIM study design including the selection of volunteers, the development of an infectious inoculum, the evaluation of host immune and viral parameters, and the definition of study end points for use in an HCV CHIM. Importantly, the study design (including number of volunteers required, cost, duration of study, and risk to volunteers) varies significantly depending on the proposed mechanism of action (sterilizing/rapid viral clearance vs. delayed viral clearance) of the vaccine under evaluation. We conclude that an HCV CHIM is now realistic, that safety and ethical concerns can be addressed with the right study design, and that, without an HCV CHIM, it is difficult to envisage how the development of an HCV vaccine will be possible.

Production and immunogenicity of different prophylactic vaccines for hepatitis C virus (Review)

Hepatitis C virus (HCV) infection is a global health challenge, and prophylactic vaccines are the most effective way to eliminate the infection. To date, numerous forms of preventive vaccines have entered the clinical trial stage, including the virus-like particle (VLP) vaccine, recombinant subunit vaccine, peptide vaccine and nucleic acid vaccine. The rational design makes it easier to obtain specific vaccine structures with a broad spectrum and strong immunogenicity. Different vaccine antigens can evoke different immune responses, including humoral and T-cell immune responses, and can be produced using different expression systems, such as bacteria, yeast, mammals, plants, insects or parasites. Intracellular and insoluble production and a narrow immune spectrum are two difficulties that limit the application of vaccines. The present study summarizes the immunogenicity of different preventive vaccines, evaluates the characteristics of different expression systems used for vaccine production, and analyzes the strategies to enhance the secretion and immune spectrum of vaccine proteins.

Peptides for Vaccine Development

This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.

The next generation of HCV vaccines: a focus on novel adjuvant development

INTRODUCTION

Considerable efforts have been made to treat and prevent acute and chronic infections caused by the hepatitis C virus (HCV). Current treatments are unable to protect people from reinfection. Hence, there is a need for development of both preventive and therapeutic HCV vaccines. Many vaccine candidates are in development to fight against HCV, but their efficacy has so far proven limited partly due to low immunogenicity.

AREAS COVERED

We explore development of novel and powerful adjuvants to achieve an effective HCV vaccine. The basis for developing strong adjuvants is to understand the innate immunity pathway, which subsequently stimulates humoral and cellular immune responses. We have also investigated immunogenicity of developed adjuvants that have been used in recent studies available in online databases such as PubMed, PMC, ScienceDirect, Google Scholar, etc.

EXPERT OPINION

Adjuvants are used as a part of vaccine formulation to boost vaccine immunogenicity and antigen delivery. Several FDA-approved adjuvants are used in licensed human vaccines. Unfortunately, no adjuvant has yet been proven to boost HCV immune responses to the extent needed for an effective vaccine. One of the promising approaches for developing an effective adjuvant is the combination of various adjuvants to trigger several innate immune responses, leading to activation of adaptive immunity.[Figure: see text].

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.

Role of artificial intelligence in peptide vaccine design against RNA viruses

RNA viruses have high rate of replication and mutation that help them adapt and change according to their environmental conditions. Many viral mutants are the cause of various severe and lethal diseases. Vaccines, on the other hand have the capacity to protect us from infectious diseases by eliciting antibody or cell-mediated immune responses that are pathogen-specific. While there are a few reviews pertaining to the use of artificial intelligence (AI) for SARS-COV-2 vaccine development, none focus on peptide vaccination for RNA viruses and the important role played by AI in it. Peptide vaccine which is slowly coming to be recognized as a safe and effective vaccination strategy has the capacity to overcome the mutant escape problem which is also being currently faced by SARS-COV-2 vaccines in circulation.Here we review the present scenario of peptide vaccines which are developed using mathematical and computational statistics methods to prevent the spread of disease caused by RNA viruses. We also focus on the importance and current stage of AI and mathematical evolutionary modeling using machine learning tools in the establishment of these new peptide vaccines for the control of viral disease.

Peptide-Based Vaccines: Current Progress and Future Challenges

Vaccines have had a profound impact on the management and prevention of infectious disease. In addition, the development of vaccines against chronic diseases has attracted considerable interest as an approach to prevent, rather than treat, conditions such as cancer, Alzheimer's disease, and others. Subunit vaccines consist of nongenetic components of the infectious agent or disease-related epitope. In this Review, we discuss peptide-based vaccines and their potential in three therapeutic areas: infectious disease, Alzheimer's disease, and cancer. We discuss factors that contribute to vaccine efficacy and how these parameters may potentially be modulated by design. We examine both clinically tested vaccines as well as nascent approaches and explore current challenges and potential remedies. While peptide vaccines hold substantial promise in the prevention of human disease, many obstacles remain that have hampered their clinical use; thus, continued research efforts to address these challenges are warranted.

