Compositions and methods for regulating erythropoiesis

Abstract

The present application discloses a previously unknown function of CD24 expressed on a subset of dendritic cells. The invention encompasses regulating CD24 on these cells to regulate erythropoiesis, induce EPO production and levels, increase RBC levels, and to treat, for example, stress-mediated erythropoiesis. The compositions and methods of the invention are useful, for example, in treating anemia.

1 . A method of stimulating erythropoiesis in a subject, said method comprising administering to said subject a pharmaceutical composition comprising a pharmaceutically-acceptable carrier, an effective amount of at least one agonist of CD24, and optionally at least one additional therapeutic agent, thereby stimulating erythropoiesis in a subject. 
     
     
         2 . The method of  claim 1 , wherein said agonist stimulates CD24 expressed on dendritic cells. 
     
     
         3 . The method of  claim 2 , wherein said dendritic cells express the cell surface molecule BDCA3/CD141. 
     
     
         4 . The method of  claim 3 , wherein said agonist is a small molecule, drag, prodrug, or an antibody directed against CD24 or a biologically active fragment or homolog of said antibody. 
     
     
         5 . The method of  claim 4 , wherein said antibody is selected from the group consisting of 4 polyclonal antibody, a monoclonal antibody, a chimeric antibody, a single-chain antibody, a synthetic antibody, isolated and identified single chain molecules produced by techniques such as phage or yeast display, and a humanized antibody. 
     
     
         6 . The method of  claim 5 , wherein said monoclonal antibody is selected from the group consisting of M1/69, 91, 30-F1, J11d, eBioSN3, and ML5, or biologically active fragments or homologs thereof. 
     
     
         7 . The method of  claim 6 , wherein said fragment is an F(ab)2 fragment. 
     
     
         8 . The method of  claim 1 , wherein said method stimulates the production of erythrocytes. 
     
     
         9 . The method of  claim 1 , wherein said method stimulates the production of reticulocytes. 
     
     
         10 . The method of  claim 1 , wherein said method stimulates the production of erythroid progenitor cells. 
     
     
         11 . The method of  claim 2 , wherein said dendritic cells are in the spleen. 
     
     
         12 . The method of  claim 2 , wherein said dendritic cells are in the bone marrow. 
     
     
         13 . The method of  claim 2 , wherein said method stimulates dendritic cells. 
     
     
         14 . The method of  claim 1 , wherein said method stimulates erythropoietin prod action. 
     
     
         15 . The method of  claim 1 , wherein said method stimulates extramedullary hematopoiesis. 
     
     
         16 . The method of  claim 1 , wherein said method increases levels of stem cell factor (SCF), granulocyte colony stimulating factor (G-CSF), and erythropoietin (EPO). 
     
     
         17 . The method of  claim 1 , wherein said method enhances CD24-mediated stress erythropoiesis. 
     
     
         18 . The method of  claim 1 , wherein said method stimulates proliferation of erythroid progenitor cells. 
     
     
         19 . The method of  claim 1 , wherein said subject has a disease, disorder, or condition associated with a decrease in erythrocyte production. 
     
     
         20 . The method of  claim 19 , wherein said disease, disorder, or condition is selected from the group consisting of aplastic anemia, hypoplastic anemia, chronic renal failure, end-stage renal disease, transplantation, renal transplantation, cancer, acquired immune deficiency syndrome, chemotherapy, radiotherapy; bone marrow transplantation, sepsis, rheumatoid arthritis, chronic persistent infection such as HIV, tuberculosis, hepatitis B, hepatitis C, chronic hepatitis, and chronic anemia in the elderly. 
     
     
         21 . The method of  claim 20 , wherein said disease, disorder, or condition is anemia. 
     
     
         22 . The method of  claim 21 , wherein said anemia is associated with hypoxic stress. 
     
     
         23 . The method of  claim 1 , wherein said additional therapeutic agent is selected from the group consisting of G-CSF, interleukin-4 (IL-4), SCF, Fms-Like Tyrosine Kinase 3 Ligand (Flt3L), EPO, bone morphogenic protein 4 (BMP4), anti-microbial agents, and host-derived danger associated-pattern molecules. 
     
