A Recovered Avian Myelocytomatosis Virus That Induces Lymphomas in Chickens: Pathogenic Properties and Their Molecular Basis

The avian myelocytomatosis virus MC29 induces neoplastic diseases in chicken, including myelocytomas and tumors of kidney and liver, which are due to the action of the v-myc gene. However, MC29 has never been reported to cause lymphoid tumors, the disease associated with activation of the c-myc gene by the insertion of a lymphoid leukosis virus genome. We have analyzed a recovered MC29 virus, HBI, which has a myc gene containing c-myc sequences, acquired by recombination with the cellular gene, and some v-myc sequences. Inoculation of HBI into chickens resulted in lymphoid tumors independent of the bursa. Antigenically these tumors were made up of T and B cells. Molecular analysis showed HBI proviral DNA in 36 of 39 tumors analyzed, with no obvious alteration of c-myc, and the HBI gag-myc fusion protein, p 108, could be detected in tumor cells. These data are discussed in terms of the mechanism of target-cell specificity for transformation by the myc gene.