Accession Number : AD0427615


Title :   DIFFERENCES IN MAXIMUM AND MINIMUM PLAQUE-FORMING TEMPERATURES AMONG SELECTED GROUP A ARBOVIRUSES,


Corporate Author : ARMY BIOLOGICAL LABS FREDERICK MD


Personal Author(s) : Brown, Arthur


Report Date : Nov 1963


Pagination or Media Count : 22


Abstract : The parent strain of Venezuelan quine encephalitis (VEE) and of Eastern equine encephalitis (EEE) viruses show distinct plaque fronts at maximum temperatures t sub f-max of 46 C. Two attenuated variants of VEE (T and A) show a t sub f-max of 43 C, and 45 C, respectively. All four viruses show indistinct plaque fronts at a minimum temperature t sub f-min of 24.5 C; as much as one per cent of the inoculum formed plaques that were distributed between the t sub f-min and 20 C. From VEE-inoculated plates, the progeny derived from one of 31 plaques selected below the t sub f-min was avirulent and resembled T. T had a selective advantage over VEE in passage experiments in liquid cultures at low temperatures. Virulent mutants of T, resembling VEE, were isolated from plaques beyond the t sub f-max of T only after overcoming a reversible interference effect in which T interfered with plaque formation of VEE above the t sub f-max. The possible relation of t sub f-max and t sub f-min to virulence among these viruses is discussed. (Author)


Descriptors :   *EQUINE ENCEPHALOMYELITIS VIRUS , TEMPERATURE , VIABILITY , SURVIVAL(PERSONNEL) , CELLS(BIOLOGY) , BIOASSAY , TISSUE CULTURE


Distribution Statement : APPROVED FOR PUBLIC RELEASE