Development of a Novel Screening Strategy Designed to Discover a New Class of HIV Drugs

Current antiretroviral treatments target multiple pathways important for human immunodeficiency virus (HIV) multiplication, including viral entry, synthesis and integration of the DNA provirus, and the processing of viral polyprotein precursors. However, HIV is becoming increasingly resistant to these "combination therapies." Recent findings show that inhibition of HIV Gag protein cleavage into its two structural proteins, matrix (MA) and capsid (CA), has a devastating effect on viral production, revealing a potential new target class for HIV treatment. Unlike the widely used HIV protease inhibitors, this new class of inhibitor would target the substrate, not the protease enzyme itself. This approach offers a distinct advantage in that inhibitors of MA/CA would only need to affect a subset of the Gag molecules to disable viral replication. To discover MA/CA-specific inhibitors, we constructed a modified MA/CA fusion peptide (MA/CAΔ) that contains the HIV protease (PR) cleavage site as well as a tetracysteine motif for fluorescent labeling. The HIV PR cleavage of MA/CAΔ can then be monitored via fluorescence polarization (FP). We have adapted this FP assay for high-throughput screening and validated it according to industry standards using a 384-well plate format. We have currently tested 24,000 compounds in this assay and here detail the screening methodology and the results of this screening campaign.