Hepatitis C virus NS3/NS4A DNA vaccine induces multiepitope T cell responses in rhesus macaques mimicking human immune responses [corrected]

Microorganisms-derived antigens for preventive anti-cancer vaccines

Cancer prevention is one of the aim with the highest priority in order to reduce the burden of cancer diagnosis and treatment on individuals as well as on healthcare systems. To this aim, vaccines represent the most efficient primary cancer prevention strategy. Indeed, anti-cancer immunological memory elicited by preventive vaccines might promptly expand and prevent tumor from progressing. Antigens derived from microorganisms (MoAs), represent the obvious target for developing highly effective preventive vaccines for virus-induced cancers. In this respect, the drastic reduction in cancer incidence following HBV and HPV preventive vaccines are the paradigmatic example of such evidence. More recently, experimental evidences suggest that MoAs may represent a "natural" anti-cancer preventive vaccination or can be exploited for developing vaccines to prevent cancers presenting highly homologous tumor-associated antigens (TAAs) (e.g. molecular mimicry). The present review describes the different preventive anti-cancer vaccines based on antigens derived from pathogens at the different stages of development.

Phase I Trial of a Therapeutic DNA Vaccine for Preventing Hepatocellular Carcinoma from Chronic Hepatitis C Virus (HCV) Infection

Chronic hepatitis C can lead to cirrhosis and hepatocellular carcinoma. We studied the safety and immunogenicity of a novel therapeutic hepatitis C virus (HCV) genotype 1a/1b consensus DNA vaccine, INO-8000, encoding HCV NS3, NS4A, NS4B, and NS5A proteins alone or co-administered with DNA-encoding IL12 (INO-9012), a human cytokine that stimulates cellular immune function, in individuals with chronic hepatitis C. This was a phase I, multisite dose-escalation trial with an expansion cohort evaluating doses of 0, 0.3, 1.0, and 3.0 mg of INO-9012 (IL12 DNA) as an addition to 6.0 mg of (INO-8000; HCV DNA vaccine). Vaccines were administered by intramuscular injection followed by electroporation at study entry and at weeks 4, 12, and 24. HCV-specific CD4+ and CD8+ T-cell immune responses were measured by IFNγ ELISpot and flow cytometry-based assays. Transient, mild-to-moderate injection site reactions unrelated to IL12 DNA dose were common. Increases in HCV-specific IFNγ production occurred in 15/20 (75%) participants. Increases in the frequency of HCV-specific CD4+ and CD8+ T cells occurred at all dose levels, with the greatest increases seen at 1.0 mg of INO-9012. HCV-specific CD8+ and CD4+ T-cell activities increased in 16/18 (89%) and 14/17 (82%) participants with available data, respectively. The vaccine regimen was safe and induced HCV-specific CD4+ and CD8+ cellular immune responses of modest magnitude in most HCV-infected participants. The addition of 1.0 mg of IL12 DNA provided the best enhancement of immune responses. The vaccine regimen had little effect on controlling HCV viremia.

PREVENTION RELEVANCE

The administration of IL12 DNA along with a hepatitis C viral antigen DNA vaccine enhanced the HCV-specific immune responses induced by the vaccine in individuals with chronic hepatitis C, an important cause of hepatocellular carcinoma. IL12 could be an effective adjuvant in vaccines targeting HCV and other oncogenic viruses.

Design of a novel multi-epitope vaccine candidate against hepatitis C virus using structural and nonstructural proteins: An immunoinformatics approach

Hepatitis C virus (HCV) infects the liver and causes chronic infection. Several mutations in the viral genome have been associated with drug resistance development. Currently, there is no approved vaccine against the HCV. The employment of computational biology is the primary and crucial step for vaccine design or antiviral therapy which can substantially reduce the duration and cost of studies. Therefore, in this study, we designed a multi-epitope vaccine using various immunoinformatics tools to elicit the efficient human immune responses against the HCV. Initially, various potential (antigenic, immunogenic, non-toxic and non-allergenic) epitope segments were extracted from viral structural and non-structural protein sequences using multiple screening methods. The selected epitopes were linked to each other properly. Then, toll-like receptors (TLRs) 3 and 4 agonists (50S ribosomal protein L7/L12 and human β-defensin 2, respectively) were added to the N-terminus of the final vaccine sequence to increase its immunogenicity. The 3D structure of the vaccine was modeled. Molecular dynamics simulations studies verified the high stability of final free vaccines and in complex with TLR3 and TLR4. These constructs were also antigenic, non-allergenic, nontoxic and immunogenic. Although the designed vaccine traits were promising as a potential candidate against the HCV infection, experimental studies and clinical trials are required to verify the protective traits and safety of the designed vaccine.

