Expression of hepatitis C virus-derived core or NS3 antigens in human dendritic cells leads to induction of pro-inflammatory cytokines and normal T-cell stimulation capabilities

Therapeutic strategies and promising vaccine for hepatitis C virus infection

Hepatitis C virus (HCV) infection is still a significant global health problem despite therapeutic advancements. Ribavirin and interferon therapy have been the sole available treatments for HCV infection for a number of years with low efficacy. Thus, currently, a number of therapeutic strategies are being used, including nanoparticles (NPs), micro-RNAs such as small interfering RNA (siRNA), RNAi-based gene silencing and antisense oligonucleotide-based microRNA-122, microRNA-155, and short hairpin RNAs (shRNAs), and immunotherapeutic approaches such as anti-programmed cell death 1(PD-1), monoclonal antibodies (mAb or moAb), and monocyte-derived dendritic cells (Mo-DCs). Furthermore, direct-acting antivirals (DAAs) and host-targeting agents (HTA) were also the current therapeutic approaches with great efficacy. In spite of different clinical trials on HCV vaccine developments, nowadays there is no effective HCV vaccine in opposition to virus due to various challenges including genetic diversity, lack of immunocompetent small animal models, shortage of HCV vaccination testing alternatives, lack of an effective tissue culture method for replicating HCV, and inadequate knowledge regarding to immune responses against HCV infection. Nowadays, mRNA vaccine, recombinant viral vector, peptides vaccine, virus-like particles, DNA vaccine, rational designed vaccine, and recombinant polyantigenic T-cell-based vaccine are novel promising candidates for HCV vaccine based on various clinical trials. This review summarizes the different therapeutic approaches and the advancements of vaccine candidates for HCV infection.

Nanomedicine as a future therapeutic approach for Hepatitis C virus

Hepatitis C virus (HCV) is not easily cleared from the human body and in most cases turned into chronic infection. This chronicity is a major cause of liver damage, cirrhosis and hepatocellular carcinoma. Therefore, immediate detection and treatment of HCV guarantees eradication of the virus and prevention of chronicity complications. Since discovery of HCV in 1989, several emerging treatments were developed such as polyethylene glycol(PEG)-ylated interferon/ribavirin, direct acting antivirals and host targeting antivirals. Despite the progress in anti-HCV therapy, there is still a pressing need of new approaches for affordable and effective drug delivery systems using nanomedicine. In this review, the contribution of nanoparticles as a promising delivery system for HCV immunizing, diagnostic and therapeutic agents are discussed.

Heterologous Immunity between Adenoviruses and Hepatitis C Virus (HCV): Recombinant Adenovirus Vaccine Vectors Containing Antigens from Unrelated Pathogens Induce Cross-Reactive Immunity Against HCV Antigens

Host immune responses play an important role in the outcome of infection with hepatitis C virus (HCV). They can lead to viral clearance and a positive outcome, or progression and severity of chronic disease. Extensive research in the past >25 years into understanding the immune responses against HCV have still resulted in many unanswered questions implicating a role for unknown factors and events. In our earlier studies, we made a surprising discovery that peptides derived from structural and non-structural proteins of HCV have substantial amino acid sequence homologies with various proteins of adenoviruses and that immunizing mice with a non-replicating, non-recombinant adenovirus vector leads to induction of a robust cross-reactive cellular and humoral response against various HCV antigens. In this work, we further demonstrate antibody cross-reactivity between Ad and HCV in vivo. We also extend this observation to show that recombinant adenoviruses containing antigens from unrelated pathogens also possess the ability to induce cross-reactive immune responses against HCV antigens along with the induction of transgene antigen-specific immunity. This cross-reactive immunity can (a) accommodate the making of dual-pathogen vaccines, (b) play an important role in the natural course of HCV infection and (c) provide a plausible answer to many unexplained questions regarding immunity to HCV.

Defining a standard and weighted mathematical index for maturation of dendritic cells

The concept of dendritic cell (DC) maturation generally refers to the changes in morphology and function of DCs. Conventionally, DC maturity is based on three criteria: loss of endocytic ability, gain of high-level capacity to present antigens and induce proliferation of T cells, and mobility of DCs toward high concentrations of CCL19. Impairment of DC maturation has been suggested as the main reason for infectivity or chronicity of several infectious agents. In the case of hepatitis C virus, this has been a matter of controversy for the last two decades. However, insufficient attention has been paid to the method of ex vivo maturation as the possible source of such controversies. We previously reported striking differences between DCs matured with different methods, so we propose the use of a standard quantitative index to determine the level of maturity in DCs as an approach to compare results from different studies. We designed and formulated a mathematically calculated index to numerically define the level of maturity based on experimental data from ex vivo assays. This introduces a standard maturation index (SMI) and weighted maturation index (WMI) based on strictly standardized mean differences between different methods of generating mature DCs. By calculating an SMI and a WMI, numerical values were assigned to the level of maturity achieved by DCs matured with different methods. SMI and WMI could be used as a standard tool to compare diversely generated mature DCs and so better interpret outcomes of ex vivo and in vivo studies with mature DCs.

