Abstract
Poxvirus infection results in the production of virus-specific surface antigen (S-antigen) which is clearly distinguished from intra-cytoplasmic virus antigen (V-antigen) (Miyamoto & Kato, 1968, 1971; Ueda, Ito & Tagaya, 1969). In a study of the development of these antigens in several different established cell lines, we observed that some cells are relatively poor producers of S- and V-antigens and that in these cells treatment with trypsin markedly enhances S-antigen production but not V-antigen production.