Broad Spectrum Peptide Vaccine Design Against Hepatitis C Virus

BACKGROUND

Hepatitis C virus (HCV) infection is a global burden. There is no peptide vaccine found as modality to cure the disease is available due to the weak cellular immune response and the limitation to induce humoral immune response.

METHODS

Five predominated HCV subtypes in Indonesia (1a, 1b, 1c, 3a, and 3k) were aligned and the conserved regions were selected. Twenty alleles of class I MHC including HLA-A, HLA-B, and HLAC types were used to predict the potential epitopes by using NetMHCPan and IEDB. Eight alleles of HLA-DRB1, together with a combination of 3 alleles of HLA-DQA1 and 5 alleles of HLA-DQB1 were utilized for Class II MHC epitopes prediction using NetMHCIIPan and IEDB. LBtope and Ig- Pred were used to predict B cells epitopes. Moreover, proteasome analysis was performed by NetCTL and the stability of the epitopes in HLA was calculated using NetMHCStabPan for Class I. All predicted epitopes were analyzed for its antigenicity, toxicity, and stability. Population coverage, molecular docking and molecular dynamics were performed for several best epitopes.

RESULTS

The results showed that two best epitopes from envelop protein, GHRMAWDMMMNWSP (E1) and PALSTGLIHLHQN (E2) were selected as promising B cell and CD8+ T cell inducers. Other two peptides, LGIGTVLDQAETAG and VLVLNPSVAATLGF, taken from NS3 protein were selected as CD4+ T cell inducer.

CONCLUSION

This study suggested the utilization of all four peptides to make a combinational peptide vaccine for in vivo study to prove its ability in inducing secondary response toward HCV.

Review on chemogenomic approaches towards hepatitis C viral targets

Hepatitis C virus (HCV) is the most prevalent viral pathogen that infects more than 185 million people worldwide. HCV infection leads to chronic liver diseases such as liver cirrhosis and hepatocellular carcinoma. Direct-acting antivirals (DAAs) are the recent combination therapy for HCV infection with reduced side effects than prior therapies. Sustained virological response (SVR) acts as a gold standard marker to monitor the success of antiviral treatment. Older treatment therapies attain 50-55% of SVR compared with DAAs which attain around 90-95%. The current review emphasizes the recent chemogenomic updates that have been unfolded through structure-based drug design of HCV drug target proteins (NS3/4A, NS5A, and NS5B) and ligand-based drug design of DAAs in achieving a stable HCV viral treatment strategies.

Global elimination of hepatitis C virus infection: Progresses and the remaining challenges

Today, with the introduction of interferon-free direct-acting antivirals and outstanding progresses in the prevention, diagnosis and treatment of hepatitis C virus (HCV) infection, the elimination of HCV infection seems more achievable. A further challenge is continued transmission of HCV infection in high-risk population specially injecting drug users (IDUs) as the major reservoir of HCV infection. Considering the fact that most of these infections remain undiagnosed, unidentified HCV-infected IDUs are potential sources for the rapid spread of HCV in the community. The continuous increase in the number of IDUs along with the rising prevalence of HCV infection among young IDUs is harbinger of a forthcoming public health dilemma, presenting a serious challenge to control transmission of HCV infection. Even the changes in HCV genotype distribution attributed to injecting drug use confirm this issue. These circumstances create a strong demand for timely diagnosis and proper treatment of HCV-infected patients through risk-based screening to mitigate the risk of HCV transmission in the IDUs community and, consequently, in the society. Meanwhile, raising general awareness of HCV infection, diagnosis and treatment through public education should be the core activity of any harm reduction intervention, as the root cause of failure in control of HCV infection has been lack of awareness among young drug takers. In addition, effective prevention, comprehensive screening programs with a specific focus on high-risk population, accessibility to the new anti-HCV treatment regimens and public education should be considered as the top priorities of any health policy decision to eliminate HCV infection.

