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Altered pathogenicity of avian myelocytomatosis (MC29) viruses with mutations in the v-myc gene
Abstract:
Avian myelocytomatosis virus MC29 inoculated into the wing web of 1-day-old Brown Leghorn chickens causes a high incidence of tumors, predominantly endotheliomas that are apparently induced directly by the action of the viral myc gene. Mutants of MC29, in which portions of the v-myc gene have been deleted and which have reduced ability to transform macrophages in vitro, induce few tumors, among which lymphomas and osteopetrosis predominate. Analysis of lymphomas from birds infected with mutant MC29 suggested that they were a result of helper virus action rather than the mutant MC29.
Insights
Avian myelocytomatosis virus MC29 causes tumors, mainly endotheliomas, via its myc gene. Mutants lacking parts of the myc gene induce fewer tumors, suggesting helper virus involvement in lymphomas.
Area of Science:
- Oncology
- Virology
- Genetics
Background:
- Avian myelocytomatosis virus MC29 (MC29) is known to induce tumors in chickens.
- The viral myc gene (v-myc) is implicated in tumor development.
Purpose of the Study:
- To investigate the role of the v-myc gene in MC29-induced tumorigenesis.
- To differentiate between direct v-myc oncogene action and helper virus involvement in tumor formation.
Main Methods:
- Inoculation of 1-day-old Brown Leghorn chickens with wild-type MC29 and MC29 mutants lacking portions of the v-myc gene.
- Tumor incidence and type analysis.
- Histopathological examination of induced tumors, particularly lymphomas.
Main Results:
- Wild-type MC29 induced a high incidence of tumors, predominantly endotheliomas, suggesting direct v-myc action.
- MC29 mutants with deleted v-myc portions showed reduced tumor induction, with lymphomas and osteopetrosis predominating.
- Analysis indicated that lymphomas in birds infected with mutant MC29 were likely caused by helper viruses, not the mutant itself.
Conclusions:
- The v-myc gene plays a crucial role in inducing endotheliomas directly.
- Tumorigenesis by MC29 mutants can be influenced by helper viruses, leading to different tumor types like lymphomas.