Properties of mouse leukemia viruses. XVI. Suppression of spontaneous fetal leukemias in AKR mice by treatment with broadly reacting antibody against the viral glycoprotein gp 71.

AKR mice were treated early in life with antibodies prepared in a goat against the major glycoprotein gp71 of Friend murine leukemia virus (FL V) and evaluated over a period of up to 2 years for various parameters associated with AKR thymoma/lymphoma. If both the mothers and offspring were given the antibody, suppression of AKR disease was observed to the degree that the 50% incidence of leukemia was delayed by about 1 year. A lesser effect was found if the treatment was initiated at an age of 3 days and application of the antibody to either mothers alone, or treatment of the mice at later times (39 days) was not successful. Thus, it was concluded that the critical period for treatment is between birth and the first few days of life. Postmortem examination of animals that were successfully treated during this early period revealed a significant proportion exhibiting a unique leukemic pattern. In addition, several died from nonleukemic neoplasms as well as other causes. Levels of virus or antiviral antibodies were also determined at various times in individual mice which had been segregated in family groups. The results demonstrated that overall, successful antibody treatment resulted in (1) suppression of virus and (2) development of significant levels of antiviral antibodies. In contrast, control mice exhibited the opposite pattern: high levels of virus and no detectable antibody. Moreover, it could be shown that antibody treatment reduced the incidence of MCF-like recombinant virus isolation. A hypothesis is presented which suggests that the main function of the administered antibody is to disturb a key event occurring during the early stages of life of the AKR mouse, which is of critical importance for the development of leukemia from 6 months of age onwards.