Bovine leucosis virus challenge infection of calves following application of BL-3 cells.

: 8 calves were vaccinated 3 times with 1.5.10(7) BL-3 cells. 2 and 6 weeks, respectively, after the 3rd vaccination each 4 calves were subjected to a challenge infection with 2.5.10(5) blood lymphocytes of a BLV-infected cow. For control a challenge infection was performed on 3 non-vaccinated calves. The vaccination caused in all calves the appearance of complement-dependent cytotoxic antibodies against BL-3 cells but not of antibodies against BLV-gp51. After the challenge infection there occurred in the sera of all vaccinated calves and of all non-vaccinated control animals antibodies against gp51, and BLV could be demonstrated in the cultivated blood lymphocytes of all animals. Consequently, the application of BL-3 cells had no protective effect against the BLV infection.