The HB-19 Pseudopeptide 5[Kpsi(CH₂N)PR]-TASP Inhibits Attachment of T Lymphocyte- and Macrophage-Tropic HIV to Permissive Cells

Abstract

The HB-19 pseudopeptide 5[Kpsi(CH2N)PR]-TASP[psi(CH2N) indicating a reduced peptide bond], which binds the cell surface-expressed nucleolin, is a potent inhibitor of HIV infection. Here, by using primary T lymphocyte cultures and an experimental cell model to monitor HIV entry, we show that HB-19 inhibits in a dose-dependent manner both T lymphocyte- and macrophage-tropic HIV isolates. Similar positively charged control pseudopeptides have no effect on HIV infection even at high concentrations. These observations, and the fact that HB-19 has no effect on SIV-mac and HIV-1 pseudotyped with VSV envelope glycoproteins, confirm the specific nature of this inhibitor against the entry process mediated by the HIV envelope glycoproteins. Finally, association of low doses of HB-19 with beta-chemokines or AZT results in an increased inhibitory effect on HIV infection. HB-19 has no inhibitory effect when added to cells a few hours after HIV entry. On the other hand, in HB-19-pretreated cells, the inhibitory effect persists for several hours, even after washing cells to remove away the unbound pseudopeptide. Under such conditions, the attachment of HIV particles to cells is inhibited as efficiently as by neutralizing monoclonal antibodies directed against the V3 loop. In view of its specific mode of action on various HIV isolates, HB-19 represents a potential anti-HIV drug.

Midkine, a cytokine that inhibits HIV infection by binding to the cell surface expressed nucleolin

“…The fact that HIV attachment is inhibited by two agents which do not compete, illustrates that virus attachment should be coordinated on one hand by heparan sulfate proteoglycans, and on the other hand by nucleolin. Consistent with the critical role of surface nucleolin in the initial steps of HIV infection, the HB-19 pseudopeptide and several physiological ligands of nucleolin (Midkine, Pleiotrophin, lactoferrin) inhibit HIV infection by blocking HIV particle attachment to CD4+ target cells [2][3][4][5][6].…”

“…The peptide corresponding to the C-terminal tail of PTN contains 11 lysine residues [8]. Consequently, the capacity of HB-19 to prevent the binding of MK to the low affinity binding site can not be accounted simply by the basic nature of HB-19 [2]. This latter was further confirmed by the use of the anti-HIV 9Arg peptide, which is composed of 9 D-arginine residues.…”

“…However, additional cell-surface components, such as heparan sulfate proteoglycans and nucleolin, appear to be implicated in the attachment of HIV particles. By using specific ligands, we have demonstrated that HIV attachment could be inhibited either by FGF-2 that uses heparan sulphate proteoglycans as low affinity receptors, or by the nucleolin binding pseudopeptide , that forms a stable complex with nucleolin [1,2]. The fact that HIV attachment is inhibited by two agents which do not compete, illustrates that virus attachment should be coordinated on one hand by heparan sulfate proteoglycans, and on the other hand by nucleolin.…”

The anti-HIV pentameric pseudopeptide HB-19 is preferentially taken up in vivo by lymphoid organs where it forms a complex with nucleolin

“…Consequently, to complement the current anti-HIV protease and reverse transcriptase drugs, several novel anti-HIV molecules have been developed that target different components implicated in the mechanism of HIV attachment and entry into cells (1). In this respect, the pentameric HB-19 pseudopeptide, 5[K (CH 2 N)PR]TASP, is an anti-HIV synthetic agent that inhibits HIV infection by binding to the cell-surfaceexpressed nucleolin and results in a block in the attachment of virus particles to cells (2)(3)(4). Nucleolin is one of the major RNA binding proteins of the nucleolus, which has also been found on the cell surface where it serves as a binding protein for different ligands including HIV (5)(6)(7).…”

“…At selected times (4,8, and 24 h) after i.v. injection of 20 g (50 Ci) of [ 3 H]-labeled HB-19, urine was collected and the rats were anesthetized and killed by cardiac blood puncture.…”