Lai A C, Pogo B G
Department of Microbiology Mount Sinai School of Medicine, City University of New York, N.Y. 10029.
Virus Res. 1989 Mar;12(3):239-50. doi: 10.1016/0168-1702(89)90042-7.
Persistent viral infections in vitro are useful to study the evolution of virus populations in the absence of immunological pressure. Several deletion mutants have been isolated in this laboratory from Friend erythroleukemia cells persistently infected with vaccinia virus strain IHD-W, designated SQAvac. Two of the mutants, which remain stable after serial passage in L cells, have been characterized. The deletion which range between 20 to 22 kb, has been localized at the left terminus comprising HindIII fragments C and N. In addition, HindIII B fragment lost the sequences that hybridize to pAG5, a plasmid containing the 3.5 kb terminal sequences and acquired different restriction sites. Phenotypic characterization of these mutants revealed that they were not replication defective since they grew in all cell lines tested and produced plaques of the same size as the wild-type. However, they were less effective in suppressing host protein synthesis. The LD50 for the mutants titered in NIH Swiss female mice was greater than 10(9) PFU as compared to 10(6) PFU for the wild-type, indicating reduced virulence in vivo. These mutants, which display different properties to previously described mutants with deletions at the left terminus, provide another valuable system to study the molecular basis of virulence of vaccinia.
体外持续病毒感染有助于在无免疫压力的情况下研究病毒群体的进化。本实验室已从持续感染痘苗病毒株IHD-W（命名为SQAvac）的Friend红白血病细胞中分离出几种缺失突变体。其中两个突变体在L细胞中连续传代后仍保持稳定，并已得到鉴定。缺失范围在20至22 kb之间，定位于左端，包括HindIII片段C和N。此外，HindIII B片段失去了与pAG5（一个含有3.5 kb末端序列的质粒）杂交的序列，并获得了不同的限制性酶切位点。这些突变体的表型特征表明，它们并非复制缺陷型，因为它们能在所有测试的细胞系中生长，并产生与野生型大小相同的噬斑。然而，它们在抑制宿主蛋白合成方面效果较差。在NIH瑞士雌性小鼠中测定的突变体半数致死剂量（LD50）大于10⁹ PFU，而野生型为10⁶ PFU，表明其体内毒力降低。这些突变体与先前描述的在左端有缺失的突变体表现出不同的特性，为研究痘苗病毒毒力的分子基础提供了另一个有价值的系统。
