Dendritic cell-based immunity and vaccination against hepatitis C virus infection

Immunomodulatory nanosystems: An emerging strategy to combat viral infections

The viral infection spreads with the assistance of a host. Traditional antiviral therapies cannot provide long-term immunity against emerging and drug-resistant viral infections. Immunotherapy has evolved as an efficient approach for disease prevention and treatment, which include cancer, infections, inflammatory, and immune disorders. Immunomodulatory nanosystems can dramatically enhance therapeutic outcomes by combating many therapeutic challenges, such as poor immune stimulation and off-target adverse effects. Recently, immunomodulatory nanosystems have emerged as a potent antiviral strategy to intercept viral infections effectively. This review introduces major viral infections with their primary symptoms, route of transmission & targeted organ, and different stages of the viral life cycle with respective traditional blockers. The IMNs have an exceptional capacity for precisely modulating the immune system for therapeutic applications. The nano sized immunomodulatory systems permit the immune cells to interact with infectious agents enhancing lymphatic drainage and endocytosis by the over-reactive immune cells in the infected areas. Immune cells that can be modulated upon viral infection via various immunomodulatory nanosystems have been discussed. Advancement in theranostics can yield an accurate diagnosis, adequate treatment, and real-time screening of viral infections. Nanosystem-based drug delivery can continue to thrive in diagnosing, treating, and preventing viral infections. The curative medicine for remerging and drug-resistant viruses remains challenging, though certain systems have expanded our perception and initiated a new research domain in antiviral treatments.

Use of Hu-PBL Mice to Study Pathogenesis of Human-Restricted Viruses

Different humanized mouse models have been developed to study human diseases such as autoimmune illnesses, cancer and viral infections. These models are based on the use of immunodeficient mouse strains that are transplanted with human tissues or human immune cells. Among the latter, mice transplanted with hematopoietic stem cells have been widely used to study human infectious diseases. However, mouse models built upon the transplantation of donor-specific mature immune cells are still under development, especially in the field of viral infections. These models can retain the unique immune memory of the donor, making them suitable for the study of correlates of protection upon natural infection or vaccination. Here, we will review some of these models and how they have been applied to virology research. Moreover, the future applications and the potential of these models to design therapies against human viral infections are discussed.

Polymeric Nanoparticles for Inhaled Vaccines

Many recent studies focus on the pulmonary delivery of vaccines as it is needle-free, safe, and effective. Inhaled vaccines enhance systemic and mucosal immunization but still faces many limitations that can be resolved using polymeric nanoparticles (PNPs). This review focuses on the use of properties of PNPs, specifically chitosan and PLGA to be used in the delivery of vaccines by inhalation. It also aims to highlight that PNPs have adjuvant properties by themselves that induce cellular and humeral immunogenicity. Further, different factors influence the behavior of PNP in vivo such as size, morphology, and charge are discussed. Finally, some of the primary challenges facing PNPs are reviewed including formulation instability, reproducibility, device-related factors, patient-related factors, and industrial-level scale-up. Herein, the most important variables of PNPs that shall be defined in any PNPs to be used for pulmonary delivery are defined. Further, this study focuses on the most popular polymers used for this purpose.

Stem cells as an ideal carrier for gene therapy: A new approach to the treatment of hepatitis C virus

BACKGROUND AND AIM

Various chemical drugs have been approved for the treatment of patients with hepatitis C, but most of these treatments are costly, and also have an inadequate response and many side effects. Also, there is no effective vaccine for hepatitis C due to its high genetic diversity. In recent decades, clinical trials have grown dramatically regarding the benefits of stem cell therapy as a modulator of immune system responses and anti-inflammatory drugs. The most promising point in stem cell therapy and similar therapies is that patients with chronic pain and severe injuries are offered drug-free treatment or surgery. In the present study, we examine the various dimensions of the use of stem cells with the approach of gene therapy carriers as a new treatment method in the treatment of Hepatitis C.

METHODS

Search terms were including gene carrier, stem cell therapy, gene therapy, liver disorders, hepatitis C virus. At first, 1000 article titles related to the mentioned keywords for different diseases were found. After removing duplicate titles and items that did not match the scope of the research, articles that met the criteria for entering the research and had usable information were selected. All abstracts of selected articles were studied by researchers. In the initial review, articles related to the title were identified and categorized based on the type of challenge.

CONCLUSION

Gene therapy, either directly and in vivo or indirectly and in vitro, requires carriers (vectors) to transfer the gene. These carriers are divided into two groups, viral and non-viral. In indirect gene therapy, living cells are isolated from a person's body and genetically modified. Stem cells have the properties to transfer the desired genes to the patient's body, including the ability to proliferate for a long time and differentiate into the tissue cells in which they are located.

