Okamoto H, Ukita M, Nishizawa T, Kishimoto J, Hoshi Y, Mizuo H, Tanaka T, Miyakawa Y, Mayumi M
Immunology Division and Division of Molecular Virology, Jichi Medical School, Tochigi-Ken 329-0498, Japan.
J Virol. 2000 Jun;74(11):5161-7. doi: 10.1128/jvi.74.11.5161-5167.2000.
TT virus (TTV) is an unenveloped, circular, and single-stranded DNA virus commonly infecting human beings worldwide. TTV DNAs in paired serum and liver tissues from three viremic individuals were separated by gel electrophoresis and characterized biophysically. TTV DNAs in sera migrated in sizes ranging from 2.0 to 2.5 kb. TTV DNAs in liver tissues, however, migrated at 2.0 to 2.5 kb as well as at 3.5 to 6.1 kb. Both faster- and slower-migrating forms of TTV DNAs in the liver were found to be circular and of the full genomic length of 3.8 kb. TTV DNAs migrating at 2.0 to 2.5 kb, from either serum or liver tissues, were sensitive to S1 nuclease but resistant to restriction endonucleases, and therefore, they were single-stranded. By contrast, TTV DNAs in liver tissues that migrated at 3.5 to 6.1 kb were resistant to S1 nuclease. They migrated at 3.7 to 4.0 kb after digestion with EcoRI, which suggests that they represent circular, double-stranded replicative intermediates of TTV. When TTV DNAs were subjected to strand-specific primer extension and then amplified by PCR with internal primers, those in serum were found to be minus-stranded DNAs while those in liver tissues were found to be a mixture of plus- and minus-stranded DNAs. These results suggest that TTV replicates in the liver via a circular double-stranded DNA.
TT病毒（TTV）是一种无包膜的环状单链DNA病毒，在全球范围内普遍感染人类。对三名病毒血症患者的配对血清和肝组织中的TTV DNA进行凝胶电泳分离，并进行生物物理特性分析。血清中的TTV DNA迁移大小范围为2.0至2.5 kb。然而，肝组织中的TTV DNA迁移大小为2.0至2.5 kb以及3.5至6.1 kb。在肝脏中迁移速度较快和较慢的TTV DNA形式均被发现是环状的，且全长为3.8 kb。来自血清或肝组织的迁移大小为2.0至2.5 kb的TTV DNA对S1核酸酶敏感，但对限制性内切酶有抗性，因此它们是单链的。相比之下，在肝脏中迁移大小为3.5至6.1 kb的TTV DNA对S1核酸酶有抗性。用EcoRI消化后，它们迁移大小为3.7至4.0 kb，这表明它们代表TTV的环状双链复制中间体。当TTV DNA进行链特异性引物延伸，然后用内部引物通过PCR扩增时，发现血清中的TTV DNA为负链DNA，而肝组织中的TTV DNA为正链和负链DNA的混合物。这些结果表明，TTV通过环状双链DNA在肝脏中复制。
