MUTAGENESIS IN GROUP A ARBOVIRUSES BY 5-AZACYTIDINE
FORT DETRICK FREDERICK MD
Pagination or Media Count:
A new cytidine analogue, 5-azacytidine 5-AzaC, not previously shown to be a viral mutagen, was highly mutagenic for an attenuated strain of Venezuelan equine encephalitis VEE virus and possibly for other strains. Treatment of the T strain, a small-plaque, attenuated variant of VEE virus, with 25 micrograms 5-AzaCml gave approximately a 2 log loss in titer compared with untreated controls, but the frequency of large-plaque revertants among survivors was increased 77- to 220-fold. The induced large-plaque formers were genetically stable mutants, and not unstable, phenotypic variants. Several types of reconstruction experiments indicated that the increased frequency of large- plaque formers resulted from induced mutation and not from selective inactivation of either variant in vitro in the absence of cells or from selection during plaquing or growth in chick embryo fibroblast cultures. Isolates with new growth-temperature characteristics also were derived from several different viral strains treated with 5-AzaC. Uridine reverses both the lethal and mutagenic action of 5-AzaC. The early stages of the viral growth cycle appeared to be particularly sensitive to both 5-AzaC action and uridine reversal.