State of the Art, Unresolved Issues, and Future Research Directions in the Fight against Hepatitis C Virus: Perspectives for Screening, Diagnostics of Resistances, and Immunization

Hepatitis C virus (HCV) still represents a major public health threat, with a dramatic burden from both epidemiological and clinical points of view. New generation of direct-acting antiviral agents (DAAs) has been recently introduced in clinical practice promising to cure HCV and to overcome the issues related to the interferon-based therapies. However, the emergence of drug resistance and the suboptimal activity of DAAs therapies against diverse HCV genotypes have been observed, determining treatment failure and hampering an effective control of HCV spread worldwide. Moreover, these treatments remain poorly accessible, particularly in low-income countries. Finally, effective screening strategy is crucial to early identifying and treating all HCV chronically infected patients. For all these reasons, even though new drugs may contribute to impacting HCV spread worldwide a preventive HCV vaccine remains a cornerstone in the road to significantly reduce the HCV spread globally, with the ultimate goal of its eradication. Advances in molecular vaccinology, together with a strong financial, political, and societal support, will enable reaching this fundamental success in the coming years. In this comprehensive review, the state of the art about these major topics in the fight against HCV and the future of research in these fields are discussed.

Method for generation of peptide-specific IgY antibodies directed to Staphylococcus aureus extracellular fibrinogen binding protein epitope

The IgY antibodies offer an attractive alternative to mammalian IgGs in research, diagnosis and medicine. The isolation of immunoglobulin Y from the egg yolks is efficient and economical, causing minimal suffering to animals. Here we present the methodology for the production of IgY antibodies specific to Staphylococcus aureus fibrinogen binding protein (Efb) and its peptidyl epitope (spanning residues 127-140). The Efb is an extracellular, adhesion protein which binds both human fibrinogen and complement C3 protein thus contributing to the high infectious potential of this pathogen. The selected epitope of Efb protein is responsible for the interaction with C3. The immunochemical characterization of both anti-Efb and epitope-specific IgY antibodies revealed their similar avidity, titer, and reactivity profile, although some differences in the hen's immune response to administered antigens is discussed.

Structure-based Epitope Mapping of Mycobacterium tuberculosis Secretary Antigen MTC28

Secretary proteins of Mycobacterium tuberculosis are key players of the mycobacterial infection pathway. MTC28 is a 28-kDa proline-rich secretary antigen of Mycobacterium tuberculosis and is only conserved in pathogenic strains of mycobacteria. Here we report the crystal structure of MTC28 at 2.8- and 2.15-Å resolutions for the structure-based epitope design. MTC28 shares a "mog1p"-fold consisting of seven antiparallel β strands stacked between α helices. Five probable epitopes have been located on a solvent-accessible flexible region by computational analysis of the structure of MTC28. Simultaneously, the protein is digested with trypsin and the resulting fragments are purified by HPLC. Such 10 purified peptide fragments are screened against sera from patients infected with pulmonary tuberculosis (PTB). Two of these 10 fragments, namely (127)ALDITLPMPPR(137) and (138)WTQVPDPNVPDAFVVIADR(156),are found to be major immunogenic epitopes that are localized on the outer surface of the protein molecule and are part of a single continuous epitope that have been predicted in silico Mutagenesis and antibody inhibition studies are in accordance with the results obtained from epitope mapping.

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

Background:

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

Objectives:

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

Materials and Methods:

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

Results:

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

Conclusions:

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

Effect of vaccine administration modality on immunogenicity and efficacy

The many factors impacting the efficacy of a vaccine can be broadly divided into three categories: features of the vaccine itself, including immunogen design, vaccine type, formulation, adjuvant and dosing; individual variations among vaccine recipients and vaccine administration-related parameters. While much literature exists related to vaccines, and recently systems biology has started to dissect the impact of individual subject variation on vaccine efficacy, few studies have focused on the role of vaccine administration-related parameters on vaccine efficacy. Parenteral and mucosal vaccinations are traditional approaches for licensed vaccines; novel vaccine delivery approaches, including needless injection and adjuvant formulations, are being developed to further improve vaccine safety and efficacy. This review provides a brief summary of vaccine administration-related factors, including vaccination approach, delivery route and method of administration, to gain a better understanding of their potential impact on the safety and immunogenicity of candidate vaccines.