Viral hepatitis update: Progress and perspectives

Viral hepatitis, secondary to infection with hepatitis A, B, C, D, and E viruses, are a major public health problem and an important cause of morbidity and mortality. Despite the huge medical advances achieved in recent years, there are still points of conflict concerning the pathogenesis, immune response, development of new and more effective vaccines, therapies, and treatment. This review focuses on the most important research topics that deal with issues that are currently being solved, those that remain to be solved, and future research directions. For hepatitis A virus we will address epidemiology, molecular surveillance, new susceptible populations as well as environmental and food detections. In the case of hepatitis B virus, we will discuss host factors related to disease, diagnosis, therapy, and vaccine improvement. On hepatitis C virus, we will focus on pathogenesis, immune response, direct action antivirals treatment in the context of solid organ transplantation, issues related to hepatocellular carcinoma development, direct action antivirals resistance due to selection of resistance-associated variants, and vaccination. Regarding hepatitis D virus, we describe diagnostic methodology, pathogenesis, and therapy. Finally, for hepatitis E virus, we will address epidemiology (including new emerging species), diagnosis, clinical aspects, treatment, the development of a vaccine, and environmental surveillance.

Challenges and Promise of a Hepatitis C Virus Vaccine

An estimated 1.5-2 million new hepatitis C virus (HCV) infections occur globally each year. Critical to the World Health Organization's (WHO) HCV elimination strategy is an 80% reduction in incidence of HCV infections by 2030. However, even among high-income countries, few are on target to achieve the WHO's incident infection-reduction goal. A preventative vaccine could have a major impact in achieving incidence-reduction targets globally. However, barriers to HCV vaccine development are significant and include at-risk populations that are often marginalized: viral diversity, limited options for testing HCV vaccines, and an incomplete understanding of protective immune responses. In part because of those factors, testing of only one vaccine strategy has been completed in at-risk individuals as of 2019. Despite challenges, immunity against HCV protects against chronic infection in some repeated HCV exposures and an effective HCV vaccine could prevent transmission regardless of risk factors. Ultimately, prophylactic vaccines will likely be necessary to achieve global HCV elimination.

Approaches, Progress, and Challenges to Hepatitis C Vaccine Development

Risk factors for hepatitis C virus (HCV) infection vary, and there were an estimated 1.75 million new cases worldwide in 2015. The World Health Organization aims for a 90% reduction in new HCV infections by 2030. An HCV vaccine would prevent transmission, regardless of risk factors, and significantly reduce the global burden of HCV-associated disease. Barriers to development include virus diversity, limited models for testing vaccines, and our incomplete understanding of protective immune responses. Although highly effective vaccines could prevent infection altogether, immune responses that increase the rate of HCV clearance and prevent chronic infection may be sufficient to reduce disease burden. Adjuvant envelope or core protein and virus-vectored nonstructural antigen vaccines have been tested in healthy volunteers who are not at risk for HCV infection; viral vectors encoding nonstructural proteins are the only vaccine strategy to be tested in at-risk individuals. Despite development challenges, a prophylactic vaccine is necessary for global control of HCV.

G2 Dendrimer as a Carrier Can Enhance Immune Responses Against HCV-NS3 Protein in BALB/c Mice

BACKGROUND

Hepatitis C virus (HCV) infection is a major issue of public health. It seems of paramount importance to find an effective vaccine against HCV infection. The best vaccine candidate should induce robust cellular responses. The aim of the current study was to evaluate immunogenicity effects of novel conjugated dendrimer G2 with the recombinant NS3 antigen as a vaccine candidate for eliciting Th1-oriented cellular responses.

METHODS

Female BALB/c mice were immunized with different regimes especially with NS3 conjugated with G2 dendrimer. The humoral responses (Total IgG and IgG iso-typing) and cellular responses (Ex vivo IFN-γ and IL-4 ELISpot assays, in vitro CTL assay and proliferation) were evaluated and compared in immunized mice.

RESULTS

The results indicated that induced specific total IgG in all mice groups immunized with rNS3 formulated with different adjuvants and IgG2a subclass was the predominant isotype in rNS3-G2 (p≤0.05). For preliminary evaluation of cellular response, ex vivo ELISpot assay has shown that the higher frequency of IFN-γ producing cells was in groups immunized with rNS3+M720 and rNS3-G2 (p= 0.0012) than control groups. Finally, the rNS3-specific CTLs activity showed the highest percentage of specific lysis (LDH release) of the target cells in rNS3-G2 and rNS3+M720 groups.

CONCLUSION

In the present study, as our knowledge, this is first time that the immunogenicity of nanodendrimer G2 as a biocompatible adjuvant with the HCV-NS3 antigen was evaluated. The results showed high capability of the regimen to induce strong Th1-orinted cellular response in mice model, indicating the dendrimer G2 as a novel adjuvant candidate for HCV vaccine studies.

