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Viral transformation is the change in growth, phenotype, or indefinite reproduction of cells caused by the introduction of inheritable material. Through this process, a virus causes harmful transformations of an in vivo cell or cell culture. The term can also be understood as DNA transfection using a viral vector. Viral transformation can occur both naturally and medically. Natural transformations can include viral cancers, such as human papillomavirus (HPV) and T-cell Leukemia virus type I. Hepatitis B and C are also the result of natural viral transformation of the host cells. Viral transformation can also be induced for use in medical treatments. Cells that have been virally transformed can be differentiated from untransformed cells through a variety of growth, surface, and intracellular observations. The growth of transformed cells can be impacted by a loss of growth limitation caused by cell contact, less oriented growth, and high saturation density. Transformed cells can lose their tight junctions, increase their rate of nutrient transfer, and increase their protease secretion. Transformation can also affect the cytoskeleton and change in the quantity of signal molecules. == Type == There are three types of viral infections that can be considered under the topic of viral transformation. These are cytocidal, persistent, and transforming infections. Cytocidal infections can cause fusion of adjacent cells, disruption of transport pathways including ions and other cell signals, disruption of DNA, RNA and protein synthesis, and nearly always leads to cell death. Persistent infections involve viral material that lays dormant within a cell until activated by some stimulus. This type of infection usually causes few obvious changes within the cell but can lead to long chronic diseases. Transforming infections are also referred to as malignant transformation. This infection causes a host cell to become malignant and can be either cytocidal (usually in the case of RNA viruses) or persistent (usually in the case of DNA viruses). Cells with transforming infections undergo immortalization and inherit the genetic material to produce tumors. Since the term cytocidal, or cytolytic, refers to cell death, these three infections are not mutually exclusive. Many transforming infections by DNA tumor viruses are also cytocidal. Table 1: Cellular effects of viral infections〔 || || Rounding of the cell Fusion with adjacent cells Appearance of inclusion bodies || Inhibit DNA, RNA, and protein synthesis Interfere with sub-cellular interactions || Insufficient movement of ions Formation of secondary messengers Activation of cellular cascades || |- | Persistent || || || || Fusion with adjacent cells Appearance of inclusion bodies Budding || Immune responses limit viral spread Antigen-antibody complexes can incorporate viral antigens causing inflammation || Rare until stimulated || |- | Transforming || || || || Unlimited cell replication || Inactivates tumor suppressor proteins Impairs cell cycle regulation || Unlimited cell replication |} 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Viral transformation」の詳細全文を読む スポンサード リンク
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