Detection and evaluation of feline oncornavirus-induced cell surface antigen(s) shed from cells in vitro

A method for preparation of soluble feline oncornavirus-induced cell surface antigens was described. This technique relied upon the natural release of antigen(s) from FL-74 feline lymphoblastoid cells during their maintenance at 37 degrees in serum-deficient medium. When concentrated and clarified spent medium from 4-day cultures was tested for its antigen content by inhibition of humoral cytotoxicity, it was found that this natural production of soluble antigen provided more feline oncornavirus-associated cell membrane antigen per cell than did a solubilization procedure in which papain was used. The shed antigen preparation was immunogenic in cats, eliciting humoral antibody that was reactive with the surface of FL-74 Cells and feline sarcoma virus-transformed nonproducer mink cells but was not reactive with feline leukemia virus in a virus neutralization assay.