Preclinical evaluation of multi antigenic HCV DNA vaccine for the prevention of Hepatitis C virus infection

Direct-acting antiviral treatment for hepatitis C virus (HCV) infection is costly and does not protect from re-infection. For human and chimpanzees, recovery from acute HCV infection correlates with host CD4+ and CD8+ T cell responses. DNA plasmids targeting the HCV non-structural antigens NS3, NS4, and NS5, were previously reported to induce robust and sustained T cell responses in mice and primates. These plasmids were combined with a plasmid encoding cytokine IL-28B, together named as VGX-6150. The dose-dependent T cell response and safety of VGX-6150 administered intramuscularly and followed by electroporation was assessed in mice. Immune responses plateaued at 20 μg/dose with IL-28B demonstrating significant immunoadjuvant activity. Mice administered VGX-6150 at 40, 400, and 800 μg given either as a single injection or as 14 injections given bi-weekly over 26 weeks showed no vaccine related changes in any clinical parameter compared to placebo recipients. There was no evidence of VGX-6150 accumulation at the injection site or in any organ 1 month following the 14^th vaccination. Based on these studies, the approximate lethal dose (ALD) exceeds 800 μg/dose and the NOAEL was 800 μg/dose in mouse. In conclusion, VGX-6150 appears safe and a promising preventive vaccine candidate for HCV infection.

Cytomegalovirus Vaccines: Current Status and Future Prospects

Congenital human cytomegalovirus (HCMV) infection can result in severe and permanent neurological injury in newborns, and vaccine development is accordingly a major public health priority. HCMV can also cause disease in solid organ transplant (SOT) and hematopoietic stem-cell transplant (HSCT) recipients, and a vaccine would be valuable in prevention of viremia and end-organ disease in these populations. Currently there is no licensed HCMV vaccine, but progress toward this goal has been made in recent clinical trials. A recombinant HCMV glycoprotein B (gB) vaccine has been shown to have some efficacy in prevention of infection in young women and adolescents, and has provided benefit to HCMV-seronegative SOT recipients. Similarly, DNA vaccines based on gB and the immunodominant T-cell target, pp65 (ppUL83), have been shown to reduce viremia in HSCT patients. This review provides an overview of HCMV vaccine candidates in various stages of development, as well as an update on the current status of ongoing clinical trials. Protective correlates of vaccine-induced immunity may be different for pregnant woman and transplant patients. As more knowledge emerges about correlates of protection, the ultimate licensure of HCMV vaccines may reflect the uniqueness of the target populations being immunized.

Adjuvanted multi-epitope vaccines protect HLA-A*11:01 transgenic mice against Toxoplasma gondii

We created and tested multi-epitope DNA or protein vaccines with TLR4 ligand emulsion adjuvant (gluco glucopyranosyl lipid adjuvant in a stable emulsion [GLA-SE]) for their ability to protect against Toxoplasma gondii in HLA transgenic mice. Our constructs each included 5 of our best down-selected CD8⁺ T cell-eliciting epitopes, a universal CD4⁺ helper T lymphocyte epitope (PADRE), and a secretory signal, all arranged for optimal MHC-I presentation. Their capacity to elicit immune and protective responses was studied using immunization of HLA-A*11:01 transgenic mice. These multi-epitope vaccines increased memory CD8⁺ T cells that produced IFN-γ and protected mice against parasite burden when challenged with T. gondii. Endocytosis of emulsion-trapped protein and cross presentation of the antigens must account for the immunogenicity of our adjuvanted protein. Thus, our work creates an adjuvanted platform assembly of peptides resulting in cross presentation of CD8⁺ T cell-eliciting epitopes in a vaccine that prevents toxoplasmosis.

Gene therapy using plasmid DNA-encoded anti-HER2 antibody for cancers that overexpress HER2

Plasmid DNA-encoded antibodies, or DNA-based monoclonal antibodies (dMAbs), are delivered by intramuscular injection and in vivo electroporation (EP) and are effective in virus neutralization, although they have not been evaluated for tumor gene therapy. Here we investigated whether a dMAb was appropriate for tumor gene therapy. We constructed the expression plasmids coding for the heavy or light chain of a parental murine antibody of Herceptin with the antibody genes codon- and RNA-optimized and fused to the Kozak-IgE leader sequence in pVax1. Transfection of the plasmids into human muscle RD cells resulted in functional expression of the antibody, and this exhibited the same in vitro antiproliferative activity as Herceptin. A single intramuscular injection and in vivo EP of the plasmids (100 μg per head) resulted in high and sustained antibody expression in the sera of normal mice and in effective inhibition of tumor growth in nude mice bearing HER2-positive human breast carcinoma BT474 xenografts. The antitumor efficacy of the anti-HER2 dMAb was similar to that of four doses of intravenously injected 10 mg kg⁻¹ Herceptin. The results demonstrate that the dMAb is effective in the treatment of HER2-positive breast cancer, suggesting that this dMAb may be applicable for tumor gene therapy.

