Antiviral activity of a Rac GEF inhibitor characterized with a sensitive HIV/SIV fusion assay

Abstract

A virus-dependent fusion assay was utilized to examine the activity of a panel of HIV-1, -2, and SIV isolates of distinct coreceptor phenotypes. This assay allowed identification of entry inhibitors, and characterization of an antagonist of a Rac guanine nucleotide exchange factor, as an inhibitor of HIV-mediated fusion.

Regulation of CXCR4 conformation by the small GTPase Rac1: implications for HIV infection

“…Several reports identified Rac1 and its downstream effectors, involved in actin dynamics, as crucial players in the entry of R5 viruses into host cells. 23,24 However, in our system, R5 HIV-1 infection was independent of Rac1, because NSC23766 treatment did not affect the infection of luciferase reporter HIV-1 pseudotyped with the R5-using BaL-26. These data confirm the specificity of Rac1 for regulating CXCR4 conformation without interfering with CCR5.…”

One Percent Tenofovir Applied Topically to Humanized BLT Mice and Used According to the CAPRISA 004 Experimental Design Demonstrates Partial Protection from Vaginal HIV Infection, Validating the BLT Model for Evaluation of New Microbicide Candidates

“…4). Prior to selection for in vivo efficacy evaluation here, each inhibitor was shown to efficiently inhibit HIV in vitro (3,5,39,43,50,52,54,56). Our experimental approach for testing these six inhibitors was a single dose of the product administered prior to exposure rather than the two doses of drug administered within 24 h as used in CAPRISA 004 (1).…”

“…NSC23766 is a small molecular inhibitor of Rac1-guanine nucleotide exchange factors (GEFs) TrioN and Tiam1. NSC23766 prevents viral entry from the inside-out by interfering with the structural modifications that occur within the cell during fusion (16,39). The combination of the reverse transcriptase inhibitors FTC-TDF, the inhibitors present in Truvada (3,43), targets postentry viral DNA synthesis.…”

Induction of the GαqSignaling Cascade by the Human Immunodeficiency Virus Envelope Is Required for Virus Entry

“…Wild-type vaccinia virus (WR strain) and recombinant vaccinia viruses expressing ␤-galactosidase (vCB21R) and T7 polymerase (vPT7-3) were obtained from the AIDS Research and Reference Reagent Program (47). Vaccinia viruses encoding an uncleaved HIV (HIV UNC ) Env (vCB-16), ADA Env (vCB-39), and HXB2 Env (vSC60) were gifts from Edward Berger, and vaccinia viruses encoding the HIV envelope from the YU2 strain (vSP-5) and constitutively active Rac GTPase (vRacV12) were gifts from C. Broder and S. Wei, respectively (46). The HIV stocks used in the assays described below were prepared by the lipofection of plasmid DNA encoding full-length proviral molecular clones, which contain the Env gene of the R5 YU2 strain in the HIV NL4-3 backbone.…”