FIG. 7.
Further analysis of receptor usage by the W141G K261E and W145R K261E mutant viruses. (A) Cell lines that do not express ALV receptors (NIH 3T3 and 293), cell lines that express only the quail Tva receptor (3T3pg950) or only the TvbS3 receptor (293tvbS3), or DF-1 cells that express the chicken Tva, TvbS3, TvbS1, and Tvc receptors were infected with 1 ml and 10-fold serial dilutions of W141G K261E, W145R K261E, RCASBP(A)AP [WT(A)], or RCASBP(B)AP [WT(B)] virus stocks, and viral titers were determined by AP assay. Results marked with an asterisk are less than 1 PFU/ml. (B) DF-1 cells chronically infected with a wild-type or mutant virus were removed from culture, fixed with paraformaldehyde, and incubated with 600 ng of chicken sTva-mIgG protein or 2,000 ng of sTvbS3-mIgG protein. The soluble receptor-envelope glycoprotein complexes were bound to a goat anti-mouse Ig antibody linked to phycoerythrin, and the levels of phycoerythrin were measured by FACS. In both graphs, results are averages from three different experiments. Error bars, standard deviations. ifu, infections unit.