Factors affecting the propagation and assay of a herpesvirus of turkeys

Cultural conditions affecting the propagation and assay of a turkey herpesvirus (HVT) in chick fibroblasts were examined. Infected cells could be assayed with ease on secondary chick fibroblasts with either agar or agarose overlays. Most of the infected cells attached to uninfected cell monolayers within three hours of addition. Adsorption of cell-free virus to cell monolayers was complete in one hour. Studies on the propagation of HVT indicated that maximum numbers of infected cells were obtained before extensive cytopathology. The number of free cells in the medium increased after infection, though only a small fraction of these was found to be infectious. Increased serum or bicarbonate in the medium did not affect the yield of infected cells. These data clarify conditions important in obtaining and assaying infected cells.