FIG. 3.

Overview of different culture conditions tested for effects on viral fitness. (A) Cultures with nonlimited life span of infected cells. Cultures were inoculated with virus at a low MOI (0.005), and the virus was allowed to spread. Cells were maintained at density below 2 × 10⁶ and the medium was replaced every day, but no fresh cells were added. (B) Cell-based rapid turnover system. Cultures were inoculated at a 0.01 MOI. Virus was passaged to an excess of fresh cells every 2 days by transferring 1/10 of cells from infected cultures. (C) Virus-based rapid turnover system. Cultures were inoculated at a 0.01 MOI. Virus was passaged to fresh cells every 2 to 3 days by transferring 1/10 of cell-free virus-containing medium. (D) DC-SIGN-based rapid turnover system. Cultures were inoculated at a 0.01 MOI. Virus was passaged to fresh cells every 2 days by prebinding of cell-free virus to Raji cells expressing DC-SIGN, washing off unbound virus, and mixing these cells with noninfected target cells.