Identification of a D-amino acid decapeptide HIV-1 entry inhibitor Ce ´sar Boggiano a,1 , Shibo Jiang b , Hong Lu b , Qian Zhao b , Shuwen Liu b , James Binley a , Sylvie E. Blondelle a, * a Torrey Pines Institute for Molecular Studies, 3550 General Atomics Court, San Diego, CA 92121, USA b Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10021, USA Received 13 June 2006 Available online 5 July 2006 Abstract Entry of human immunodeficiency virus type 1 (HIV-1) virion into host cells involves three major steps, each being a potential target for the development of entry inhibitors: gp120 binding to CD4, gp120-CD4 complex interacting with a coreceptor, and gp41 refolding to form a six-helix bundle. Using a D-amino acid decapeptide combinatorial library, we identified peptide DC13 as having potent HIV-1 fusion inhibitory activity, and effectively inhibiting infection by several laboratory-adapted and primary HIV-1 strains. While DC13 did not block binding of gp120 to CD4, nor disrupt the gp41 six-helix bundle formation, it effectively blocked the binding of an anti- CXCR4 monoclonal antibody and chemokine SDF-1a to CXCR4-expressing cells. However, because R5-using primary viruses were also neutralized, the antiviral activity of DC13 implies additional mode(s) of action. These results suggest that DC13 is a useful HIV-1 core- ceptor antagonist for CXCR4 and, due to its biostability and simplicity, may be of value for developing a new class of HIV-1 entry inhibitors. Ó 2006 Elsevier Inc. All rights reserved. Keywords: HIV-1; Entry inhibitor; CXCR4 antagonist; D-Peptides Membrane attachment and fusion are the first steps in the human immunodeficiency virus type 1 (HIV-1) infec- tion process. Although most of the therapies against HIV-1 are directed toward the inhibition of reverse trans- criptase and protease enzymes, therapeutic approaches involving inhibition of HIV-1 mediated membrane fusion and entry are gaining importance, especially given their potential use in microbicide formulations [1]. Inhibition of HIV-1 entry may be achieved by (1) block- ing gp120 binding to CD4; (2) disrupting interaction of gp120-CD4 complex with the coreceptor (chemokine recep- tors CXCR4 or CCR5); or (3) interference with the confor- mational changes in the N- and C-terminal helices of gp41(NHR and CHR, respectively) that lead to formation of a six-helix bundle and bring virus and target membranes close together during the later stages of fusion. In the early 1990s, Jiang et al. [2] and Wild et al. [3] discovered two related peptides derived from the gp41 CHR region, SJ- 2176 and T-20, respectively, which inhibited HIV-1 medi- ated membrane fusion with nanomolar potencies. These peptides were shown to block HIV fusion with the target cell by interacting with the gp41 NHR region thereby inter- fering with the formation of the six-helix bundle structure [4–8]. T-20 is capable of reducing HIV-1 load in infected patients to undetectable levels [9], and is an effective thera- py for those patients who have failed to respond to reverse transcriptase and protease inhibitors [10]. However, clinical application of T-20 is limited due to its lack of oral bio- availability, high production cost, and emergence of drug-resistant strains in patients [11]. Other peptide inhib- itors reported include the 15-mer L-peptide T22 [12,13] and a 15-mer L-peptide derived from bee venom [14] both 0006-291X/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2006.06.150 * Corresponding author. Present address: Burnham Institute for Medical Research, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA. Fax: +1 858 713 9930. E-mail address: sylvieb@burnham.org (S.E. Blondelle). 1 Present address: Molecular Pathogenesis Program, Skirball Institute of Biomolecular Medicine, NYU, 540 First Ave. SK 2-17, New York, NY 10016, USA. www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 347 (2006) 909–915 BBRC