Quantitative Titration of Vaccinia Virus on the Chorioallantoic Membrane

Abstract

Summary: Detailed studies of vaccinia virus titrations on the chorioallantoic membrane of the embryonated egg are described. Experiments to determine the optimal experimental techniques for such titrations indicate that the use of membranes free from non-specific damage is essential. In addition, 12-day-old eggs inoculated with 0.2 ml of virus suspension and incubated for 3 days give results of considerable precision. Within a range of 3 to 20 pocks per membrane, a linear relationship exists between the number of pocks and virus dilution. Precision is greatest when pock counts number between 10 and 20 per membrane. Various aspects of pock-counting titrations with vaccinia virus are discussed.