Priming of hepatitis C virus-specific cytotoxic t lymphocytes in mice following portal vein injection of a liver-specific plasmid DNA

Abstract

The immunology of hepatitis C virus (HCV) infection should be studied in the context of HCV antigen expression in the liver, because HCV primarily infects this organ. Indeed, the nature, function, and fate of T cells primed after antigen expression in the liver might differ from those primed when antigens are expressed systemically or in other organs, because the nature of the antigen-presenting cells (APCs) involved may be different. In addition, the normal liver contains a resident population of lymphocytes that differ from those present at other sites. Thus, we investigated whether HCV-specific CD8 ؉ cytotoxic T cells (CTLs) could be elicited following portal vein (PV) injection of plasmid DNA in mice whose hepatic veins were transiently occluded. We show that PV injection of mice with ''naked'' DNA expressing the HCV-NS5a protein, under the control of a liver-specific enhancer/promoter, resulted in NS5a expression in the liver and the priming of HCVspecific CTLs. These results suggested that such a model might be relevant to the study of HCV-specific immune responses primed during natural infection. (HEPATOLOGY 2000;31:1327-1333.)Hepatitis C virus (HCV), a positive-strand RNA virus member of the Flaviviridae family, 1 is recognized as a major public health concern. In addition to being one of the leading causes of chronic liver disease, 2 chronic HCV infection has been associated with autoimmune syndromes, immune complex disorders, and mixed cryoglobulinemia. 3,4 One of the most striking features of HCV is that it seems able, in most instances, to circumvent eradication by the immune system. It is estimated that up to 75% of patients infected with HCV become chronically infected, 2,5-7 despite the fact that most patients generate HCV-specific antibody, [8][9][10][11][12] as well as CD4 ϩ and CD8 ϩ T-cell responses. [13][14][15][16] On the other hand, there is evidence that humoral and T-cell-mediated immune responses to HCV infection can, at least in some instances, determine the outcome of HCV infection and disease. [17][18][19][20] In spite of recent progress in the management of chronic HCV disease, the current therapies for chronic HCV infection often do not result in viral clearance. 21,22 Thus, there is a growing interest in developing immune-based therapies for HCV. To develop such therapies, one must understand the immune responses to HCV infection, because they should provide insight into the mechanisms involved in limiting HCV replication in infected hosts. Despite the fact that substantial efforts have been made to decipher the immunology of HCV infection, it remains poorly understood. The main factors responsible for the relatively slow progress in this field are the unavailability of a small animal model for infection and disease, and inefficient systems for cultivating the virus. Because acute hepatitis in humans has been difficult to study, most attempts aimed at clarifying the immune responses to HCV have been conducted in patients with chronic hepatitis or in chimpanzees, the only reliable a...

Recently primed CD8+ T cells entering the liver induce hepatocytes to interact with naïve CD8+ T cells in the mouse

“…This has been described in systems in which HCs presented antigen to naïve or activated CD8 ϩ T cells. [27][28][29] Other data suggest that HCs can prime CD8 ϩ T cell responses in vivo, 30,31 but the difference between the HC and the HC* phenotype was not accounted for in these studies. Distinguishing HCs* and HCs may resolve some conflicting data in the field.…”

Identification of Immunodominant Hepatitis C Virus (Hcv)–Specific Cytotoxic T–Cell Epitopes by Stimulation With Endogenously Synthesized Hcv Antigens

“…Experimental strategies similar to that described in the present report were applied to study antigen-specific cytotoxic activity in animal models, and to analyze CTL responses to melanoma-associated antigens and to other viral proteins in humans. [18][19][20][21][22][23][38][39][40][41][42] Recently, Wong et al reported the successful use of vaccinia vectors to expand HCV-specific CTL from the peripheral blood of patients with chronic HCV infection. 43 These results extend the finding of a previous report 16 based on a single patient with acute hepatitis C, but confirm the potential problem of this approach caused by simultaneous exposure of PBMC to vaccinia virus antigens and EBV antigens (vaccinia-infected EBV-immortalized B cells being used in such a system both as stimulators of PBMC expansion and as targets for analysis of cytotoxic activity) that can determine the expansion of vaccinia-and EBV-specific CTL together with HCV-specific CTL.…”

“…Recombinant viruses and plasmids encoding viral genes represent a particularly promising approach to induce antibody-and cellmediated immune responses, and they have recently been used for in vivo immunization against HCV. [18][19][20][21][22][23] These vectors allow the endogenous synthesis of viral antigens to occur inside human cells, thereby creating the conditions for natural cytosolic generation of viral peptides, their transport to the lumen of the endoplasmic reticulum, binding to HLA class I molecules, and presentation on the cell surface. In this study, we describe the use of 4 adenoviruses carrying the core, core-E1-E2, E2, NS3-NS4A, or NS3-NS5A genes to stimulate cytotoxic T cells in vitro.…”

Treatment of hepatocellular carcinoma

“…For the prevention of HCV infection, however, there is no effective vaccine available to date. While several HCV vaccination concepts are being evaluated, including HCV proteins, 80 HCV-like particles 81 as well as intravenous, intrahepatic, intra-epidermal, intramuscular or oral cDNA immunisation, [82][83][84][85][86] it is not to be expected that a vaccine against HCV infection will become commercially available within the next few years.…”