Detection of group and interspecies reactivities in mammalian C-type virus p30 proteins and corresponding human antigens.

We previously reported the presence of RNA tumor virus related antigens in human leukemic sera. The antigens were detected by the ELISA method in 30%-40% of patients with acute leukemia [ l , 21. Since these antigens from human Sera that crossreact with primate C-type viral p30 protein had been observed with the ELISA method and since retroviral group and interspecies reactivities had been previously characterized mostly by competition radioimmunoassay, we examined the applicability and reliability of the ELISA method for the detection of group and interspecific determinants in p30 proteins of mammalian C-type retroviruses [4]. The specificity of the observed reaction was further demonstrated by competition ELISA, by preabsorption of the coating antibody with homologous and heterologous antigen, and by ELISA with F (ab'), fragments of the IgG molecules [ 5 ] . After exclusion of rheumatoid factor (RF) interference, the immunoaffinity purified human antigen was characterized by SDS polyacrylamide gel electrophoretic analysis, enzymatic digest, and peptide maps. The antigen found in human leukemic Sera is a protein distinct from common Serum proteins.