title: Construction of doxycyline-dependent mini-HIV-1 variants for the development of a virotherapy against leukemias.
abstract: T-cell acute lymphoblastic leukemia (T-ALL) is a high-risk type of blood-cell cancer. We describe the improvement of a candidate therapeutic virus for virotherapy of leukemic cells. Virotherapy is based on the exclusive replication of a virus in leukemic cells, leading to the selective removal of these malignant cells. To improve the safety of such a virus, we constructed an HIV-1 variant that replicates exclusively in the presence of the nontoxic effector doxycycline (dox). This was achieved by replacement of the viral TAR-Tat system for transcriptional activation by the Escherichia coli-derived Tet system for inducible gene expression. This HIV-rtTA virus replicates in a strictly dox-dependent manner. In this virus, additional deletions and/or inactivating mutations were introduced in the genes for accessory proteins. These proteins are essential for virus replication in untransformed cells, but dispensable in leukemic T cells. These minimized HIV-rtTA variants contain up to 7 deletions/inactivating mutations (TAR, Tat, vif, vpR, vpU, nef and U3) and replicate efficiently in the leukemic SupT1 T cell line, but do not replicate in normal peripheral blood mononuclear cells. These virus variants are also able to efficiently remove leukemic cells from a mixed culture with untransformed cells. The therapeutic viruses use CD4 and CXCR4 for cell entry and could potentially be used against CXCR4 expressing malignancies such as T-lymphoblastic leukemia/lymphoma, NK leukemia and some myeloid leukemias.
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands. r.jeeninga@amc.uva.nl
authors.forename: Rienk E
authors.initials: RE
authors.lastname: Jeeninga
authors.forename: Barbara
authors.initials: B
authors.lastname: Jan
authors.forename: Henk
authors.initials: H
authors.lastname: van den Berg
authors.forename: Ben
authors.initials: B
authors.lastname: Berkhout
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015704:CD4 Antigens / Q000096:biosynthesis; D045744:Cell Line, Tumor; D004318:Doxycycline / Q000494:pharmacology*; D017353:Gene Deletion; D015696:Gene Products, tat / Q000378:metabolism; D005814:Genes, Viral; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism / Q000821:virology*; D007963:Leukocytes, Mononuclear / Q000821:virology; D019718:Receptors, CXCR4 / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000821:virology; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D000900:Anti-Bacterial Agents; D015704:CD4 Antigens; D015696:Gene Products, tat; D019718:Receptors, CXCR4; D054322:tat Gene Products, Human Immunodeficiency Virus; D004318:Doxycycline