Studies on the early antigens induced by vaccinia virus.

Abstract Antisera directed against vaccinia-induced early antigen(s) detectable by immunofluorescence on the surface of infected cells (S-antigen) were prepared by immunizing rabbits with rabbit kidney cells infected with a conditional lethal mutant. Rabbit sera against soluble early antigen preparations from HeLa cells infected with the mutant were also reactive to the S-antigen. These sera did not stain cytoplasmic inclusions when infected cells were acetone-fixed. The reactivity of the antisera was not affected by extensive absorption of the sera with host cell antigens. Neither types of antisera neutralized vaccinia virus, but fixed complement when reacted with a homogenate of vaccinia-infected cells as well as with soluble early antigen preparations. Two precipitation bands were observed by immunodiffusion between these sera and a homogenate of vaccinia-infected CAM, which coalesced with a portion of several bands formed between a hyperimmune anti-vaccinia rabbit serum and the same antigen. The relationship between the S-antigen and the soluble early antigens was discussed.