Hepatitis C Virus Core and E2 Protein Expression in Transgenic Mice

Abstract

to other flaviviruses. [12][13][14][15] Recently it was demonstrated that Transgenic mice have been produced that express the HCV core can form homodimers and probably multimers 16 hepatitis C virus (HCV) core protein in the liver under similar to the nucleocapsid proteins of retroviruses 17,18 and the transcriptional control of the mouse major urinary HBV. 19,20 In vitro expression of HCV core in different cell protein promoter. These animals express the full length lines has generated conflicting data in terms of protein size, core protein in cytoplasm of their hepatocytes at levels posttranslational modification, and subcellular localizacomparable to those detected in naturally infected pation. 12,15,21,22 [25][26][27][28][29] They are both believed to be that it inhibits HBV replication in HuH-7 cells after trantransmembrane glycoproteins, with C-terminal hydrophobic sient transfection in vitro. We have also produced anchors. After synthesis and glycosylation, E1 and E2 fold transgenic mice in which a C-terminally truncated and associate primarily through noncovalent interactions (aa384-715) glycosylated HCV E2 protein is expressed in with a slow kinetics as shown in vitro by pulse-chase experithe liver under the transcriptional control of the mouse ments. 30 The HCV glycoproteins are predominantly localized albumin promoter. Despite the high level expression of in the endoplasmic reticulum (ER) and are not translocated HCV E2 protein, no evidence of liver disease was debeyond the cis Golgi. 28,30 Purified E1E2 oligomers have been tected in these animals. These results suggest that the used to successfully immunize chimpanzees against chal-HCV core and E2 proteins are not cytopathic for the lenge with low doses of homologous HCV-1, 31 but it is not hepatocyte in vivo, and they represent an initial step in known if the protection is mediated by neutralizing antibodthe development of a small animal model of HCV immuies or other immune mechanisms. nopathology. (HEPATOLOGY 1997;25:719-727.)In the absence of an efficient cell culture system and convenient animal models to study HCV pathogenesis, we have Hepatitis C virus (HCV) is a parenterally transmitted hep-produced transgenic mice in which HCV core and HCV E2 atotropic virus that, like hepatitis B virus (HBV), causes are expressed in the liver under the control of the developacute and chronic hepatitis and hepatocellular carcinoma. [1][2][3][4] mentally regulated, liver-specific mouse major urinary pro-HCV is a positive stranded RNA virus whose genome (about tein (MUP) and constitutively active mouse albumin (ALB) 9.6 kb) contains a single uninterrupted open reading frame promoters. The characteristics of these animals form the ba-(ORF) that encodes a polyprotein of 3010-3011 amino sis for the current report. acids. 1,[5][6][7][8] In vitro studies have demonstrated that the polyprotein is processed by cellular and viral proteases to produce MATERIALS AND METHODSat least ten different viral structural and nonstructural proteins, whose order is C-E1-E2-E2/p7...

Transgenic models for Hepatitis C virus pathogenesis

“…In a similar transgenic line, reported by Honda et al 12 a major consequence of core expression was a modification in the Fas-induced apoptotic response, but no liver morphological alterations in untreated animals were described. Finally, no liver pathology was observed in the HCV core transgenic mice reported by Pasquinelli et al 13 It is worth noting that similar contradictory results, in terms of modulation of cellular proliferation, transformation and have also been reported in cell culture system apoptotis. 14 Transgenic animals carrying HCV sequences coding for other structural proteins were also generated.…”

Hepatitis C virus acts as a tumor accelerator by blocking apoptosis in a mouse model of hepatocarcinogenesis

“…Among HCV transgenic mice without tumor phenotype, two models expressing core have been reported by Pasquinelli et al 10 and our group. 2 Neither model showed histologically recognizable steatosis, adenoma, or HCC.…”

Signal transduction cascades and hepatitis B and C related hepatocellular carcinoma

“…Nuclear localization of core protein was observed in the livers of the older, cancer-prone transgenic mice studied by Koike et al, 124 while this was a rare finding in the younger transgenic mice studied by Kawamura et al 127 The transgenic mice studied by Pasquinelli et al exhibited core protein in the cytoplasm fraction only by Western blot analysis; none was observed in nuclear extracts. 128 In fact, core protein was not detected by immunohistochemical staining of liver sections. Therefore, it is possible that the contradictory observations regarding tumorogenesis in HCV core transgenic mice reported in these studies are the result of differences in core protein expression and nuclear localization where it may function as a transcription factor.…”

“…124,126 However, a different study by Pasquinelli et al also observed "no significant liver injury" in transgenic mice expressing HCV core protein up to 18 months of age. 128 Nuclear translocation of the core protein may be important in hepatocyte transformation. Nuclear localization of core protein was observed in the livers of the older, cancer-prone transgenic mice studied by Koike et al, 124 while this was a rare finding in the younger transgenic mice studied by Kawamura et al 127 The transgenic mice studied by Pasquinelli et al exhibited core protein in the cytoplasm fraction only by Western blot analysis; none was observed in nuclear extracts.…”