Co-incubation with core proteins of HBV and HCV leads to modulation of human dendritic cells

Hepatitis B and C (HBV and HCV) are hepatotropic viruses in humans with approximately 350 and 170 million chronic carriers respectively. Since both viruses have similar modes of transmission, many people are co-infected. Co-infection is common in intravenous drug users, HIV-positive individuals, and transplant recipients. Compared to mono-infected patients, co-infected patients exhibit exacerbated liver cirrhosis, hepatocellular carcinoma, and liver failure. Some of the pathogenic effects may be attributed in part to the structural core proteins of both viruses-ones that have displayed immunomodulatory properties. Yet, the effects of their combined interaction on the human immune system remain a mystery. We aimed to elucidate the combined effects of HBV and HCV core proteins on human dendritic cells' (DCs) ability to present antigens and stimulate antigen-specific T-cells. We observed that when DCs, differentiated from human peripheral blood monocytes, were co-incubated with both core proteins, IL-10 production was dramatically enhanced, IL-6, TNF-α, and IL-12 production was significantly reduced, and HLA-DR expression was downregulated. This instant functional and phenotypic modulation of DCs induced by a combination of HBV and HCV core proteins can allow them to behave like tolerizing DCs, inefficiently presenting antigens to CD4+ T-cells and even suppressing induction of the cellular immune response. These results reveal an important mechanism by which HBV and HCV synergistically induce immune tolerance early in infection that may be instrumental in establishing chronic, persistent infections.

Alternate reading frame protein (F protein) of hepatitis C virus: paradoxical effects of activation and apoptosis on human dendritic cells lead to stimulation of T cells

Hepatitis C virus (HCV) leads to chronic infection in the majority of infected individuals due to lack, failure, or inefficiency of generated adaptive immune responses. In a minority of patients, acute infection is followed by viral clearance. The immune correlates of viral clearance are not clear yet but have been extensively investigated, suggesting that multispecific and multifunctional cellular immunity is involved. The generation of cellular immunity is highly dependent upon how antigen presenting cells (APCs) process and present various viral antigens. Various structural and non-structural HCV proteins derived from the open reading frame (ORF) have been implicated in modulation of dendritic cells (DCs) and APCs. Besides the major ORF proteins, the HCV core region also encodes an alternate reading frame protein (ARFP or F), whose function in viral pathogenesis is not clear. In the current studies, we sought to determine the role of HCV-derived ARFP in modulating dendritic cells and stimulation of T cell responses. Recombinant adenovirus vectors containing F or core protein derived from HCV (genotype 1a) were prepared and used to endogenously express these proteins in dendritic cells. We made an intriguing observation that endogenous expression of F protein in human DCs leads to contrasting effects on activation and apoptosis of DCs, allowing activated DCs to efficiently internalize apoptotic DCs. These in turn result in efficient ability of DCs to process and present antigen and to prime and stimulate F protein derived peptide-specific T cells from HCV-naive individuals. Taken together, our findings suggest important aspects of F protein in modulating DC function and stimulating T cell responses in humans.

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.

Vaccination with dendritic cells pulsed with hepatitis C pseudo particles induces specific immune responses in mice

AIM

To explore dendritic cells (DCs) multiple functions in immune modulation.

METHODS

We used bone-marrow derived dendritic cells from BALB/c mice pulsed with pseudo particles from the hepatitis C virus to vaccinate naive BALB/c mice. Hepatitis C virus (HCV) pseudo particles consist of the genotype 1b derived envelope proteins E1 and E2, covering a non-HCV core structure. Thus, not a single epitope, but the whole "viral surface" induces immunogenicity. For vaccination, mature and activated DC were injected subcutaneously twice.

RESULTS

Humoral and cellular immune responses measured by enzyme-linked immunosorbent assay and interferon-gamma enzyme-linked immunosorbent spot test showed antibody production as well as T-cells directed against HCV. Furthermore, T-cell responses confirmed two highly immunogenic regions in E1 and E2 outside the hypervariable region 1.

