Modification of Oncogenic Effects of S-Polyoma Virus by “Attenuated“ M-Polyoma Virus

Summary

An “attenuated” polyoma-virus variant (M polyoma) was used to modify the response of C3Hf/Bi mice to the highly oncogenic variant (S polyoma) of identical origin but maintained on P388 D₁ cells under different culture conditions. When C3Hf/Bi mice less than 24 hours old received M virus, followed by S virus at 10 days of age, only 3 of 37 (8%) developed polyoma-type tumors. Few primary sites of tumor induction were observed. In contrast, recipients of control tissue culture medium on the day of birth, followed by S-polyoma virus on the 10th day, had a high frequency of polyoma-type tumors, 47.5 percent (19 of 40), appearing as early as 3 months. Many primary sites of induction were seen. Lesions of the renal-cortical tubules were more common and more severe in this group. Neutralizing and hemagglutination-inhibiting-antibody titers were observed at low levels in C3Hf/Bi mice at the time of introduction of S virus and reached high levels by the 20th to 30th day. Although the suppression of oncogenicity of S virus may therefore be the result of viral antibody produced by infection with M virus, the possible effects of viral interference or “interferon” production must also be considered.