Properties of mouse leukemia viruses. XVII. Factors required for successful treatment of spontaneous AKR leukemia by antibodies against gp71

AKR mice were treated with heterologous anti-gp71 antibodies under various conditions in order to establish the optimal criteria for effective suppression of leukemia development. The strongest effect was observed when mice were treated at birth; and when this regimen was used, prior treatment of the mothers did not provide additional protection. If treatment was delayed until Day 3 (Schwarz et al., 1979), the beneficial effect of the serum diminished sharply, emphasizing the presence of a narrow window very early in the life of the AKR mouse when antibody must be present in order to have an effect on subsequent leukemia development. A number of parameters were examined in the experimental mice and as in our previous study (Schwarz et al., 1979), suppression of leukemia, which occurred in 68% of the animals, correlated with elimination of viremia and appearance of natural antiviral antibodies. Interestingly, our results suggest that antibody therapy is primarily effective against the thymic form of the disease. The availability of nonviremic, antibody-positive animals afforded us the opporounity to examine if these characteristics could be transmitted to the offspring. From selected mating crosses, we successfully derived both F1 and F2 generations of AKR mice which possessed high titers of antiviral antibodies and were nonviremic at 21–28 weeks of age. It appeared that a maternal effect may be responsible for this phenomenon. The implications of these findings are discussed in relation to the development of AKR leukemogenesis.