Resistance of W38−/− chickens to ALV-J infection. (A) In vitro infection of fibroblasts derived from W38+/+, W38+/−, and W38−/− embryos with GFP-transducing J subgroup-specific retrovirus RCASBP(J)GFP. Chicken DF1 and Japanese quail QT6 cells were used as susceptible and resistant controls, respectively. Each value represents the mean of two technical replicates. Each group is characterized as mean ± SD (***P < 0.001, analysis of variance followed by unpaired t test). (B) RT-PCR quantification of ALV-J env gene in the serum of RCASBP(J)GFP-infected chickens. Each value represents relative units as the mean of triplicate quantifications of individual chickens. For the group of W38+/− chickens, the means ± SD are shown. (C) In vivo tumor induction in W38+/+, W38+/−, and W38−/− chickens. Weights of tumors induced with either 500 or 250 FFU are given as individual values and means ± SD. (D) In vitro infection of fibroblasts derived from W38+/+, W38+/−, and W38−/− embryos with GFP-transducing J subgroup-specific retroviruses RCASBP(J)GFP (HPRS; black), RCASBP(JPDRC)GFP (PDRC; red), RCASBP(JADOL)GFP (ADOL; blue), RCASBP(JWB)GFP (WB; green), and RCASBP(JZB)GFP (ZB; brown). Each value represents the mean of four technical replicates. Each group is characterized as mean ± SD.