Vaccination with protein-transduced dendritic cells elicits a sustained response to hepatitis C viral antigens

Dendritic cell-mediated, DNA-based vaccination against hepatitis C induces the multi-epitope-specific response of humanized, HLA transgenic mice

Hepatitis C virus (HCV) is the etiologic agent of chronic liver disease, hepatitis C. Spontaneous resolution of viral infection is associated with vigorous HLA class I- and class II-restricted T cell responses to multiple viral epitopes. Unfortunately, only 20% of patients clear infection spontaneously, most develop chronic disease and require therapy. The response to chemotherapy varies, however; therapeutic vaccination offers an additional treatment strategy. To date, therapeutic vaccines have demonstrated only limited success. Vector-mediated vaccination with multi-epitope-expressing DNA constructs alone or in combination with chemotherapy offers an additional treatment approach. Gene sequences encoding validated HLA-A2- and HLA-DRB1-restricted epitopes were synthesized and cloned into an expression vector. Dendritic cells (DCs) derived from humanized, HLA-A2/DRB1 transgenic (donor) mice were transfected with these multi-epitope-expressing DNA constructs. Recipient HLA-A2/DRB1 mice were vaccinated s.c. with transfected DCs; control mice received non-transfected DCs. Peptide-specific IFN-γ production by splenic T cells obtained at 5 weeks post-immunization was quantified by ELISpot assay; additionally, the production of IL-4, IL-10 and TNF-α were quantified by cytokine bead array. Splenocytes derived from vaccinated HLA-A2/DRB1 transgenic mice exhibited peptide-specific cytokine production to the vast majority of the vaccine-encoded HLA class I- and class II-restricted T cell epitopes. A multi-epitope-based HCV vaccine that targets DCs offers an effective approach to inducing a broad immune response and viral clearance in chronic, HCV-infected patients.

Chronic ethanol diet increases regulatory T-cell activity and inhibits hepatitis C virus core-specific cellular immune responses in mice

AIM

Chronic ethanol consumption is associated with persistent hepatitis C viral (HCV) infection. This study explores the role of the host cellular immune response to HCV core protein in a murine model and how chronic ethanol consumption alters T-cell regulatory (Treg) populations.

METHODS

BALB/c mice were fed an isocaloric control or ethanol liquid diet. Dendritic cells (DC) were isolated after expansion with a hFl3tL-expression plasmid and subsequently transfected with HCV core protein. Core-containing DC (1 × 10(6) ) were s.c. injected (×3) in mice every 2 weeks. Splenocytes from immunized mice were isolated and stimulated with HCV core protein to measure generation of viral antigen-specific Treg, as well as secretion of interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-4. Cytotoxicity was measured by lactate dehydrogenase release from HCV core-expressing syngeneic SP2/19 myeloma cells.

RESULTS

Splenocytes from mice immunized with ethanol-derived and HCV core-loaded DC exhibited significantly lower in vitro cytotoxicity compared to mice immunized with HCV core-loaded DC derived from isocaloric pair-fed controls. Stimulation with HCV core protein triggered higher IL-2, TNF-α and IL-4 release in splenocytes following immunization with core-loaded DC derived from controls as compared to chronic ethanol-fed mice. Splenocytes derived from mice immunized with core-loaded DC isolated from ethanol-fed mice exhibited a significantly higher CD25(+) FOXP3(+) and CD4(+) FOXP3(+) Treg population.

CONCLUSION

These results suggest that immunization with HCV core-containing DC from ethanol-fed mice induces an increase in the CD25(+) FOXP3(+) and CD4(+) FOXP3(+) Treg population and may suppress HCV core-specific CD4(+) and CD8(+) T-cell immune responses.

Enhanced in vivo targeting of murine nonparenchymal liver cells with monophosphoryl lipid A functionalized microcapsules

