Bovine lymphocytic leukemia: studies of etiology, pathogenesis and mode of transmission. Progress report, November 1, 1979-October 31, 1980

Abstract

The primary project objectives are to elucidate the cause(s) and early pathogenesis of the adult form of lymphosarcoma in cattle. This goal is to be accomplished through experimental transmission of the disease. For these studies large quantities of bovine leukemia virus (BLV) were propagated in short-term, mitogen stimulated, lymphocyte cultures. Cultures containing abundant BLV particles were pooled (33 liters total) and further processed by continuous flow, density gradient, ultracentrifugation. This higly concentrated, cell free, BLV preparation was then used as inoculum for 12 late stage bovine fetuses (inoculated in utero) and two newborn calves. Extensive monitoring studies have been carrid out on these inoculated animals to detect precancerous changes and to obtain a detailed description of the events preceding the development of lymphosarcoma. These extensive records on lymphosarcoma associated blood parameters have established that all of the inoculated animals became persistently BLV infected. However, after more than five years of incubation, no cases of lymphosarcoma developed. Consequently, during the past seven months, five of these well characterized animals have been subjected to frequent BLV re-exposure in order to study BLV-host interactions in previously infected adults and to potentially accelerate tumor formation in these animals.