Immunization with a Recombinant Vaccinia Virus That Encodes Nonstructural Proteins of the Hepatitis C Virus Suppresses Viral Protein Levels in Mouse Liver

Satoshi Sekiguchi,Yoshimi Tobita,Yukiko Hayashi,Kyosuke Mizuno,Takaji Wakita,Tomoko Chiyo,Kiminori Kimura,Kyoko Tsukiyama-Kohara,Takahiro Ohtsuki,Toshiyuki Tanaka,Masayuki Miyasaka,Kouji Matsushima,Yuko Tokunaga,Michinori Kohara,Tsunekazu Hishima,Fumihiko Yasui,Naglaa H Shoukry

doi:10.1371/journal.pone.0051656

Abstract

Chronic hepatitis C, which is caused by infection with the hepatitis C virus (HCV), is a global health problem. Using a mouse model of hepatitis C, we examined the therapeutic effects of a recombinant vaccinia virus (rVV) that encodes an HCV protein. We generated immunocompetent mice that each expressed multiple HCV proteins via a Cre/loxP switching system and established several distinct attenuated rVV strains. The HCV core protein was expressed consistently in the liver after polyinosinic acid–polycytidylic acid injection, and these mice showed chronic hepatitis C-related pathological findings (hepatocyte abnormalities, accumulation of glycogen, steatosis), liver fibrosis, and hepatocellular carcinoma. Immunization with one rVV strain (rVV-N25), which encoded nonstructural HCV proteins, suppressed serum inflammatory cytokine levels and alleviated the symptoms of pathological chronic hepatitis C within 7 days after injection. Furthermore, HCV protein levels in liver tissue also decreased in a CD4 and CD8 T-cell-dependent manner. Consistent with these results, we showed that rVV-N25 immunization induced a robust CD8 T-cell immune response that was specific to the HCV nonstructural protein 2. We also demonstrated that the onset of chronic hepatitis in CN2-29(+/−)/MxCre(+/−) mice was mainly attributable to inflammatory cytokines, (tumor necrosis factor) TNF-α and (interleukin) IL-6. Thus, our generated mice model should be useful for further investigation of the immunological processes associated with persistent expression of HCV proteins because these mice had not developed immune tolerance to the HCV antigen. In addition, we propose that rVV-N25 could be developed as an effective therapeutic vaccine.

Highlights

Hepatitis C virus (HCV) is a major public health problem; approximately 170 million people are infected with HCV worldwide [1]
We found that immunization with recombinant vaccinia virus (rVV)-N25 suppressed HCV core protein levels in the livers of transgenic mice; this suppression was mediated by CD4 and CD8 T cells, as has been previously reported [8]
We found that within 28 days after immunization the HCV core protein levels were significantly lower in livers of rVV-N25-treated mice than in those of control mice (Figure 3A)

Summary

Introduction

Hepatitis C virus (HCV) is a major public health problem; approximately 170 million people are infected with HCV worldwide [1]. Transgenic mice that express HCV proteins have been generated to study HCV expression [3,4]; in each of these cases, the relevant transgenes is expressed during embryonic development; the transgenic mice become immunotolerant to the transgenic products, and the adult mice are not useful for investigations of the pathogenesis of chronic hepatitis C. To address this problem, we developed a system that can drive conditional expression of an HCV transgene; our system involves the Cre/loxP system and a recombinant adenovirus capable of expressing Cre recombinase [5,6]. Here, we used a Cre/loxP switching system to generate an immunocompetent mouse model of HCV protein expression; with this system, we could study the host immune responses against HCV proteins

Objectives

Methods

Results

Conclusion