A broad spectrum of infectious liver diseases emphasizes the need of microparticles for targeted delivery of immunomodulatory substances to the liver. Microcapsules (MCs) are particularly attractive for innovative drug and vaccine formulations, enabling the combination of antigen, drugs, and adjuvants. The present study aimed to develop microcapsules characterized by an enhanced liver deposition and accelerated uptake by nonparenchymal liver cells (NPCs). Initially, two formulations of biodegradable microcapsules were synthesized from either hydroxyethyl starch (HES) or mannose. Notably, HES-MCs accumulated primarily in the liver, while mannose particles displayed a lung preference. Functionalization of HES-MCs with anti-CD40, anti-DEC205, and/or monophosphoryl lipid A (MPLA) enhanced uptake of MCs by nonparenchymal liver cells in vitro. In contrast, only MPLA-coated HES-MCs promoted significantly the in vivo uptake by NPCs. Finally, HES-MCs equipped with MPLA, anti-CD40, and anti-DEC205 induced the secretion of TNF-α, IL-6 by Kupffer cells (KCs), and IFN-γ and IL-12p70 by liver dendritic cells (DCs). The enhanced uptake and activation of KCs by MPLA-HES-MCs is a promising approach to prevent or treat infection, since KCs are exploited as an entry gate in various infectious diseases, such as malaria. In parallel, loading and activating liver DCs, usually prone to tolerance, bears the potential to induce antigen specific, intrahepatic immune responses necessary to prevent and treat infections affecting the liver.

Peptide-pulsed dendritic cells induce the hepatitis C viral epitope-specific responses of naïve human T cells

Hepatitis C virus (HCV) is a major cause of liver disease. Spontaneous resolution of infection is associated with broad, MHC class I- (CD8(+)) and class II-restricted (CD4(+)) T cell responses to multiple viral epitopes. Only 20% of patients clear infection spontaneously, however, most develop chronic disease. The response to chemotherapy varies; therapeutic vaccination offers an additional treatment strategy. To date, therapeutic vaccines have demonstrated only limited success in clinical trials. Vector-mediated vaccination with multi-epitope-expressing DNA constructs provides an improved approach. Highly-conserved, HLA-A2-restricted HCV epitopes and HLA-DRB1-restricted immunogenic consensus sequences (ICS, each composed of multiple overlapping and highly conserved epitopes) were predicted using bioinformatics tools and synthesized as peptides. HLA binding activity was determined in competitive binding assays. Immunogenicity and the ability of each peptide to stimulate naïve human T cell recognition and IFN-γ production were assessed in cultures of total PBMCs and in co-cultures composed of peptide-pulsed dendritic cells (DCs) and purified T lymphocytes, cell populations derived from normal blood donors. Essentially all predicted HLA-A2-restricted epitopes and HLA-DRB1-restricted ICS exhibited HLA binding activity and the ability to elicit immune recognition and IFN-γ production by naïve human T cells. The ability of DCs pulsed with these highly-conserved HLA-A2- and -DRB1-restricted peptides to induce naïve human T cell reactivity and IFN-γ production ex vivo demonstrates the potential efficacy of a multi-epitope-based HCV vaccine targeted to dendritic cells.

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

Hepatitis C virus (HCV) has chronically infected an estimated 170 million people worldwide. There are many impediments to the development of an effective vaccine for HCV infection. Dendritic cells (DC) remain the most important antigen-presenting cells for host immune responses, and are capable of either inducing productive immunity or maintaining the state of tolerance to self and non-self antigens. Researchers have recently explored the mechanisms by which DC function is regulated during HCV infection, leading to impaired antiviral T-cell responses and so to persistent viral infection. Recently, DC-based vaccines against HCV have been developed. This review summarizes the current understanding of DC function during HCV infection and explores the prospects of DC-based HCV vaccine. In particular, it describes the biology of DC, the phenotype of DC in HCV-infected patients, the effect of HCV on DC development and function, the studies on new DC-based vaccines against HCV infection, and strategies to improve the efficacy of DC-based 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.

Immunization with aspartate-β-hydroxylase-loaded dendritic cells produces antitumor effects in a rat model of intrahepatic cholangiocarcinoma

