C-type virus protein p30 in blood from inbred mice correlates with their later incidence of leukemia

The major core protein, p30, of mouse C-type viruses was quantitated radioimmunologically in lymphoid organs and blood from inbred strains of mice. The concentration of p30 in thymus and spleen had a weak and moderate correlation, respectively, to leukemia frequency. In contrast, the concentration of p30 in blood from mice with a high incidence of leukemia (strains AKR and C58) was 100-fold increased at 2 months of age compared with 10 strains with a low incidence of the disease. The SJL mice, which have a high incidence of reticulum cell neoplasms, showed generally elevated, but variable, values. The high concentration in AKR blood developed during the first weeks of life. Approximately one-third of the DBA/2 mice had elevated levels after 4 to 5 months, whereas the values from mice of the 129 strain were low irrespective in their age. The major part of p30 appeared to be associated with the erythrocytes. The concentration of p30 in the blood seems to reflect the presence of replicating virus in mice. It identifies among the inbred strains a high leukemia group one-half year prior to disease.