Mechanism of pock formation by Shope fibroma virus on monolayers of rabbit cells.

Israeli, Ella (Rambam Hospital, Haifa, Israel). Mechanism of pock formation by Shope fibroma virus on monolayers of rabbit cells. J. Bacteriol. 92:727-732. 1966.-The mechanism of pock formation by the Shope fibroma virus (SFV) on rabbit cultures in vitro was studied with the use of p-fluorophenylalanine, 5-bromodeoxyuridine, and 5-iododeoxyuridine. The inhibitors were used to inhibit, and to initiate, virus replication at different times after infection. It was shown that pock formation required virus replication to a threshold value of 25 plaque-forming units per pock area, and that this amount of virus can be accumulated during a period about 3 days less than that required for pock formation. Inhibition of virus growth, and of cell multiplication, after this threshold has been reached, did not prevent pock development. A delay in the onset of virus growth required to reach the threshold virus content, caused an about equivalent delay in the time of pock formation. In the absence of inhibitors, pocks were not formed after infection of 84 rabbit embryo clones, or five mixtures of clones containing five to seven clones each. The results indicate that pock formation by SFV in vitro was the result of cell aggregation, and not of cell multiplication, in special types of cells.