Dendritic cells (DCs) capture and process proteins and present peptides on the cell surface in the context of major histocompatibility complex I and II molecules to induce antigen-specific T cell immune responses. The aims of this study were to (1) employ an expanded and purified DC population and load them with aspartate-β-hydroxylase (ASPH), a highly expressed tumor-associated cell surface protein, and (2) to determine if immunization induced antitumor effects in an orthotopic rat model of intrahepatic cholangiocarcinoma. Splenocytes were incubated with ASPH-coated beads and passed through a magnetic field to yield an 80% pure DC OX62+ population. This DC subset was stimulated with granulocyte-macrophage colony-stimulating factor, interleukin-4, CD40L, and interferon-γ, resulting in a 40-fold increase in interleukin-12A messenger RNA expression to subsequently generate a T helper 1-type immune response. After incubation with the cytokine cocktail, DCs were found to have matured, as demonstrated by increased expression of CD40, CD80, and CD86 costimulatory molecules. Immunization with ASPH-loaded DCs induced antigen-specific immunity. A clone of the parental tumorigenic rat BDEneu cholangiocyte cell line, designated BDEneu-CL24, was found to have the highest number of cells expressing this surface protein (97%); it maintained the same phenotypic characteristics of the parental cell line and was used to produce intrahepatic tumors in immunocompetent syngeneic Fisher-344 rats. Immunization with ASPH-loaded DCs generated cytotoxicity against cholangiocarcinoma cells in vitro and significantly suppressed intrahepatic tumor growth and metastasis, and was associated with increased CD3+ lymphocyte infiltration into the tumors.

CONCLUSION

These findings suggest that immunization with ASPH-loaded DCs may constitute a novel therapeutic approach for intrahepatic cholangiocarcinoma, because this protein also appears to be highly conserved and expressed on human hepatobiliary tumors.

Chronic alcohol-induced liver disease inhibits dendritic cell function

BACKGROUND/AIMS

We have compared dendritic cell (DC) function derived from the alcoholic liver disease (ALD) sensitive Long-Evans (LE) and resistant Fischer rat strains to determine if the influence of ethanol on DCs was dependent on ALD.

METHODS

The LE and Fischer rats were fed an ethanol-containing or isocaloric control liquid diet for 8 weeks and comparisons were made to LE rats injected with thioacetamide as a liver disease control. DCs were isolated from the spleen after expansion with human Fms-like tyrosine kinase receptor 3 ligand plasmid. Maturation markers CD86, CD80, CD40 and MHC-II were analysed by flow cytometry with or without lipopolysaccharide and poly I:C stimulation. Production of tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin (IL)-12p40 and IL-10 cytokines and the antigen presentation ability of DCs was determined.

RESULTS

Only LE rats developed ALD characterized by liver injury, elevated alanine aminotransferase levels and steatosis; CD86 and CD40 expression was decreased in LE but not Fischer rats. Reduced TNF-α, IFN-γ, IL-12, proinflammatory and enhanced IL-10 cytokine production was found in DCs isolated from ethanol-fed LE but not Fischer rats. Allostimulatory activity was reduced in LE compared with the Fischer strain. In contrast, DCs isolated from thioacetamide-induced liver damage displayed a reduction only in IL-12p40; TNF-α, IL-10 and IFN-α production as well as antigen presenting ability remained intact compared with controls.

CONCLUSIONS

ALD sensitive LE rats exhibited characteristics of a suppressed DC phenotype that was not observed following thioacetamide-induced liver disease, which suggests an important role for ALD in altering the host cellular and humoral immune responses.

Ethanol inhibits antigen presentation by dendritic cells

Previous studies suggest that altered virus-specific T-cell responses observed during chronic ethanol exposure may be due to abnormal functioning of dendritic cells (DCs). Here we explored the effects of ethanol on exogenous antigen presentation by DCs. BALB/c, C57BL/6, and CBA/caj mice were fed ethanol or an isocaloric control diet for 8 weeks. The splenic DC population was expanded using an Flt3L expression plasmid via tail vein injection. DCs were purified and assessed for antigen presentation and processing and for peptide-major histocompatibility complex class I and II (MHCI and MHCII) formation on the cell surface. Interleukin-2 (IL-2) was measured as an indicator of antigen-specific T-cell activation by DCs in coculture. Antigen processing and peptide-MHCII complexes were evaluated by flow cytometry. We observed that ethanol not only suppressed allogeneic peptide presentation to T cells by DCs but also altered presentation of exogenous ovalbumin (OVA) peptide 323-339 to an OVA-specific DO11 T-cell line as well as to OVA-sensitized primary T cells. Smaller amounts of peptide-MHCII complexes were found on the DCs isolated from the spleens of ethanol-fed mice. In contrast to MHCII presentation, cross-presentation of exogenous OVA peptide via MHCI by DCs remained intact. More importantly, ethanol-exposed DCs had reduced B7-DC and enhanced ICOS-L (inhibitory) costimulatory molecule expression. Ethanol inhibits exogenous and allogeneic antigen presentation and affects the formation of peptide-MHCII complexes, as well as altering costimulatory molecule expression on the cell surface. Therefore, DC presentation of peptides in a favorable costimulatory protein environment is required to subsequently activate T cells and appears to be a critical target for the immunosuppressive effects of ethanol.

