Baines Joel D, Hsieh Chyong-Ere, Wills Elizabeth, Mannella Carmen, Marko Michael
Department of Microbiology and Immunology, C5132 Veterinary Medical Center, New York State College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
J Virol. 2007 Mar;81(6):2726-35. doi: 10.1128/JVI.02571-06. Epub 2007 Jan 10.
Cells infected with herpes simplex virus type 1 (HSV-1) were conventionally embedded or freeze substituted after high-pressure freezing and stained with uranyl acetate. Electron tomograms of capsids attached to or undergoing envelopment at the inner nuclear membrane (INM), capsids within cytoplasmic vesicles near the nuclear membrane, and extracellular virions revealed the following phenomena. (i) Nucleocapsids undergoing envelopment at the INM, or B capsids abutting the INM, were connected to thickened patches of the INM by fibers 8 to 19 nm in length and < or =5 nm in width. The fibers contacted both fivefold symmetrical vertices (pentons) and sixfold symmetrical faces (hexons) of the nucleocapsid, although relative to the respective frequencies of these subunits in the capsid, fibers engaged pentons more frequently than hexons. (ii) Fibers of similar dimensions bridged the virion envelope and surface of the nucleocapsid in perinuclear virions. (iii) The tegument of perinuclear virions was considerably less dense than that of extracellular virions; connecting fibers were observed in the former case but not in the latter. (iv) The prominent external spikes emanating from the envelope of extracellular virions were absent from perinuclear virions. (v) The virion envelope of perinuclear virions appeared denser and thicker than that of extracellular virions. (vi) Vesicles near, but apparently distinct from, the nuclear membrane in single sections were derived from extensions of the perinuclear space as seen in the electron tomograms. These observations suggest very different mechanisms of tegumentation and envelopment in extracellular compared with perinuclear virions and are consistent with application of the final tegument to unenveloped nucleocapsids in a compartment(s) distinct from the perinuclear space.
感染单纯疱疹病毒1型（HSV-1）的细胞在高压冷冻后进行常规包埋或冷冻置换，并用醋酸铀染色。附着在内核膜（INM）上或在内核膜处正在被包裹的衣壳、核膜附近细胞质囊泡内的衣壳以及细胞外病毒粒子的电子断层扫描显示了以下现象。（i）在内核膜处正在被包裹的核衣壳，或与内核膜相邻的B衣壳，通过长度为8至19纳米、宽度小于或等于5纳米的纤维与内核膜的增厚斑块相连。这些纤维同时接触核衣壳的五重对称顶点（五聚体）和六重对称面（六聚体），尽管相对于衣壳中这些亚基的各自频率，纤维与五聚体的接触比与六聚体更频繁。（ii）类似尺寸的纤维在核周病毒粒子中连接病毒粒子包膜和核衣壳表面。（iii）核周病毒粒子的被膜密度明显低于细胞外病毒粒子；在前一种情况下观察到连接纤维，而在后一种情况下未观察到。（iv）细胞外病毒粒子包膜上突出的外部刺突在核周病毒粒子中不存在。（v）核周病毒粒子的病毒粒子包膜似乎比细胞外病毒粒子的更致密、更厚。（vi）在单切片中靠近核膜但明显与之不同的囊泡，如电子断层扫描所示，源自核周空间的延伸。这些观察结果表明，与核周病毒粒子相比，细胞外病毒粒子的被膜化和包裹机制非常不同，并且与在与核周空间不同的隔室中对无包膜核衣壳应用最终被膜一致。
