Nef is required for optimal SIV replication in rhesus astrocytes. (A) Astrocytes were infected with SIV/17E-Fr or SIV/Fr-2 [input normalized by TCID50 (multiplicity of infection = 0.1)]. (B) Astrocytes were infected with SIV/17E-Fr, SIV/17E-Fr(−myr), SIV/17E-Fr(−nef), or SIV/17E-FrΔnef [input normalized by TCID50 (multiplicity of infection = 0.1)]. (C) Astrocytes were infected with SIV/17E-Fr, SIV/Fr-2, SIV/17E-Fr(−myr), or SIV/17E-FrΔnef [input normalized by particle number (50 ng of p27)]. Supernatants in all experiments were sampled at various times postinfection (PI) and assayed for viral p27. Data are representative of several independent experiments.