Type 2 autoimmune hepatitis murine model: The influence of genetic background in disease development

https://doi.org/10.1016/j.jaut.2005.11.001Get rights and content

Abstract

Genetic predisposition is recognized as an important factor for the development of autoimmune hepatitis (AIH). To assess the potential contribution of MHC and non-MHC genes, type 2 AIH was reproduced in three mice strains, taking advantage of their different genetic makeup with regard to MHC and non-MHC genes. Mice (C57BL/6, 129/Sv and BALB/c) were DNA vaccinated with a pCMV-CTLA4-CYP2D6-FTCD plasmid coding for the extracellular region of CTLA-4 and for the antigenic region of the CYP2D6 and FTCD, and with pCMV-IL12. ALT and total IgG levels, liver histology, FACS analysis and liver T-cell cytotoxicity assays were monitored up to 8 months post-injection. C57BL/6 mice showed elevated serum ALT levels, autoantibodies, antigen-specific cytotoxic T-cells and lobular and periportal inflammatory infiltrate. The 129/Sv mice showed slightly elevated ALT levels, sparse liver lobular infiltrate and cytotoxic T-cells. The BALB/c mice showed no liver inflammation. All mice had elevated total serum IgG levels. This murine model of type 2 AIH shows that MHC and non-MHC genes contribute to the susceptibility to autoimmune hepatitis. The understanding of the genetic determinants implicated in AIH development will be a major advance in the study of its pathogenesis and could lead to a better diagnostic approach and preventive strategies.

Introduction

Autoimmune hepatitis (AIH) is a disease of unknown aetiology characterized by a progressive destruction of the hepatic parenchyma by the immune system [1], [2], [3]. Progression to cirrhosis and end stage liver disease may occur in 10–20% of cases and liver transplantation may be necessary [1], [3], even when the appropriate available treatment is administered. Particular characteristics of this disease are the presence of a hypergammaglobulinemia and circulating autoantibodies. These autoantibodies allowed the classification of AIH into two types. Type 1 is characterized by the presence of anti-smooth muscle and/or anti-nuclear antibodies, whereas type 2 shows anti-liver kidney microsomal type 1 and/or anti-liver cytosol type 1 antibodies [4], [5], [6]. Previous work has shown that the targets of LKM1 and LC1 antibodies are cytochrome P-450 2D6 (CYP2D6) [7], and formiminotransferase cyclodeaminase (FTCD) [8], respectively; both autoantigens are mainly expressed in hepatocytes [9], [10].

A model of type 2 autoimmune hepatitis using xenoimmunization with human CYP2D6 and FTCD antigens of wild-type C57BL/6 mice was recently developed in our laboratory [11]. These mice showed an increase of serum alanine aminotransferase (ALT) levels, circulating anti-LKM1 and anti-LC1 autoantibodies associated with massive infiltration of the liver by lymphocytes. This model is particularly appropriate for the study of the influence of the genetic background on the development of the disease. Susceptibility to autoimmune hepatitis in humans has been shown to be related to both the MHC haplotype and to non-MHC genes [12], [13], [14], [15], [16]. Further studies have implicated different loci with either type 1 or type 2 autoimmune hepatitis [17], [18], [19], [20].

To evaluate the importance of the genetic background on the development of AIH and to further validate our animal model of type 2 AIH, we have compared the susceptibility of three mouse strains displaying similar or different MHC and non-MHC genes to develop a type 2 AIH.

Section snippets

DNA vaccination

The DNA vaccination was done using the pRc/CMV-CTLA-4-CYP2D6-FTCD vector as described [11] along with pVR-IL12 plasmid (kindly provided by G. Prud’homme, Montreal, Canada). All the plasmids were propagated in E. coli by standard techniques and purified using QIAGEN Endofree Plasmid Giga Kit (QIAGEN, Santa Clarita, CA), according to the manufacturer's guidelines.

C57BL/6, BALB/c and 129/Sv mice were used due to their different genetic makeup (Table 1). In mouse, the H-2 denomination refers to

Alanine aminotransferase and total IgG levels

Serum ALT levels were used to monitor disease activity. As opposed to the other two strains, the C57BL/6 mice showed abnormal ALT levels by 3 months post-injection (Fig. 1). These elevated levels were maintained throughout the 7 month study. As was previously reported [11], 60% of C57BL/6 mice developed an AIH following peripheral plasmids vaccination; the others were considered non-responders. Total IgG levels show a statistically significant elevation for the 129/Sv and BALB/c strains while

Discussion

This study clearly shows that both MHC and non-MHC genes contribute to the development of type 2 autoimmune hepatitis in this murine model. The clear difference observed in both disease occurrence and intensity in the various strains (as summarized in Table 1) highlights the importance of the genetic makeup in the development of AIH. These observations show that the genetic susceptibility is based on both a particular MHC and non-MHC background. This suggests that a class II MHC haplotype (H-2b

Acknowledgments

The authors wish to thank Professor Claude C. Roy, MD, for critical reading. We are grateful to Ms. Troesch for the FACS analysis. This work was supported by the Canadian Institutes of Health Research grant (mop_36524) to F.A.

References (32)

  • A.C. Chernavsky et al.

    Simultaneous expression of Th1 cytokines and IL-4 confers severe characteristics to type I autoimmune hepatitis in children

    Hum Immunol

    (2004)
  • M.S. Longhi et al.

    Impairment of CD4(+)CD25(+) regulatory T-cells in autoimmune liver disease

    J Hepatol

    (2004)
  • H.R. Haghighi et al.

    Assessment in mice of vapA-DNA vaccination against Rhodococcus equi infection

    Vet Immunol Immunopathol

    (2005)
  • F. Alvarez

    Autoimmune hepatitis

  • E.L. Krawitt

    Autoimmune hepatitis

    N Engl J Med

    (1996)
  • E. Martini et al.

    Antibody to liver cytosol (anti-LCI) in patients with autoimmune chronic active hepatitis type 2

    Hepatology

    (1988)

    • Cited by (0)

    View full text
    Copyright © 2005 Elsevier Ltd. All rights reserved.