Oncornavirus envelope glycoprotein in serum of mice

Sera of all mice tested except 129_Gix- contained the envelope glycoprotein of murine oncornaviruses. In serum of New Zealand mice, where the envelope was found in greatest concentration, most of it was present as free glycoprotein, not as virions or a protein-antibody complex. The identity of the protein was demonstrated by antibody binding and purification of a specific component of about 70,000 daltons. The virion 30,000-dalton protein and the virion internal protein of 12,000 or 15,000 daltons were detected in measurable quantities only in serum of high incidence of leukemia mice. Serum antibodies to the purified virus glycoprotein could not be detected, either with Rauscher virus gp69/71 or Gross virus gp70. Control studies showed that antibodies against the viral glycoproteins of Rauscher and Gross viruses were present in serum of BALB/c mice immunized with Friend virus or Friend virus-induced BALB/c tumor cells expressing the viral envelope glycoprotein.