FIG. 5.

Induction of green fluorescence by infections with triple virus or transduction with retroviral particles induced by triple virus. CV-1 cells directly infected (1 PFU per cell) with the triple virus showed a strong fluorescence 12 h after infection (A), while the wild-type (wt) virus did not induce a signal (B). The characteristic cytopathic effects could be observed in the phase contrast picture (lower panels). Supernatants of CV-1 cells infected with the triple virus were used to transduce NIH 3T3 cells. Green fluorescence of NIH 3T3 clones after 6 days is shown (C). A parallel experiment with the same cells transduced with control supernatants (wild-type virus-infected CV-1 cells) did not result in a signal (D).