Inhibition of HIV Replication by Apolipoprotein A-I Binding Protein Targeting the Lipid Rafts Larisa Dubrovsky, a Adam Ward, a Soo-Ho Choi, b Tatiana Pushkarsky, a Beda Brichacek, a Christophe Vanpouille, c Alexei A. Adzhubei, a,d Nigora Mukhamedova, e Dmitri Sviridov, e Leonid Margolis, c Richard B. Jones, a * Yury I. Miller, b Michael Bukrinsky a a The George Washington University School of Medicine and Health Sciences, Washington, DC, USA b University of California San Diego, La Jolla, California, USA c Eunice Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA d Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia e Baker Heart and Diabetes Research Institute, Melbourne, Victoria, Australia ABSTRACT Apolipoprotein A-I binding protein (AIBP) is a protein involved in regu- lation of lipid rafts and cholesterol efflux. AIBP has been suggested to function as a protective factor under several sets of pathological conditions associated with in- creased abundance of lipid rafts, such as atherosclerosis and acute lung injury. Here, we show that exogenously added AIBP reduced the abundance of lipid rafts and in- hibited HIV replication in vitro as well as in HIV-infected humanized mice, whereas knockdown of endogenous AIBP increased HIV replication. Endogenous AIBP was much more abundant in activated T cells than in monocyte-derived macrophages (MDMs), and exogenous AIBP was much less effective in T cells than in MDMs. AIBP inhibited virus-cell fusion, specifically targeting cells with lipid rafts mobilized by cell activation or Nef-containing exosomes. MDM-HIV fusion was sensitive to AIBP only in the presence of Nef provided by the virus or exosomes. Peripheral blood mono- nuclear cells from donors with the HLA-B*35 genotype, associated with rapid pro- gression of HIV disease, bound less AIBP than cells from donors with other HLA ge- notypes and were not protected by AIBP from rapid HIV-1 replication. These results provide the first evidence for the role of Nef exosomes in regulating HIV-cell fusion by modifying lipid rafts and suggest that AIBP is an innate factor that restricts HIV replication by targeting lipid rafts. IMPORTANCE Apolipoprotein A-I binding protein (AIBP) is a recently identified in- nate anti-inflammatory factor. Here, we show that AIBP inhibited HIV replication by targeting lipid rafts and reducing virus-cell fusion. Importantly, AIBP selectively re- duced levels of rafts on cells stimulated by an inflammatory stimulus or treated with extracellular vesicles containing HIV-1 protein Nef without affecting rafts on nonacti- vated cells. Accordingly, fusion of monocyte-derived macrophages with HIV was sen- sitive to AIBP only in the presence of Nef. Silencing of endogenous AIBP significantly upregulated HIV-1 replication. Interestingly, HIV-1 replication in cells from donors with the HLA-B*35 genotype, associated with rapid progression of HIV disease, was not inhibited by AIBP. These results suggest that AIBP is an innate anti-HIV factor that targets virus-cell fusion. KEYWORDS HIV, AIBP, Nef, extracellular vesicles, exosomes, lipid rafts, fusion, HLA A polipoprotein A-I binding protein (AIBP) was discovered in a screen of proteins that physically associate with apolipoprotein A-I (1). Although intracellular functions of AIBP have been proposed previously (2, 3), it is well established that secreted AIBP regulates cholesterol trafficking and lipid rafts in the plasma membrane in vertebrate Citation Dubrovsky L, Ward A, Choi S-H, Pushkarsky T, Brichacek B, Vanpouille C, Adzhubei AA, Mukhamedova N, Sviridov D, Margolis L, Jones RB, Miller YI, Bukrinsky M. 2020. Inhibition of HIV replication by apolipoprotein A-I binding protein targeting the lipid rafts. mBio 11:e02956-19. https://doi .org/10.1128/mBio.02956-19. Editor Thomas E. Smithgall, University of Pittsburgh School of Medicine Copyright © 2020 Dubrovsky et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Address correspondence to Michael Bukrinsky, mbukrins@gwu.edu. [This article was published on 21 January 2020 with Dmitri Sviridov's first name misspelled as “Dmitry” in the byline. The byline was updated in the current version, posted on 12 March 2020.] * Present address: Richard B. Jones, Weill Cornell Medical College, New York, New York, USA. Received 18 November 2019 Accepted 11 December 2019 Published RESEARCH ARTICLE Host-Microbe Biology crossm January/February 2020 Volume 11 Issue 1 e02956-19 ® mbio.asm.org 1 21 January 2020 on July 22, 2020 by guest http://mbio.asm.org/ Downloaded from on July 22, 2020 by guest http://mbio.asm.org/ Downloaded from on July 22, 2020 by guest http://mbio.asm.org/ Downloaded from