Relationship Between Immunologic Maturation and Viral Oncogenesis in Hamsters

Summary

The development of immunocompetence to sheep erythrocytes (S-RBC) was studied in hamsters and related to susceptibility of the animals to tumor induction by adenovirus 12 and simian virus 40 (SV40). Both normal and virus-infected hamsters were challenged with S-RBC at 1, 2, 3, 4, or 6 weeks of life, and the number of antibody plaque-forming cells (PFC) was determined by the localized hemolytic plaque technique in cigar gel. Normal control hamsters formed very few splenic antibody plaques when immunized at 1 week of age. Immunoresponsiveness increased rapidly thereafter so that, by the 3d–4th week of age, relatively large numbers of antibody forming cells appeared after S-RBC immunization. Nonimmune hamsters had very few “background” PFC until the 2d–4th week of life. Inoculation of test hamsters at birth with either SV40 or adenovirus 12 had little or no effect on the capacity of the animals to respond subsequently to S-RBC at 3 or 4 weeks of age. The number of PFC was moderately depressed when challenged at 1 and 2 weeks of age, as compared to noninfected controls. There was no detectable effect on development of background PFC to S-RBC. Susceptibility to tumorigenesis was directly related to the age of the animal at infection. More than 95% of the animals inoculated before 3 days old developed tumors between 90 and 150 days of age. About 20–25% of the hamsters developed tumors when infected at 1 or 2 weeks of age, and none developed tumors with either virus when 3 weeks old or older.