FIG. 2.

Chronically infected PERV cell lines. (A) Level (cpm) of RT in the supernatant of 293T cells transfected with the following proviral constructs and passaged at 3- to 5-day intervals for approximately 50 days: PERV-A14/220 (A14/220) (1), PERV-Ap60 (A) and PERV-Bp17 (B) (2), and MLV 4070A (5). (B) Infectious titers of chronically infected cell lines, transduced with the p5G2 vector at a multiplicity of infection of >7 at day 40 of culture. Virus-containing supernatant was harvested 2 days later and titrated on human 293 cells. Levels of virus packaging the neomycin resistance gene were measured by G418 selection and represented as infectious per milliliter.