Replicating C-Type Virus in Phytohemagglutinin-Treated Buffy-Coat Cultures of Bovine Origin23

Abstract

Confirming previous work from other laboratories, numerous C-type, virus-like particles were observed in phytohemagglutinin (PHA)-treated, short-term cultures of buffy-coat (BC) cells from cows with lymphosarcoma or persistent lymphocytosis. In a detailed electron microscopic study of BC cultures from a cow with persistent lymphocytosis from a high-incidence lymphosarcoma family (BF-044), we conclusively demonstrated the occurrence of budding processes and thus the viral nature of the C-type particles. Addition of PHA to the cultures usually increased viral replication. However, virus was also consistently in control (non-PHA-treated) cultures and, in two experiments, in numbers at least equal to those in the PHA-treated cultures. This, together with the conspicuous absence of the virus in the BC cells before cultivation, indicated that the in vitro maintenance of these cells, and not PHA, is mainly responsible for the expression and/or replication of the virus. Our finding of virus in cultures grown without serum ruled out introduction of the virus via the fetal calf serum used to supplement the culture medium. Limited epidemiologic data emphasized the association of this virus with the occurrence of lymphosarcoma and/or lymphocytosis in the cattle population.