Frequency, Private Specificity, and Cross-Reactivity of Preexisting Hepatitis C Virus (HCV)-Specific CD8+ T Cells in HCV-Seronegative Individuals: Implications for Vaccine Responses

T cell responses play a critical role in controlling or clearing viruses. Therefore, strategies to prevent or treat infections include boosting T cell responses. T cells specific for various pathogens have been reported in unexposed individuals and an influence of such cells on the response toward vaccines is conceivable. However, little is known about their frequency, repertoire, and impact on vaccination. We performed a detailed characterization of CD8(+) T cells specific to a hepatitis C virus (HCV) epitope (NS3-1073) in 121 HCV-seronegative individuals. We show that in vitro HCV NS3-1073-specific CD8(+) T cell responses were rather abundantly detectable in one-third of HCV-seronegative individuals irrespective of risk factors for HCV exposure. Ex vivo, these NS3-1073-specific CD8(+) T cells were found to be both naive and memory cells. Importantly, recognition of various peptides derived from unrelated viruses by NS3-1073-specific CD8(+) T cells showed a considerable degree of T cell cross-reactivity, suggesting that they might in part originate from previous heterologous infections. Finally, we further provide evidence that preexisting NS3-1073-specific CD8(+) T cells can impact the T cell response toward peptide vaccination. Healthy, vaccinated individuals who showed an in vitro response toward NS3-1073 already before vaccination displayed a more vigorous and earlier response toward the vaccine.

IMPORTANCE

Preventive and therapeutic vaccines are being developed for many viral infections and often aim on inducing T cell responses. Despite effective antiviral drugs against HCV, there is still a need for a preventive vaccine. However, the responses to vaccines can be highly variable among different individuals. Preexisting T cells in unexposed individuals could be one reason that helps to explain the variable T cell responses to vaccines. Based on our findings, we suggest that HCV CD8(+) T cells are abundant in HCV-seronegative individuals but that their repertoire is highly diverse due to the involvement of both naive precursors and cross-reactive memory cells of different specificities, which can influence the response to vaccines. The data may emphasize the need to personalize immune-based therapies based on the individual's T cell repertoire that is present before the immune intervention.

The role of pre-existing cross-reactive antibodies in determining the efficacy of vaccination in humans: study protocol for a randomized controlled trial

BACKGROUND

Epidemic viral diseases have become more prevalent.. Among the various strategies to prevent such epidemics, vaccination is the most cost-effective. However, populations that are immunized are typically already exposed to multiple previous vaccinations or natural infections. Studies from this and other laboratories have revealed that pre-existing dengue antibodies can either inhibit or enhance subsequent dengue infection depending on the pre-existing antibody levels. While cross-reactive antibody is potentially pathogenic in dengue, how it impacts immune response to vaccination is unclear. Aggregated at the site of vaccination and the respective draining lymph nodes are antigen-presenting and immune regulatory cells that express Fc receptors and play pivotal roles in determining the magnitude and polarity of the immune response. Vaccine uptake by these antigen-presenting cells may thus be either inhibited or enhanced when vaccines are opsonized with cross-reactive antibodies.

DESIGN

In view of the limited knowledge on how cross-reactive antibodies affect vaccination outcome, we propose a study that exploits the known cross reactivity between Japanese encephalitis (JE) virus antibody and yellow fever (YF) vaccine. We hypothesize that cross-reactive antibodies impact antibody response to YF at the point vaccination in a concentration-dependent manner by altering both vaccine uptake and the innate immune response by antigen presenting cells. We will structure an open-label clinical trial on sequential vaccination with JE and YF vaccines, with different time intervals between vaccinations. This would test immune response to YF vaccination in subjects with different titer of cross-reactive JE vaccine-derived antibodies. The clinical materials obtained in the trial will drive basic laboratory investigations directed at elucidating how heterologous antibody affect vaccination at the molecular level. YF neutralizing antibody titer will be measured using plaque reduction neutralization test against the vaccine strain YF17D. Innate immune response will be characterized genetically using either microarray or digital PCR (or both). The innate immune response will also be characterized at the protein and metabolite level using Luminex bead technology and lipidomic/metabolomic approaches.

DISCUSSION

This proposed study represents one of the first to examine the role of cross-reactive antibodies in modulating immune responses to vaccines, the findings of which may re-shape vaccination strategy.

TRIAL REGISTRATION

Clinical Trials.gov registration number: NCT01943305 (3 September 2013).

