Spontaneous immune response of bovine leukemia-virus-infected cattle against five different viral proteins.

The sera from cattle exposed to bovine leukemia virus (BLV) have been studied by the radioimmunoprecipitation assay (RIPA) of disrupted virus proteins. All sera of animals with the adult form of lymphosarcoma precipitated four different viral proteins: gp51, gp35, p24 and p12. In contrast, the sera of five animals with the juvenile or thymic forms of bovine lymphosarcoma were completely devoid of precipitating activity against BLV proteins, confirming the absence of relationship between these rare malignant diseases and BLV infection. The sera of non-leukemic cattle from areas of high risk of exposure to BLV were either negative or positive to a lower degree than the sera of lymphosarcomatous cows. When positive they precipitated gp51, p24 and p12. Only one serum precipitated gp35. The difference was probably quantitative, the sera of leukemic animals having higher levels of precipitating activity against all the viral proteins. The anti-gp51 reactivity was in most cases the strongest, whatever the origin of the serum. In the rare sera which were positive in the classical anti-gp51 radioimmunoassay (RIA) but negative in the anti-p24 RIA, an anti-p24 activity was, however, detected by the RIPA. These results suggest that BLV-infected cows regularly produce antibodies reacting with four different viral proteins including minor viral components. In three cases with no other special features a low level of activity was detected against a fifth component: p15. There was no apparent correlation, however, between the antibody response and an hypothetical protection against BLV-induced disease.