Functional analysis of Tumor necrosis Factor α(TNFα) on infections immunity.

冠状病毒对消化器官、呼吸器官、肝脏和中枢神经系统表现出不同的细胞趋向性和不同菌株的毒力，组织趋向性和毒力的差异机制尚不清楚。小鼠肝炎病毒（MHV）感染可导致小鼠急性和重型肝炎、慢性肝炎、急性脑炎和脱髓鞘，目前正在研究脊髓灰质炎脑炎等人类脱髓鞘疾病的模型。提示宿主免疫，特别是TNFα、IL-1、IL-6等炎症细胞因子在MHV致重型肝炎、急性脑炎、脱髓鞘危象中起重要作用。因此，为了研究菌株间细胞趋向性和毒力差异的分子基础，我们进行了RT-PCR RFLP分析，并测定和比较了S糖蛋白基因、orf3、3-1、4和orf7在疫苗株、减毒株和毒力株之间的序列。结果表明，1957 ~ 1995年在日本暴发的TGEV毒株存在2个株系。虽然有报道称orf3,3 - 1,4区域缺失与病毒致病性存在相关性，但我们的结果是orf3,3 - 1,4区域缺失对病毒致病性没有直接影响。我们已经分离到新的TGEV菌株，该菌株在S糖蛋白基因区域缺失，该区域可能与致病性有关，并且TGEV菌株缺乏血凝能力。由于体内TNFα在小鼠冠状病毒感染中的作用尚不确定，我们试图评估其在ip诱导的TNFα缺陷B6小鼠（TNFα-/-小鼠）MHV-3感染中的作用。结果表明，TNFα-/-小鼠的存活率显著高于对照组B6小鼠。另一方面，TNFα-/-小鼠与对照组6小鼠的肝脏病毒生长无显著差异。这些结果表明，引起暴发性肝炎的主要原因不是病毒对肝细胞的直接损伤。同时，约40%的tnf - α-/-小鼠在MHV-3感染后死亡，但tnf - α-/-小鼠在MHV-3感染后的存活时间比对照组B6小鼠长。病理观察发现，两株小鼠均出现肝细胞凋亡。这些结果表明，TNFα在暴发性肝炎的发生中起重要作用，另一方面表明在病毒性肝炎的发生中还有其他因素。少

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 gastroenterit … More is 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