Bovine Leukemia Virus Control Research Articles

Lymphocyte colony formation by aleukemic sheep infected with bovine leukemia virus

The objective of this study was to investigate the effects of bovine leukemia virus (BLV) infection in sheep. A prospective study of the serologic, hematologic, and histologic changes of sheep infected with BLV was conducted. Antibodies to BLV were detectable in the sheep 3 weeks after exposure to blood from an infected cow and persisted during a 120 week examination period, whereas all control sheep remained seronegative. There were no statistically significant differences between the leucocyte counts, lymphocyte counts, and lymphocyte percentages of the infected and control sheep during the first 120 weeks of this study. However, one sheep did develop a leukopenia and lymphopenia 95 weeks after it became infected and died of histologically-confirmed lymphosarcoma 10 days later. A lymphocyte colony assay was used to study the effects of BLV infection on colony formation by sheep lymphocytes in vitro. There was no significant difference in the number of lymphocyte colonies formed by BLV infected and control sheep. Nor was there a significant difference in the number of colonies formed by lymphocytes from the BLV infected sheep, when the autologous sheep serum was replaced with either pooled serum from the infected sheep or with pooled serum from the control sheep. BLV infection in aleukemic sheep does not appear to have an adverse affect on colony formation by lymphocytes in vitro.

Use of glycoprotein antigen in the immunodiffusion test for bovine leukemia virus antibodies

The agar gel immunodiffusion (AGID) test for detection of bovine leukemia virus (BLV) antibody was modified by substitution of glycoprotein antigen for p 24, the etherstable, internal viral antigen used in earlier investigations. This modified AGID test was compared with a complement fixation (CF) test that had shown superior sensitivity to the first AGID procedure. Sera from 263 cattle in commercial dairy herds were tested. The glycoprotein AGID test detected BLV antibodies in 171 sera, but the CF test detected only 134. In monthly examinations of sera from animals in a BLV experimental herd, the AGID test consistently detected more infected cattle. After experimental or natural infection, 14 of 19 cattle seroconverted to both the AGID and CF tests the same month. When antibodies were detected by only one test, it was usually the AGID test. Colostral antibodies in 2 calves from BLV-infected dams were detected longer by the AGID test than by the CF. These results show that the glycoprotein AGID test is more sensitive than the CF test for detection of BLV antibodies in cattle sera. The AGID test also offers distinct advantages in its simplicity and specificity and promises to be a useful tool for the development of BLV control and eradication programs.