Abstract:
Compounds, which inhibit the binding of gp120 to CD4 as well as 17b and methods for their use in inhibiting the HIV fusion process, are provided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/409,285, filed Mar. 23, 2009, now allowed, which is a divisional of U.S. application Ser. No. 11/305,401, filed Dec. 16, 2005, now U.S. Pat. No. 7,556,808, which claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/644,172, filed Jan. 14, 2005 and U.S. Provisional Application No. 60/637,091, filed Dec. 16, 2004, all of which are hereby incorporated by reference in their entirety herein. 
    
    
     STATEMENT REGARDING FEDERALLY SUPPORTED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under (NIH Grant No. P01 GM 056550-08/C210JC awarded by National Institutes of Health. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     Acquired immunodeficiency syndrome (AIDS), the global epidemic disease caused by HIV-1, has created an urgent need for new classes of antiviral agents (UNAIDS/World Health Organization (2003) AIDS Epidemic Update (UNAIDS—World Health Organization, Geneva)). The envelope glycoprotein of HIV-1 is a trimer consisting of three gp120 exterior envelope glycoproteins and gp41 transmembrane glycoproteins (Chan et al. Cell 1997, 89, 263-273; Wyatt et al. Science 1998, 280, 1884-1888; Tan et al. Proc. Natl. Acad. Sci. USA 1997, 94, 12303-12308). Viral infection is initiated by gp120 binding to CD4 on the host cell surface (Klatzmann et al. Nature 1984, 312, 767-768; Dalgleish et al. Nature 1984, 312, 763-767). The binding of these two proteins promotes a conformational change in gp120 that increases its affinity with a second host cell receptor, one of the chemokine receptors, CCR5 and CXCR4 (Trkola et al. Nature 1996, 384, 184-187; Feng et al. Science 1996, 872-877; Doranz et al. Cell 1996, 85, 1149-1158; Dragic et al. Nature 1996, 381, 667-673; Wu et al. Nature 1996, 384, 179-183). The interaction of gp120 with its receptors is thought to promote further conformational rearrangements in HIV-1 envelope that drive fusion of the viral and host cell membranes. Blocking of these interactions between gp120 and cell surface receptors is an attractive goal for preventing HIV-infection. 
     A 12-residue peptide [RINNPWSEAMM (SEQ ID NO:1)] was discovered by phage library (Ferrer et al. J. Virol. 1999, 73, 5795-5802). Its mode of action showed (Biorn et al. Biochemistry 2004, 43, 1928-1938) that, the peptide inhibited the interaction of gp120 to CD4 and 17b, an antibody that recognizes an epitope overlapping the CCR5 binding site, with micromolar affinity. The various mutations and truncations of the peptide confirmed that the entire sequence with the large aromatic residue Trp next to Pro is critical for binding. 
     SUMMARY OF THE INVENTION 
     A modified peptide with 4-phenyl, 1, 4 disubstituted 1,2,3 triazole, fabricated through click chemistry, has now been identified, which inhibits the binding of gp120 to CD4 as well as 17b at IC 50  values of 22 and 29 nanomolar, respectively. 
     Accordingly, the present invention relates to compositions comprising this modified peptide or mutants or fragments thereof, methods for designing new antagonists based upon this peptide or mutants or fragments thereof and methods for using this peptide or mutants or fragments thereof and newly designed antagonists to inhibit the HIV fusion process. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  shows the structure of a native peptide with proline. 
         FIG. 1B  shows the structure of X in peptide 5 of the present invention comprising a (2S,4S)-4-(4-phenyl-1H-1,2,3-triazol-1-yl)pyrrolidine-2-carboxylic acid) substituted proline. 
         FIGS. 2A and 2B  are line graphs from experiments measuring direct binding of peptide 5 over immobilized YU2 gp120.  FIG. 2A , provides response sensorgrams for increasing concentrations (5 nmol to 5 μmol) of peptide 5 binding to the immobilized YU2 gp120.  FIG. 2B  provides a fit of direct binding data to a steady state 1:1 binding model. Req. was calculated from 280 to 295 seconds in each concentration sensorgram and plotted against the concentration of the peptide. Equilibrium binding constants for YU2-peptide 5 interaction are KA=7.99×10 7  M −1  and KD=1.28×10 −8  M. 
         FIGS. 3A and 3B  are response sensorgrams of complete inhibition of binding experiments of YU2 gp120 to CD4 ( FIG. 3A ) and 17b ( FIG. 3B ) by peptide 5. The CD4 and 17b were immobilized on a CM5 sensor chip. YU2 gp120 (100 nmol) was passed over the surface in the absence or presence of 10 nmol to 1 μmol of peptide 5. 
         FIG. 4  is a response sensorgram of peptide 5 competition with CD4 in the reverse orientation over immobilized YU2 gp120. CD4 (50 nM) was passed over a high-density YU2 gp120 surface in absence or presence of 10 to 250 nM of peptide 5. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Recent advances of Cu(I)-catalyzed Huigen 1-3 dipolar cycloaddition of azides and terminal alkynes affords 1,4-disubstituted 1, 2, 3-triazoles with superior regioselectivity, and almost quantitative transformation under extremely mild conditions (Rostovtsev et al. Angew. Chem. Int. Ed. 2002, 41, 2596-2599; Tornoe et al. J. Org. Chem. 2002, 67, 3057-3064). The simple and robust features of this methodology have found application in drug discovery, bioconjugation and material science (Wang et al. J. Am. Chem. Soc. 2003, 125, 3192-3193; Deiters et al. J. Am. Chem. Soc. 2003, 125, 11782-11783; Link et al. J. Am. Chem. Soc. 2003, 125, 11164-11165; Speers et al. Chemistry &amp; Biology, 2004, 11, 535-546; Fazio et al. J. Am. Chem. Soc. 2002, 124, 14397-14402; Manetsch et al. J. Am. Chem. Soc. 2004, 126, 12809-12818; Helms et al. J. Am. Chem. Soc. 2004, 126, 15020-15021). 
     In our study of the entry inhibitor, RINNIPWSEAMM (SEQ ID NO:1), we were interested in replacing proline of this peptide, referred to herein as peptide 1 (structure shown in  FIG. 1A ), with γ-amino proline (Amp). We used surface plasmon resonance to verify the direct interactions of peptides to YU2 gp120. Surface plasmone resonance analysis showed that peptide 4 (RINNIAmpSEAMM; SEQ ID NO:4) with cis-γ-amino proline had no effect on gp120. However, intermediate peptide 2 (RINNIHypSEAMM; SEQ ID NO:2) and intermediate peptide 3 (RINNIAzpSEAMM; SEQ ID NO:3), with trans-4-hydroxyproline (Hyp) and cis-4-azidoproline (Azp), respectively, retain the binding properties. Peptide 3 showed a marginally increased binding effect to YU2 gp120, with equilibrium constant K D , 2.87 micromolar. Further, peptide 5 (RINNIXSEAMM; SEQ ID NO:5; structure of X depicted in  FIG. 1B ) exhibited enhanced binding affinity to gp120 and enhanced inhibition of cell surface receptor binding, as compared to the starting peptide (SEQ ID NO:1/peptide 1). 
     The equilibrium constant K D  for all peptides 1-5, in direct binding analysis over immobilized gp120, are given in Table 1. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Sequences of peptide and their direct binding kinetic 
               
