Entry of DNA viruses into cells and establishment of infection

动物DNA病毒感染细胞的早期阶段，即病毒粒子附着于细胞表面、病毒粒子穿透细胞、病毒粒子向细胞核转运以及病毒粒子进入细胞核的机制尚不清楚，尽管这些事件对于病毒感染的建立是必不可少的。为了更好地了解病毒感染的这些方面，我们研究了影响猿猴病毒40 （SV40）感染建立效率的因素。我们发现一些细胞成分在病毒感染的建立中起着重要的作用。病毒粒子纯化后，粗制SV40的斑块形成活性和t抗原合成活性明显降低。纯化后的病毒粒子与猴CV-1细胞提取物孵育后，活性完全恢复，猴CV-1细胞是sV40的宿主细胞。这种活性来源于CV-1细胞中磷脂的功能。由磷脂组成的脂质体与病毒粒子相互连接。这种结合提高了病毒粒子对宿主细胞的吸附效率。电镜观察发现，病毒粒子通过胞吞作用被细胞内化。然后我们检查了细胞质结构和功能抑制剂对感染建立的影响。结果表明，病毒粒子向细胞核运输需要微管的功能，而感染的建立不需要微丝和溶酶体的功能。在本研究的过程中，很快就清楚地认识到，由于无法获得用于检测病毒早期蛋白质的抗体，对其他DNA病毒感染早期机制的研究受到了阻碍。为了制备这种抗体，我们从腺病毒12型（Ad12）的E1A基因DNA序列中合成了两个肽段。我们现在正在研究Ad12感染细胞的早期阶段，使用抗血清和针对这些肽的单克隆抗体。少

The mechanism of the early phase of infection of a cell with animal DNA viruses, i.e., attachment of virions to cell surface, virion's penetration into the cell, transportation of virions towards the cell nucleus, and virion's entry into the nucleus, remains still unclear, although these events are indispensable for the establishment of viral infection. To better understand these aspects of viral infection, we examined factors affecting the efficiency of establishment of infection with simian virus 40 (SV40). We found that some cellular components play essential roles for the establishment of viral infection.Plaque-forming activity and T-antigen synthesizing activity in the crude preparation of SV40 markedly decreased after the purification of virions. A full restoration of the activity occurred after the incubation of the purified virions with the extract of monkey CV-1 cells, host cells for productive infection with sV40. this activity was derived from the function of phospholipids o … More f CV-1 cells. The constructed liposomes composed of the phospholipids became associated with virions on side-to-side. This association enhanced the efficiency of adsorption of the virions to host cells. Electron microscopy revealed that virions adsorbed to cells were internalized by endocytosis. We then examined the effects of inhibitors of the cytoplasmic structures and functions on the establishment of infection. Results indicate that the function of microtubules is required for the transportation of virions towards the cell nucleus, and that the function of microfilaments and lysosomes is not required for the establishment of infection.During the course of the present study, it soon became clear that studies to understand the mechanism of the early phase of infection with other DNA viruses are hindered by the unavailability of antibodies useful for detection of the immediate early proteins of the viruses. To prepare antibodies for this purpose, we synthesized two peptides derived from the DNA sequence of the E1A gene of adenovirus type 12 (Ad12). We are now investigating the early phase of infection of cells with Ad12 by using antisera and monoclonal antibodies against these peptides. Less