Figure 3.

MLV-lacZ (ALV-B)/TVB-EGF complexes are stable at 37^oC. MLV-lacZ (ALV-B) (A) or MLV-lacZ (ALV-B Env)/TVB-EGF (B) complexes were incubated at 37°C for different time intervals before addition to M5:S3/T cells or to M5 cells, respectively. The number of infected cells was measured by lacZ staining. The results shown reflect the percentage remaining of the starting virus titer (at t = 0). The starting titer of MLV-lacZ (ALV-B) was approximately 2 × 10⁵ lacZ-positive colonies per ml and that of the virion/TVB-EGF complexes was approximately 3 × 10⁴ lacZ-positive colonies per ml.