Effects of prophylactic treatment with the methanol extraction residue fraction of tubercle bacilli (MER) on the development of Rous sarcomas of chickens following challenge with the Rous sarcoma virus.

Three-month-old chickens were treated with the methanol extraction residue fraction of tubercle bacilli (MER) under different conditions, and subsequently challenged with living Rous sarcoma virus. The birds developed progressively growing sarcomas following viral challenge. A substantial proportion of the hosts which had been pretreated with MER under optimal circumstances (38 to 58%) showed complete and long-lasting regression of the neoplasms, and the survival of many of the animals that did succumb to progressively growing tumors was prolonged. An absolute condition for prophylactic efficacy of MER treatment in this model system was injection of the agent into the same body area (wing) into which subsequent viral challenge was introduced. The quantity of MER employed and the timing of the prophylactic administration were also decisive variables.