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

BACKGROUND

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Intradermal immunization with wall teichoic acid (WTA) elicits and augments an anti-WTA IgG response that protects mice from methicillin-resistant Staphylococcus aureus infection independent of mannose-binding lectin status

The objectives of this study were to investigate the immune response to intradermal immunization with wall teichoic acid (WTA) and the effect of MBL deficiency in a murine model of infection with methicillin-resistant Staphylococcus aureus (MRSA). WTA is a bacterial cell wall component that is implicated in invasive infection. We tested susceptibility to MRSA infection in wild type (WT) and MBL deficient mice using two strains of MRSA: MW2, a community-associated MRSA (CA-MRSA); and COL, a healthcare-associated MRSA (HA-MRSA). We also performed in vitro assays to investigate the effects of anti-WTA IgG containing murine serum on complement activation and bacterial growth in whole blood. We found that MBL knockout (KO) mice are relatively resistant to a specific MRSA strain, MW2 CA-MRSA, compared to WT mice, while both strains of mice had similar susceptibility to a different strain, COL HA-MRSA. Intradermal immunization with WTA elicited and augmented an anti-WTA IgG response in both WT and MBL KO mice. WTA immunization significantly reduced susceptibility to both MW2 CA-MRSA and COL HA-MRSA, independent of the presence of MBL. The protective mechanisms of anti-WTA IgG are mediated at least in part by complement activation and clearance of bacteria from blood. The significance of these findings is that 1) Intradermal immunization with WTA induces production of anti-WTA IgG; and 2) This anti-WTA IgG response protects from infection with both MW2 CA-MRSA and COL HA-MRSA even in the absence of MBL, the deficiency of which is common in humans.

Neutralizing antibodies induced by cell culture-derived hepatitis C virus protect against infection in mice

BACKGROUND & AIMS

Hepatitis C virus (HCV) infection is a major cause of liver cancer, so strategies to prevent infection are needed. A system for cell culture of infectious HCV particles (HCVcc) has recently been established; the inactivated HCVcc particles might be used as antigens in vaccine development. We aimed to confirm the potential of HCVcc as an HCV particle vaccine.

METHODS

HCVcc derived from the J6/JFH-1 chimeric genome was purified from cultured cells by ultrafiltration and ultracentrifugation purification steps. Purified HCV particles were inactivated and injected into female BALB/c mice with adjuvant. Sera from immunized mice were collected and their ability to neutralize HCV was examined in naive Huh7.5.1 cells and urokinase-type plasminogen activator-severe combined immunodeficiency mice (uPA(+/+)-SCID mice) given transplants of human hepatocytes (humanized livers).

RESULTS

Antibodies against HCV envelope proteins were detected in the sera of immunized mice; these sera inhibited infection of cultured cells with HCV genotypes 1a, 1b, and 2a. Immunoglobulin G purified from the sera of HCV-particle-immunized mice (iHCV-IgG) inhibited HCV infection of cultured cells. Injection of IgG from the immunized mice into uPA(+/+)-SCID mice with humanized livers prevented infection with the minimum infectious dose of HCV.

CONCLUSIONS

Inactivated HCV particles derived from cultured cells protect chimeric liver uPA(+/+)-SCID mice against HCV infection, and might be used in the development of a prophylactic vaccine.

Ever closer to a prophylactic vaccine for HCV

Introduction

With 3 – 4 million new infections occurring annually, hepatitis C virus (HCV) is a major global health problem. There is increasing evidence to suggest that HCV will be highly amenable to a vaccine approach, and despite advances in treatment, a vaccine remains the most cost-effective and realistic means to significantly reduce the worldwide mortality and morbidity associated with persistent HCV infection.

Areas covered

In this review we discuss immune responses to HCV during natural infection, and describe how they may inform vaccine design. We introduce the current candidate vaccines for HCV and compare how these fare against the expected requirements of an effective prophylactic HCV vaccine in relation to the breadth, functionality, magnitude and phenotype of the vaccine-induced immune response.

Expert opinion

Although the correlates of immune protection against HCV are not completely defined, we now have vaccine technologies capable of inducing HCV-specific adaptive immune responses to an order of magnitude that are associated with protection during natural infection. The challenge next is to i) establish well-characterised cohorts of people at risk of HCV infection for vaccine efficacy testing and ii) to better understand the correlates of protection in natural history studies. If these can be achieved, a vaccine against HCV appears a realistic goal.

