FIG. 1.
A 15-amino-acid peptide derived from the TVB receptor binds to ASLV-B SU. (A) Four overlapping biotinylated synthetic peptides derived from the first 45 residues of TVBS1 and TVBS3 (3). Residues corresponding to Cys-46, Cys-59, and Cys-62 were changed to serines (underlined). (B) TVB32-46 binds to an ASLV-B SU-immunoglobulin fusion protein. An ELISA was performed with the biotinylated peptides bound to streptavidin-coated plates and a subgroup B ASLV SU-immunoglobulin fusion protein, SUB-rIgG (12). The bound SUB-rIgG was detected by using an HRP-conjugated secondary antibody and a colorimetric substrate. (C) TVB32-46 binds specifically to SUB-rIgG. The ELISA was performed as for panel B with wells that were either coated (+TVB32-46) or not (−TVB32-46) with peptide and also with equal amounts of subgroup A- and E-specific SU-immunoglobulin proteins (SUA-rIgG and SUE-rIgG, respectively). (D) TVB32-46 binds to native ASLV-B Env expressed at the surfaces of infected cells. Chicken DF1 cells chronically infected with a subgroup B virus encoding EGFP [RCASBP(B)-EGFP] were incubated with increasing amounts of biotinylated TVB32-46 and with SA-APC (circle). For control purposes, uninfected DF1 cells were incubated with the maximal amount (a 10 μM concentration) of peptide used (square). The cell-associated APC fluorescent signal was quantified by flow cytometry. Data in panels B, C, and D are means and standard deviations (error bars) from at least two independent experiments that were performed in triplicate.