Separation of a Soluble Antigen and Infectious Particles of Bovine Viral Diarrhea Viruses and their Relationship to Hog Cholera.

A soluble antigen present in infectious tissue culture fluids was separated from the infective virus particle by ultracentrifugation of two serologically related strains of bovine viral diarrhea viruses, NADL-MD and Oregon C24V. Neutralizing antibodies against the two viruses were absent in four hog cholera antisera, but present in significant titer in the commercially prepared antiserum. Precipitin tests utilizing the agar double diffusion technique formed a single line of identity between the concentrated soluble antigen of both viruses and NADL-MD and hog cholera antisera. No lines were observed using concentrated virus pellet and noninfected BEK cell antigens or control SPF calf and swine sera.