Isolation and characterization of a novel retrovirus from sheep affected by pulmonary carcinoma

Sheep pulmonary carcinoma (SPC) has been shown to be associated in nature with a retrovirus, by electron microscopic, biochemical, and epidemiological criteria and by experimental transmission. In this study, a retrovirus has been isolated from SPC tumors which were experimentally induced by inoculation with a cell-free, reverse transcriptase containing fraction from a spontaneous field case of SPC, and propagated in culture. This novel virus was shown to be unrelated to murine, avian, and bovine leukemia viruses, to be exogenous to the ovine species, and to have only limited genetic relatedness to the lentiviridae (maedi-visna and caprine arthritis encephalitis virus).