A Simple Technic for Demonstrating Plaque Formation with Virus of Vaccinia.

Abstract

Single cell suspensions of chick embryo tissue were prepd. by putting the embryo through a strainer followed by differential centrifugation. These cells in nutrient fluid were added to Carrel flasks coated with a plasma clot. The cell sheet which formed over night at 37[degree]C was washed, the virus added, and the flask incubated for 1 hr. The cell sheet was then covered with a plasma clot and nutrient fluid was added. Plaques were visible upon staining with neutral red after 48 hrs. They appeared as round opaque areas of destroyed cells surrounded by pinkly stained living cells and reached a max. diam. of 1 mm. at 5 days. The plaques were absent when the virus was absent and their number increased in proportion to the concn. of the virus. The number of plaques correlated with the number of pox produced on the chorioallantoic membrane of the chick embryo and specific antibody reduced both the number of plaques and pox by 95%.