Co-Infection and Cancer: Host–Pathogen Interaction between Dendritic Cells and HIV-1, HTLV-1, and Other Oncogenic Viruses

Dendritic cells (DCs) function as a link between innate and adaptive immune responses. Retroviruses HIV-1 and HTLV-1 modulate DCs to their advantage and utilize them to propagate infection. Coinfection of HTLV-1 and HIV-1 has implications for cancer malignancies. Both viruses initially infect DCs and propagate the infection to CD4+ T cells through cell-to-cell transmission using mechanisms including the formation of virologic synapses, viral biofilms, and conduits. These retroviruses are both neurotrophic with neurovirulence determinants. The neuropathogenesis of HIV-1 and HTLV-1 results in neurodegenerative diseases such as HIV-associated neurocognitive disorders (HAND) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Infected DCs are known to traffic to the brain (CNS) and periphery (PNS, lymphatics) to induce neurodegeneration in HAND and HAM/TSP patients. Elevated levels of neuroinflammation have been correlated with cognitive decline and impairment of motor control performance. Current vaccinations and therapeutics for HIV-1 and HTLV-1 are assessed and can be applied to patients with HIV-1-associated cancers and adult T cell leukemia/lymphoma (ATL). These diseases caused by co-infections can result in both neurodegeneration and cancer. There are associations with cancer malignancies and HIV-1 and HTLV-1 as well as other human oncogenic viruses (EBV, HBV, HCV, HDV, and HPV). This review contains current knowledge on DC sensing of HIV-1 and HTLV-1 including DC-SIGN, Tat, Tax, and current viral therapies. An overview of DC interaction with oncogenic viruses including EBV, Hepatitis viruses, and HPV is also provided. Vaccines and therapeutics targeting host–pathogen interactions can provide a solution to co-infections, neurodegeneration, and cancer.

Development of a Nanocarrier-Based Splenic B Cell-Targeting System for Loading Antigens in Vitro

B cells are types of lymphocytes that are involved in the production of antibodies against pathogens. They also deliver and present antigens for the priming of T cells. Recently, we developed an in vivo splenic marginal zone (MZ) B cell-targeting liposomes decorated with polyethylene glycol (PEG) containing a hydroxyl-terminus group (HO-PEG-Lip). In an expansion of a previous study, we used HO-PEG-Lip as an in vitro antigen delivery tool to splenic B cells to test the ability of this formulation to overcome the limitations of the poor antigen uptake ability of B cells for implantation. To achieve our purpose, various factors were optimized. These factors include cell number, liposome concentration, pre-opsonization of liposomes, fresh serum concentration, and incubation time, all of which affect the extent of interaction between liposomes and B cells. As a result, we confirmed that the HO-PEG-Lip required incubation at 37 °C for at least 20 min with 50% mouse fresh serum followed by a subsequent incubation at 37 °C for at least another 30 min with splenic B cells. By using such a loading system, fluorescein isothiocyanate (FITC)-labeled ovalbumin (OVA), a model antigen, encapsulated in HO-PEG-Lip could be efficiently loaded into splenic B cells. In addition, HO-PEG-Lip and FITC-labeled OVA encapsulated in HO-PEG-Lip were efficiently associated with MZ-B cells with high levels of complement receptors (CRs) rather than follicular B cells with low levels of CRs. These results propose a novel and useful system to efficiently load antigens into B cells in vitro by taking advantage of complement systems.

Threshold dynamics of a HCV model with virus to cell transmission in both liver with CTL immune response and the extrahepatic tissue

In this paper, a deterministic model characterizing the within-host infection of Hepatitis C virus (HCV) in intrahepatic and extrahepatic tissues is presented. In addition, the model also includes the effect of the cytotoxic T lymphocyte (CTL) immunity described by a linear activation rate by infected cells. Firstly, the non-negativity and boundedness of solutions of the model are established. Secondly, the basic reproduction number R01 and immune reproduction number R02 are calculated, respectively. Three equilibria, namely, infection-free, CTL immune response-free and infected equilibrium with CTL immune response are discussed in terms of these two thresholds. Thirdly, the stability of these three equilibria is investigated theoretically as well as numerically. The results show that when R01<1 , the virus will be cleared out eventually and the CTL immune response will also disappear; when R02<1<R01 , the virus persists within the host, but the CTL immune response disappears eventually; when R02>1 , both of the virus and the CTL immune response persist within the host. Finally, a brief discussion will be given.

In the era of rapid mRNA-based vaccines: Why is there no effective hepatitis C virus vaccine yet?

