Evidence that avian tumour virus-immune chicken sera recognize only viral structural antigens on the surface of avian tumour virus-infected cells.

The specificity of the humoral response of chickens to avian tumour viruses (ATV) was investigated by reacting ATV-immune sera with Triton X-100 extracts of uninfected, infected and transformed chicken embryo fibroblasts. Analysis of these immune reactions by polyacrylamide gel electrophoresis revealed that avian leukosis virus-challenged and Rous sarcoma virus-challenged chickens recognized only two major cell surface antigens of 100000 and 29000 mol. wt. which were present on transformed and non-transformed virus-producing cells. No labelled antigens were precipitated from uninfected cells or transformed cells producing the envelope-defective mutant RSV(-). The antigens were shown to be related to the major envelope glycoproteins of the virus and to contain group-specific determinants common to ATV subgroups B and C. No group-specific determinants common to ATV subgroups A and B or subgroups A and C were detected. Chickens were found to have a strong antibody response to the 100000 and 29000 mol. wt. proteins prior to and during tumour rejection, even in the absence of neutralizing antibody to the challenge virus. No tumour-specific surface antigen distinct from the virion structural antigens was detected by any of the immune chicken sera on any of the transformed cells tested.