Methods of treating sickle cell disease

Abstract

The present invention relates to methods of treating sickle cell disease comprising reducing, in a subject in need of such treatment, the adherence between sickle RBCs and leukocytes. It is based, at least in part, on the discovery that leukocytes play a direct role in the initiation of venular occlusion. The present invention further provides for methods for identifying agents which decrease SS-RBC/leukocyte adherence and for animal models which may be used to further elucidate the mechanism of vaso-occlusion in sickle cell crises.

What is claimed is:  
     
         1 . A method of treating sickle cell disease comprising administering, to a subject in need of such treatment, a therapeutic amount of an agent which decreases venular occlusion by sickle erythrocytes adherent to leukocytes by inhibiting binding between elements selected from the group consisting of an endothelial cell, a platelet, a leukocyte, and a sickle erythrocyte/leukocyte complex.  
     
     
         2 . The method of  claim 1  wherein venular occlusion is decreased by inhibiting a process selected from the group consisting of the adherence of sickle erythrocytes to leukocytes, the adherence of leukocytes to the venule endothelium, and the adherence of a sickle erythrocyte/leukocyte complex to the venule endothelium.  
     
     
         3 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits the binding of a leukocyte via a selectin molecule.  
     
     
         4 . The method of  claim 3 , wherein the selectin molecule is selected from the group consisting of P-selectin, E-selectin, and L-selectin.  
     
     
         5 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits a cytokine.  
     
     
         6 . The method of  claim 5 , wherein the cytokine is tumor necrosis factor alpha.  
     
     
         7 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits the binding between one or more elements selected from the group consisting of leukocytes, sickle erythrocyte/leukocyte complexes, and endothelial cells, via a β 2  integrin molecule.  
     
     
         8 . The method of  claim 7 , wherein the β 2  integrin molecule is selected from the group consisting of α L β 2 (LFA-1), α M β 2  (Mac-1), α χ β 2 , and α D β 2 .  
     
     
         9 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits a change in the conformation of β 2  integrins into a high-affinity state.  
     
     
         10 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits binding between elements selected from the group consisting of endothelial cells, platelets, leukocytes and sickle erythrocyte/leukocyte complexes by inhibiting binding via a β 3  integrin.  
     
     
         11 . The method of  claim 10 , wherein the β 3  integrin is selected from the group consisting of α IIb β 3  and α V β 3  integrin.  
     
     
         12 . The method of  claim 11 , wherein the agent is selected from the group consisting of murine monoclonal antibody 7E3, as deposited with the American Type Culture Collection and assigned accession number ATCC HB 8832, the humanized chimeric equivalent of 7E3 which is c7E3, the Fab fragment of c7E3, the monoclonal antibody LM609 and a humanized version thereof.  
     
     
         13 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits binding between one or more elements selected from the group consisting of leukocytes, sickle erythrocyte/leukocyte complexes, and endothelial cells, via a β 1  integrin molecule.  
     
     
         14 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits the binding of a leukocyte or a sickle erythrocyte/leukocyte complex to von Willebrand factor.  
     
     
         15 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits the binding of a leukocyte or a sickle erythrocyte/leukocyte complex to thrombospondin.  
     
     
         16 . The method of  claim 1 , which comprises administering, to the subject, an agent which inhibits the binding of a leukocyte or a sickle erythrocyte/leukocyte complex to a molecule selected from the group consisting of ICAM-1 and VCAM-1  
     
     
         17 . A method for identifying an agent useful in treating sickle cell disease comprising: (i) contacting SS-RBCs and leukocytes in the presence of a test agent; 
 (ii) comparing the binding of SS-RBCs and leukocytes in the presence of a test agent to the level of binding in the absence of a test agent    wherein a decrease in adhesion of SS-RBC to leukocytes in the presence of the test agent as compared to the adhesion in the absence of the test agent indicates the identification of an agent useful in treating sickle cell disease.    
     
     
         18 . The method of  claim 17  wherein the adhesion of SS-RBCs to leukocytes is detected by co-precipitation assays.  
     
     
         19 . The method of  claim 17  wherein the adhesion of SS-RBCs to leukocytes is detected by co-sedimentation assays.  
     
     
         20 . The method of  claim 17  wherein the adhesion of SS-RBCs to leukocytes is detected by co-retention on a solid matrix.  
     
     
         21 . The method of  claim 17  further comprising determining whether the agent inhibits adhesion of non-sickled RBCs to leukocytes.  
     
     
         22 . The method of  claim 17  wherein the adhesion of RBCs to leukocytes is measured using intravital microscopy.