Abstract
Plaque formation by the HF strain of herpes simplex virus in HeLa cells under agar overlay was possible when a line of this strain highly adapted to HeLa cells was used, whereas the homologous strain, passaged in eggs or lowly adapted to HeLa cells did not form any visible plaques using the same technique. Experiments were performed to investigate the influence of different diluents, cellular factors and conditions of virus adsorption. It was found that 0.1% yolk-saline could replace the ordinarily used main-tenance medium as a diluent. Among three lines of S3 HeLa cells maintained indifferent laboratories, a subclone possessing a rapid cellular growth rate showed the highest sensitivity to the virus. Monolayers which scarcely covered the whole glass surface were most suitable for virus inoculation. Such monolayers could be stored at 20C for 2 days before use without lowering the efficiency of plaque formation. The highest titer of virus was obtained when adsorption of inoculated virus was allowed to take place at 37C for 2hr. This titer was about equal to the plaque titer obtained in primary chick embryo cell cultures.
