Abstract
Summary
Four viruses, wild measles (Woodfolk), attenuated measles (Edmonston strain), and JAC and LEC SSPE viruses, were compared for their susceptibility to 6-azauridine, an RNA inhibitor. All four were found susceptible to the drug. When the drug was incorporated into the agar overlayer of the infected tissue culture, the SSPE viruses were inhibited by the concentation of 1 μg/ml and blocked by the concentration of 10 μg/ml, whereas the other two viruses showed inhibition and block at concentrations of 10 μg/ml and 100 μg/ml, respectively. When the drug was added 1 hr postinfection, the SSPE viruses were inhibited by 1 μg/ml and blocked by 10 μg/ml. Under the same circumstances the measles viruses showed some inhibition of synthesis, but could not be blocked, even by the concentration of 100 μg/ml. Addition of the drug 18 hr postinfection still substantially inhibited synthesis of SSPE viruses, but did not block it completely. The two measles viruses were only minimally affected by the drug added at the later time. The greater sensitivity of the SSPE viruses to the action of 6-azauridine serves as an additional characteristic distinguishing them from measles virus.
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