Prevention of Gross virus-induced leukemia in progeny of immunized female rats.

In rats and mice, infection with Gross leukemia virus is age dependent, and leukemogenesis takes place only before and shortly after birth. A shift from complete susceptibility to total resistance occurs at about 2 weeks of age. In order to transmit resistance to induction of leukemia, we gave adult female rats of 3 different strains a single injection of Gross leukemia virus before or during pregnancy. Offspring of these and of nonimmunized control mothers were treated by injection with Gross leukemia virus at 1 to 4 days of age. All 61 rats born from control, nonimmunized mothers died with leukemia 62 to 90 days after injection, while none of the offspring of immunized mothers developed leukemia 7 to 10 months after injection. Sera of protective mothers reacted significantly with the type-specific antigen in complement fixation tests.