QUALITY CHANGES IN VACCINIA VIRUS DURING ADAPTATION TO GROWTH IN CULTURES OF EARLE'S L CELLS.

Sharp, D. G. (University of North Carolina School of Medicine, Chapel Hill), P. Sadhukhan, and G. J. Galasso. Quality changes in vaccinia virus during adaptation to growth in cultures of Earle's L cells. J. Bacteriol. 88:309-312. 1964.-Although particle production improves rapidly with passage of vaccinia (mouse neurotropic strain) virus in L cells, plaque production improves much more slowly. Beyond the passage when maximal particle yield was reached (18th), further improvement in plaquing quality of 1,000-fold was observed. Particle count and plaque titrations showed that plaquing efficiency improves at comparable rates in either plaque-to-plaque passage on plates or in tube cultures inoculated at high multiplicity. The host cell is probably exerting some influence in addition to that of the selection of mutants from the initial population.