Dendritic cells in alcoholic liver injury and fibrosis

Alcohol consumption impairs the development of innate and adaptive immune responses, however the exact mechanism by which alcohol leads to immune defects remains to be established. Dendritic cells (DCs) form a heterogeneous population of hematopoietic cells that are present in all tissues including the liver. DC are initially described playing a key role in the induction of innate and adaptive immune response against specific antigens. In our presentation, we discussed few new aspects of DC development, critical assessment of DC in non-lymphoid organs and the impact of alcohol consumption on DC function. Understanding the mechanism by which DC modulate liver function after alcohol consumption may help uncover novel therapeutic strategies for the treatment of these conditions.

A phase I clinical trial of dendritic cell immunotherapy in HCV-infected individuals

BACKGROUND & AIMS

HCV patients who fail conventional interferon-based therapy have limited treatment options. Dendritic cells are central to the priming and development of antigen-specific CD4(+) and CD8(+) T cell immunity, necessary to elicit effective viral clearance. The aim of the study was to investigate the safety and efficacy of vaccination with autologous dendritic cells loaded with HCV-specific cytotoxic T cell epitopes.

METHODS

We examined the potential of autologous monocyte-derived dendritic cells (MoDC), presenting HCV-specific HLA A2.1-restricted cytotoxic T cell epitopes, to influence the course of infection in six patients who failed conventional therapy. Dendritic cells were loaded and activated ex vivo with lipopeptides. In this phase 1 dose escalation study, all patients received a standard dose of cells by the intradermal route while sequential patients received an increased dose by the intravenous route.

RESULTS

No patient showed a severe adverse reaction although all experienced transient minor side effects. HCV-specific CD8(+) T cell responses were enumerated in PBMC by ELIspot for interferon-gamma. Patients generated de novo responses, not only to peptides presented by the cellular vaccine but also to additional viral epitopes not represented in the lipopeptides, suggestive of epitope spreading. Despite this, no increases in ALT levels were observed. However, the responses were not sustained and failed to influence the viral load, the anti-HCV core antibody response and the level of circulating cytokines.

CONCLUSIONS

Immunotherapy using autologous MoDC pulsed with lipopeptides was safe, but was unable to generate sustained responses or alter the outcome of the infection. Alternative dosing regimens or vaccination routes may need to be considered to achieve therapeutic benefit.

Generation of cellular immune responses to HCV NS5 protein through in vivo activation of dendritic cells

Chronic hepatitis C (HCV) infection is a substantial medical problem that leads to progressive liver disease, cirrhosis, and hepatocellular carcinoma (HCC). The aim of this study was to achieve sustained cellular immune responses in vivo to a HCV nonstructural protein using dendritic cell (DC)-based immunization approach. We targeted the HCV NS5 protein to DCs in vivo by injecting microparticles loaded with this antigen. The DC population was expanded in BALB/C mice (H-2(d) ) by hydrodynamic injection of a plasmid pUMVC3-hFLex expressing the secreted portion of the human Fms-like tyrosine kinase receptor-3 ligand (hFlt3). Mice were subsequently injected with microparticles coated with HCV NS5 protein via the tail vein. Cellular immune responses were determined with respect to secretion of INFγ and IL2 by CD4(+) cells and cytotoxic T-lymphocyte (CTL) assays in vitro; inhibition of tumour cell growth was employed for the assessment of CD8(+) generated activity in vivo. We found that Flt3L treatment expanded the DC population in the spleen to 43%, and such cells displayed a striking upregulation of CD86 as well as CD80 and CD40 co-stimulating molecules. Viral antigen-specific T(H) 1 cytokine secretion by splenocytes was generated, and CTL activity against syngeneic NS5 expressing myeloma target cells was observed. In addition, these cells inhibited tumour growth indicating that NS5-specific robust CTL activity was operative in vivo. Thus, the capability of activating DCs in vivo using the methods described is valuable as a therapeutic vaccine strategy for chronic HCV infection.

