DESIGN, INTRACELLULAR EXPRESSION, AND ACTIVITY OF A HUMAN ANTI-HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 GP120 SINGLE-CHAIN ANTIBODY

A single-chain antibody, derived from a human monoclonal antibody that recognizes the CD4 binding region of the human immunodeficiency virus type 1 (HIV-1) envelope protein, has been designed for intracellular expression in eukaryotic cells. The single-chain antibody is composed of an immunoglobulin heavy-chain leader sequence and heavy- and light- chain variable regions that are joined by an inter-chain linker. The a ntibody is stably expressed and retained in the endoplasmic reticulum and is not toxic to the cells. The antibody binds to the envelope prot ein within the cell and inhibits processing of the envelope precursor and syncytia formation. The infectivity of the HIV-1 particles produce d by cells that express the single-chain antibody is substantially red uced. These studies illustrate the feasibility of designing antibodies that bind and inactivate molecules intracellularly. Antibodies that a ct on target molecules within cells should provide a useful tool for r esearch as well as for control of infectious and other diseases.