               
                 constants with surface immobilized YU2 gp120 
               
             
          
           
               
                   
                 SEQ ID NO/ 
                   
               
               
                 Peptide sequence 
                 Peptide Number 
                 K D   
               
               
                   
               
               
                 RINNIPWSEAMM 
                 SEQ ID NO: 1/Peptide 1 
                 4.46 × 10 −6 M 
               
               
                 RINNI Hyp WSEAMM 
                 SEQ ID NO: 2/Peptide 2 
                 23.6 × 10 −6 M 
               
               
                 RINNI Azp WSEAMM 
                 SEQ ID NO: 3/Peptide 3 
                 2.81 × 10 −6 M 
               
               
                 RINNI Amp WSEAMM 
                 SEQ ID NO: 4/Peptide 4 
                 — 
               
               
                 RINNI X WSEAMM 
                 SEQ ID NO: 5/Peptide 5 
                 8-13 × 10 −9 M 
               
               
                   
               
             
          
         
       
     
     The peptides were synthesized using Fmoc-chemistry on PAL-PEG-PS resin. The trans-4-hydroxyl group of proline in peptide 2 was converted to peptide 3 through the trans-4-mesylate, followed by azide displacement. The cis-4-azido group on proline was converted to cis-4-amine using trimethylphosphine, dioxane water mixture (Lundquist et al. Org. Lett. 2002, 4, 3219-3221). The [3+2] cycloaddition reaction was carried out on resin. The resin was suspended in acetonitrile, water, DIEA and pyridine (4:4:2:1) mixture. The phenylacetylene was added followed by a catalytic amount CuI. The peptide was cleaved from the resin using TFA. The peptides were synthesized individually for large quantities. 
     Additional experiments were conducted with peptide 5. 
     Increasing concentrations of peptide were passed over an immobilized high density (5000 RU) surface.  FIG. 2  shows the direct binding of peptide 5 YU2 gp120. Buffer injections and controls were subtracted for all reported data. The equilibrium constant K D  was calculated from the fit of direct binding to a steady state 1:1 binding model as a function of Req. (280 to 295 seconds of each curve) vs. concentration peptide 5. 
     To assess the inhibition of binding of gp120 to CD4 and 17b, the analyte YU2 gp120 (100 nmol) in the absence or presence of peptide 5 was passed over immobilized CD4, 17b and control 2B6R Fab. The peptide 5 exhibited no direct binding to CD4, 17b or control 2B6R. 
       FIG. 3  shows that increasing concentration of peptide 5 from 0 to 1 micromolar leads to almost complete inhibition of binding of gp120 to both sCD4 and 17b surfaces. The IC 50  values for peptide 5 inhibition of binding to YU2 gp120 to sCD4 and 17b were calculated by using the fraction of the initial rate (6-20 s) of YU2 gp120 binding in the presence verses absence of peptide 5 and plotting these against the log of peptide concentration. 
     Using the same high density gp120 surface, we confirmed the inhibition in the reverse orientation.  FIG. 4  shows the inhibition of binding of 100 nmol sCD4 to surface immobilized gp120 by increasing concentrations of peptide 5. 
     Thus, as demonstrated herein, peptide 5 ( FIG. 1B ) comprising a cis-γ-substituted proline (2S,4S)-4-(4-phenyl-1H-1,2,3-triazol-1-yl)pyrrolidine-2-carboxylic acid) strongly inhibits the interaction of gp120 to both CD4 and 17b with similar IC 50  values or 23 and 29 nmol, respectively. The results with this peptide encourage its utilization in inhibiting the HIV fusion process and as a lead tool in the drug discovery process. Mutants as well as fragments of peptide 5 are also expected to exhibit similar properties as described herein. The strong (close to nanomolar) inhibition of binding of gp120 by peptide 5 to both host cell receptors is indicative of its utility as an antagonist of the HIV-1 fusion process and in designing new compounds, including, but not limited to, mutants of peptide 5, fragments of peptide 5 and small organic molecule antagonists of the HIV-1 fusion process.