Monoclonal integration of bovine leukemia virus (BLV) proviral DNA into bovine genomes was detected in peripheral blood from two clinical cases of enzootic bovine leukosis (EBL) without enlargement of superficial lymph nodes. A BLV-specific probe hybridized with 1 to 3 EcoRI and HindIII fragments in these 2 atypical EBL cattle by Southern blotting and hybridization, as well as in 3 typical EBL ...

The etiology of sporadic bovine leukosis (SBL) is not known. Long-term monolayer cultures were made from calf (CLS), thymic (TLS) and skin (SLS) forms, and serological tests, electron microscopic observations and reverse transcriptase assays were employed for the detection of an etiological agent. Bovine leukosis virus (BLV) antigen and reverse transcriptase activities remained negative in cult...

Bovine papillomavirus (BPV) DNA sequences were detected in different tissues, in addition to epithelium. Cytogenetic abnormalities were observed in blood lymphocytes. The presence of more than one virus in a single tissue is a difficult aspect to evaluate, especially when the DNA sequences are detected in tissues that are not specifically targeted by the virus. BPV and bovine leukemia virus (BL...

Dendritic cells (DCs) are most potent antigen presenting cells (APCs) with unique ability to prime effective immune responses. They express higher levels of MHC class II and accesory molecules on their surface, than other professional APCs. The investigations were performed on DCs generated from blood with the use of microbeads magnetically labeled with mouse anti human CD14. Flow cytometry was...

The DNA from 17 lymphoid tumors induced by bovine leukemia virus (BLV) was digested with the restriction endonuclease EcoRI. Filter hybridization analysis using radioactive probes specific for the BLV genome showed that all tumors contained at least one or a portion of one provirus. Digestion of these proviruses with Sac I demonstrated that deletions occurred in about 25% of the cases and invol...

The objective of the present study was to analyze the apoptotic process in peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophil leukocytes (PMN) in cows clinically affected with lymphosarcoma. Thirteen cows were studied. Of them, eight, that were referred because of inappetance, loss of body condition, diarrhoea, constipation, protrusion of third eyelid, and exophthalmia, ...

This article reports the selection of bovine leukemia virus (BLV) variants after continuous passage in cell lines or experimental animals. Two wild BLV strains isolated from 2 naturally infected Holstein dairy cows in Brazil (cow codes: 485 and 141) were used for the experimental infection of 1 sheep and FLK cells, and 1 rabbit and CC81 cells. Viral DNA was isolated several months after infecti...

BACKGROUND Bovine leukemia virus (BLV) is worldwide distributed and highly endemic in Argentina. Among the strategies to prevent BLV dissemination, a control plan based on the selective segregation of animals according to their proviral load (PVL) is promising for our dairy productive system. The objective of this work was to study the relationship between the blood PVL and the antibody level, ...

Bovine leukemia virus (BLV) is the etiologic agent of enzootic bovine leukosis. The virus adopts a strategy based on the lack of viral expression in vivo; only very rare BLV-infected B lymphocytes express viral information. When the cells are isolated from animals in persistent lymphocytosis and cultivated ex vivo, a tremendous increase in viral expression occurs. To gain insight into this mech...