FIG 2.

Multicycle growth kinetics of parental rBC and rGBT and their chimeric derivatives in chicken embryo fibroblast (DF-1) cells. (a and b) rBC-based chimeras in which the envelope-associated protein genes M, F, and HN were replaced by their counterparts from rGBT individually (a) or in combination (b). (c and d) The converse: rGBT-based chimeras in which the M, F, and HN genes were replaced by their counterparts from rBC individually (c) or in combination (d). (e and f) rBC-based chimeras in which the polymerase-associated N, P, and L protein genes and the trailer (Tr) were replaced by their counterparts from rGBT individually (e) or in combination (f). (g and h) rGBT-based chimeras in which N, P, L, and Tr were replaced by their counterparts from rBC individually (g) or in combination. Briefly, DF-1 cells were infected at a multiplicity of infection of 0.01, supernatant samples were collected at 8-h intervals until 64 h postinfection, and virus titers were determined by TCID₅₀ limiting dilution assay and calculated using the method of Reed and Muench (24). Each time the supernatant was collected, an equal volume of maintenance medium was replaced. Asterisks indicate test of significance of the virus titer of a chimeric virus compared to the parental virus of that group at 24 h; P values were calculated based on a two-tailed, unpaired t test (95% confidence levels). ***, P = 0.0001 to 0.001, extremely significant; **, P = 0.001 to 0.01, very significant; *, P = 0.01 to 0.05, significant.