Immune response to oncornaviruses and tumor-associated antigens in the chicken.

Two principal virus-directed antigens have been identified on the surface of oncornavirus-infected chick embryo cells. One is identical with the major virus type-specific envelope antigen, which is a glycoprotein with a molecular weight of 85,000. The 2nd antigen (tumor-specific cell surface antigen) is specific for transformed cells, i.e., absent from productively infected but nontransformed cells. This antigen has been identified as a glycoprotein with a molecular weight of 100,000 and was not found in the mature virion. Remarkably, both antigens induce humoral as well as cellular immunity in the chicken. It could be shown that cells can be killed in cytotoxic assays via either the tumor-specific cell surface antigen or the virus envelope glycoprotein alone.