Hepatitis C virus (HCV) is responsible for no less than 71 million people chronically infected and is one of the most frequent indications for liver transplantation worldwide. Despite direct-acting antiviral therapies fuel optimism in controlling HCV infections, there are several obstacles regarding treatment accessibility and reinfection continues to remain a possibility. Indeed, the majority of new HCV infections in developed countries occur in people who inject drugs and are more plausible to get reinfected. To achieve global epidemic control of this virus the development of an effective prophylactic or therapeutic vaccine becomes a must. The coronavirus disease 19 (COVID-19) pandemic led to auspicious vaccine development against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus, which has renewed interest on fighting HCV epidemic with vaccination. The aim of this review is to highlight the current situation of HCV vaccine candidates designed to prevent and/or to reduce HCV infectious cases and their complications. We will emphasize on some of the crossroads encountered during vaccine development against this insidious virus, together with some key aspects of HCV immunology which have, so far, hampered the progress in this area. The main focus will be on nucleic acid-based as well as recombinant viral vector-based vaccine candidates as the most novel vaccine approaches, some of which have been recently and successfully employed for SARS-CoV-2 vaccines. Finally, some ideas will be presented on which methods to explore for the design of live-attenuated vaccines against HCV.

An overview of the recent findings of cell-based therapies for the treatment and management of COVID-19

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic taking the lives of millions. The virus itself not only invades and destroys the angiotensin-converting enzyme 2 (ACE2)-expressing cells of the lungs, kidneys, liver, etc. but also elicits a hyperinflammatory immune response, further damaging the tissue leading to acute respiratory distress syndrome (ARDS) and death. Although vaccines, as a prime example of active immunotherapy, have clearly disrupted the transmission of virus and reduced mortality, hospitalization, and burden of disease, other avenues of immunotherapy are also being explored. One such approach would be to adoptively transfer modified/unmodified immune cells to the critically ill. Here, we compiled and summarized the immunopathogenesis of SARS-CoV-2 and the recent preclinical and clinical data on the potential of cell-based therapies in the fight against COVID-19.

An outlook on antigen-specific adoptive immunotherapy for viral infections with a focus on COVID-19

Although not a standard-of-care yet, adoptive immunotherapeutic approaches have gradually earned a place within the list of antiviral therapies for some of fatal and hard-to-treat viral diseases. To maintain robust antiviral immunity and to effectively target the viral particles and virally-infected cells, immune cells capable of recognizing the viral antigens are required. While conventional vaccination can induce these cells in vivo; another option is to prime and generate antigen-specific immune cells ex vivo. This approach has been successfully trialed for virulent opportunistic viral infections after bone marrow transplantation. Amid the crisis of SARS-CoV2 pandemic, which has been followed by the success of certain early-authorized vaccines; some institutions and companies have explored the effects of viral-specific adoptive cell transfers (ACTs) in trials, as alternative treatments. Aimed at outlining a perspective on antigen-specific adoptive immunotherapy for viral infections, this review article specifically provides an appraisal of ACT-based studies/trials on SARS-CoV2 infection.

A Role for Extracellular Vesicles in SARS-CoV-2 Therapeutics and Prevention

Extracellular vesicles (EVs) are the common designation for ectosomes, microparticles and microvesicles serving dominant roles in intercellular communication. Both viable and dying cells release EVs to the extracellular environment for transfer of cell, immune and infectious materials. Defined morphologically as lipid bi-layered structures EVs show molecular, biochemical, distribution, and entry mechanisms similar to viruses within cells and tissues. In recent years their functional capacities have been harnessed to deliver biomolecules and drugs and immunological agents to specific cells and organs of interest or disease. Interest in EVs as putative vaccines or drug delivery vehicles are substantial. The vesicles have properties of receptors nanoassembly on their surface. EVs can interact with specific immunocytes that include antigen presenting cells (dendritic cells and other mononuclear phagocytes) to elicit immune responses or affect tissue and cellular homeostasis or disease. Due to potential advantages like biocompatibility, biodegradation and efficient immune activation, EVs have gained attraction for the development of treatment or a vaccine system against the severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) infection. In this review efforts to use EVs to contain SARS CoV-2 and affect the current viral pandemic are discussed. An emphasis is made on mesenchymal stem cell derived EVs' as a vaccine candidate delivery system.

Nanocarrier vaccines for SARS-CoV-2

The SARS-CoV-2 global pandemic has seen rapid spread, disease morbidities and death associated with substantive social, economic and societal impacts. Treatments rely on re-purposed antivirals and immune modulatory agents focusing on attenuating the acute respiratory distress syndrome. No curative therapies exist. Vaccines remain the best hope for disease control and the principal global effort to end the pandemic. Herein, we summarize those developments with a focus on the role played by nanocarrier delivery.