Cellular immunogenicity of a multi-epitope peptide vaccine candidate based on hepatitis C virus NS5A, NS4B and core proteins in HHD-2 mice

To develop a vaccine against hepatitis C virus (HCV), a multi-epitope peptide was synthesized from nonstructural proteins containing HLA-A2 epitopes inducing mainly responses in natural infection. The engineered vaccine candidate, VAL-44, consists of multiple epitopes from the HCV NS5A, NS4B and core proteins. Immunization with the VAL-44 peptide induced higher CTL responses than those by the smaller VL-20 peptide. VAL-44 induced antigen-specific IFN-γ-producing CD4+ T cells and CD8+ T cells. VAL-44 elicited a Th1-biased immune response with secretion of high amounts of IFN-γ and IL-2, compared with VL-20. These results suggest that VAL-44 can elicit strong cellular immune responses. The VAL-44 peptide stimulated IFN-γ production from viral-specific peripheral blood mononuclear cells (PBMCs) of patients infected with HCV. These results suggest that VAL-44 could be developed as a potential HCV multi-epitope peptide vaccine.

Role of T-cell epitope-based vaccine in prophylactic and therapeutic applications

Prophylactic and therapeutic vaccines against viral infections have advanced in recent years from attenuated live vaccines to subunit-based vaccines. An ideal prophylactic vaccine should mimic the natural immunity induced by an infection, in that it should generate long-lasting adaptive immunity. To complement subunit vaccines, which primarily target an antibody response, different methodologies are being investigated to develop vaccines capable of driving cellular immunity. T-cell epitope discovery is central to this concept. In this review, the significance of T-cell epitope-based vaccines for prophylactic and therapeutic applications is discussed. Additionally, methodologies for the discovery of T-cell epitopes, as well as recent developments in the clinical testing of these vaccines for various viral infections, are explained.

Hepatitis C virus-mediated modulation of cellular immunity

The hepatitis C virus (HCV) is a major cause of chronic liver disease globally. A chronic infection can result in liver fibrosis, liver cirrhosis, hepatocellular carcinoma and liver failure in a significant ratio of the patients. About 170 million people are currently infected with HCV. Since 80 % of the infected patients develop a chronic infection, HCV has evolved sophisticated escape strategies to evade both the innate and the adaptive immune system. Thus, chronic hepatitis C is characterized by perturbations in the number, subset composition and/or functionality of natural killer cells, natural killer T cells, dendritic cells, macrophages and T cells. The balance between HCV-induced immune evasion and the antiviral immune response results in chronic liver inflammation and consequent immune-mediated liver injury. This review summarizes our current understanding of the HCV-mediated interference with cellular immunity and of the factors resulting in HCV persistence. A profound knowledge about the intrinsic properties of HCV and its effects on intrahepatic immunity is essential to be able to design effective immunotherapies against HCV such as therapeutic HCV vaccines.

Therapeutic vaccination against chronic hepatitis C virus infection

Approximately 170 million people worldwide are chronic carriers of Hepatitis C virus (HCV). To date, there is no prophylactic vaccine available against HCV. The standard-of-care therapy for HCV infection involves a combination of pegylated interferon-α and ribavirin. This therapy, which is commonly associated with side effects, has a curative rate varying from 43% (HCV genotype 1) to 80% (HCV genotype 2). In 2011, two direct-acting antiviral agents, telaprevir and boceprevir, were approved by the US Food and drug Administration and are now being used in combination with standard-of-care therapy in selected patients infected with HCV genotype 1. Although both drugs are promising, resulting in a shortening of therapy, these drugs also induce additional side effects and have reduced efficacy in patients who did not respond to standard-of-care previously. An alternative approach would be to treat HCV by stimulating the immune system with a therapeutic vaccine ideally aimed at (i) the eradication of HCV-infected cells and (ii) neutralization of infectious HCV particles. The challenge is to develop therapeutic vaccination strategies that are either at least as effective as antiviral drugs but with lower side effects, or vaccines that, when combined with antiviral drugs, can circumvent long-term use of these drugs thereby reducing their side effects. In this review, we summarize and discuss recent preclinical developments in the area of therapeutic vaccination against chronic HCV infection. Although neutralizing antibodies have been described to exert protective immunity, clinical studies on the induction of neutralizing antibodies in therapeutic settings are limited. Therefore, we will primarily discuss therapeutic vaccines which aim to induce effective cellular immune response against HCV.

Advances in hepatitis C virus vaccines, part two: advances in hepatitis C virus vaccine formulations and modalities

INTRODUCTION

Developing a vaccine against HCV is an important medical and global priority. Unavailability and potential dangers associated with using attenuated HCV viral particles for vaccine preparation have resulted in the use of HCV genes and proteins formulated in novel vaccine modalities.

