Characterization of a variant virus from ascitic fluid of subacute granulomatous serositis in interferon-gamma-deficient C57BL/6 mice persistently infected with murine coronavirus strain JHM.
Previously, we showed that intraperitoneal infection with murine coronavirus strain JHM (JHMV) established a persistent infection with subacute granulomatous serositis in interferon-gamma-deficient C57BL/6 (B6-GKO) mice. Herein, we characterize a variant virus from B6-GKO mice persistently infected with JHMV. Viruses were isolated from ascites at 25 d post-infection and cloned by limiting dilution on DBT cells; one variant was named 25V16G. To compare pathogenicity in vivo, we inoculated 25V16G and JHMV intraperitoneally into 8- to 12-week-old B6-GKO mice. Whereas nearly all of the B6-GKO mice infected with JHMV survived over 14 d, all of those infected with 25V16G died by 9 d post-infection. Histopathological examination revealed that 25V16G induced acute fulminant hepatitis in B6-GKO mice, whereas JHMV caused severe but focal hepatitis. The virus titer of 25V16G in the liver was 50- and 250-fold higher than that of JHMV at 5 and 7 d post-infection, respectively. However, there was no significant difference in viral growth between 25V16G and JHMV in cell lines cultured in vitro. Nucleotide sequencing of the S gene of 25V16G and JHMV revealed a deletion of 29 amino acids encompassing S(511-539), which covers a major cytotoxic T lymphocyte (CTL) epitope in C57BL/6 mice, and two point mutations resulting in amino acid changes in the S protein of 25V16G. One explanation for the greater pathogenicity of 25V16G is that 25V16G escapes CTL-mediated protection in B6-GKO mice. This experimental model may be used to assess the role of IFN-gamma in viral persistence in vivo.
Kyuwa
Shigeru
S
Department of Biomedical Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan. akyuwa@mail.ecc.u-tokyo.ac.jp
Takagaki
Satoshi
S
Matsuyama
Shutoku
S
Taguchi
Fumihiro
F
Saegusa
Junzo
J
Iwakura
Yoichiroh
Y
Tagawa
Yoh-Ichi
Y
Yoshikawa
Yasuhiro
Y
D000818:Animals; D001202:Ascitic Fluid / Q000821:virology; D005260:Female; D014644:Genetic Variation; D006524:Hepatitis, Viral, Animal / Q000276:immunology / Q000473:pathology / Q000821:virology*; D007371:Interferon-gamma / Q000172:deficiency / Q000235:genetics; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D006517:Murine hepatitis virus / Q000235:genetics / Q000472:pathogenicity*; D017354:Point Mutation; D012700:Serositis / Q000473:pathology / Q000821:virology*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000235:genetics; D014774:Virulence
D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus; D007371:Interferon-gamma