INHIBITION OF HIV-1 TAT-MEDIATED LTR TRANSACTIVATION AND HIV-1 INFECTION BY ANTI-FAT SINGLE-CHAIN INTRABODIES

Genes encoding the rearranged immunoglobulin heavy and light chain var iable regions of anti-HIV-l Tat, exon 1 or exon 2 specific monoclonal antibodies have been used to construct single chain intracellular anti bodies 'intrabodies' for expression in the cytoplasm of mammalian cell s. These anti-Tat single chain intrabodies (anti-Tat sFvs) are additio nally modified with a C-terminal human C-kappa domain to increase cyto plasmic stability and/or the C-terminal SV40 nuclear localization sign al to direct the nascent intrabody to the nuclear compartment, respect ively. The anti-Tat sFvs with specific binding activity against the N- terminal activation domain of Tat, block Tat-mediated transactivation of HIV-1 LTR as well as intracellular trafficking of Tat in mammalian cells. As a result, the transformed lymphocytes expressing anti-Tat sF vs are resistant to HIV-1 infection. Thus, these studies demonstrate t hat stably expressed single chain intrabodies and their modified forms can effectively target molecules in the cytoplasm and nuclear compart ments of eukaryotic cells. Furthermore, these studies suggest that ant i-Tat sFvs used either alone or in combination with other genetically based strategies may be useful for the gene therapy of HIV-1 infection and AIDS.