CONCLUSION

Our results indicate dendritic cells as a promising vaccination model for HCV infection that should be evaluated further.

Hepatitis C virus modulates human monocyte-derived dendritic cells

This study is to examine the monocyte-derived dendritic cell (DC) response to hepatitis C virus (HCV) in a cell culture system. Adherence-derived DCs were incubated with various titres of JFH-1 (HCV genotype 2a), generated from transfected Huh 7.5 cells or co-incubated with Newcastle disease virus (NDV). Infection and the type 1 interferon (IFN) response were assessed by real-time reverse transcriptase-polymerase chain reaction, morphology by light microscopy and immunophenotype by flow cytometry. Our data demonstrated no viral replication or particle release from DC after HCV infection. Morphologically, monocytes showed a tendency to shift to immature DCs when cultured with HCV, when compared with control monocytes. This shift was confirmed by flow cytometry and appeared to be related to viral titres. There was also an increase in immature DC numbers. HCV infection induced IFNβ expression in DCs, and the amount seemed to be inversely correlated with viral titres indicating that HCV has the capacity to negatively regulate such cells. However, IFNα does not appear to be affected by direct contact with the virus. A strong IFNβ signal induced by NDV in DC was substantially diminished by HCV. HCV negatively affects the maturation of DCs and suppresses the type 1 IFN response of DC. Our results suggest a mechanism of viral evasion of host immunity.

Immunomodulation by hepatitis C virus-derived proteins: targeting human dendritic cells by multiple mechanisms

Hepatitis C virus (HCV) has the ability to persist in the majority of infected people. Strong, multispecific and sustained T-cell response is correlated with viral clearance. The mechanisms of chronicity by HCV are unclear. HCV could restrain the immune system and establish chronic infection by modulating dendritic cell (DC) function, T-cell function or both. DC dysfunction has been postulated to be either due to direct HCV infection or by the presence of HCV proteins. In this report, for the first time, we have examined whether soluble HCV proteins can impair DC function or directly inhibit T-cell responses in the cells obtained from healthy uninfected people. Our studies revealed that different HCV proteins used distinct mechanisms to down-regulate DC functions. Individual HCV proteins, Core, NS3, NS4, NS5 as well as fused Polyprotein (Core-NS3-NS4) were found to impair functions of both immature DCs and mature DCs by regulating the expression of co-stimulatory and antigen presentation molecules, strikingly reducing IL-12 secretion, inducing the expression of FasL to mediate apoptosis, interfering with allo-stimulatory capacity, inhibiting toll-like receptor signaling and inhibiting nuclear translocation of NFkappaB in DCs. Interestingly, HCV proteins did not directly inhibit T-cell proliferation. Our findings clearly demonstrate that HCV proteins impair T-cell responses indirectly by inhibiting DCs that could result in a sub-optimal cellular immune response allowing for persistent HCV infections. These studies delineate important mechanisms by which initial DC dysfunction can establish contributing to chronicity. Our data are in agreement with earlier observations that DCs are impaired in HCV infected people.

HCV-core and NS3 antigens play disparate role in inducing regulatory or effector T cells in vivo: Implications for viral persistence or clearance

A distinguishing feature of HCV is its ability to persist in majority of the infected people. We investigated the role of HCV-core and NS3 in inducing effector T cells to mediate antiviral immunity. Our studies revealed that immunization with recombinant adenoviral vector containing HCV-core or NS3 leads to differential development of regulatory vs. effector T cells in mice, resulting in distinct outcomes of virus infection. For the first time, our studies directly demonstrate that HCV-core enhances both CD4(+) and CD8(+) T(regs) which possibly contribute to persistent infection, whereas HCV NS3 induces both CD4(+) and CD8(+) effector T cells to allow viral clearance.

Early viraemia clearance during antiviral therapy of chronic hepatitis C improves dendritic cell functions

Plasma and cellular HCV RNA and core antigen were tested in monocyte-derived DC (MDDC) from chronic hepatitis C patients undergoing treatment with peg-interferon alpha2b/ribavirin. DC allostimulatory capacity, HCV-specific T-cell reactivity and IL-12 production were measured at baseline and treatment week (TW)12. Using DC and autologous CD4(+)T-cells, obtained at baseline and TW12, we performed cross-over experiments to determine the relative role of DC and/or T-cells for impaired immune reactivity to HCV. HCV RNA and HCV core plasma levels had an impact on DC phenotype and allostimulatory capacity. In contrast, HCV genome/core protein, although detectable in DC from some patients had no effect on DC function. Antiviral immunity at TW12 was not improved in patients who remained HCV RNA positive, while early viraemia clearance (TW12) improved antiviral responses. The cross-over experiment revealed that changes in DC, rather than CD4(+)T cells have a major role for enhanced anti-HCV responses.

