Blasco R, Moss B
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
J Virol. 1992 Jul;66(7):4170-9. doi: 10.1128/JVI.66.7.4170-4179.1992.
The roles of intracellular naked (INV), cell-associated enveloped (CEV), and extracellular enveloped (EEV) forms of vaccinia virus in cell-to-cell and longer-range spread were investigated by using two closely related strains of vaccinia virus, WR and IHD-J. We confirmed previous results that WR and IHD-J produced similar amounts of INV and formed similar-size primary plaques but that IHD-J produced 10 to 40 times more EEV and spread to distant cells much more efficiently than did WR. Nevertheless, cells infected with WR and IHD-J had similar amounts of CEV, indicating that wrapping and transport of WR virions were unimpaired. A WR mutant with a deletion in VP37, the major outer envelope protein, formed normal amounts of INV; however, the generation of CEV was blocked and plaque formation was inhibited. These results suggested that CEV is the form of virus that mediates cell-to-cell spread. Marker rescue experiments indicated that the differences in EEV production by WR and IHD-J were not due to sequence differences in VP37. The low amount of WR EEV could be attributed to retention of CEV on the cell membrane. In support of this hypothesis, mild treatment with trypsin released as much or more infectious virus from cells infected with WR as it did with cells infected with IHD-J. Most of the virus released by trypsin sedimented with the buoyant density of EEV. Also, addition of trypsin to cells following inoculation with WR led to a comet-shaped distribution of secondary plaques characteristic of IHD-J. These results demonstrated that the release of CEV from the cell surface was limiting for extracellular virus formation and affirmed the role of EEV in long-range spread.
通过使用两种密切相关的痘苗病毒株WR和IHD-J，研究了痘苗病毒的细胞内裸病毒（INV）、细胞相关包膜病毒（CEV）和细胞外包膜病毒（EEV）形式在细胞间和远距离传播中的作用。我们证实了先前的结果，即WR和IHD-J产生的INV数量相似，形成的初级噬斑大小相似，但IHD-J产生的EEV比WR多10至40倍，并且比WR更有效地传播到远处的细胞。然而，感染WR和IHD-J的细胞中CEV的数量相似，这表明WR病毒粒子的包裹和运输没有受损。一种在主要外膜蛋白VP37中缺失的WR突变体形成了正常数量的INV；然而，CEV的产生被阻断，噬斑形成受到抑制。这些结果表明，CEV是介导细胞间传播的病毒形式。标记拯救实验表明，WR和IHD-J在EEV产生上的差异不是由于VP37的序列差异。WR EEV数量少可能归因于CEV保留在细胞膜上。支持这一假设的是，用胰蛋白酶轻度处理从感染WR的细胞中释放的感染性病毒与从感染IHD-J的细胞中释放的一样多或更多。胰蛋白酶释放的大多数病毒以EEV的浮力密度沉淀。此外，在接种WR后向细胞中添加胰蛋白酶会导致出现IHD-J特有的彗星状二级噬斑分布。这些结果表明，CEV从细胞表面的释放限制了细胞外病毒的形成，并证实了EEV在远距离传播中的作用。
