Partial characterization of two temperature-sensitive mutants of junin virus

Two temperature sensitive (ts) mutants of Junin virus, a member of Arenaviridae, have been partially characterized. Both mutants, named ts-32 and ts-40, had a relative plating efficiency 40 degrees C/34 degrees C lower than 10(-3) an exhibited a leak yield below 10(-4). Standard growth curves showed that at 34 degrees C the viral mutants multiplied slower than wt virus and at high multiplicity did not display autointerference. No differences in thermolability were observed between wt and ts mutants. By contrast, when the pathogenic properties of the mutants were investigated they were significantly attenuated for mice. At the restrictive temperature both mutants were unable to synthesize viral-specific polypeptides, while at the permissive temperature the pattern was similar to wt virus. Shift-up and down experiments suggested that ts defect is expressed between 2 and 4 hours post-infection. It is concluded that ts-32 and ts-40 are early function mutants. The possible nature of their defect is discussed.