Packageable Antiviral Therapeutics against Human Immunodeficiency Virus Type 1: Virion-Targeted Virus Inactivation by Incorporation of a Single-Chain Antibody against Viral Integrase into Progeny Virions

To determine their activities as an antiviral agent packageable within virions and suitable for continued expression in cells, we tested a single-chain antibody (scAb) against human immunodeficiency virus type 1 (HIV-1) integrase and its three fusion proteins: fused to viral protein R (scab-Vpr), a double-cassette of the WXXF motif binding to Vpr (scAb-WXXF), and viral major capsid protein (scAb-CA), respectively. Cotransfection of human 293T cells with expression plasmid for scAb-Vpr or-WXXF along with HIV-1 clone pLAI resulted in the production of a normal amount of progeny virions with infectivity decreased by more than 10³-fold. Immunoblot analyses showed that scAb-Vpr or-WXXF was associated with virions, whereas scAb or scAb-CA was not, suggesting that scAb-Vpr or-WXXF was incorporated into virions. The incorporation of scAb-WXXF appeared to be Vpr dependent, because the fusion protein was associated with the wild-type but not with Vpr-truncated HIV-1 virions. Since G418-selected HeLa clones carrying expression plasmid for scAb-WXXF were obtained much more frequently than those for scAb-Vpr, scAb-WXXF was inferred to be less toxic to cells than scAb-Vpr. These results suggest that scAb-WXXF may serve as a novel class of antiviral therapeutic that inactivates progeny HIV virions from within.