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

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

How successful is nuclear targeting by nanocarriers?

The nucleus is ultimately the final target for many therapeutics treating various disorders including cancers, heart dysfunction and brain disorders. Owing to their specialized cell uptake and trafficking mechanisms, nanoparticles (NPs) allow drug targeting where degradation sensitive therapeutics could be delivered to their target tissues and cell in active form and sufficient concentration. However, it has recently become increasingly obvious that cytosolic internalization of a drug molecule does not entail its interaction with its subcellular target and hence careful nanoparticle design and optimization is required to enable nuclear targeting. This review, discusses the barriers to NP nuclear delivery; crossing the cell membrane, endo/lysosomal escape, cytoplasmic trafficking and finally nuclear entry focusing on how NP synthesis and modification could allow for bypassing each of the aforementioned barriers and successfully reaching the nucleus. Examples of nuclear targeted NPs are also discussed, stressing on the critical aspects of nuclear targeting and pointing out how the disease state might change the normal NP path and how such change could be exploited to increase efficiency of nuclear targeting. Finally, the criteria set for the evaluation of nanocarriers for nuclear delivery are discussed highlighting that quantitative rather than qualitative evaluation is required to evaluate how successful nanocarriers for nuclear delivery are, particularly with regards to the amount of drug delivered and released in the nucleus.

Immunization with a Recombinant Expression Vector Encoding NS3/NS4A of Hepatitis C Virus Genotype 3a Elicits Cell-Mediated Immune Responses in C57BL/6 Mice

Today, hepatitis C virus (HCV) infection is considered as one of the most significant international health concerns. Although novel therapeutic regimens against the infection have shown satisfactory results, no approved vaccine exists yet. This study aimed to evaluate the immunogenicity of a DNA vaccine candidate for HCV-3a, based on nonstructural proteins NS3/NS4A, in C57BL/6 mice. Immunogenicity effect of pDisplay-NS3/NS4A was analyzed through immunization with 100 and 200 μg concentrations of the construct with complete Freund's adjuvant, monophosphoryl lipid A (MPL), or without adjuvant. The frequencies of different splenic mononuclear cells were measured using the Mouse Th1/Th2/Th17 Phenotyping Kit. Moreover, the number of T-CD8(+) cells was determined using conjugated anti-CD8a and anti-CD3e antibodies by flow cytometry. As observed, the frequencies of Th1, T-CD8(+), and Th2 cells increased in all the experimental groups, compared with the controls. The highest levels of the respective cells were seen in the group immunized with 200 μg of the construct with MPL. Also, there were positive correlations between the frequency of Th1 cells and those of Th2 and T-CD8(+) cells in all the immunized groups, but were significant in those receiving adjuvants. The frequency of Th17 cells did not statistically change among the groups. Taken together, our findings revealed that the constructed DNA vaccine encoding HCV-3a NS3/NS4A gene induces the cell-mediated immune responses significantly. However, its coadministration with adjuvants exhibits more efficient results than the recombinant plasmid alone. Further study is currently underway to evaluate the specific immune responses and recognize the responsible antigenic epitopes.

Evolution of the Humoral Response during HCV Infection: Theories on the Origin of Broadly Neutralizing Antibodies and Implications for Vaccine Design

Similar to human immunodeficiency virus (HIV)-1, vaccine-induced elicitation of broadly neutralizing (bNt) antibodies (Abs) is gaining traction as a key goal toward the eradication of the hepatitis C virus (HCV) pandemic. Previously, the significance of the Ab response against HCV was underappreciated given the prevailing evidence advancing the role of the cellular immune response in clearance and overall control of the infection. However, recent findings have driven growing interest in the humoral arm of the immune response and in particular the role of bNt responses due to their ability to confer protective immunity upon passive transfer in animal models. Nevertheless, the origin and development of bNt Abs is poorly understood and their occurrence is rare as well as delayed with emergence only observed in the chronic phase of infection. In this review, we characterize the interplay between the host immune response and HCV as it progresses from the acute to chronic phase of infection. In addition, we place these events in the context of current hypotheses on the origin of bNt Abs against the HIV-1, whose humoral immune response is better characterized. Based on the increasing significance of the humoral immune response against HCV, characterization of these events may be critical in understanding the development of the bNt responses and, thus, provide strategies toward effective vaccine design.

