Analysis of virus-receptor interaction and its application in veterinary science

用可溶性的CEACAM1受体(SoMHVR)研究了小鼠肝炎病毒(MHV)与其受体CEACAM1(MHVR)的相互作用。从MHV敏感的BALB/c小鼠分离的soMHVR1对MHV具有高亲和力和中和活性，而从MHV耐药的SJL小鼠分离的soMHVR2具有低的亲和力和中和活性。我们从MHV-JHMV中分离到了耐soMHVR1中和突变病毒(Srr7)。Srr7与野生型JHMV对表达MHVR1的细胞的感染效率相当，但对表达MHVR2的细胞的感染效率比wt病毒低2倍以上。srr7的低效感染是由于其低融合活性，即进入细胞的能力低所致。这些结果表明，MHVR2与野生型S蛋白的结合引发了其构象变化，而Srr7 S蛋白则未发生构象变化。我们还发现，soMHVR1激活或增强了MHVR缺陷细胞的MHV感染。这表明，soMHVR的结合将融合阴性的S蛋白转化为融合阳性的表型。利用该系统，我们可以在无细胞体系中进一步研究MHV与受体的相互作用，以及MHV颗粒在与受体相互作用后的动力学。小鼠白血病病毒FV-4r的env蛋白在小鼠对多种白血病病毒的抵抗力中起着重要作用。我们通过逆转录病毒载体表达Env，使易感小鼠对白血病病毒产生抵抗力。我们通过将一种无毒病毒通过鸡来传播，从而开发出一种高致病性的甲型流感病毒。这种转化伴随着HA蛋白的突变，导致蛋白的切割能力增强。这表明，HA的裂解能力影响流感病毒的致病性。

We have investigated the interaction of mouse hepatitis virus (MHV) and its receptor CEACAM1 (MHVR) by using soluble form of MHVR (soMHVR). soMHVR1 derived from MHV-susceptible BALB/c mouse showed high affinity and neutralizing activity to MHV, while soMHVR2 isolated from MHV-resistant SJL mouse was low in affinity and neutralization activity. We have isolated mutant virus resistant to neutralization (srr7) by soMHVR1 from MHV-JHMV. Srr7 infected as efficiently as wild type JHMV to cells expressing MHVR1, but did more than 2 logs less efficiently than wt virus to cells expressing MHVR2.This inefficient infection of srr7 was revealed to be due to its low fusogenicity, namely low capability to enter into these cells. These results suggested that the binding ofMHVR2 to wild type S protein triggered its conformational change, while it failed to do so for srr7 S proteins. We have also found that soMHVR1 activated or potentiated MHV infection to MHVR-deficient cells. This implied that binding of soMHVR converted fusion-negative S protein to fusion-positive phenotype. Using this system, we can further investigate in cell-free system the interaction of MHV and receptor as well as dynamics MHV particles following its interaction with receptor. Env protein ofmurine leukemia virus Fv-4r plays an important role for the resistance of mice to various leukemia viruses. We have conferred the resistance against leukemia virus to otherwise susceptible mice by expressing Env using retrovirus vectors. We have developed a highly pathogenic influenza A virus by passaging an avirulent virus through chickens. This conversion was accompanied with the mutations in HA protein, which resulted in enhanced cleavability of the protein. This suggested that HA cleavability influenced the pathogenicity of influenza virus.