Heterogeneity of Bovine Antibodies Produced against Bovine Viral Diarrhea (BVD) Viruses and against a Soluble Antigen of BVD Produced in Cell Cultures

Abstract

Summary Sera from calves inoculated with a cytopathogenic bovine viral diarrhea (BVD) virus, a noncytopathogenic BVD virus, or with a soluble antigen (SA) from a BVD virus were fractionated into heavy (19 S) and light (7 S) components of γ-globulins by sucrose gradient ultracentrifugation. These antiserum fractions were tested for precipitating antibodies, for fluorescing antibodies, and for their capacities to neutralize BVD virus in cell cultures. Most 19 S fractions elicited lines of precipitation with a SA of BVD virus, but only the 7 S fraction produced from injections of SA into a calf precipitated, and only weakly, with the BVD-SA in Ouchterlony plates. All fractions, except a 19 S, combined with viral antigen produced in swine kidney cell line (PK-15) cultures in an indirect fluorescent antibody test. The 19 S fraction predominated in the bovine sera studied and persisted for as long as 20 weeks. Restimulation of animals with antigen did not produce a secondary effect and the “early-19 S,” “late-7 S” responses were not present in this immunologic system. The results of these studies are discussed in relation to studies of heterogeneity of other antigen-antibody systems, especially those dealing with viral systems.