FIG 1.
Pteropus alecto cells restrict primate lentiviruses. Cells from diverse mammalian species were infected with the indicated single-round retroviral vectors encoding eGFP in 3-fold dilutions over a 3-log range of viral inputs. At 72 h postinfection, cells were analyzed for eGFP expression and the percentage of GFP-positive cells was used to calculate the number of transducing units (TU) per milliliter of vector for each cell line. Bars represent the average titer ± standard deviation. N.D., not determined. This experiment was repeated at least 3 times for each virus with the same results. To overcome the lack of compatible viral receptors on bat cells, and to enable comparable viral attachment and entry results, vesicular stomatitis virus glycoprotein G (VSV-G) was used to pseudotype viral vectors, with the exception of foamy virus, which does not require pseudotyping in order to infect diverse vertebrate cell lines. Additionally, to standardize transcriptional activity and enable direct comparison of viral infectivities, the vectors employed an internal CMV promoter that mediates eGFP expression. For HIV-1, a nearly full-length HIV-1 NL4-3-derived env-negative reporter virus (HIV-1LTR) that expresses eGFP from the nef open reading frame under HIV-1 U3 and Tat control (70) was also tested.