Decreased interferon-alpha production and impaired regulatory function of plasmacytoid dendritic cells induced by the hepatitis C virus NS 5 protein

pDC are known to produce large amount of IFN-alpha/beta in response to viruses, and act as a major link between the innate and adaptive immune response. This study concentrated on the interaction of human peripheral blood derived pDC with HCV NS3, NS4, and NS5 proteins, and their maturation, cytokine secretion and functional properties. It was shown that HCV NS5 interferes with CD40L induced maturation of pDC as indicated by decreased expression of CD83 and CD86 markers. CpG ODN stimulated HCV NS3 and NS5 treated pDC showed decreased production of IFN-alpha. In the case of NS3, IFN-alpha production was reduced to 126 pg/ml as compared to 245 pg/ml in controls (P < 0.01), and with NS5, IFN-alpha production was reduced to 92 pg/ml as compared to 238 pg/ml in controls (P < 0.05). In the presence of HCV NS5, the T cell stimulatory capacity of pDC was impaired, as indicated by decreased proliferation of T cells, and decreased production by the T cells of IFN-gamma, which were down to 86 pg/ml as compared to 260 pg/ml in controls (P < 0.05). These results suggest that HCV NS5 impairs pDC function and is in agreement with several other in vivo studies indicating decreased numbers of, and dysfunctional pDC, in chronic HCV infected patients.

Immune responses in hepatitis C virus infection and mechanisms of hepatitis C virus persistence

Immune responses against hepatitis C virus (HCV) play a crucial role in the pathogenesis of chronic hepatitis C. HCV infection often persists and leads to chronic hepatitis and eventually cirrhosis. Accumulated data suggest that HCV proteins suppress host immune responses through the suppression of functions of immune cells, such as cytotoxic T lymphocytes, natural killer cells, and dendritic cells. They also suppress the type 1 interferon signaling system. The resulting insufficient immune responses against HCV lead to the sustained infection. The appropriate control of immune responses would contribute to the eradication of HCV and the improvement of hepatitis, but there are still many issues to be clarified. This review describes the scientific evidence to support these emerging concepts, and will touch on the implications for improving antiviral therapy.

The functional evaluation of dendritic cell vaccines based on different hepatitis C virus nonstructural genes

Hepatitis C virus (HCV) nonstructural (NS) genes are relatively conserved and play critical roles in cellular immune responses against HCV. The aim of the study was to evaluate the immunogenicity of the different HCV NS genes through transduction of DCs and presentation to T cells. Monocyte-derived DCs from healthy donors were infected with the recombinant adenovirus (Ad) harboring HCV NS3 (AdNS3), NS4 (NS4A and NS4B; AdNS4), NS5 (NS5A and NS5B; AdNS5), NS3/NS4 (AdNS3/NS4), and NS4/NS5 (AdNS4/NS5) genes, and then used to stimulate autologous lymphocytes in vitro. Antigen-specific cellular immune responses were detected by interferon-gamma (IFN-gamma), interleukin 4 (IL-4), and Granzyme B (GrB) enzyme-linked immunospot assays (ELISPOT). DCs expressing different HCV NS genes all induced positive immune responses. Furthermore, DCs transfected with AdNS3/NS4 were superior to DCs infected with AdNS3 or AdNS4 in inducing HCV-specific immunity. The same results were obtained when we compared DCs infected with AdNS4/NS5 to AdNS4 or AdNS5. DCs transduced with NS3/NS4 or NS4/NS5 had similar ability to elicit specific immune responses to HCV.

Review article: vaccination and viral hepatitis - current status and future prospects

BACKGROUND

Viral hepatitis is the most common cause of liver disease in the world. In the past 25 years, vaccines have become available for two of the five hepatitis viruses, and, where implemented, vaccination has become a key component of hepatitis prevention.

AIMS

To provide an update on recent advances in the use of current hepatitis vaccines and to examine progress in the development of vaccines for the remaining hepatitis viruses.

METHODS

A Medline search was undertaken to identify the recent relevant literature. Search terms included hepatitis vaccines, hepatitis vaccination and hepatitis A-E vaccines.

