Investigations of the reproductive capacity temperature marker of polioviruses

The effects of increased incubation temperature upon the replication cycle of an rct 40 − and an rct 40 + strain were studied. It was found with CHAT, the rct 40 − strain, that the higher temperatures did not inhibit the rate at which the virus was absorbed or at which it entered into the eclipse phase of its reproductive cycle. The production of infectious CHAT-RNA by infected cells, however, was found to be markedly reduced at 40°C as compared to 37°. With Mahoney, an rct 40 + strain, similar amounts of infectious RNA were produced at the two temperatures. The plating efficiency of Mahoney was improved if infected monolayers were incubated for a short time at the higher temperature; a result which may be correlated with the observation that a temperature of 40° appears to stimulate the entrance of virus into the eclipse phase. A sensitive test of the “rct” marker was developed, employing an increased incubation temperature for a limited period of time during the early part of plaque formation. The effect of deuterium oxide upon the replication cycle of poliovirus was studied. Of particular interest was the fact that CHAT virus replicated and formed plaques at 40° if infected cells were deuterated. The progeny of CHAT plaques which developed at 40° showed an increased tendency (compared to parental virus) to form plaques after limited exposure of infected monolayers to 40°.