AREAS COVERED

In part one of this review, advances in basic knowledge for HCV vaccine design were provided. Herein, a detailed and correlated patents (searched by Espacenet) and literatures (searched by Pubmed) review on HCV vaccine formulations and modalities is provided, including: subunit, DNA, epitopic-peptide/polytopic, live vector- and whole yeast-based vaccines. Less-touched areas in vaccine studies such as mucosal, plant-based, and chimeric HBV/HCV vaccines are also discussed. Furthermore, results of preclinical/clinical studies on selected HCV vaccines as well as pros and cons of different strategies are reviewed. Finally, potential strategies for creation and/or improvement of HCV vaccine formulations are discussed.

EXPERT OPINION

Promising outcomes of a few HCV vaccine modalities in phase I/II clinical trials predict the accessibility of at least partially effective vaccines to inhibit or treat the chronic state of HCV infection (specially in combination with standard antiviral therapy). ChronVac-C (plasmid DNA), TG4040 (MVA-based), and GI-5005 (whole yeast-based) might be the most obvious HCV vaccine candidates to be approved in the near future.

Sustained viral load reduction in treatment-naive HCV genotype 1 infected patients after therapeutic peptide vaccination

BACKGROUND

Novel antivirals augment treatment efficacy in chronic HCV infection, to overcome limitations on safety profile alternative approaches are warranted. The effect of a therapeutic peptide vaccine on HCV viral load was investigated in treatment-naïve genotype 1 HCV patients.

METHODS

Fifty patients received 8 intradermal IC41 vaccinations biweekly with topical application of the TLR7 agonist imiquimod (Group A). In Group B, 21 patients received a condensed schedule of 16 subcutaneous vaccinations weekly without imiquimod.

RESULTS

At Week 16 Group A (n=44) showed a statistically significant (p=0.0013) HCV viral load decline of 0.21 log. 24 weeks after the last vaccination the viral load decreased by 0.47 log (p<0.0001) in 34 subjects. This effect was more pronounced in 17 patients with high baseline HCV (>2×10(6)IU/ml) with a 0.61 log decline, which was statistically significant (p<0.02) starting two weeks after the third vaccination. No apparent effect on HCV viral load was observed in Group B (n=21). In Group A eight patients (24%) showed a viral load response defined as a decline of >0.8 log. Overall, about 30-55% of patients showed T cell responses during the vaccination series and up to six months in both groups. No significant correlations between the HCV viral load decrease and T cell immune response were detected.

CONCLUSIONS

This is the first report on a significant antiviral effect of a peptide vaccine in HCV infected patients. Response kinetics with increased HCV RNA decline 24 weeks after the last IC41 vaccination is encouraging.

Vaccination for hepatitis C virus: closing in on an evasive target

Hepatitis C virus (HCV) infects more than 170 million people globally and is a leading cause of liver cirrhosis, transplantation and hepatocellular carcinoma. Current gold-standard therapy often fails, has significant side effects in many cases and is expensive. No vaccine is currently available. The fact that a significant proportion of infected people spontaneously control HCV infection in the setting of an appropriate immune response suggests that a vaccine for HCV is a realistic goal. A comparative analysis of infected people with distinct clinical outcomes has enabled the characterization of many important innate and adaptive immune processes associated with viral control. It is clear that a successful HCV vaccine will need to exploit and enhance these natural immune defense mechanisms. New HCV vaccine approaches, including peptide, recombinant protein, DNA and vector-based vaccines, have recently reached Phase I/II human clinical trials. Some of these technologies have generated robust antiviral immunity in healthy volunteers and infected patients. The challenge now is to move forward into larger at-risk or infected populations to truly test efficacy.

Targeting of Toll-like receptors: a decade of progress in combating infectious diseases

Toll-like receptors (TLRs) recognise highly conserved molecular structures, collectively known as pathogen-associated molecular patterns. In the past two decades, development and clinical implementation of TLR ligands-ie, chemically modified synthetic derivatives of naturally occurring ligands and fully synthetic small molecules-have been topics of intense research. Targeted manipulation of TLR signalling has been applied clinically to boost vaccine effectiveness, promote a robust T helper 1-predominant immune response against viral infection, or dampen the exaggerated inflammatory response to bacterial infection. Use of these new therapeutic molecules as adjuncts to conventional pharmacotherapy or stand-alone treatments might offer solutions to unmet clinical needs or could replace existing partly effective therapeutic strategies.