Human lung-on-chips: Advanced systems for respiratory virus models and assessment of immune response

Respiratory viral infections are leading causes of death worldwide. A number of human respiratory viruses circulate in all age groups and adapt to person-to-person transmission. It is vital to understand how these viruses infect the host and how the host responds to prevent infection and onset of disease. Although animal models have been widely used to study disease states, incisive arguments related to poor prediction of patient responses have led to the development of microfluidic organ-on-chip models, which aim to recapitulate organ-level physiology. Over the past decade, human lung chips have been shown to mimic many aspects of the lung function and its complex microenvironment. In this review, we address immunological responses to viral infections and elaborate on human lung airway and alveolus chips reported to model respiratory viral infections and therapeutic interventions. Advances in the field will expedite the development of therapeutics and vaccines for human welfare.

Dendritic cells in COVID-19 immunopathogenesis: insights for a possible role in determining disease outcome

SARS-CoV-2 is the causative agent of the COVID-19 pandemic. This novel coronavirus emerged in China, quickly spreading to more than 200 countries worldwide. Although most patients are only mildly ill or even asymptomatic, some develop severe pneumonia and become critically ill. One of the biggest unanswered questions is why some develop severe disease, whilst others do not. Insight on the interaction between SARS-CoV-2 and the immune system and the contribution of dysfunctional immune responses to disease progression will be instrumental to the understanding of COVID-19 pathogenesis, risk factors for worst outcome, and rational design of effective therapies and vaccines. In this review we have gathered the knowledge available thus far on the epidemiology of SARS-COV-2 infection, focusing on the susceptibility of older individuals, SARS-CoV-2-host cell interaction during infection and the immune response directed at SARS-CoV-2. Dendritic cells act as crucial messengers linking innate and adaptative immunity against viral infections. Thus, this review also brings a focused discussion on the role of dendritic cells and their immune functions during SARS-CoV-2 infection and how immune evasion strategies of SARS-CoV-2 and advancing age mediate dendritic cell dysfunctions that contribute to COVID-19 pathogenesis and increased susceptibility to worst outcomes. This review brings to light the hypothesis that concomitant occurrence of dendritic cell dysfunction/cytopathic effects induced by SARS-CoV-2 and/or aging may influence disease outcome in the elderly. Lastly, a detailed discussion on the effects and mechanisms of action of drugs currently being tested for COVID-19 on the function of dendritic cells is also provided.

Combination of three adjuvants enhances the immunogenicity of a recombinant protein containing the CTL epitopes of non-structural proteins of hepatitis C virus

Hepatitis C virus (HCV) can cause chronic infection and evade the immune response. The generation and maintenance of an effective T-cell response is important for immune-mediated control of HCV infection. The purpose of this study was to obtain recombinant mosaic proteins containing the cytotoxic T lymphocyte (CTL) epitopes of HCV fused with different adjuvants and analyse their immunogenicity. A recombinant polyepitope protein comprising HLA-A2-restricted CTL epitopes of the NS3, NS4ab and NS5a proteins of HCV was designed. Adjuvant compounds, the T-helper (Th) epitope PADRE, lipopeptide from Neisseria meningiditis and interleukin 2 (IL-2) were included in the fusion proteins. Three proteins differing in their adjuvant content were expressed in Escherichia coli and purified. The purified proteins formed nanosized particles. The proteins were characterized by their ability to cause proliferation of spleen cells, induce expression of cytokine genes and production of interferon gamma by T lymphocytes of immunized mice. The obtained recombinant vaccine proteins effectively stimulate dendritic cells, which in turn specifically activate Th1 and Th2 lymphocytes. Adjuvant components act additively to enhance the stimulation of dendritic cells and polarize them in the direction of Th1 lymphocyte activation. Analysis of spleen cell proliferation, expression of Th1 and Th2 cytokines and production of interferon gamma by lymphocytes of immunized mice after specific stimulation in vitro revealed that recombinant protein comprising CTL epitopes of HCV, Th epitope PADRE, lipoprotein and IL-2 induced the highest response of T-lymphocytes.