Priming with two DNA vaccines expressing hepatitis C virus NS3 protein targeting dendritic cells elicits superior heterologous protective potential in mice

Development an effective vaccine may offer an alternative preventive and therapeutic strategy against HCV infection. DNA vaccination has been shown to induce robust humoral and cellular immunity and overcome many problems associated with conventional vaccines. In this study, mice were primed with either conventional pVRC-based or suicidal pSC-based DNA vaccines carrying DEC-205-targeted NS3 antigen (DEC-NS3) and boosted with type 5 adenoviral vectors encoding the partial NS3 and core antigens (C44P). The prime boost regimen induced a marked increase in antigen-specific humoral and T-cell responses in comparison with either rAd5-based vaccines or DEC-205-targeted DNA immunization in isolation. The protective effect against heterogeneous challenge was correlated with high levels of anti-NS3 IgG and T-cell-mediated immunity against NS3 peptides. Moreover, priming with a suicidal DNA vaccine (pSC-DEC-NS3), which elicited increased TNF-α-producing CD4+ and CD8+ T-cells against NS3-2 peptides (aa 1245-1461), after boosting, showed increased heterogeneous protective potential compared with priming with a conventional DNA vaccine (pVRC-DEC-NS3). In conclusion, a suicidal DNA vector (pSC-DEC-NS3) expressing DEC-205-targeted NS3 combined with boosting using an rAd5-based HCV vaccine (rAd5-C44P) is a good candidate for a safe and effective vaccine against HCV infection.

Strong HCV NS3/4a, NS4b, NS5a, NS5b-specific cellular immune responses induced in Rhesus macaques by a novel HCV genotype 1a/1b consensus DNA vaccine

Chronic HCV is a surreptitious disease currently affecting approximately 3% of the world's population that can lead to liver failure and cancer decades following initial infection. However, there are currently no vaccines available for the prevention of chronic HCV. From patients who acutely resolve HCV infection, it is apparent that a strong and broad cytotoxic T lymphocyte (CTL) response is important in HCV clearance. DNA vaccines are naked plasmid DNA molecules that encode pathogen antigens to induce a pathogen-specific immune response. They are inexpensive to produce and have an excellent safety profile in animals and humans. Additionally, DNA vaccines are able to induce strong CTL responses, making them well-suited for an HCV vaccine. We aimed to maximize vaccine recipients' opportunity to induce a broad T cell response with a novel antigenic sequence, multi-antigen vaccine strategy. We have generated DNA plasmids encoding consensus sequences of HCV genotypes 1a and 1b non-structural proteins NS3/4a, NS4b, NS5a, and NS5b. Rhesus macaques were used to study the immunogenicity of these constructs. Four animals were immunized 3 times, 6 weeks apart, at a dose of 1.0mg per antigen construct, as an intramuscular injection followed by in vivo electroporation, which greatly increases DNA uptake by local cells. Immune responses were measured 2 weeks post-immunization regimen (PIR) in immunized rhesus macaques and showed a broad response to multiple HCV nonstructural antigens, with up to 4680 spot-forming units per million peripheral blood mononuclear cells (PBMCs) as measured by Interferon-γ ELISpot. In addition, multiparametric flow cytometry detected HCV-specific CD4+ and CD8+ T cell responses by intracellular cytokine staining and detected HCV-specific CD107a+/GrzB+ CD8+ T cells indicating an antigen specific cytolytic response 2 weeks PIR compared with baseline measurements. At the final study time point, 6 weeks PIR, HCV-specific CD45RA- memory-like T cells remained detectable in peripheral blood. Data presented in this manuscript support the notion that vaccine immunogenicity studies using a macaque model can be used to depict key anti-HCV nonstructural antigenic cellular immune responses and support the development of DNA-based prophylactic HCV vaccines.

Synthetic DNA approach to cytomegalovirus vaccine/immune therapy

There is no licensed vaccine or cure for human cytomegalovirus (CMV), a ubiquitous β-herpes virus that infects 60-95 % of adults worldwide. Infection is a major cause of congenital abnormalities in newborns, contributes to development of childhood cerebral palsy and medulloblastoma, can result in severe disease in immunocompromised patients, and is a major impediment during successful organ transplantation. While CMV has been increasingly associated with numerous inflammatory diseases and cancers, only recently has it been correlated with increased risk of heart disease in adults, the number-one killer in the USA. These data, among others, suggest that subclinical CMV infection, or microinfection, in healthy individuals may play more of a causative role than an epiphenomenon in development of CMV-associated pathologies. Due to the myriad of diseases and complications associated with CMV, an efficacious vaccine would be highly valuable in reducing human morbidity and mortality as well as saving billions of dollars in annual health-care costs and disability adjusted life years (DALY) in the developing world. Therefore, the development of a safe efficacious CMV vaccine or immune therapy is paramount to the public health. This review aims to provide a brief overview on aspects of CMV infection and disease and focuses on current vaccine strategies. The use of new synthetic DNA vaccines might offer one such approach to this difficult problem.

