Snitkovsky S, Young J A
Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston MA 02115, USA.
Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):7063-8. doi: 10.1073/pnas.95.12.7063.
TVA, the cellular receptor for subgroup A avian leukosis viruses (ALV-A) can mediate viral entry when expressed as a transmembrane protein or as a glycosylphosphatidylinositol-linked protein on the surfaces of transfected mammalian cells. To determine whether mammalian cells can be rendered susceptible to ALV-A infection by attaching a soluble form of TVA to their plasma membranes, the TVA-epidermal growth factor (EGF) fusion protein was generated. TVA-EGF is comprised of the extracellular domain of TVA linked to the mature form of human EGF. Flow cytometric analysis confirmed that TVA-EGF is a bifunctional reagent capable of binding simultaneously to cell surface EGF receptors and to an ALV-A surface envelope-Ig fusion protein. TVA-EGF prebound to transfected mouse fibroblasts expressing either wild-type or kinase-deficient human EGF receptors, rendered these cells highly susceptible to infection by ALV-A vectors. Viral infection was blocked specifically in the presence of a recombinant human EGF protein, demonstrating that the binding of TVA-EGF to EGF receptors was essential for infectivity. These studies have demonstrated that a soluble TVA-ligand fusion protein can mediate viral infection when attached to specific cell surfaces, suggesting an approach for targeting retroviral infection to specific cell types.
禽白血病病毒A亚群（ALV-A）的细胞受体TVA，当作为跨膜蛋白或糖基磷脂酰肌醇连接蛋白在转染的哺乳动物细胞表面表达时，可介导病毒进入。为了确定通过将可溶性形式的TVA附着于哺乳动物细胞质膜上，是否能使其对ALV-A感染敏感，制备了TVA-表皮生长因子（EGF）融合蛋白。TVA-EGF由与人类EGF成熟形式相连的TVA细胞外结构域组成。流式细胞术分析证实，TVA-EGF是一种双功能试剂，能够同时结合细胞表面的EGF受体和ALV-A表面包膜-Ig融合蛋白。预先结合到表达野生型或激酶缺陷型人类EGF受体的转染小鼠成纤维细胞上的TVA-EGF，使这些细胞对ALV-A载体感染高度敏感。在重组人EGF蛋白存在的情况下，病毒感染被特异性阻断，表明TVA-EGF与EGF受体的结合对感染性至关重要。这些研究表明，可溶性TVA-配体融合蛋白附着于特定细胞表面时可介导病毒感染，提示了一种将逆转录病毒感染靶向特定细胞类型的方法。
