TYPE OF PLAQUES AS A GENETIC CHARACTER OF POX GROUP VIRUSES

In the studied strains of pox group viruses there were found two types of plaques - transparent ones with smooth edges and clouded ones with uneven edges. The latter type of plaques was formed by strains with a marked neuropathogenicity for laboratory animals. The strain of ectromelia virus, in contrast to strains of smallpox vaccine, and cow- and rabbit pox, forms small- size plaques and is not capable of producing plaques at 38C. Strains of the virus of natural smallpox and alastrim were found to be incapable of forming plaques in the chicken fibroblast tissue culture at 36 and 38C. None of the studied strains of pox group viruses formed plagues at 40C. Differences in the capacity of the studied strains of pox group viruses to form plaques, as well as differences in size and type of plaques, were preserved in the process of passages in tissue cultures, chick embryos and animals, which is indicative of a genetic nature of this character.