Isolation and characterisation of oncornavirus from primary cultures of tissues from cattle with leukemia.

The purpose of this investigation was to search for oncornavirus in primary cell cultures obtained from leukemic cattle organs and lymphocytes and to study their molecular-biological properties and role in the etiology of cattle leukemia. The investigation was carried out on 25 primary trypsinized cell culutres of lymph nodes, spleens, kidneys and lymphocytes from cattle with acute and chronic leukemia. It was demonstrated that all cell cultures from leukemic cattle (in contrast to cell cultures from healthy cattle) released oncornavirus into the culture medium. The virus possesses the main properties of oncornaviruses: it has a virion of C-type structure with a density of 1.16--1.18g/ml in a 20--60 per cent sucrose gradient, which may be induced by 5-bromodeoxyuridine, inhibited by Actino-mycin D, has reverse transcriptase activity, contains 60S RNA, that is annealed in the reaction of molecular hybridization with DNA of lymph nodes of cattle with leukemia. The propagation of the isolated oncornavirus in continuous cell lines of calf kidney culture was demonstrated. Experimental inoculation of purified oncornavirus was carried out on 60 baby calves and 15 lambs from leukosis free herds or flocks. Several of the calves later showed evidence of virus infection.