Progress in the development of preventive and therapeutic vaccines for hepatitis C virus

Hepatitis C virus (HCV) is a blood borne disease estimated to chronically infect 3% of the worlds' population causing significant morbidity and mortality. Current medical therapy is curative in approximately 50% of patients. While recent treatment advances of genotype 1 infection using directly acting antiviral agents (DAAs) are encouraging, there is still a need to develop vaccine strategies capable of preventing infection. Moreover, vaccines may also be used in future in combination with DAAs enabling interferon-free treatment regimens. Viral and host specific factors contribute to viral evasion and present important impediments to vaccine development. Both, innate and adaptive immune responses are of major importance for the control of HCV infection. However, HCV has evolved ways of evading the host's immune response in order to establish persistent infection. For example, HCV inhibits intracellular interferon signalling pathways, impairs the activation of dendritic cells, CD8(+) and CD4(+) T cell responses, induces a state of T-cell exhaustion and selects escape variants with mutations CD8(+) T cell epitopes. An effective vaccine will need to produce strong and broadly cross-reactive CD4(+), CD8(+) T cell and neutralising antibody (NAb) responses to be successful in preventing or clearing HCV. Vaccines in clinical trials now include recombinant proteins, synthetic peptides, virosome based vaccines, tarmogens, modified vaccinia Ankara based vaccines, and DNA based vaccines. Several preclinical vaccine strategies are also under development and include recombinant adenoviral vaccines, virus like particles, and synthetic peptide vaccines. This paper will review the vaccines strategies employed, their success to date and future directions of vaccine design.

[Synthetic peptide vaccines]

This review considers the stages of the development of synthetic peptide vaccines against infectious agents, novel approaches and technologies employed in this process, including bioinformatics, genomics, proteomics, large-scale peptide synthesis, high-throughput screening methods, the use of transgenic animals for modelling human infections. An important role for the development and selection of efficient adjuvants for peptide immunogens is noted. Examples of synthetic peptide vaccine developments against three infectious diseases (malaria, hepatitis C, and foot-and-mouth disease) are given.

Synthetic peptide vaccines

This review considers the stages of the development of synthetic peptide vaccines against infectious agents, novel approaches and technologies employed in this process, including bioinformatics, genomics, proteomics, large-scale peptide synthesis, high-throughput screening methods, the use of transgenic animals for modelling human infections. An important role for the development and selection of efficient adjuvants for peptide immunogens is noted. Examples of synthetic peptide vaccine developments against three infectious diseases (malaria, hepatitis C, and foot-and-mouth disease) are given.

New antiviral therapies for chronic hepatitis C

Chronic hepatitis C is an important health issue worldwide. The current standard therapy is based on a combination of pegylated-interferon (pegIFN) and ribavirin (RBV), but this treatment leads to only ~50% sustained virological response (SVR) in patients with HCV genotype 1 and high viral loads, who were mostly null-responders or relapsers. Among HCV genotypes other than HCV genotype 1, especially HCV genotype 4 patients show only 40-70% SVR by this treatment. Although new drugs also depend on the combination of pegIFN and RBV, it appears that these drugs improve not only rapid virological response (RVR) but also early virological response, leading to SVR in these patients. In the near future, we predict higher SVR rates in chronic hepatitis C patients treated with these new drugs.

Development of novel antiviral therapies for hepatitis C virus

Over 170 million people worldwide are infected with hepatitis C virus (HCV), a major cause of liver diseases. Current interferon-based therapy is of limited efficacy and has significant side effects and more effective and better tolerated therapies are urgently needed. HCV is a positive, single-stranded RNA virus with a 9.6 kb genome that encodes ten viral proteins. Among them, the NS3 protease and the NS5B polymerase are essential for viral replication and have been the main focus of drug discovery efforts. Aided by structure-based drug design, potent and specific inhibitors of NS3 and NS5B have been identified, some of which are in late stage clinical trials and may significantly improve current HCV treatment. Inhibitors of other viral targets such as NS5A are also being pursued. However, HCV is an RNA virus characterized by high replication and mutation rates and consequently, resistance emerges quickly in patients treated with specific antivirals as monotherapy. A complementary approach is to target host factors such as cyclophilins that are also essential for viral replication and may present a higher genetic barrier to resistance. Combinations of these inhibitors of different mechanism are likely to become the essential components of future HCV therapies in order to maximize antiviral efficacy and prevent the emergence of resistance.