Hantaviruses use αvβ3 integrins on the surface of human host cells as a gateway to invasion, hence compounds that target this receptor may be used as antiviral agents. To accomplish this aim, new peptidomimetic compounds were selected based on similarity to a cyclic peptide known to bind the αvβ3 receptor. This first round of biological screening identified peptidomimetic molecules which were effective hantavirus inhibitors in the low micromolar range, two thousand times more potent than the original cyclic peptide. Pharmacophore models were built to broaden the structural diversity of the second set of compounds screened. Structure-activity relationships (SAR) were drawn from the entire dataset. Further characterization by dose-response studies revealed that three compounds had potency in the nanomolar range. Selectivity assays with a panel of hantaviruses supported the mechanism of inhibition by targeting the αvβ3 receptor, through the β3 integrin.

Specific therapy is not available for hantavirus cardiopulmonary syndrome caused by Andes virus (ANDV).Peptides capable of blocking ANDV infection in vitro were identified using antibodies against ANDV surface glycoproteins Gn and Gc to competitively elute a cyclic nonapeptide-bearing phage display library from purified ANDV particles. Phage was examined for ANDV infection inhibition in vitro, and nonapeptides were synthesized based on the most-potent phage sequences. Three peptides showed levels of viral inhibition which were significantly increased by combination treatment with anti-Gn-and anti-Gc-targeting peptides. These peptides will be valuable tools for further development of both peptide and nonpeptide therapeutic agents.Andes virus (ANDV), an NIAID category A agent linked to hantavirus cardiopulmonary syndrome (HCPS), belongs to the family Bunyaviridae and the genus Hantavirus and is carried by Oligoryzomys longicaudatus rodents (11). HCPS is characterized by pulmonary edema caused by capillary leak, with death often resulting from cardiogenic shock (9, 16). ANDV HCPS has a case fatality rate approaching 40%, and ANDV is the only hantavirus demonstrated to be capable of direct personto-person transmission (15, 21). There is currently no specific therapy available for treatment of ANDV infection and HCPS.Peptide ligands that target a specific protein surface can have broad applications as therapeutics by blocking specific proteinprotein interactions, such as preventing viral engagement of host cell receptors and thus preventing infection. Phage display libraries provide a powerful and inexpensive tool to identify such peptides. Here, we used selection of a cyclic nonapeptide-bearing phage library to identify peptides capable of binding the transmembrane surface glycoproteins of ANDV, Gn and Gc, and blocking infection in vitro.To identify peptide sequences capable of recognizing ANDV, we panned a cysteine-constrained cyclic nonapeptide-bearing phage display library (New England Biolabs) against density gradient-purified, UV-treated ANDV strain CHI-7913 (a gift from Hector Galeno, Santiago, Chile) (17, 18). To increase the specificity of the peptides identified, we eluted phage by using monoclonal antibodies (Austral Biologicals) prepared against recombinant fragments of ANDV Gn (residues 1 to 353) or Gc (residues 182 to 491) glycoproteins (antibodies 6B9/F5 and 6C5/D12, respectively). Peptide sequences were determined for phage from iterative rounds of panning, and the ability of phage to inhibit ANDV infection of Vero E6 cells was determined by immunofluorescent assay (IFA) (7). Primary IFA detection antibodies were rabbit polyclonal anti-Sin Nombre hantavirus (SNV) nucleoprotein (N) antibodies which exhibit potent cross-reactivity against other hantavirus N antigens (3). ReoPro, a commercially available Fab fragment which partially blocks infection of hantaviruses in vitro by binding the entry receptor integrin ␤ 3 (5), was used as a positive control (80 g/ml) along with the original antibody used for p...

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Viral entry into susceptible host cells typically results from multivalent interactions between viral surface proteins and host entry receptors. In the case of Sin Nombre virus (SNV), a New World hantavirus that causes hantavirus cardiopulmonary syndrome, infection involves the interaction between viral membrane surface glycoproteins and the human integrin ␣ v ␤ 3 . Currently, there are no therapeutic agents available which specifically target SNV. To address this problem, we used phage display selection of cyclic nonapeptides to identify peptides that bound SNV and specifically prevented SNV infection in vitro. We synthesized cyclic nonapeptides based on peptide sequences of phage demonstrating the strongest inhibition of infection, and in all cases, the isolated peptides were less effective at blocking infection (9.0% to 27.6% inhibition) than were the same peptides presented by phage (74.0% to 82.6% inhibition). Since peptides presented by the phage were pentavalent, we determined whether the identified peptides would show greater inhibition if presented in a multivalent format. We used carboxyl linkages to conjugate selected cyclic peptides to multivalent nanoparticles and tested infection inhibition. Two of the peptides, CLVRNLAWC and CQATTARNC, showed inhibition that was improved over that of the free format when presented on nanoparticles at a 4:1 nanoparticle-to-virus ratio (9.0% to 32.5% and 27.6% to 37.6%, respectively), with CQATTARNC inhibition surpassing 50% when nanoparticles were used at a 20:1 ratio versus virus. These data illustrate that multivalent inhibitors may disrupt polyvalent protein-protein interactions, such as those utilized for viral infection of host cells, and may represent a useful therapeutic approach.Peptide ligands that bind and recognize a protein surface and block specific protein-protein interactions can have broad applications as therapeutic reagents. For example, a virus particle can enter a host cell by specific binding interaction between a viral surface protein and a host cell surface receptor, thus initiating receptor-mediated endocytosis prior to infection. Viral infection can be prevented by blocking the viral protein-host receptor protein interaction. Specific peptides can be developed to block this protein-protein interface, either by mimicking one of the binding partners or through novel binding interactions.

Dexras1 is a novel GTP-binding protein that shares structural similarity with the Ras family of small molecular weight GTPases and is strongly and rapidly induced during treatment with dexamethasone. The function of Dexras1 and its contribution to glucocorticoid-dependent signaling in the corticotroph cell are unknown. The present study was undertaken to examine the potential role of Dexras1 in the regulation of peptide hormone secretion in the AtT-20 corticotroph cell line. To determine the effects of Dexras1 expressed independently of glucocorticoid treatment, expression plasmids for wild-type and constitutively active mutant Dexras1 proteins were cotransfected with human GH (hGH), which provides an ectopic marker for the stimulus-coupled secretory pathway. GTP binding properties and the GTP to GDP ratio of wild-type and mutant Dexras1 proteins were examined in transiently transfected AtT-20 and COS-7 cells. Stimulated and constitutive components of secretion were assessed after 2-h incubations with 5 mM 8-Br-cAMP or control. cAMP treatment led to a 2-fold increase in hGH secretion relative to control. Cotransfection of wild-type Dexras1 had no effect on cAMP-stimulated hGH secretion, but a constitutively active mutant, Dexras[A178V], attenuated stimulated secretion by 86% (P < 0.01). A double-mutant containing a deletion of the carboxyl terminus isoprenylation site, Dexras[A178V/C277term], did not inhibit cAMP-stimulated hGH secretion, indicating that the effect is prenylation dependent. These findings suggest that activation of Dexras1 has important functional consequences leading to inhibition of stimulus-secretion coupling in corticotroph cells. Because Dexras1 messenger RNA is strongly and rapidly induced during glucocorticoid treatment, these results raise the possibility that Dexras1 may participate in the signal transduction pathways that govern the rapid regulatory effects of glucocorticoids on peptide hormone secretion in corticotroph cells.