RESULTS

Dramatic vaccine-induced declines in the incidence of both hepatitis A and B have occurred in the USA. Strategies to integrate hepatitis A vaccine into universal childhood immunization are being adopted. Similarly, strategies with the goal of eliminating transmission of hepatitis B have been promulgated. A vaccine for hepatitis E has been reported to be effective and safe, but progress in the development of vaccines for hepatitis C and D has been limited.

CONCLUSION

During the next few decades, the goals of eliminating hepatitis A and B virus transmission may be reached in the USA and elsewhere.

Expression of the alternative reading frame protein of Hepatitis C virus induces cytokines involved in hepatic injuries

Hepatitis C virus (HCV) Core has been implicated in immune-mediated mechanisms associated with the development of chronic hepatic diseases. Discovery of different alternative reading frame proteins (ARFPs) expressed from the HCV Core coding sequence challenges properties assigned to Core. This study was designed to evaluate the immunomodulatory functions of Core and ARFPs in monocytes, dendritic cells (DCs), macrophages (Mphi) and hepatocytes, cells that are all capable of supporting HCV replication. THP-1 cells, monocyte-derived Mphi and DCs, and Huh7 cells were infected by using adenoviruses (Ad) encoding Core, CE1E2 and a Core sequence modified so that the Core protein is wild type, but no ARFPs are expressed (CDeltaARFP). THP-1 cells and DCs infected with Ad encoding Core or CE1E2 produced significant levels of interleukin-6 (IL-6), IL-8, MCP-1 and MIP-1beta, whereas production of these chemokines with AdCDeltaARFP was reduced or abolished. Similar effects on IL-8 production were observed in Huh7 cells and on IL-6 and MIP-1beta in Mphi. Wild-type Core sequence, but not CDeltaARFP, could trans-activate the IL-8 promoter and this activation was not associated with activation of p38/p42-44MAPK. This study illustrates, for the first time, the critical importance of ARFP expression in immunomodulatory functions attributed to Core expression and suggests a potential involvement of ARFP in mechanisms associated with HCV pathogenesis.

HCV immunopathogenesis: virus-induced strategies against host immunity

Worldwide more than 170 million people are chronically infected with the hepatitis C virus (HCV), which is a frequent cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Unlike infection with other hepatotropic viruses, only a small percentage of acute HCV infections are cleared, and most infected individuals develop lifelong HCV infection in the absence of efficient treatment. It is believed that both viral and host factors contribute to the inability of the host immune system to clear the initial infection and lead to the high propensity of chronic HCV infection.

Induction of Primary Human T Cell Responses against Hepatitis C Virus-Derived Antigens NS3 or Core by Autologous Dendritic Cells Expressing Hepatitis C Virus Antigens: Potential for Vaccine and Immunotherapy

Hepatitis C virus (HCV)-specific T cell responses have been suggested to play significant role in viral clearance. Dendritic cells (DCs) are professional APCs that play a major role in priming, initiating, and sustaining strong T cell responses against pathogen-derived Ags. DCs also have inherent capabilities of priming naive T cells against given Ags. Recombinant adenoviral vectors containing HCV-derived Core and NS3 genes were used to endogenously express HCV Core and NS3 proteins in human DCs. These HCV Ags expressing DCs were used to prime and stimulate autologous T cells obtained from uninfected healthy donors. The DCs expressing HCV Core or NS3 Ags were able to stimulate T cells to produce various cytokines and proliferate in HCV Ag-dependent manner. Evidence of both CD4(+) and CD8(+) T cell responses against HCV Core and NS3 generated in vitro were obtained by flow cytometry and Ab blocking experiments. Further, in secondary assays, the T cells primed in vitro exhibited HCV Ag-specific proliferative responses against recombinant protein Ags and also against immunodominant permissive peptide epitopes from HCV Ags. In summary, we demonstrate that the dendritic cells expressing HCV Ags are able to prime the Ag-specific T cells from uninfected healthy individuals in vitro. These studies have implications in designing cellular vaccines, T cell adoptive transfer therapy or vaccine candidates for HCV infection in both prophylactic and therapeutic settings.

Hepatitis C virus core protein: an update on its molecular biology, cellular functions and clinical implications

The present review article is an update on various features of hepatitis C virus (HCV) core protein including its molecular biology, role in HCV replication, involvement in HCV pathogenesis, etiological role in hepatocellular carcinogenesis, significance in diagnosis and vaccination against HCV infection. Core protein is a structural protein of HCV virus and has only recently been characterized. It was found to play a major role in HCV-induced viral hepatitis. Although published information shows a lot about the clinical significance of HCV core protein, several studies are still needed to demonstrate its exact significance in viral biology and underlying HCV pathogenesis.