Genetically Modified Mouse Mesenchymal Stem Cells Expressing Non-Structural Proteins of Hepatitis C Virus Induce Effective Immune Response

Hepatitis C virus (HCV) is one of the major causes of chronic liver disease and leads to cirrhosis and hepatocarcinoma. Despite extensive research, there is still no vaccine against HCV. In order to induce an immune response in DBA/2J mice against HCV, we obtained modified mouse mesenchymal stem cells (mMSCs) simultaneously expressing five nonstructural HCV proteins (NS3-NS5B). The innate immune response to mMSCs was higher than to DNA immunization, with plasmid encoding the same proteins, and to naïve unmodified MSCs. mMSCs triggered strong phagocytic activity, enhanced lymphocyte proliferation, and production of type I and II interferons. The adaptive immune response to mMSCs was also more pronounced than in the case of DNA immunization, as exemplified by a fourfold stronger stimulation of lymphocyte proliferation in response to HCV, a 2.6-fold higher rate of biosynthesis, and a 30-fold higher rate of secretion of IFN-γ, as well as by a 40-fold stronger production of IgG2a antibodies to viral proteins. The immunostimulatory effect of mMSCs was associated with pronounced IL-6 secretion and reduction in the population of myeloid derived suppressor cells (MDSCs). Thus, this is the first example that suggests the feasibility of using mMSCs for the development of an effective anti-HCV vaccine.

Immunotherapy with interferon-α-induced dendritic cells for chronic HCV infection (the results of pilot clinical trial)

The key role of T cells in hepatitis C virus (HCV) elimination and the ability of dendritic cells (DCs) to induce antiviral T cell responses suggest that DC vaccines could be a promising approach in the treatment of chronic HCV infection. The aim of our study was to evaluate, whether immunotherapy with DCs is safe and elicits anti-HCV T cell responses. Ten patients with HCV (genotype 1) were vaccinated with monocyte-derived DCs, generated in the presence of IFN-α (IFN-DCs) and pulsed with recombinant HCV Core and NS3 proteins. Treatment schedule included four subcutaneous vaccinations with 1 week interval and six vaccinations with month interval. No serious adverse events or an increase in hepatitis C biochemical activity were registered after vaccination. Using ex vivo assays for the detection of proliferative responses, IFN-γ production and CD8⁺ degranulation have shown that immunotherapy elicited antigen-specific responses in all patients although individual heterogeneity existed within their types, magnitude, and timing. Core/NS3-specific proliferative response and CD8⁺ T cell degranulation have already been registered after the first course of vaccination. Of note, Core-specific responses had higher magnitude. The appearance of antigen-specific IFN-γ responses was registered after the second vaccination course. Vaccination did not cause Th2 response and expansion of the CD4⁺CD25⁺CD127^- regulatory T cells. Generated immune responses failed to provide virus elimination. Nevertheless, there were inverse correlations between viral load and NS3-specific proliferation (R _S = 0.62; p = 0.05) and IFN-γ secretion (R _S = - 0.82; p = 0.001) at 6-month post-treatment period. Immunotherapy with IFN-DCs was safe and elicited HCV-specific T cell responses which were insufficient to eliminate viruses but could be implicated in the restriction of viral replication.

Rational design of nanoparticles towards targeting antigen-presenting cells and improved T cell priming

Vaccination is a promising strategy to trigger and boost immune responses against cancer or infectious disease. We have designed, synthesized and characterized aliphatic-polyester (poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) to investigate how the nature of protein association (adsorbed versus entrapped) and polymer/surfactant concentrations impact on the generation and modulation of antigen-specific immune responses. The ability of the NP formulations to target dendritic cells (DC), be internalized and activate the T cells was characterized and optimized in vitro and in vivo using markers of DC activation and co-stimulatory molecules. Ovalbumin (OVA) was used as a model antigen in combination with the engraftment of CD4⁺ and CD8⁺ T cells, carrying a transgenic OVA-responding T cell receptor (TCR), to trace and characterize the activation of antigen-specific CD4⁺ and CD8⁺ lymph node T cells upon NP vaccination. Accordingly, the phenotype and frequency of immune cell stimulation induced by the NP loaded with OVA, isolated or in combination with synthetic unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotide (ODN) motifs, were characterized. DC-NP interactions increased with incubation time, presenting internalization values between 50 and 60% and 30-40%, in vitro and in vivo, respectively. Interestingly, animal immunization with antigen-adsorbed NP up-regulated major histocompatibility complex (MHC) class II (MHCII), while NP entrapping the antigen up-regulated MHCI, suggesting a more efficient cross-presentation. On the other hand, rather surprisingly, the surfactant used in the NP formulation had a major impact on the activation of antigen presenting cells (APC). In fact, DC collected from lymph nodes of animals immunized with NP prepared using poly(vinil alcohol) (PVA), as a surfactant, expressed significantly higher levels of CD86, MHCI and MHCII. In addition, those NP prepared with PVA and co-entrapping OVA and the toll-like receptor (TLR) ligand CpG, induced the most profound antigen-specific T cell response, by both CD4⁺ and CD8⁺ T cells, in vivo. Overall, our data reveal the impact of NP composition and surface properties on the type and extension of induced immune responses. Deeper understanding on the NP-immune cell crosstalk can guide the rational development of nano-immunotherapeutic systems with improved and specific therapeutic efficacy and avoiding off-target effects.

