関川 賢二 農林水産省, 家畜衛生試験場・生体防御部, 部長(研究職)
MACHIDA Noboru Faculty of Agriculture, Tokyo University of Agriculture and Technology, Assosiate Professor, 農学部, 助教授 (20219364)
HONDA Eiichi Faculty of Agriculture, Tokyo University of Agriculture and Technology, Professor, 農学部, 教授 (20109507)
SEKIKAWA Kenji National Innstitute Section Head of Animal Health
|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1998 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Coronaviruses show different cell tropism , like the digestive organs, respiratory organs, liver and central nerve system, and virulence between different stains, and the mechanisms is of differences on tissue tropisms and virulence is not clear. Mouse hepatitis virus(MHV) infection lead to acute and fulmiant hepatitis, chronic hepatitis, acute encephalitis and demyelination in mice, and have been studying model of human demyelination diseases including polioencephalitis. It was suggested that the host immunity, especially inflammation cytokine like TNFα, IL-1 and IL-6, play a important role on the crisis of fulmiant hepatitis, acute encephalitis and demyelination induced by MHV.
So, for the purpose of studing the molecular bases of the differences of cell tropism and virulent beween strains we have performed RT-PCR RFLP analysis and determination and comparison of sequence of S glycoprotein gene, ORF 3,3-1,4 and ORF 7 between vaccine, attenuated and virulent Transmissible gastroenter
itis virus (TGEV) 9 strains. And it was shown that TGEV strains outbreaked in Japan between 1957 and 1995 were separated 2 gropes. Although a correlation between the presence of deletions of ORF3, 3-1, 4 region and viral pathogenicity has been reported, we had the results that the deletion of ORF3, 3-1, 4 region had no influence directly on pathogenicity. We have isolated new TGEV strain that have deletions on the regions of S glycoprotein gene, the region were expected to relate with pathogenicity, and the TGEV strain was deficient in the ability of hemagglutination.
Since the role of TNFα in murine coronavirus infection in vivo uncertain, we attempted to evaluate its role in i.p. iduced MHV-3 infection of TNFα deficient B6 mice(TNFα-/- mice). It was shown that the survival rate of TNFα-/- mice was significantly higher than that of control B6 mice. On the other hand, there was no significant difference on viral growth in the liver between TNFα-/- mice and control 6 mice. These results show that the main causes of fulminant hepatitis was not the direct damage of hepatocytes by the virus. In the meantime, about 40% TNFα-/- mice were dead after MHV-3 infection, but thelength of survival after MHV-3 infection of TNFα-/- mice were longer than that of control B6 mice. And there were apoptotic hepatocyte death both strain mice by detail pathohistlogical observations. These results show that TNFα play a important role on the arisingof fulminant hepatitis, on the other hand it was indicated that there were another factors on the virul hepatitis. Less