Influence of HIV and HCV on T cell antigen presentation and challenges in the development of vaccines

Some of the central challenges for developing effective vaccines against HIV and hepatitis C virus (HCV) are similar. Both infections are caused by small, highly mutable, rapidly replicating RNA viruses with the ability to establish long-term chronic pathogenic infection in human hosts. HIV has caused 60 million infections globally and HCV 180 million and both viruses may co-exist among certain populations by virtue of common blood-borne, sexual, or vertical transmission. Persistence of both pathogens is achieved by evasion of intrinsic, innate, and adaptive immune defenses but with some distinct mechanisms reflecting their differences in evolutionary history, replication characteristics, cell tropism, and visibility to mucosal versus systemic and hepatic immune responses. A potent and durable antibody and T cell response is a likely requirement of future HIV and HCV vaccines. Perhaps the single biggest difference between the two vaccine design challenges is that in HCV, a natural model of protective immunity can be found in those who resolve acute infection spontaneously. Such spontaneous resolvers exhibit durable and functional CD4⁺ and CD8⁺ T cell responses (Diepolder et al., 1995; Cooper et al., 1999; Thimme et al., 2001; Grakoui et al., 2003; Lauer et al., 2004; Schulze Zur Wiesch et al., 2012). However, frequent re-infection suggests partial or lack of protective immunity against heterologous HCV strains, possibly indicative of the degree of genetic diversity of circulating HCV genotypes and subtypes. There is no natural model of protective immunity in HIV, however, studies of “elite controllers,” or individuals who have durably suppressed levels of plasma HIV RNA without antiretroviral therapy, has provided the strongest evidence for CD8⁺ T cell responses in controlling viremia and limiting reservoir burden in established infection. Here we compare and contrast the specific mechanisms of immune evasion used by HIV and HCV, which subvert adaptive human leukocyte antigen (HLA)-restricted T cell immunity in natural infection, and the challenges these pose for designing effective preventative or therapeutic vaccines.

In Silico Identification and Conservation Analysis of B-cell and T-Cell Epitopes of Hepatitis C Virus 3a Genotype Enveloped Glycoprotein 2 From Pakistan: A Step Towards Heterologous Vaccine Design

BACKGROUND

Hepatitis C virus (HCV) is known for the eminent global disease burden responsible for encumbering public health. Development of an effective vaccine is the major need of the day; however, several obstacles loom ahead of this objective. One of the major barriers is that as a RNA virus, it mutates rapidly resulting in high sequence divergence and several viral isolates in the world. Theglycoprotein 2 (gpE2) is the primary component of HCV envelope with direct interaction with the host cell surface receptors; it is an indispensable target of neutralizing antibodies and hence, should be a fundamental component of vaccine design.

OBJECTIVES

This study focused on B-cells and T-cells epitopes prediction in HCV gpE2, particularly in 3a genotype, in Pakistan and identification of the conserved epitopes among various 3a isolates at global level, principally conserved across HCV major genotypes.

MATERIALS AND METHODS

Epitope finding was done by using online available bioinformatics tools including Immune Epitope Database (IEDB), ProPred-I, and ProPred. Conservation of these epitopes was found by aligning selected gpE2 sequences using MultAlin online software and conservancy analysis tool available at IEDB.

RESULTS

Many B-cell and T-cell epitopes predicted in gpE2 were found conserved among HCV 3a genotypes whereas few were conserved in other genotypes anticipating these epitopes as potential candidates of producing strong B-cell and T-cell response against HCV 3a and other genotypes.

CONCLUSIONS

HCV gpE2 is an ideal target for HCV vaccine. Prediction of epitope immunogenicity and characterization on the basis of peptide sequences will be significantly helpful for development of a heterologous vaccine against HCV variants.

Will there be a vaccine to prevent HCV infection?

Prevention of hepatitis C virus (HCV) infection by vaccination has been a priority since discovery of the virus and the need has not diminished over the past 25 years. Infection rates are increasing in developed countries because of intravenous drug use. Reducing transmission will be difficult without a vaccine to prevent persistence of primary infections, and also secondary infections that may occur after cure of chronic hepatitis C with increasingly effective direct-acting antiviral (DAA) regimens. Vaccine need is also acute in resource poor countries where most new infections occur and DAAs may be unaffordable. Spontaneous resolution of HCV infection confers durable protection, but mechanisms of immunity remain obscure and contested in the context of vaccine design. A vaccine must elicit a CD4+ helper T cell response that does not fail during acute infection. The need for neutralizing antibodies versus cytotoxic CD8+ T cells is unsettled and reflected in the design of two very different vaccines evaluated in humans for safety and immunogenicity. Here we review the status of vaccine development and the scientific and practical challenges that must be met if the burden of liver disease caused by HCV is to be reduced or eliminated.