Ex vivo antigen-pulsed PBMCs generate potent and long lasting immunity to infection when administered as a vaccine

Numerous studies have demonstrated that administration of antigen (Ag)-pulsed dendritic cells (DCs) is an effective strategy for enhancing immunity to tumors and infectious disease organisms. However, the generation and/or isolation of DCs can require substantial time and expense. Therefore, using inactivated F. tularensis (iFt) Ag as a model immunogen, we first sought to determine if DCs could be replaced with peripheral blood mononuclear cells (PBMCs) during the ex-vivo pulse phase and still provide protection against Ft infection. Follow up studies were then conducted using the S. pneumoniae (Sp) vaccine Prevnar ®13 as the Ag in the pulse phase followed by immunization and Sp challenge. In both cases, we demonstrate that PBMCs can be used in place of DCs when pulsing with iFt and/or Prevnar ®13 ex vivo and re-administering the Ag-pulsed PBMCs as a vaccine. In addition, utilization of the i.n. route for Ag-pulsed PBMC administration is superior to use of the i.v. route in the case of Sp immunization, as well as when compared to direct injection of Prevnar ®13 vaccine i.m. or i.n. Furthermore, this PBMC-based vaccine strategy provides a more marked and enduring protective immune response and is also capable of serving as a multi-organism vaccine platform. The potential for this ex-vivo vaccine strategy to provide a simpler, less time consuming, and less expensive approach to DC-based vaccines and vaccination in general is also discussed.

Analysis of peripheral blood dendritic cells as a non-invasive tool in the follow-up of patients with chronic hepatitis C

Hepatitis C virus (HCV) has a high propensity to establish chronic infections. Failure of HCV-infected individuals to activate effective antiviral immune responses is at least in part related to HCV-induced impairment of dendritic cells (DCs) that play a central role in activating T cell responses. Although the impact of HCV on DC phenotype and function is likely to be more prominent in the liver, major HCV-induced alterations are detectable in peripheral blood DCs (pbDCs) that represent the most accessible source of DCs. These alterations include numerical reduction, impaired production of inflammatory cytokines and increased production of immunosuppressive IL10. These changes in DCs are relevant to our understanding the immune mechanisms underlying the propensity of HCV to establish persistent infection. Importantly, the non-invasive accessibility of pbDCs renders the analysis of these cells a convenient procedure that can be serially repeated in patient follow-up. Accordingly, the study of pbDCs in HCV-infected patients during conventional treatment with pegylated interferon and ribavirin indicated that restoration of normal plasmacytoid DC count may represent an additional mechanism contributing to the efficacy of the dual therapy. It also identified the pre-treatment levels of plasmacytoid DCs and IL10 as putative predictors of response to therapy. Treatment of chronic HCV infection is changing, as new generation direct-acting antiviral agents will soon be available for use in interferon-free therapeutic strategies. The phenotypic and functional analysis of pbDCs in this novel therapeutic setting will provide a valuable tool for investigating mechanisms underlying treatment efficacy and for identifying predictors of treatment response.

Current Advances in Virus-Like Particles as a Vaccination Approach against HIV Infection

HIV-1 virus-like particles (VLPs) are promising vaccine candidates against HIV-1 infection. They are capable of preserving the native conformation of HIV-1 antigens and priming CD4+ and CD8+ T cell responses efficiently via cross presentation by both major histocompatibility complex (MHC) class I and II molecules. Progress has been achieved in the preclinical research of HIV-1 VLPs as prophylactic vaccines that induce broadly neutralizing antibodies and potent T cell responses. Moreover, the progress in HIV-1 dendritic cells (DC)-based immunotherapy provides us with a new vision for HIV-1 vaccine development. In this review, we describe updates from the past 5 years on the development of HIV-1 VLPs as a vaccine candidate and on the combined use of HIV particles with HIV-1 DC-based immunotherapy as efficient prophylactic and therapeutic vaccination strategies.