Alcohol and hepatitis C virus--interactions in immune dysfunctions and liver damage

Hepatitis C virus infection affects 170 million people worldwide, and the majority of individuals exposed to HCV develop chronic hepatitis leading to progressive liver damage, cirrhosis, and hepatocellular cancer. The natural history of HCV infection is influenced by genetic and environmental factors of which chronic alcohol use is an independent risk factor for cirrhosis in HCV-infected individuals. Both the hepatitis C virus and alcohol damage the liver and result in immune alterations contributing to both decreased viral clearance and liver injury. This review will capture the major components of the interactions between alcohol and HCV infection to provide better understanding for the molecular basis of the dangerous combination of alcohol use and HCV infection. Common targets of HCV and alcohol involve innate immune recognition and dendritic cells, the critical cell type in antigen presentation and antiviral immunity. In addition, both alcohol and HCV affect intracellular processes critical for hepatocyte and immune cell functions including mitochondrial and proteasomal activation. Finally, both chronic alcohol use and hepatitis C virus infection increase the risk of hepatocellular cancer. The common molecular mechanisms underlying the pathological interactions between alcohol and HCV include the modulation of cytokine production, lipopolysaccharide (LPS)-TLR4 signaling, and reactive oxygen species (ROS) production. LPS-induced chronic inflammation is not only a major cause of progressive liver injury and fibrosis, but it can also contribute to modification of the tissue environment and stem cells to promote hepatocellular cancer development. Alteration of these processes by alcohol and HCV produces an environment of impaired antiviral immune response, greater hepatocellular injury, and activation of cell proliferation and dedifferentiation.

Hepatitis C virus infection and immunomodulatory therapies

Hepatitis C virus (HCV) infection remains a large-scale and significant health concern. The combination of subcutaneously administered pegylated interferon and oral ribavirin is the FDA-approved regimen for the treatment of chronic HCV infection. Combination therapy may result in a sustained virologic response leading to HCV eradication, with a reduction in risk for cirrhosis, hepatic decompensation, and hepatocellular carcinoma. However, the combination of PEG-IFN and ribavirin does not universally result in cure in all patients who undergo treatment. In this article, the authors discuss immunomodulatory therapies and clinical trials in the treatment of HCV infection.

Neutrophils sequestered in the liver suppress the proinflammatory response of Kupffer cells to systemic bacterial infection

The liver plays a major role in clearing bacteria from the bloodstream. Rapid clearance is primarily the function of fixed tissue macrophages (Kupffer cells) that line the hepatic sinusoids. Although Kupffer cells play a critical role in blood clearance, the actual elimination of the bulk of bacteria taken up by the liver depends upon the accumulation of bactericidal neutrophils. Subsequent experiments demonstrating neutrophils inside Kupffer cells derived from infected animals prompted our speculation that neutrophils modulate the proinflammatory response of Kupffer cells to bacteria cleared from the bloodstream. Indeed, we report here that neutrophils accumulated in the liver sinusoids suppress cytokine and chemokine mRNA expression and protein production by Kupffer cells. Using listeriosis in mice as an experimental model, we found that IL-1beta, IL-6, IL-10, IL-12, TNF-alpha, MIP-1alpha, keratinocyte-derived chemokine, and MCP-1 mRNA levels were >or=10-fold more in the livers of Listeria-infected, relative to noninfected control, mice at 0.5-2 h after i.v. infection. Most message levels were sharply diminished thereafter, correlating inversely with increased neutrophil sequestration. Relative to intact animals, mice rendered neutrophil deficient exhibited marked increases in cytokine/chemokine mRNA expression and protein production in the liver subsequent to infection. Moreover, purified Kupffer cells derived from infected, neutrophil-depleted mice produced significantly more IL-6, IL-10, IL-12, TNF-alpha, keratinocyte-derived chemokine, and MCP-1 in culture. These findings document the critical role of neutrophils in moderating the proinflammatory response of Kupffer cells to bacteria taken up by the liver.

Hepatitis C virus and alcohol

This review will focus on the prevalence of hepatitis c virus (HCV) infection in alcoholics with and without liver disease. Evidence will be presented to demonstrate that ethanol and chronic HCV infection synergistically accelerate liver injury. Some of the major postulated mechanisms responsible for disease progression include high rates of apoptosis, lipid peroxidation, and generation of free radicals and reactive oxygen species with reduced antioxidant capacity of the liver. Acquisition and persistence of HCV infection may be due to the adverse effects of ethanol on humoral and cellular immune responses to HCV. Dendritic cells (DC) appear to be one of the major targets for ethanol's action and DC dysfunction impairs the ability of the host to generate viral specific cluster of differentiation 4 (CD4+) and cluster of differentiation 8 (CD8+) immune responses. There is a relationship between increased alcohol intake and decreased response to interferon (IFN) therapy, which may be reversed by abstinence. Clinical studies are needed to optimize treatment responses in alcoholic patients with chronic HCV infection.

