Protection against bovine leukemia virus infection in two breeds of cattle.

Calves of two breeds--Brown Latvian and Black and White, were immunized against bovine leukemia virus with an immunogen produced from short-term cultured blood lymphocytes of BLV-positive Brown Latvian cows. The immunogen contained the viral proteins gp51 and p24 as well as some cellular proteins. As determined by bioassay in sheep, it did not contain infective bovine leukemia virus. The calves were challenged by BLV-producing lymphocytes 2 weeks after the immunization procedure. Effective protection against BLV infection was induced by the tested immunogen in all Brown Latvian calves for 6 months and in 70% of the Black and White calves.