Intradermal delivery of DNA encoding HCV NS3 and perforin elicits robust cell-mediated immunity in mice and pigs

Currently, no vaccine is available against hepatitis C virus (HCV), and although DNA vaccines have considerable potential, this has not been realised. Previously, the efficacy of DNA vaccines for human immunodeficiency virus (HIV) and HCV was shown to be enhanced by including the gene for a cytolytic protein, viz. perforin. In this study, we examined the mechanism of cell death by this bicistronic DNA vaccine, which encoded the HCV non-structural protein 3 (NS3) under the control of the CMV promoter and perforin is controlled by the SV40 promoter. Compared with a canonical DNA vaccine and a bicistronic DNA vaccine encoding NS3 and the proapoptotic gene NSP4, the perforin-containing vaccine elicited enhanced cell-mediated immune responses against the NS3 protein in vaccinated mice and pigs, as determined by ELISpot and intracellular cytokine staining, whereas a mouse challenge model suggested that the immunity was CD8(+) T-cell-dependent. The results of the study showed that the inclusion of perforin in the DNA vaccine altered the fate of NS3-positive cells from apoptosis to necrosis, and this resulted in more robust immune responses in mice and pigs, the latter of which represents an accepted large animal model in which to test vaccine efficacy.

Dendritic cells: The warriors upfront-turned defunct in chronic hepatitis C infection

Hepatitis C virus (HCV) infection causes tremendous morbidity and mortality with over 170 million people infected worldwide. HCV gives rise to a sustained, chronic disease in the majority of infected individuals owing to a failure of the host immune system to clear the virus. In general, an adequate immune response is elicited by an efficient antigen presentation by dendritic cells (DCs), the cells that connect innate and adaptive immune system to generate a specific immune response against a pathogen. However, HCV seems to dysregulate the activity of DCs, making them less proficient antigen presenting cells for the optimal stimulation of virus-specific T cells, hence interfering with an optimal anti-viral immune response. There are discordant reports on the functional status of DCs in chronic HCV infection (CHC), from no phenotypic or functional defects to abnormal functions of DCs. Furthermore, the molecular mechanisms behind the impairment of DC function are even so not completely elucidated during CHC. Understanding the mechanisms of immune dysfunction would help in devising strategies for better management of the disease at the immunological level and help to predict the prognosis of the disease in the patients receiving antiviral therapy. In this review, we have discussed the outcomes of the interaction of DCs with HCV and the mechanisms of DC impairment during HCV infection with its adverse effects on the immune response in the infected host.

Dynamical analysis on a chronic hepatitis C virus infection model with immune response

A mathematical model for HCV infection is established, in which the effect of dendritic cells (DC) and cytotoxic T lymphocytes (CTL) on HCV infection is considered. The basic reproduction numbers of chronic HCV infection and immune control are found. The obtained results show that the infection dies out finally as the basic reproduction number of HCV infection is less than unity, and the infection becomes chronic as it is greater than unity. In the presence of chronic infection, the existence of immune control equilibrium is discussed completely, which illustrates that the backward bifurcation may occur under certain conditions, and that the two quantities, the sizes of the activated DC and the removed CTL during their average life-terms, play a critical role in controlling chronic HCV infection and immune response. The occurrence of backward bifurcation implies that there may be bistability for the model, i.e., the outcome of infection depends on the initial situation. By choosing the activated rate of non-activated DC or the cross-representation rate of activated DC as bifurcation number, Hopf bifurcation for certain condition shows the existence of periodic solution of the model. Again, numerical simulations suggest the dynamical complexity of the model including the instability of immune control equilibrium and the existence of stable periodic solution.

Modulation of antigen-specific T-cells as immune therapy for chronic infectious diseases and cancer

T-cell responses are induced by antigen presenting cells (APC) and signals from the microenvironment. Antigen persistence and inflammatory microenvironments in chronic infections and cancer can induce a tolerant state in T-cells resulting in hyporesponsiveness, loss of effector function, and weak biochemical signaling patterns in response to antigen stimulation. Although the mechanisms of T-cell tolerance induced in chronic infection and cancer may differ from those involved in tolerance to self-antigen, the impaired proliferation and production of IL-2 in response to antigen stimulation are hallmarks of all tolerant T cells. In this review, we will summarize the evidence that the immune responses change from non-self to “self”-like in chronic infection and cancer, and will provide an overview of strategies for re-balancing the immune response of antigen-specific T cells in chronic infection and cancer without affecting the homeostasis of the immune system.

Enhanced virus-specific CD8+ T cell responses by Listeria monocytogenes-infected dendritic cells in the context of Tim-3 blockade

In this study, we engineered Listeria monocytogens (Lm) by deleting the LmΔactA/ΔinlB virulence determinants and inserting HCV-NS5B consensus antigens to develop a therapeutic vaccine against hepatitis C virus (HCV) infection. We tested this recombinant Lm-HCV vaccine in triggering of innate and adaptive immune responses in vitro using immune cells from HCV-infected and uninfected individuals. This live-attenuated Lm-HCV vaccine could naturally infect human dendritic cells (DC), thereby driving DC maturation and antigen presentation, producing Th1 cytokines, and triggering CTL responses in uninfected individuals. However, vaccine responses were diminished when using DC and T cells derived from chronically HCV-infected individuals, who express higher levels of inhibitory molecule Tim-3 on immune cells. Notably, blocking Tim-3 signaling significantly improved the innate and adaptive immune responses in chronically HCV-infected patients, indicating that novel strategies to enhance the potential of antigen presentation and cellular responses are essential for developing an effective therapeutic vaccine against HCV infection.

