Experiments are proposed to analyze immunity in chickens to avian sarcoma virus-induced tumors in order to define the role of endogenous retrovirus on the expression of tumor immunity. The working hypothesis to be tested is that immunological tolerance to the envelope glycoprotein of the endogenous retrovirus (subgroup E) is a predisposing factor to the formation of sarcomas at sites distal to the wing web site of inoculation of exogenous retrovirus (subgroups A-D). The proposed analysis will involve a comparison of tumor immunity in the context of subgroup B or subgroup G virus infection; the envelope glycoprotein of subgroup B, but not of subgroup G, virus is antigenically crossreactive with endogenous envelope glycoprotein so that immunological tolerance to the endogenous envelope glycoprotein should influence the expression of immunity to only the subgroup B virus. Our preliminary results indicate that the absence of virus neutralizing antibody does not facilitate distal sarcoma formation in the context of subgroup G virus infection, and experiments are proposed to ascertain the role of T cells in limiting distal sarcomas. Additional analysis will be aimed at determining the mechanism of formation of distal sarcomas, whether in fact formation involves virus spread or cell metastasis.
