Mice were immunized against Moloney sarcoma virus (MSV) challenge by the serial inoculation of increasing doses of live MSV preparations. Only 15% of vaccinated mice developed tumors after challenge with a dose of MSV sufficient to cause tumors in 100% of control mice. This resistance was not accompanied by detectable levels of MSV-neutralizing antibody. Adult mice susceptible to MSV tumor induction displayed antibody levels following tumor regression that were sufficient to neutralize greater than 103.2 median effective doses of MSV. Antibody titers were independent of initial MSV dose but were directly related to tumor duration.

The pathogenesis of MSV-induced tumors in weanling and adult mice was characterized by spontaneous regression of tumors (rhabdomyosarcomas) followed by a relapse phase. Onset of relapse was correlated with architectural changes in the mesenchymal region surrounding splenic follicles. This was followed by the appearance of metastatic lesions in various organs and subsequent death.

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This investigation was supported in part by USPHS Training Grant CA-05175.

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