Review article: investigational agents for chronic hepatitis C

BACKGROUND

The need for effective treatment for chronic hepatitis C infection has driven the development of novel antiviral agents that target specific steps in the viral replication cycle.

AIM

To evaluate the current literature concerning investigational agents for chronic hepatitis C virus infection.

METHODS

Resources used included PubMed, conference proceedings from the American and European Liver Associations' meetings 2005-2008 and the National Institute of Health's clinical trials website (http://www.clinicaltrials.gov). The focus was restricted to investigational agents that have progressed beyond preclinical development.

RESULTS

Over 50 investigational agents for chronic hepatitis C infection are currently in clinical development. Specifically targeted anti-viral therapy for HCV (STAT-C) shows great promise with NS3/4a protease inhibitors now entering phase 3 programmes. New interferon-alpha and ribavirin formulations aim to optimize anti-viral efficacy yet limit toxicity. Other candidates include novel immunomodulators and therapeutic vaccines.

CONCLUSIONS

A new era of therapy for chronic hepatitis C beckons, promising increased cure rates with shortened duration of therapy. However, the era will not be without challenges including viral resistance, drug toxicity and the need to optimize combination therapy in the face of a rapidly evolving therapeutic arsenal.

Generation of immune responses against hepatitis C virus by dendritic cells containing NS5 protein-coated microparticles

Dendritic cells (DCs) internalize and process antigens as well as activate cellular immune responses. The aim of this study was to determine the capacity of DCs that contain antigen-coated magnetic beads to induce immunity against the nonstructural hepatitis C virus (HCV) antigen 5 (NS5). Splenocytes derived from Fms-like tyrosine kinase receptor 3 (Flt3) ligand-pretreated BALB/c mice were incubated with magnetic beads coated with HCV NS5, lipopolysaccharide (LPS), and/or anti-CD40; purified; and used for immunization. Cellular immunity was measured using cytotoxic T-lymphocyte (CTL) and T-cell proliferation assays, intracellular cytokine staining, and a syngeneic tumor challenge using NS5-expressing SP2/0 myeloma cells in vivo. Splenocytes isolated from animals vaccinated with DCs containing beads coated with NS5, LPS, and anti-CD40 secreted elevated levels of interleukin-2 (IL-2) and gamma interferon in the presence of NS5. The numbers of CD4(+), IL-2-producing cells were increased >5-fold in the group immunized with DCs containing beads coated with NS5, LPS, and anti-CD40, paralleled by an enhanced splenocyte proliferative response. Immunization promoted antigen-specific CTL activity threefold compared to the level for control mice and significantly reduced the growth of NS5-expressing tumor cells in vivo. Thus, strategies that employ NS5-coated beads induce cellular immune responses in mice, which correlate well with the natural immune responses that occur in individuals who resolve HCV.

Strategies for loading dendritic cells with hepatitis C NS5a antigen and inducing protective immunity

Dendritic cell (DC)-based vaccination strategies are promising for the treatment of cancers and infectious diseases including hepatitis C virus (HCV). As the induction of T cell-mediated immune responses by DC vaccination is highly dependent on efficient antigen loading of the DCs, the purpose of this study was to identify an optimal nonviral DC loading strategy for HCV NS5a. Furthermore, the efficacy of immunization with the NS5a-loaded DCs in comparison to plasmid encoding NS5a and NS5a protein was evaluated. Transfection of DCs with mRNA was most efficient with close to 100% of DCs expressing NS5a, whereas approximately 10% of protein-pulsed DCs and <1% of plasmid-transfected DCs expressed NS5a, suggesting remarkably different loading efficiencies. Vaccination of mice with NS5a mRNA-transfected DCs or NS5a protein-pulsed DCs resulted in significantly stronger CD4(+) and CD8(+) T-cell responses and protection from challenge with vaccinia virus expressing NS3/NS4/NS5, in comparison to vaccination with NS5a DNA-transfected DCs, plasmid encoding NS5 or rNS5a protein formulated with alum. Furthermore, vaccination with NS5a mRNA-transfected DCs was superior to vaccination with rNS5a-pulsed DCs. These data have important clinical implications, with mRNA-transfected DCs providing a safe and effective vaccination strategy against hepatitis C and possibly other pathogens.

