Gastroenterology

Gastroenterology

Volume 122, Issue 2, February 2002, Pages 352-365
Gastroenterology

Basic Research
Steatosis and liver cancer in transgenic mice expressing the structural and nonstructural proteins of hepatitis C virus☆,☆☆,★,★★

https://doi.org/10.1053/gast.2002.31001Get rights and content

Abstract

Background and Aims: The aim of this study was to determine whether expression of hepatitis C virus proteins alters hepatic morphology or function in the absence of inflammation. Methods: Transgenic C57BL/6 mice with liver-specific expression of RNA encoding the complete viral polyprotein (FL-N transgene) or viral structural proteins (S-N transgene) were compared with nontransgenic littermates for altered liver morphology and function. Results: FL-N transcripts were detectable only by reverse-transcription polymerase chain reaction, and S-N transcripts were identified in Northern blots. The abundance of viral proteins was sufficient for detection only in S-N transgenic animals. There was no inflammation in transgenic livers, but mice expressing either transgene developed age-related hepatic steatosis that was more severe in males. Apoptotic or proliferating hepatocytes were not significantly increased. Hepatocellular adenoma or carcinoma developed in older male animals expressing either transgene, but their incidence reached statistical significance only in FL-N animals. Neither was ever observed in age-matched nontransgenic mice. Conclusions: Constitutive expression of viral proteins leads to common pathologic features of hepatitis C in the absence of specific anti-viral immune responses. Expression of the structural proteins enhances a low background of steatosis in C57BL/6 mice, while additional low level expression of nonstructural proteins increases the risk of cancer.

GASTROENTEROLOGY 2002;122:352-365

Section snippets

Production of transgenic mice

The plasmid pGEMAlbSVPA-B1(−) contains the murine albumin enhancer/promoter30 with a downstream SV40 intron/polyadenylation cassette. Complementary DNA (cDNA) corresponding to the full-length polyprotein-coding region (core to NS5B, nts 342–9378) or the structural protein-coding region only (core to E2/p7, nts 342–2771) of the genotype 1b, HCV-N strain of HCV31, 32 was inserted into this vector between newly engineered XhoI sites flanking the albumin enhancer/promoter and SV40 sequence,

Transgene expression in FL-N and S-N transgenic mice

Transgenic mice were designed to express either the full-length HCV-N open reading frame (FL-N) or the segment encoding the structural proteins only (S-N: core and the 2 envelope proteins, E1 and E2-p7; Figure 1).

. Hepatitis C transgene organization. (A) The HCV open reading frame within the FL-N transgene encodes the entire polyprotein of a genotype 1b strain of HCV. (B) The S-N transgene encodes the amino third of the polyprotein and thus expresses only the structural proteins core, E1, and

Discussion

The HCV-transgenic mice that we have derived constitutively express low levels of RNA encoding the complete viral polyprotein, or higher levels of the RNA segment encoding only the structural proteins of the virus, under control of a liver-specific promoter. Protein expression was confirmed directly only in the mice expressing the structural region of the polyprotein and was insufficient for detection even with sensitive immunohistochemical techniques in mice with the full-length reading frame

Acknowledgements

The authors thank Annette Martin for critically reviewing the manuscript, Brian West for assistance in the interpretation of histopathology, Elbert Whorton for assistance with statistical analysis, and Li-Hua Ping and Geneviêve Inchauspé for generously providing HCV-specific antibodies.

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    ☆

    Address requests for reprints to: Stanley M. Lemon, M.D., Department of Microbiology and Immunology, The University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-1019. e-mail: [email protected]; fax: (409) 772-3757.

    ☆☆

    Dr. Lerat's present address: Institut de Génétique Moléculaire, CNRS, Montpellier, France. Dr. Gosert's present address: Institute for Medical Microbiology, University of Basel, Basel, Switzerland.

    ★

    Supported in part by the National Institute of Allergy and Infectious Diseases (U19-AI40035). H.L. was the recipient of a McLaughlin Fellowship from the University of Texas Medical Branch.

    ★★

    Drs. Lerat and Honda contributed equally to this work.

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    Copyright © 2002 American Gastroenterological Association. Published by Elsevier Inc. All rights reserved.