Oglesbee M, Krakowka S
Department of Veterinary Pathobiology, Ohio State University.
Lab Invest. 1993 Jan;68(1):109-17.
Using canine distemper virus (CDV) encephalomyelitis as a model for morbillivirus-induced intranuclear inclusion body (INB) formation, we previously demonstrated that the cellular basis for INB within infected astrocytes are viral antigen-associated nucleolar derivatives known as complex nuclear bodies. Here, we examined the relationship between the cellular stress response and intranuclear CDV protein trafficking so that we may begin to define cellular events leading to formation of complex nuclear bodies containing viral protein.
Confocal dual-label immunofluorescence microscopy was used to simultaneously determine the distribution of CDV antigen and the major inducible 70 kilodalton (kd) heat shock protein (i.e., 72 kd heat shock protein (HSP)) within infected canine central nervous tissue. This dual-label immunofluorescent technique was also used to test the relationship between cellular stress and CDV core protein distribution in a CDV persistently infected cell line.
The cytoplasm of INB-positive astrocytes expressed elevated 72 kd HSP characteristic of the cellular stress response; INB contained 72 kd HSP and the major CDV nucleocapsid protein (i.e., N). Intranuclear inclusion bodies did not stain positively for the CDV nucleocapsid phosphoprotein nor was intranuclear N protein observed in the absence of nuclear or elevated cytoplasmic 72 kd HSP. In the persistently infected cell line, induction of the cellular stress response elevated 72 kd HSP and produced translocation of the CDV N protein to the nucleus from its normal location in the cytoplasm of unstressed infected cells. As observed in vivo, the transport was specific to N and was correlated to the induction of complex nuclear bodies. The latter was documented by transmission electron microscopy, where complex nuclear bodies formed in shocked infected cells, but not shocked uninfected cells or nonshocked infected cells.
CDV infection in vivo induces the cellular stress response. Paradoxically, this normally protective cellular response mediates redistribution of viral N protein from the cytoplasm into infected cell nuclei, which is the likely basis for complex nuclear body formation and a unique form of virus-induced cytopathic effect.
以犬瘟热病毒（CDV）脑脊髓炎作为麻疹病毒诱导核内包涵体（INB）形成的模型，我们先前证明，受感染星形胶质细胞内INB的细胞基础是与病毒抗原相关的核仁衍生物，称为复合核体。在此，我们研究了细胞应激反应与核内CDV蛋白运输之间的关系，以便我们能够开始确定导致含有病毒蛋白的复合核体形成的细胞事件。
共聚焦双标记免疫荧光显微镜用于同时确定受感染犬中枢神经组织内CDV抗原和主要诱导型70千道尔顿（kd）热休克蛋白（即72 kd热休克蛋白（HSP））的分布。这种双标记免疫荧光技术还用于测试细胞应激与CDV持续感染细胞系中CDV核心蛋白分布之间的关系。
INB阳性星形胶质细胞的细胞质表达了细胞应激反应特有的升高的72 kd HSP；INB含有72 kd HSP和主要的CDV核衣壳蛋白（即N）。核内包涵体对CDV核衣壳磷蛋白染色不呈阳性，在没有核或升高的细胞质72 kd HSP的情况下也未观察到核内N蛋白。在持续感染的细胞系中，细胞应激反应的诱导使72 kd HSP升高，并使CDV N蛋白从不应激感染细胞细胞质中的正常位置转运到细胞核。如在体内观察到的，这种转运对N具有特异性，并且与复合核体的诱导相关。后者通过透射电子显微镜记录，其中复合核体在受冲击的感染细胞中形成，但在受冲击的未感染细胞或未受冲击的感染细胞中不形成。
体内CDV感染诱导细胞应激反应。矛盾的是，这种通常具有保护作用的细胞反应介导病毒N蛋白从细胞质重新分布到受感染的细胞核中，这可能是复合核体形成的基础以及病毒诱导的细胞病变效应的一种独特形式。
