Entry of DNA viruses into cells and establishment of infection

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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