HIV-1 Env DNA vaccine plus protein boost delivered by EP expands B- and T-cell responses and neutralizing phenotype in vivo

An effective HIV vaccine will most likely require the induction of strong T-cell responses, broadly neutralizing antibodies (bNAbs), and the elicitation of antibody-dependent cellular cytotoxicity (ADCC). Previously, we demonstrated the induction of strong HIV/SIV cellular immune responses in macaques and humans using synthetic consensus DNA immunogens delivered via adaptive electroporation (EP). However, the ability of this improved DNA approach to prime for relevant antibody responses has not been previously studied. Here, we investigate the immunogenicity of consensus DNA constructs encoding gp140 sequences from HIV-1 subtypes A, B, C and D in a DNA prime-protein boost vaccine regimen. Mice and guinea pigs were primed with single- and multi-clade DNA via EP and boosted with recombinant gp120 protein. Sera were analyzed for gp120 binding and induction of neutralizing antibody activity. Immunization with recombinant Env protein alone induced low-titer binding antibodies with limited neutralization breath. In contrast, the synthetic DNA prime-protein boost protocol induced significantly higher antibody binding titers. Furthermore, sera from DNA prime-protein boost groups were able to neutralize a broader range of viruses in a panel of tier 1 clade B viruses as well as multiple tier 1 clade A and clade C viruses. Further investigation of synthetic DNA prime plus adaptive EP plus protein boost appears warranted.

Proteome-wide screening reveals immunodominance in the CD8 T cell response against classical swine fever virus with antigen-specificity dependent on MHC class I haplotype expression

Vaccination with live attenuated classical swine fever virus (CSFV) vaccines induces a rapid onset of protection which has been associated with virus-specific CD8 T cell IFN-γ responses. In this study, we assessed the specificity of this response, by screening a peptide library spanning the CSFV C-strain vaccine polyprotein to identify and characterise CD8 T cell epitopes. Synthetic peptides were pooled to represent each of the 12 CSFV proteins and used to stimulate PBMC from four pigs rendered immune to CSFV by C-strain vaccination and subsequently challenged with the virulent Brescia strain. Significant IFN-γ expression by CD8 T cells, assessed by flow cytometry, was induced by peptide pools representing the core, E2, NS2, NS3 and NS5A proteins. Dissection of these antigenic peptide pools indicated that, in each instance, a single discrete antigenic peptide or pair of overlapping peptides was responsible for the IFN-γ induction. Screening and titration of antigenic peptides or truncated derivatives identified the following antigenic regions: core₂₄₁₋₂₅₅ PESRKKLEKALLAWA and NS3₁₉₀₂₋₁₉₁₂ VEYSFIFLDEY, or minimal length antigenic peptides: E2₉₉₆₋₁₀₀₃ YEPRDSYF, NS2₁₂₂₃₋₁₂₃₀ STVTGIFL and NS5A₃₀₇₀₋₃₀₇₈ RVDNALLKF. The epitopes are highly conserved across CSFV strains and variable sequence divergence was observed with related pestiviruses. Characterisation of epitope-specific CD8 T cells revealed evidence of cytotoxicity, as determined by CD107a mobilisation, and a significant proportion expressed TNF-α in addition to IFN-γ. Finally, the variability in the antigen-specificity of these immunodominant CD8 T cell responses was confirmed to be associated with expression of distinct MHC class I haplotypes. Moreover, recognition of NS₁₂₂₃₋₁₂₃₀ STVTGIFL and NS3₁₉₀₂₋₁₉₁₂ VEYSFIFLDEY by a larger group of C-strain vaccinated animals showed that these peptides could be restricted by additional haplotypes. Thus the antigenic regions and epitopes identified represent attractive targets for evaluation of their vaccine potential against CSFV.

Optimized and enhanced DNA plasmid vector based in vivo construction of a neutralizing anti-HIV-1 envelope glycoprotein Fab

