characteristic features in common with the genome of other retroviruses: long terminal repeats (L TR), and coding regions for internal proteins (gag), for re verse transcriptase (pol), and for glycosylated virion surface proteins (env) , ar ranged in the sequence gag, pol, env from the 5' to the 3' end of the genome. However, the HTL V genome also contains some specific features not shared with all other retroviruses: the LTR regions are unusually long (745 base pairs, with 298 base pairs constituting the R region), but unlike the long L TRs of mouse mammary tumor viruses, they do not contain open reading frames. A stretch of noncoding sequences separates the gag and the pol genes. Most interestingly, the HTLV genome contains a region between the 3' end of the env gene and the L TR, called the pX region, that encompasses four open reading frames. Leukemic T cells freshly obtained from patients contain the HTL V provirus but usually do not express it. However, once established in culture, these cells produce viral proteins and release type C particles. Likewise, T cells infected and transformed by HTL V in vitro synthesize virus. Such producing cell lines have been widely used in seroepidemiological surveys and continue to be of importance for detailed studies of viral proteins and nucleic acids.
Human T-Cell Leukemia/Lymphoma Viruses — An Introduction.- Isolation, Characterization, and Biological Effects of the First Human Retroviruses: The Human T-Lymphotropic Retrovirus Family. With 1 Figure.- Human T-Cell Leukemia/Lymphoma Viruses (HTLV): A Unique Family of Pathogenic Retroviruses. With 2 Figures.- Epidemiology of Adult T-Cell Leukemia/Lymphoma in Japan. With 9 Figures.- Human T-Cell Leukemia/Lymphoma Viruses: Clinical and Epidemiologic Features.- Clinical Aspects of Adult T-Cell Leukemia/Lymphoma.- The Epidemiology of Human T-Cell Leukemia/Lymphoma Virus. With 5 Figures.- Adult T-Cell Leukemia/Lymphoma and Its Clinical Subtypes from the Viewpoints of Viral Etiology.- A Retrovirus Associated with a Human Leukemia, Adult T-Cell Leukemia.- Biology of Human T-Cell Leukemia Virus: Search for an Animal System. With 7 Figures.- Molecular Biology of Human T-Cell Leukemia Virus Associated with Adult T-Cell Leukemia. With 9 Figures.- Structure and Function of the Genome of HTLV. With 7 Figures.- Some Perspectives on the Molecular Mechanism of in Vitro Transformation and in Vivo Leukemogenesis by HTLV. With 3 Figures.- Primary Structure and Processing of gag and env Gene Products of Human T-Cell Leukemia Viruses HTLV-ICR and HTLV-IATK. With 9 Figures.- Envelope Properties of Human T-Cell Leukemia Viruses. With 3 Figures.- Human T-Cell Leukemia/Lymphoma Virus: Studies of Host-Virus Interaction. With 9 Figures.