Characterization of antibodies responsible for the inhibition of BLV induced early polycaryoxytosis.

A quantitative in vitro assay (EPI) was developed for the serological detection of bovine leukemia virus (BLV) infection in cattle. Positive sera react in inhibiting early polycaryocytosis (EP) induced by BLV. We report here experiments which demonstrate that BLV induced antibodies are responsible for this inhibition. Serum fractionation by gel filtration and affinity chromatography indicates that EP inhibiting activity is mediated by immunoglobulins of the IgG class but not by those of the IgM or other classes. Furthermore, in view of their ion-exchange chromatographic behaviour, these antibodies were attributed to the IgG1 subclass. We also ruled out the participation in the EP inhibition rection of the other compounds like polypeptides, including serum complement and interferon or DNA and RNA. These results demonstrate that EP inhibition by bovine sera is specific of BLV induced antibodies.