Monoclonal antibody preparations have demonstrated considerable clinical utility in the treatment of specific malignancies, as well as inflammatory and infectious diseases. Antibodies are conventionally delivered by passive administration, typically requiring costly large-scale laboratory development and production. Additional limitations include the necessity for repeat administrations, and the length of in vivo potency. Therefore, the development of methods to generate therapeutic antibodies and antibody like molecules in vivo, distinct from an active antigen-based immunization strategy, would have considerable clinical utility. In fact, adeno-associated viral (AAV) vector mediated delivery of immunoglobulin genes with subsequent generation of functional antibodies has recently been developed. As well, anon-viral vector mediated nucleic acid based delivery technology could permit the generation of therapeutic/prophylactic antibodies in vivo, obviating potential safety issues associated with viral vector based gene delivery. This delivery strategy has limitations as well, mainly due to very low in vivo production and expression of protein from the delivered gene. In the study reported here we have constructed an "enhanced and optimized" DNA plasmid technology to generate immunoglobulin heavy and light chains (i.e., Fab fragments) from an established neutralizing anti-HIV envelope glycoprotein monoclonal antibody (VRC01). This "enhanced" DNA (E-DNA) plasmid technology includes codon/RNA optimization, leader sequence utilization, as well as targeted potentiation of delivery and expression of the Fab immunoglobulin genes through use of "adaptive" in vivo electroporation. The results demonstrate that delivery by this method of a single administration of the optimized Fab expressing constructs resulted in generation of Fab molecules in mouse sera possessing high antigen specific binding and HIV neutralization activity for at least 7 d after injection, against diverse HIV isolates. Importantly, this delivery strategy resulted in a rapid increase (i.e., in as little as 48 h) in Fab levels when compared with protein-based immunization. The active generation of functional Fab molecules in vivo has important conceptual and practical advantages over conventional ex vivo generation, purification and passive delivery of biologically active antibodies. Further study of this technique for the rapid generation and delivery of immunoglobulin and immunoglobulin like molecules is highly relevant and timely.

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

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

A heterologous prime/boost vaccination strategy enhances the immunogenicity of therapeutic vaccines for hepatitis C virus

Background. We explored the concept of heterologous prime/boost vaccination using 2 therapeutic vaccines currently in clinical development aimed at treating chronically infected hepatitis C virus (HCV) patients: prime with a DNA-based vaccine expressing HCV genotype 1a NS3/4A proteins (ChronVac-C) and boost with a modified vaccinia virus Ankara vaccine expressing genotype 1b NS3/4/5B proteins (MVATG16643).

Methods. Two ChronVac-C immunizations 4 weeks apart were delivered intramuscularly in combination with in vivo electroporation and subsequently 5 or 12 weeks later boosted by 3 weekly subcutaneous injections of MVATG16643. Two mouse strains were used, and we evaluated quality, magnitude, and functionality of the T cells induced.

Results. DNA prime/MVA boost regimen induced significantly higher levels of interferon γ (IFN-γ) or interleukin 2 (IL-2) ELISpot responses compared with each vaccine alone, independent of the time of analysis and the time interval between vaccinations. Both CD8⁺ and CD4⁺ T-cell responses as well as the spectrum of epitopes recognized was improved. A significant increase in polyfunctional IFN-γ/tumor necrosis factor α (TNF-α)/CD107a⁺ CD8⁺ T cells was detected following ChronVac-C/MVATG16643 vaccination (from 3% to 25%), and prime/boost was the only regimen that activated quadrifunctional T cells (IFN-γ/TNF-α/CD107a/IL-2). In vivo functional protective capacity of DNA prime/MVA boost was demonstrated in a Listeria-NS3-1a challenge model.

Conclusions. We provide a proof-of-concept that immunogenicity of 2 HCV therapeutic vaccines can be improved using their combination, which merits further clinical development.

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.

Haplessly hoping: macaque major histocompatibility complex made easy

Major histocompatibility complex (MHC) gene products control the repertoire of T cell responses that an individual may create against pathogens and foreign tissues. This text will review the current understanding of MHC genetics in nonhuman primates, with a focus on Mauritian-origin cynomolgus macaques (Macaca fascicularis) and Indian-origin rhesus macaques (Macaca mulatta). These closely related macaque species provide important experimental models for studies of infectious disease pathogenesis, vaccine development, and transplantation research. Recent advances resulting from the application of several cost effective, high-throughput approaches, with deep sequencing technologies have revolutionized our ability to perform MHC genotyping of large macaque cohorts. Pyrosequencing of cDNA amplicons with a Roche/454 GS Junior instrument, provides excellent resolution of MHC class I allelic variants with semi-quantitative estimates of relative levels of transcript abundance. Introduction of the Illumina MiSeq platform significantly increased the sample throughput, since the sample loading workflow is considerably less labor intensive, and each instrument run yields approximately 100-fold more sequence data. Extension of these sequencing methods from cDNA to genomic DNA amplicons further streamlines the experimental workflow and opened opportunities for retrospective MHC genotyping of banked DNA samples. To facilitate the reporting of MHC genotypes, and comparisons between groups of macaques, this text also introduces an intuitive series of abbreviated rhesus MHC haplotype designations based on a major Mamu-A or Mamu-B transcript characteristic for ancestral allele combinations. The authors believe that the use of MHC-defined macaques promises to improve the reproducibility, and predictability of results from pre-clinical studies for translation to humans.