FIG. 4.

Marker transfer of the comet-forming phenotype. BS-C-1 cells were infected with vΔA36R and were then transfected with the PCR product of the A33R ORF of vΔA36R.c1 (A) or that of vaccinia virus strain WR (B) or with the PCR product of the B5R ORF of vΔA36R.c3 (D) or with that of WR (E). The cells were harvested after incubation for 2 days, and the diluted lysates were analyzed by plaque assay in BS-C-1 cells with fluid medium. Plaque-purified recombinant viruses, obtained by marker transfer of the A33R (C) and B5R (F) ORFs of vΔA36R.c1 and vΔA36R.c3, respectively, were assayed on BS-C-1 cell monolayers with fluid medium.