FIG. 2.

Selection of ALV(A) variants resistant to quail sTva-mIgG receptor interference. Viral growth was monitored by ELISA for the ALV CA protein. (A) TF/sTva-4 cells, a cell line derived from DF-1 cells transfected with the TFANEO/stva-mIgG plasmid and expressing quail sTva-mIgG protein, were challenged with ∼5 × 10⁶ IFU of RCASBP(A)AP preadsorbed with supernatant containing quail sTva-mIgG protein prior to infection (□). As controls, the TFANEO-alone DF-1 cell line was challenged with ∼1 IFU (●) or ∼10 IFU (■) of RCASBP(A)AP. The arrows indicate the 3-day period of transient cytotoxicity observed in the challenged TF/sTva-4 culture. (B) Uninfected TF/sTva-4 cells were infected with 0.1 ml of day 24 supernatant from the challenged TF/sTva-4 culture (□) and 0.1 ml of supernatant from a TFANEO-alone culture (●) (see panel A). O.D., optical density.