Tim-3 alters the balance of IL-12/IL-23 and drives TH17 cells: role in hepatitis B vaccine failure during hepatitis C infection

Hepatitis B virus (HBV) vaccination is recommended for individuals with hepatitis C virus (HCV) infection given their shared risk factors and increased liver-related morbidity and mortality upon super-infection. Vaccine responses in this setting are often blunted, with poor response rates to HBV vaccinations in chronically HCV-infected individuals compared to healthy subjects. In this study, we investigated the role of T cell immunoglobulin mucin domain-3 (Tim-3)-mediated immune regulation in HBV vaccine responses during HCV infection. We found that Tim-3, a marker for T cell exhaustion, was over-expressed on monocytes, leading to a differential regulation of IL-12/IL-23 production which in turn TH17 cell accumulation, in HCV-infected HBV vaccine non-responders compared to HCV-infected HBV vaccine responders or healthy subjects (HS). Importantly, ex vivo blockade of Tim-3 signaling corrected the imbalance of IL-12/IL-23 as well as the IL-17 bias observed in HBV vaccine non-responders during HCV infection. These results suggest that Tim-3-mediated dysregulation of innate to adaptive immune responses is involved in HBV vaccine failure in individuals with chronic HCV infection, raising the possibility that blocking this negative signaling pathway might improve the success rate of HBV immunization in the setting of chronic viral infection.

Hepatitis C virus vaccines--progress and perspectives

Approximately 170 million individuals, representing 3% of the global population, are infected with hepatitis C virus (HCV). Whereas strategies for antiviral therapies have markedly improved resulting in clinical licensing of direct-acting antivirals, the development of vaccines has been hampered by the high genetic variability of the virus as well as by the lack of suitable animal models for proof-of-concept studies. Nevertheless, there are several promising vaccine candidates in preclinical and clinical development. After a brief summary of the molecular virology and immunology relevant to vaccine development, this review explains the model systems used for preclinical vaccine development, and highlights examples for most recently developed HCV vaccine candidates.

Mechanisms of CpG-induced CD40 expression on murine bone marrow-derived dendritic cells

Aberrant CD40 expression by dendritic cells (DCs), induced by microbial stimuli, such as CpG, contributes to the pathogenesis of many human/murine diseases, particularly autoimmune and inflammatory diseases. Given the importance of CD40 in these diseases, and the contribution of DCs to the diseases process, it is very important to investigate the mechanisms of CD40 expression induced by CpG on DCs. In this study, we made the observation that CpG-B is a potent inducer on CD40 expression on murine bone marrow-derived DCs. Based on this finding, we undertook an analysis of the molecular basis of CpG-induced CD40 expression on DCs. By using selective inhibitors, it was demonstrated that MAPKs (JNK and p38 MAPK but not ERK) and NF-κB were involved in CpG-induced CD40 expression on DCs. In addition, RNA interference analysis revealed that IRF8 was a key transcription factor in the basal expression of CD40 upon CpG stimulation. Moreover, up-regulating miRNA-146a in DCs effectively decreased CD40 expression by targeting TRAF6 and IRAK1. Thus, our results have elucidated the molecular mechanisms underlying CpG-induced CD40 expression and DC maturation.

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

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

Dendritic cells and vaccine design for sexually-transmitted diseases

Dendritic cells (DCs) are major antigen presenting cells (APCs) that can initiate and control host immune responses toward either immunity or tolerance. These features of DCs, as immune orchestrators, are well characterized by their tissue localizations as well as by their subset-dependent functional specialties and plasticity. Thus, the level of protective immunity to invading microbial pathogens can be dependent on the subsets of DCs taking up microbial antigens and their functional plasticity in response to microbial products, host cellular components and the cytokine milieu in the microenvironment. Vaccines are the most efficient and cost-effective preventive medicine against infectious diseases. However, major challenges still remain for the diseases caused by sexually-transmitted pathogens, including HIV, HPV, HSV and Chlamydia. We surmise that the establishment of protective immunity in the female genital mucosa, the major entry and transfer site of these pathogens, will bring significant benefit for the protection against sexually-transmitted diseases. Recent progresses made in DC biology suggest that vaccines designed to target proper DC subsets may permit us to establish protective immunity in the female genital mucosa against sexually-transmitted pathogens.