Figure 1.

The TVA-EGF protein. (A) A model of TVA-EGF mediated ALV-A infection. TVA-EGF is comprised of the extracellular domain of TVA fused via a proline-rich linker region to the mature form of human EGF (see Materials and Methods). TVA-EGF was predicted to bind to ALV-A SU ENV and to cell surface EGFRs, promoting viral entry. (B) TVA-EGF was produced in the extracellular supernatants of transfected human 293 cells. Samples of extracellular supernatants taken from 293 cells that were either not transfected (−) or transfected with plasmid DNA encoding TVA-EGF (+) were subjected to SDS/PAGE. After transfer to a nitrocellulose membrane, the TVA-EGF protein was detected by immunoblotting with an ALV-A SU-Ig fusion protein (11) and a horseradish peroxidase-coupled secondary antibody followed by enhanced chemiluminescence (Amersham). Molecular mass markers are given in kDa.