[Biological and genetic properties of a polyploid-forming mutant of the Venezuelan equine encephalomyelitis virus].

Some genetic and biological properties of the multiploid -forming mutant of Venezuelan equine encephalomyelitis virus as well as of standard and multiploid virions isolated from its population were analysed. The mutant steadily retained the capacity for formation of multiploid virions comprising up to 20% of the population both in passages in CEF culture and in the progeny of multiploid and standard virions. Owing to this, the concentration of multiploid virions in the population of this mutant remains at a constant level. Formation of multiploid virions compensates for the temperature-sensitive defect inherent in the standard virions which is associated with later stages of virus replication.