title: Envelope is a major viral determinant of the distinct in vitro cellular transformation tropism of human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2.
abstract: Human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 are related deltaretroviruses but are distinct in their disease-inducing capacity. These viruses can infect a variety of cell types, but only T lymphocytes become transformed, which is defined in vitro as showing indefinite interleukin-2-independent growth. Studies have indicated that HTLV-1 has a preferential tropism for CD4+ T cells in vivo and is associated with the development of leukemia and neurological disease. Conversely, the in vivo T-cell tropism of HTLV-2 is less clear, although it appears that CD8+ T cells preferentially harbor the provirus, with only a few cases of disease association. The difference in T-cell transformation tropism has been confirmed in vitro as shown by the preferential transformation of CD4+ T cells by HTLV-1 versus the transformation of CD8+ T cells by HTLV-2. Our previous studies showed that Tax and overlapping Rex do not confer the distinct T-cell transformation tropisms between HTLV-1 and HTLV-2. Therefore, for this study HTLV-1 and HTLV-2 recombinants were generated to assess the contribution of LTR and env sequences in T-cell transformation tropism. Both sets of proviral recombinants expressed p19 Gag following transfection into cells. Furthermore, recombinant viruses were replication competent and had the capacity to transform T lymphocytes. Our data showed that exchange of the env gene resulted in altered T-cell transformation tropism compared to wild-type virus, while exchange of long terminal repeat sequences had no significant effect. HTLV-2/Env1 preferentially transformed CD4+ T cells similarly to wild-type HTLV-1 (wtHTLV-1), whereas HTLV-1/Env2 had a transformation tropism similar to that of wtHTLV-2 (CD8+ T cells). These results indicate that env is a major viral determinant for HTLV T-cell transformation tropism in vitro and provides strong evidence implicating its contribution to the distinct pathogenesis resulting from HTLV-1 versus HTLV-2 infections.
authors.affiliation: Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Green
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D015686:Gene Products, env / Q000502:physiology*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D015367:Human T-lymphotropic virus 2 / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D011995:Recombination, Genetic; D020079:Terminal Repeat Sequences / Q000235:genetics
chemical_list: D015686:Gene Products, env