Temperature-sensitive mutants of equine arteritis virus.

Seventeen temperature-sensitive mutants of equine arteritis virus, a nonarthropod-borne togavirus, have been isolated. 5-Fluorouracil, o-methylhydroxylamine and ethyl methanesulphonate were used as mutagens. The mutants were characterized by their ability to synthesize virus RNA and virus proteins at the permissive (35 degrees C) and restrictive temperature (40 degrees C) using autoradiography of cells labelled with 3H-uridine in the presence of actinomycin D and immunofluorescence respectively. Among the mutants, four were unable to synthesize virus RNA and virus proteins at 40 degrees C (RNA-/protein-). The other mutants were RNA-/protein+ (3); RNA +/-/protein- (2); RNA+/protein+ (6) and RNA+/protein- (1).