Herpes-Type Virus Isolated in Cell Culture From Tumors of Chickens With Marek's Disease. II. Studies In Vivo

Summary

This investigation was designed to provide further evidence on whether a herpes-type virus (HTV) isolated from the tumors of chickens with Marek's disease (MD) was involved in the etiology of the condition. Virus was isolated in cell culture from all 8 field outbreaks of the disease and from 30 of 38 tumors examined. The HTV was also recovered from 4 laboratory strains of MD previously maintained by bird-to-bird passage. In vivo experiments showed the MD infectivity for chicks of cell cultures infected with the HTV was associated quantitatively with the titer of cells in those cultures carrying the virus. Furthermore, the spontaneous occurrence of the HTV in cultures derived from the kidneys of apparently normal chickens was associated with the ability of those infected cells to induce MD when inoculated into susceptible chicks. The MD infectivity for chicks of HTV-infected cultured cells was entirely cell-associated, and the propagation of MD infectivity for chicks in cell culture was inhibited by 2′-deoxy-5-iodo-uridine. Both these properties were common with those of the HTV. These findings are convincing evidence that the HTV is associated with the etiology of MD. This conclusion is discussed briefly in relation to other oncogenic DNA viruses.