Palmitic Acid Is a Novel CD4 Fusion Inhibitor That Blocks HIV Entry and Infection

Mailman Research Center, McLean Hospital, Harvard Medical School, Belmont, Massachusetts 02478, USA.
AIDS research and human retroviruses (Impact Factor: 2.33). 12/2009; 25(12):1231-41. DOI: 10.1089/aid.2009.0019
Source: PubMed


The high rate of HIV-1 mutation and the frequent sexual transmission highlight the need for novel therapeutic modalities with broad activity against both CXCR4 (X4) and CCR5 (R5)-tropic viruses. We investigated a large number of natural products, and from Sargassum fusiforme we isolated and identified palmitic acid (PA) as a natural small bioactive molecule with activity against HIV-1 infection. Treatment with 100 microM PA inhibited both X4 and R5 independent infection in the T cell line up to 70%. Treatment with 22 microM PA inhibited X4 infection in primary peripheral blood lymphocytes (PBL) up to 95% and 100 microM PA inhibited R5 infection in primary macrophages by over 90%. Inhibition of infection was concentration dependent, and cell viability for all treatments tested remained above 80%, similar to treatment with 10(-6)M nucleoside analogue 2', 3'-dideoxycytidine (ddC). Micromolar PA concentrations also inhibited cell-to-cell fusion and specific virus-to-cell fusion up to 62%. PA treatment did not result in internalization of the cell surface CD4 receptor or lipid raft disruption, and it did not inhibit intracellular virus replication. PA directly inhibited gp120-CD4 complex formation in a dose-dependent manner. We used fluorescence spectroscopy to determine that PA binds to the CD4 receptor with K(d) approximately 1.5 +/- 0.2 microM, and we used one-dimensional saturation transfer difference NMR (STD-NMR) to determined that the PA binding epitope for CD4 consists of the hydrophobic methyl and methelene groups located away from the PA carboxyl terminal, which blocks efficient gp120-CD4 attachment. These findings introduce a novel class of antiviral compound that binds directly to the CD4 receptor, blocking HIV-1 entry and infection. Understanding the structure-affinity relationship (SAR) between PA and CD4 should lead to the development of PA analogs with greater potency against HIV-1 entry.

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    • "After investigating a large number of natural products, we showed Sargassum fusiforme (S. fusiforme) algae to have HIV inhibiting properties [1], [2]. From S. fusiforme we isolated and identified palmitic acid (PA) as a bioactive molecule that inhibited both X4- and R5-tropic HIV entry to CD4+ cells [3]. We also identified 2-bromopalmitate (2-BP) as a more potent analog, which showed approximately 20-fold increase in efficacy as compared to PA [4]. "
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    ABSTRACT: AIDS is a global pandemic that has seen the development of novel and effective treatments to improve the quality of life of those infected and reduction of spread of the disease. Palmitic Acid (PA), which we identified and isolated from Sargassum fusiforme, is a naturally occurring fatty acid that specifically inhibits HIV entry by binding to a novel pocket on the CD4 receptor. We also identified a structural analogue, 2-bromopalmitate (2-BP), as a more effective HIV entry inhibitor with a 20-fold increase in efficacy. We have used the structure-activity relationship (SAR) of 2-BP as a platform to identify new small chemical molecules that fit into the various identified active sites in an effort to identify more potent CD4 entry inhibitors. To validate further drug development, we tested the PA and 2-BP scaffold molecules for genotoxic potential. The FDA and International Conference on Harmonisation (ICH) recommends using a standardized 3-test battery for testing compound genotoxicity consisting of the bacterial reverse mutation assay, mouse lymphoma assay, and rat micronucleus assay. PA and 2-BP and their metabolites tested negative in all three genotoxicty tests. 2-BP is the first derivative of PA to undergo pre-clinical screening, which will enable us to now test multiple simultaneous small chemical structures based on activity in scaffold modeling across the dimension of pre-clinical testing to enable transition to human testing.
    Full-text · Article · Mar 2014 · PLoS ONE
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    • "Lipotoxicity refers to the cytotoxic effects of excess fat accumulation in cells and has been implicated as one of the contributing factors to diseases like obesity, diabetes and non-alcoholic fatty liver [16] [17] [18]. Previously it was reported that PA has been identified as a novel CD4 fusion inhibitor that blocks HIV entry and infection [19] [20], as an antibacterial compound [21]. PA also shows selective cytotoxicity to human leukemic cells, but no cytotoxicity to normal HDF cells [22]. "

    Full-text · Article · Sep 2012 · Food and Nutrition Sciences
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    • "Peripheral blood lymhocytes (PBL) and macrophages (Mφ's) are primary targets for in vivo HIV-1 infection and replication in systemic circulation as well as in vaginal submucosa, and previously we demonstrated ability of PA treatment to inhibit ongoing virus replication in these physiologically relevant cells [6]. However, PA inhibited HIV replication in PBL with approximately 10-fold greater efficacy as compared to inhibition in Mφ's [6]. Because CD4 cell surface HIV receptor expression varies between different cell types, here we wanted to ascertain PA's inhibition efficacy that is independent of in vivo cell surface expression. "
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    ABSTRACT: Approximately 80% of all new HIV-1 infections are acquired through sexual contact. Currently, there is no clinically approved microbicide, indicating a clear and urgent therapeutic need. We recently reported that palmitic acid (PA) is a novel and specific inhibitor of HIV-1 fusion and entry. Mechanistically, PA inhibits HIV-1 infection by binding to a novel pocket on the CD4 receptor and blocks efficient gp120-to-CD4 attachment. Here, we wanted to assess the ability of PA to inhibit HIV-1 infection in cervical tissue ex vivo model of human vagina, and determine its effect on Lactobacillus (L) species of probiotic vaginal flora. Our results show that treatment with 100-200 µM PA inhibited HIV-1 infection in cervical tissue by up to 50%, and this treatment was not toxic to the tissue or to L. crispatus and jensenii species of vaginal flora. In vitro, in a cell free system that is independent of in vivo cell associated CD4 receptor; we determined inhibition constant (Ki) to be ∼2.53 µM. These results demonstrate utility of PA as a model molecule for further preclinical development of a safe and potent HIV-1 entry microbicide inhibitor.
    Full-text · Article · Sep 2011 · PLoS ONE
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