[Preparation and characteristics of temperature-sensitive mutants of the Venezuelan equine encephalomyelitis virus].

Fifteen ts mutants of Venezuelan equine encephalomyelitis (VEE) virus have been produced and studied. Two of them were isolated from a virus population grown in the presence of 5-fluorouracyl and 13 from a virus suspension treated with nitrous acid. The efficiency of plating 40 degrees/35 degrees of various mutants varied from 2 X 10(-2) to 6 X 10(-6). Three ts mutants had RNA- phenotype (RNA synthesis at a nonpermissive temperature was 1.5-3.3% of that of the wild type), 11 ts mutants had RNA+ phenotype (RNA synthesis decreased insignificantly, 32-75%), and one ts mutant was intermediate (18%).