Generation and characterization of an immunogenic dendritic cell population

Dendritic cells (DCs) capture, internalize and process antigens leading to the induction of antigen-specific immune responses. The aim of this study was to develop, implement and characterize an efficient approach for DC-based immunization. Dendritic cells were expanded in vivo by hydrodynamic delivery of a human flt3 ligand expression plasmid. Splenic DCs were isolated and purified with magnetic beads linked to hepatitis C virus (HCV) nonstructural protein-5 (NS5), anti-CD40 and/or LPS. The DCs that contained beads were purified by passage over a magnetic column and subsequently phenotyped. Enrichment resulted in a population consisting of 80% CD11c(+) cells. Uptake of uncoated microparticles promoted DC maturation and the expression of CD80, CD86, and MHC-II molecules; beads coated with LPS and anti-CD40 further increased the expression of these co-stimulatory molecules, as well as the secretion of IL-12. Mice immunized subcutaneously with DCs containing beads coated with HCV NS5 protein, anti-CD40 and LPS exhibited significant antigen-specific, increases in IFN-gamma-producing CD4(+) T cells and CTL activity. This approach combines three critical elements necessary for efficient DC-based immunization that include DC enrichment, maturation and antigen targeting.

Hepatitis B virus precore protein augments genetic immunizations of the truncated hepatitis C virus core in BALB/c mice

DNA immunization has been used to induce either humoral or cellular immune responses against many antigens, including hepatitis C virus (HCV). In addition, DNA immunizations can be enhanced or modulated at the nucleotide level. Genetic immunizations were examined in BALB/c mice through the use of plasmids and chimeric DNA constructs encoding HCV core proteins and hepatitis B virus (HBV) precore (preC) regions. Plasmids encoding the truncated HCV core induced potent humoral and cellular responses to HCV; pcDNA3.0A-C154 produced a stronger antibody response than pcDNA3.0A-C191 (P < 0.01) and pcDNA3.0A-C69 (P < 0.05). HBV preC enhanced the humoral and cellular immune responses of BALB/c mice to HCV; however, pcDNA3.0A-C69preC resulted in a weak cytotoxic T lymphocyte (CTL) response. In addition, the humoral and cellular immune responses to HCV of groups immunized with pcDNA3.0A-C154preC and pcDNA3.0A-C191preC plasmids were higher than those of groups immunized with pcDNA3.0A-C154 and pcDNA3.0A-C191. In vivo CTL responses verified that mice immunized with preC core fused DNAs showed significantly high specific lysis compared with mice immunized with HCV cores only (P < 0.01). In our study, pcDNA3.0A-C154preC led to the highest immune response among all DNA constructs.

CONCLUSION

DNA that encodes truncated HCV core proteins may lead to increased immune responses in vivo, and these responses may be enhanced by HBV preC.

Monocyte-derived dendritic cells from chronic HCV patients are not infected but show an immature phenotype and aberrant cytokine profile

BACKGROUND

Chronic hepatitis C virus (HCV) infection is characterized by an insufficient immune response, possibly owing to impaired function of antigen-presenting cells such as myeloid dendritic cells (DCs). Therapeutic vaccination with in vitro generated DCs may enhance the immune response. Subsets of DCs can originate from monocytes, but the presence of HCV in monocytes that develop into DCs in vitro may impair DC function. Therefore, we studied the presence of HCV RNA in monocytes and monocyte-derived DCs from chronic HCV patients.

METHODS

Monocytes were cultured with granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4) for 6 days, and then with GM-CSF, IL-4, tumour necrosis factor-alpha (TNF-alpha), prostaglandin E2, IL-1beta and IL-6 for 2 days to generate mature DCs. HCV RNA was assessed by polymerase chain reaction. Surface molecules were assessed by flow cytometry. Cytokine production was assessed by cytokine bead array.

