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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010mCD4-HS12: Closing and Locking Doors for HIV-1 EntryF. Baleux 1* , P. Clayette 2 , F. Arenzana-Seisdedos 3 , D. Bonnaffe 4 , andH. Lortat-Jacob 51 Institut Pasteur, URA CNRS 2128, Unité de Chimie des Biomolécules, Paris, 75015;2 SPI-Bio, Fontenay aux Roses, 92260; 3 Institut Pasteur, INSERM U819,Unité de Pathogénie Virale, Paris, 75015; 4 UPS, UMR 8182, ICMO,Orsay, 9400; 5 IBS, UMR 5075, Grenoble, 38027, FranceIntroductionHIV entry is mediated by sequential attachment of gp120 viral glycoprotein to CD4 cellreceptor then GPCR cell coreceptor, mainly CCR5 or CXCR4. Following CD4 attachment,gp120 undergoes conformational changes that expose the CD4 induced epitope (CD4i),which in turn, binds to coreceptor. Besides binding to CD4 and GPCR, HIV also binds toglycosaminoglycans at the cell surface, mainly heparan sulfates (HS). Moreover, the CD4iepitope contains heparin binding sites (HBS) that can be targeted by short HS fragments[1,2].Results and DiscussionAn original and new concept has been developed to inhibit attachment and entry of HIV-1:mCD4-HS12 [3]. Composed of a miniCD4 peptide covalently linked to a synthetic sulfateddodecasaccharide, this bis-acting molecule binds to gp120, expose the CD4i epitope whichin turn, is locked by the polyanionic part HS12 (Figure 1). Based on mCD4/gp120 structure[4], a new miniCD4 peptide was designed, bearing a single lysine residue suitably locatedto reach the CD4i heparin binding site (R419, K421, K432). After mCD4 Fmoc solid phasepeptide synthesis, a maleimide moiety was introduced on the Lys5 side chain. Thesynthetic sulfated dodecasaccharide was derivatized by a thioacetyl group. Hydroxylaminetreatment generates the free thiolated HS12 that reacts with maleimide activated mCD4,affording the mCD4-HS12 conjugate. This molecule fully inhibits the binding of sCD4-gp120 complex to 17b mAb (often used as coreceptor surrogate) when evaluated byBiacore experiments. More interestingly, mCD4-HS12 turned out to be a potent antiviralmolecule when evaluated in cellulo (Table 1).Fig. 1. mCD4-HS12 mode of action.38