INTRACELLULAR ANTIBODIES AS A NEW CLASS OF THERAPEUTIC MOLECULES FOR GENE-THERAPY

Intracellularly expressed antibodies, referred to as ''intrabodies,'' can be designed to bind and inactivate target molecules inside cells. In our previous study, mammalian cells were transduced to produce an a nti-gp120 single-chain intrabody sFv105 to inactivate human immunodefi ciency virus type-1 (HIV-1) infection. Here, an inducible expression v ector was constructed in which the sFv105 intrabody, which reacts with the CD4-binding site of HIV-1 gp120, is under the control of the HIV- 1 long terminal repeat (LTR)/promoter. The sFv105 intrabody is inducib ly expressed after HIV-1 infection or in the presence of Tat protein a nd is retained intracellularly. A human CD4(+) lymphocyte line transfo rmed with the expression vector exhibits resistance to the virus-media ted syncytium formation and a decreased ability to support HIV-1 produ ction. Surface gp120 expression is markedly reduced and surface CD4 is restored to normal following HIV-1 infection in the transformed lymph ocytes. Cell-surface phenotype, replication rate, morphology, and resp onse to mitogenic stimulation of the transformed cells are also normal . Thus, intrabodies are a new class of active molecules that may be us eful for the gene therapy of acquired immunodeficiency virus (AIDS) an d other diseases.