Bachelder R E, Bilancieri J, Lin W, Letvin N L
Harvard Medical School, Beth Israel Hospital, Boston, Massachusetts 02215, USA.
J Virol. 1995 Sep;69(9):5734-42. doi: 10.1128/JVI.69.9.5734-5742.1995.
To explore the role of the CD4 molecule in human immunodeficiency virus (HIV) infection following initial virus-CD4 binding, we have characterized CD4-specific antibodies raised by immunizing an HIV-1-infected human with human recombinant soluble CD4 (rsCD4). Fabs were selected from a human recombinant Fab library constructed from the bone marrow of this immunized individual. Here, we describe a human rsCD4-specific recombinant Fab clone selected by panning the library over complexes of human rsCD4 and recombinant HIV-1 envelope protein. While this Fab does not bind to CD4-positive T-cell lines or to human T lymphocytes, it recognizes cell surface-expressed CD4 following the incubation of these cells with a recombinant form of HIV-1 gp120 or with HIV-1 virions. The Fab is not HIV-1 envelope specific, since it does not bind to recombinant gp120 or to native cell surface-expressed HIV-1 envelope proteins. As confirmation of its CD4 specificity, we show that this Fab immunoprecipitates a 55-kDa protein, corresponding to the molecular mass of cellular CD4, from an H9 cell lysate. The specificity of this human Fab provides evidence for a virus-induced conformational change in cell surface-expressed on CD4. The characterization of this altered CD4 conformation and its effects on the host cell will be important in defining postbinding events in HIV infection.
为了探究CD4分子在人类免疫缺陷病毒（HIV）与CD4初始结合后的感染过程中的作用，我们对用重组人可溶性CD4（rsCD4）免疫HIV-1感染的人类所产生的CD4特异性抗体进行了表征。从该免疫个体的骨髓构建的人重组Fab文库中筛选出Fab片段。在此，我们描述了一个通过用人rsCD4和重组HIV-1包膜蛋白的复合物淘选文库而选择的人rsCD4特异性重组Fab克隆。虽然该Fab不与CD4阳性T细胞系或人T淋巴细胞结合，但在用重组形式的HIV-1 gp120或HIV-1病毒体孵育这些细胞后，它能识别细胞表面表达的CD4。该Fab不是HIV-1包膜特异性的，因为它不与重组gp120或天然细胞表面表达的HIV-1包膜蛋白结合。作为其CD4特异性的证实，我们表明该Fab能从H9细胞裂解物中免疫沉淀出一种55 kDa的蛋白质，其分子量与细胞CD4的分子量相对应。这种人Fab的特异性为细胞表面表达的CD4上病毒诱导的构象变化提供了证据。这种改变的CD4构象的表征及其对宿主细胞的影响对于确定HIV感染中的结合后事件将是重要的。