RESULTS

HCV RNA was present in monocytes in 11 of 13 patients, but undetectable in mature DCs in 13 of 13 patients. The morphology of patient DCs was comparable with DCs from healthy controls, but the percentage of cells expressing surface molecules CD83 (P=0.001), CD86 (P=0.023) and human leucocyte antigen-DR (P=0.028) was lower in HCV patients. Compared with control DCs, patient DCs produced enhanced levels of IL-10 (P=0.0079) and IL-8 (P=0.0079), and lower levels of TNF-alpha (P=0.032), IL-6 (P=NS) and IL-1beta (P=0.0079). Patient and control DCs did not produce IL-12.

CONCLUSIONS

Monocyte-derived DCs from chronic HCV patients are not infected but show an immature phenotype and aberrant cytokine profile.

Dendritic cell function during chronic hepatitis C virus and human immunodeficiency virus type 1 infection

Hepatitis C virus (HCV) infection can persist despite HCV-specific T-cell immunity and can have a more aggressive course in persons coinfected with human immunodeficiency virus type 1 (HIV-1). Defects in antigen-presenting, myeloid dendritic cells (DCs) could underlie this T-cell dysfunction. Here we show that monocyte-derived DCs from persons with chronic HCV infection, with or without HIV-1 coinfection, being treated with combination antiretroviral therapy produced lower levels of interleukin 12 (IL-12) p70 in response to CD40 ligand (CD40L), whereas the expression of DC surface activation and costimulatory molecules was unimpaired. The deficiency in IL-12 production could be overcome by addition of gamma interferon (IFN-gamma) with CD40L, resulting in very high, comparable levels of IL-12 production by DCs from HCV- and HIV-1-infected subjects. Smaller amounts of IL-12 p70 were produced by DCs treated with the immune modulators tumor necrosis factor alpha and IL-1beta, with or without IFN-gamma, and the amounts did not differ among the uninfected and infected subjects. Blocking of IL-10 with an anti-IL-10 monoclonal antibody in the CD40L-stimulated DC cultures from HCV-infected persons increased the level of IL-12 p70 production. The ability of DCs from HCV-infected persons to stimulate allogeneic CD4+ T cells or induce IL-2, IL-5, or IL-10 in a mixed lymphocyte reaction was not impaired. Thus, myeloid DCs derived from persons with chronic HCV infection or with both HCV and HIV-1 infections have defects in IL-12 p70 production related to IL-10 activity that can be overcome by treatment of the DCs with CD40L and IFN-gamma. DCs from these infected subjects have a normal capacity to stimulate CD4+ T cells. The functional effectiveness of DCs derived from HCV-infected individuals provides a rationale for the DC-based immunotherapy of chronic HCV infection.

Chronic ethanol consumption impairs cellular immune responses against HCV NS5 protein due to dendritic cell dysfunction

BACKGROUND & AIMS

Alcoholic patients with and without chronic liver disease have a high incidence of infection with hepatitis C virus (HCV). Long-term ethanol consumption in mice has been associated with a strikingly reduced CD8(+) cytotoxic T-lymphocyte (CTL) response to HCV nonstructural proteins following DNA-based immunization. This study evaluated the effect of ethanol on dendritic cells (DCs) as a mechanism(s) for reduced CTL activity.

METHODS

Mice were fed an ethanol-containing or isocaloric pair-fed control diet for 8 weeks, followed by DC isolation from the spleen. DCs were evaluated with respect to endocytosis properties, cell surface markers, allostimulatory activity, and cytokine production following stimulation. Immune responses to HCV NS5 protein were generated by genetic immunization. Syngeneic transfer was used to determine if DC dysfunction contributed to abnormal cellular immune responses.

RESULTS

Long-term ethanol exposure resulted in a reduced number of splenic DCs but did not alter endocytosis capacity. There was an increase in the myeloid and a reduction in the lymphoid DC population. Ethanol reduced expression of CD40 and CD86 costimulatory molecules on resting DCs, which was corrected following stimulation with lipopolysaccharide or poly I:C. There was impaired allostimulatory activity. Cytokine profiles of DCs isolated from ethanol-fed mice were characterized by enhanced interleukin (IL)-1beta and IL-10 and decreased tumor necrosis factor alpha, IL-12, interferon gamma, and IL-6 secretion. Impaired CTL responses to NS5 were corrected by syngeneic transfer of control DCs.

CONCLUSIONS

Altered DC function is one of the major changes induced by long-term ethanol consumption, which subsequently impairs the cellular immune response necessary for viral clearance.