FIG. 1.
sCD134 activation of FIV Env. (a) sCD134 activation of FIV Env-mediated, CXCR4-dependent viral entry. Target CrFK cells were infected with β-Gal FIV particles pseudotyped with the Env of FIV-PPR, a primary FIV isolate (21). Particles were preincubated in the absence or presence of sCD134-Fc (100 nM). Viral entry was detected 48 h later by a β-Gal assay. Infection in the presence of AMD3100 (1 μg/ml), a CXCR4 antagonist, was used to show the strict dependence on CXCR4 for viral entry. (b) One-domain (D1) and wild-type (WT) CD134-Fc fusion proteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and revealed by Coomassie blue staining. (c) Dose-response curve of sCD134-Fc for activation of viral entry. Target CrFK cells were infected with β-Gal FIV particles pseudotyped with the Env of FIV-PPR, a primary FIV isolate. Particles were preincubated in the presence of Fc alone, one-domain sCD134 (sCD134D1-Fc), wild-type soluble CD134 (sCD134WT-Fc) at the indicated concentrations. Viral entry was assessed 48 h later by a β-Gal assay. RLU, relative light units.