Nuclear polyhedrosis virus detection: relative capabilities of clones developed from Trichoplusia ni ovarian cell line TN-368 to serve as indicator cells in a plaque assay.

Cloned cell lines from the established Trichoplusia ni line TN-368 appear to differ from one another in their relative capabilities to serve as plaque assay indicator cell lines for Autographa californica nuclear polyhedrosis virus. Although there seems to be little correlation between their relative generation times and their efficiency in supporting plaque formation as indicator cell lines, there does seem to be a relationship within a given line between its capability to serve as an indicator and its phase of growth as a population; i.e., lag, logarithmic, or stationary. Both the parent line and clone 10 were more efficient indicators when they were in the logarithmic phase of growth than when in either the lag or stationary phases. Also, there appears to be a rough correlation between the capability of a given clone to serve as an indicator and the rate at which polyhedra first appear in the nuclei of the infected cells, with the best indicators producing polyhedra first. Increased incubation time has no effect on equalizing the plaque assay results for the less efficient clones. It was observed, also, that those clones that are the least efficient as plaque assay indicators produce the most external PFU per cell.