Latent Period in Monkey Kidney and HeLa Cell Monolayer Cultures Infected with Poliomyelitis Virus ∗

Summary

By repeated replacement of the supernatant fluid in a culture of monkey kidney cells or HeLa cells inoculated with poliomyelitis virus, non-adsorbed parental virus can be removed, and the earliest release of progeny virus can be measured. Under the conditions described a constant latent period of 3½−4 hours was obtained for monkey kidney cultures after multiplicities of exposure ranging from 280-28 PFU/cell and for HeLa cultures after multiplicities of exposure of 0.7 PFU/cell. In the monkey kidney cells lower multiplicities of exposure increased the latent period to 4-5 hours, and in HeLa cells higher multiplicities of exposure reduced the latent period to 3−3½ hours. A variation of pH during the adsorption period between the values 6.0−8.0 did not perceptibly affect the latent period or the amount of virus released. The length of time allowed for adsorption, when greater than 15 minutes, did not affect the latent period or the amount of virus released. When only 5 minutes were allowed, the latent period was lengthened and the yield was diminished. The lowering of temperature during adsorption from 37°C to 20°C diminished the yield of virus. Virus propagation at 20° was negligible.