Mechanism of enhanced plaque formation by poliovirus in poxvirus-infected cells.

The mechanism of the enhancement by Yaba virus (YV) of poliovirus plaque formation was studied. Poliovirus adsorbed equally well to both YV-infected and normal J INET cells. Infectious RNA of poliovirus was also enhanced in YVinfected cells, thus indicating the step or sequence of steps of poliovirus growth cycle enhanced by YV may be those subsequent to poliovirus uncoating. One-step growth experiments revealed that the final yield and the release of progeny poliovirus were enhanced in YV-infected cells. This may account for the enhancement of the plaque size of poliovirus. The enhancement of the plaque number of the superinfecting virus by YV appeared to result from the interaction between a single YV-infected cell and a single infecting polio virus genome which failed to express its function under ordinary conditions. This enhancement may be brought about by the disturbance by YV of a host cellular defence mechanism other than that mediated by interferon.