Identification of a Novel HIV-1 Inhibitor Targeting Vif-dependent Degradation of Human APOBEC3G [Microbiology]

February 27th, 2015 by Pery, E., Sheehy, A., Nebane, N. M., Brazier, A. J., Misra, V., Rajendran, K. S., Buhrlage, S. J., Mankowski, M. K., Rasmussen, L., White, E. L., Ptak, R. G., Gabuzda, D.

APOBEC3G (A3G) is a cellular cytidine deaminase that restricts HIV-1 replication by inducing G-to-A hypermutation in viral DNA and by deamination-independent mechanisms. HIV-1 Vif binds to A3G, resulting in its degradation via the 26S proteasome. Therefore, this interaction represents a potential therapeutic target. To identify compounds that inhibit interaction between A3G and HIV-1 Vif in a high-throughput format, we developed a homogeneous time-resolved fluorescence resonance energy transfer (TR-FRET) assay. A 307,520 compound library from the NIH Molecular Libraries Small Molecule Repository (MLSMR) was screened. Secondary screens to evaluate dose-response performance and off-target effects, cell-based assays to identify compounds that attenuate Vif-dependent degradation of A3G, and assays testing antiviral activity in peripheral blood mononuclear cells (PBMCs) and T cells were employed. One compound, N.41, showed potent antiviral activity in A3G(+) but not in A3G(-) T cells and had an IC50 as low as 8.4 uM and TC50 >100 uM when tested against HIV-1Ba-L replication in PBMCs. N.41 inhibited the Vif-A3G interaction, increased cellular A3G levels and incorporation of A3G into virions, thereby attenuating virus infectivity in a Vif-dependent manner. N.41 activity was also species- and Vif-dependent. Preliminary structure-activity relationship (SAR) studies suggest that a hydroxyl moiety located at a phenylamino group is critical for N.41 anti-HIV activity and identified N.41 analogs with better potency (IC50 as low as 4.2 uM). These findings identify a new lead compound that attenuates HIV replication by liberating A3G from Vif regulation and increasing its innate antiviral activity.