In vitro infection of lymphoid cells by thymotropic radiation leukemia virus grown in vitro.

Abstract

Murine lymphoid cells were infected in vitro with purified leukemogenic radiation leukemia virus (RadLV) produced by virus-induced lymphoblast cell lines. Thymocytes were shown to be highly susceptible to infection by the virus, whereas murine or other fibroblasts were refractory to it. Murine bone marrow and spleen cells were shown to be much less sensitive to infection by this thymotropic RadLV. By comparison, a B-tropic RadLV isolate (RadLV*), propagated on a mouse fibroblast cell line, was noninfectious for lymphoid cells but infected fibroblasts. A correlation was shown to exist between in vitro infection of thymocytes, as assayed by immunofluorescence, and in vivo leukemogenicity of the thymotropic RadLV. This constitutes a rapid in vitro test for in vivo leukemogenicity of a natural lymphatic leukemia virus.

Effects of Thymosin on Cytotoxicity and Virus Production in Akr Mice*

“…The possibility that a thymosin-sensitive population of spleen cells may also exert some type of feedback control on the cells responsible for replication of endogenous ecotropic retrovirus in the spleen can not be discounted. These data offer additional support for the concept that replication of specific types of endogenous viruses may require specific lymphocyte subpopulations.z2p 23 Although thymosin affected the production of endogenous ecotropic virus in all of the lymphoid tissues examined (young and aged mice), the most notable changes occurred in the thymuses from both groups. A nearly equal but opposite effect on virus titers was observed in thymocytes from young and aged mice, with a decrease and increase in the numbers of XC plaques seen in nonleukemic (young) and preleukemic (aged) animals, respectively.…”

Leukemogenic activity of thymotropic, ecotropic, and xenotropic radiation leukemia virus isolates

“…Viruses. Thymotropic virus was produced by the cloned in vitro RadLV thymoma cell lines that were described previously (2,5). Thymotropic virus titers were estimated by using the indirect fluorescent-antibody (FA) technique to assay normal C57BL/6 thymocytes infected with this virus (5).…”

“…In contrast, RadLV that has been passaged in vivo by serial cell-free induction of thymomas ("enriched" RadLV) induced in 80 to 100% of inoculated mice a lymphosarcoma that is histologically indistinguishable from the primary Xirradiation-induced thymoma, but that produces ample leukemogenic RadLV. The enriched in vivo RadLV preparations are thymotropic (i.e., the virus has affinity for mouse lymphocytes in general and for thymus lymphocytes in particular [1, 4,5]). Leukemogenic RadLV isolates that were purified in quantity from in vitro-propagated thymoma cell lines (2) were also shown to have affinity for thymocytes, both in vivo (4) and in vitro (5).…”

“…The enriched in vivo RadLV preparations are thymotropic (i.e., the virus has affinity for mouse lymphocytes in general and for thymus lymphocytes in particular [1, 4,5]). Leukemogenic RadLV isolates that were purified in quantity from in vitro-propagated thymoma cell lines (2) were also shown to have affinity for thymocytes, both in vivo (4) and in vitro (5).…”

A highly leukemogenic radiation leukemia virus isolate is a thymotropic, immunosuppressive retrovirus with a unique rna structure

“…ciardi-Castagnoli et al, 1978;Haran-Ghera, 1978). However, isolation and in vitro cloning of a thymotropic and leukemogenic RadLV has become a difficult task because mature T cells are refractory to retroviral infection and/or transformation in vitro (Haas and Hilgers, 1975;Decleve et ul., 1975; n n Kaplan and Lieberman, 1976). RadLV has thus been propagated in vivo by serial inoculations into susceptible hosts or by establishment of RadLVinduced thymoma cell lines constitutively producing the leukemogenic virus Haran-Ghera and Rubio, 1977).…”