A New Mutant of Dermovaccinia Virus

Abstract

DURING the course of serial one-day egg passages of a strain of the chorioallantoic membrane-adapted dermovacoinia virus (DIE strain)¹, a new minute pock mutant was observed. This arose at the 13th one-day egg passage, when tiny pocks mixed with larger pocks typical of dermovaccinia were seen. The former increased in proportion during further one-day egg passages, and finally excluded the original virus. The mutant strain (DIs) was obtained in a pure form by two cycles of clone purification. These were initiated by a single pock produced on one chorioallantoie membrane by the inoculation of limiting dilutions of the fifteenth one-day egg passage. Some biological characteristics of this mutant were investigated and are described in this communication.