Berger E A, Fuerst T R, Moss B
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1988 Apr;85(7):2357-61. doi: 10.1073/pnas.85.7.2357.
Infection of helper T lymphocytes by human immunodeficiency virus is initiated by a specific interaction of the viral envelope glycoprotein with CD4, an integral membrane glycoprotein of the target cell. We have adapted a vaccinia virus-based mammalian cell expression system to produce variants of the CD4 molecule for structure-function studies. In this report we demonstrate that a truncated 180-amino acid fragment representing approximately the N-terminal half of the extracellular region of CD4 is found primarily in soluble form in the extracellular medium. Epitope analysis with a panel of anti-CD4 murine monoclonal antibodies indicates that the fragment reacts with those antibodies known to block the interaction between CD4 and the human immunodeficiency virus envelope glycoprotein but reacts poorly or not at all with those antibodies that do not block this interaction. We also show that the fragment forms a specific complex with a soluble form of gp120, the CD4-binding subunit of the viral envelope glycoprotein. These results indicate that this soluble CD4 fragment contains an active binding site for human immunodeficiency virus.
人类免疫缺陷病毒对辅助性T淋巴细胞的感染是由病毒包膜糖蛋白与靶细胞的一种整合膜糖蛋白CD4的特异性相互作用引发的。我们采用了一种基于痘苗病毒的哺乳动物细胞表达系统来生产用于结构功能研究的CD4分子变体。在本报告中，我们证明了一个截短的180个氨基酸的片段，其大约代表CD4细胞外区域的N端一半，主要以可溶形式存在于细胞外培养基中。用一组抗CD4鼠单克隆抗体进行的表位分析表明，该片段与那些已知可阻断CD4与人类免疫缺陷病毒包膜糖蛋白之间相互作用的抗体发生反应，但与那些不阻断这种相互作用的抗体反应较弱或根本不反应。我们还表明，该片段与病毒包膜糖蛋白的CD4结合亚基gp120的可溶形式形成特异性复合物。这些结果表明，这种可溶性CD4片段含有一个针对人类免疫缺陷病毒的活性结合位点。
