Variability in the characteristics of pocks produced on the chick chorioallantois by white pock mutants of cowpox and other poxviruses

Abstract

White pock mutants of cowpox virus produce pocks in the CAM which ‘mimic’ those produced by the parent virus, in macroscopic and microscopic appearance, and in the amount of virus they contain. The proportion of such ‘atypical’ pocks was influenced by the age and source of embryo, incubation temperature and position of the CAM during incubation. Similar results were obtained with white pock mutants isolated from strains of vaccinia, rabbitpox and monkeypox. The appearance of pocks produced by variola, alastrim, ectromelia and vaccinia (Lister) was unaffected by changes in environmental conditions.I would like to thank Professor K. McCarthy, Professor K. R. Dumbell, Dr C. H. Taylor-Robison and Dr C. R. Madeley for their interest and for kindly providing virus strains, and Miss M. Seyfang for technical assistance.I would like to thank the Committee on Research, Liverpool University, for a grant towards the cost of the colour plate.