Human liver chimeric mice as a novel model for the study of hepatitis E virus infections.
Ibrahim M.Sayed, Lieven Verhoye1, Ali Farhoudi1, Yannick Debing2, Johan Neyts2, Geert Leroux-Roels1, Robert Purcell3, Suzanne Emerson3, Philip Meuleman1
1Center for Vaccinology, Ghent University, Ghent, Belgium
2Rega Institute, KUL, Leuven, Belgium
3Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, USA
The hepatitis E virus (HEV) is anenterically transmitted virus that belongs to the Hepeviridae family and is subdivided into 4 genotypes (gt1-4). HEV ofgt 1 and gt2 are mainly restricted to developing countries and can only infect humans. Genotype 3 and 4 viruses can also infect pigs andrepresent an emerging problem in industrialized areas, in particular in Europe.HEV usually causes an acute self-limitedinfection but in people with suppressedimmunity, caused by pregnancy, disease or immunosuppressive therapy, the infection can evolve tochronicity. Pregnant women, people with underlying liver disease and immune suppressed patients are at risk of developing severe and sometimes fatale complications. HEV infection can be treated with ribavirin (RBV) and/or interferon, but these molecules are contra-indicated in certain patient groups. In addition HEV isolates with decreased sensitivity to RBV have recently been identified. Therefore new antiviral molecules are needed for the treatment of HEV infection.
Although HEV can be cultured in vitro it can only be studied in vivo in non-human primates. However,the use of these animals is hampered by financial andethical concerns. Therefore we wanted to evaluate whether mice of which the liver is largely repopulated with primary human hepatocytes are susceptible to HEV infection.
uPA+/+-SCID mice transplanted with human hepatocytes were inoculated with different preparations of HEV of gt 1 or gt3.A first group of mice wasintrasplenically injected with a filtered stool suspension from agt 1 HEV-infected chimpanzee (Sar Strain). A secondgroup was inoculated intrasplenically with cell culture-derived HEV(HEVcc) of gt 3. Athird group received an oral dose ofHEVcc via gavage.Non-transplanted mice inoculated with the same preparations served as negative controls. Plasma and stool samples were collected weekly and viral RNA was quantified usingan in-house qRT-PCR.
HEV RNAcould bedetected in plasma and stool of the mice from group 1. The viral titer increased over time reaching levels up to 1.54x107IU/ml in plasma and 4.8x108 IU/ml in 10% (w/v) stool suspension. The viral load was significantly higher in the stool thanin the plasma. In some mice the virus was only detectable in stool. Interestingly, naïve humanized mice becameinfected afterintrasplenic injection of a stool suspension derived from HEV RNA positive mice, indicating the presence of infectious viral particles. Upon RBV therapy (50 to 100 mg/kg daily) a rapid drop in viral load was observed, resulting in HEV negativity within about 2 weeks. After cessation of therapy viral rebound was observed.
While HEVcc-inoculated mice (group 2) became actively infected, the viral load in stool was relatively low compared to the group 1 mice. The viral load in plasma remained below the limit of quantification. HEV RNA could not be detected in control mice and in mice that were orally exposed to HEVcc (group 3).
In conclusion, human liver chimeric mice can be infected with HEV. This small animal model will be a valuable tool for the in vivo study of HEV and the evaluation of novel antiviral molecules.