     
         24 . The method of  claim 23 , wherein said host-derived danger associated-pattern molecule is HMGB1 or Hsp70. 
     
     
         25 . The method of  claim 1 , wherein said composition is administered at least twice. 
     
     
         26 - 32 . (canceled) 
     
     
         33 . The method of  claim 1 , wherein said method increases erythrocyte levels. 
     
     
         34 . The method of  claim 4 , wherein said antibody is administered at a dose ranging from about 0.1 mg/kg to about 23.0 mg/kg body weight. 
     
     
         35 - 36 . (canceled) 
     
     
         37 . The method of  claim 1 , wherein said subject is human. 
     
     
         38 . A method of treating a disease, disorder, or condition associated with a decrease in erythrocyte production, said method comprising administering to a subject in need thereof a pharmaceutical composition comprising a pharmaceutically-acceptable carrier, an effective amount of at least one agonist of CD24, and optionally at least one additional therapeutic agent, thereby treating a disease, disorder, or condition associated with a decrease in erythrocyte production. 
     
     
         39 . The method of  claim 38 , wherein said agonist stimulates CD24 expressed on dendritic cells. 
     
     
         40 . The method of  claim 39 , wherein said dendritic cells express the cell surface molecule BDCA3/CD141. 
     
     
         41 . The method of  claim 40 , wherein said agonist is small molecule, drug, prodrug, or an antibody, or a biologically active fragment or homolog thereof, directed against CD24. 
     
     
         42 . The method of  claim 41 , wherein said antibody is selected from the group consisting of a polyclonal antibody, a monoclonal antibody, a chimeric antibody, a single-chain antibody, a synthetic antibody, and a humanized antibody. 
     
     
         43 . The method of  claim 42 , wherein said monoclonal antibody is selected from the group consisting of M1/69, 91, 30-F1, J11d, eBioSN3, and ML5, or biologically active fragments or homologs thereof. 
     
     
         44 . The method of  claim 43 , wherein said fragment is a F(ab)2 fragment. 
     
     
         45 . The method of  claim 38 , wherein said method stimulates the production of erythrocytes. 
     
     
         46 . The method of  claim 38 , wherein said method stimulates the production of reticulocytes. 
     
     
         47 . The method of  claim 38 , wherein said method stimulates the production of erythroid progenitor cells. 
     
     
         48 . The method of  claim 39 , wherein said dendritic cells are in the spleen. 
     
     
         49 . The method of  claim 39 , wherein said dendritic cells are in the bone marrow. 
     
     
         50 . The method of  claim 39 , wherein said method stimulates dendritic cells. 
     
     
         51 . The method of  claim 38 , wherein said method stimulates erythropoietin production. 
     
     
         52 . The method of  claim 38 , wherein said method stimulates extramedullary hematopoiesis. 
     
     
         53 . The method of  claim 38 , wherein said method increases levels of SCF, G-CSF, and EPO. 
     
     
         54 . The method of  claim 38 , wherein said method enhances CD24-mediated stress erythropoiesis. 
     
     
         55 . The method of  claim 38 , wherein said method stimulates proliferation of erythroid progenitor cells. 
     
     
         56 . The method of  claim 38 , wherein said subject has a disease, disorder, or condition associated with a decrease in erythrocyte production. 
     
     
         57 . The method of  claim 56 , wherein said disease, disorder, or condition is selected from the group consisting of aplastic anemia, hypoplastic anemia, chronic renal failure, end-stage renal disease, transplantation, renal transplantation, cancer, acquired immune deficiency syndrome, chemotherapy, radiotherapy, bone marrow transplantation, sepsis, rheumatoid arthritis, chronic persistent infection such as HIV, tuberculosis, hepatitis B, hepatitis C, chronic hepatitis, and chronic anemia in the elderly. 
     
     
         58 . The method of  claim 57 , wherein said disease, disorder, or condition is anemia. 
     
     
         59 . The method of  claim 58 , wherein said anemia is associated with hypoxic stress. 
     
     
         60 - 70 . (canceled) 
     
     
         71 . The method of  claim 41 , wherein said antibody is administered at a dose ranging from about 0.1 mg/kg to about 25.0 mg/kg body weight. 
     
     
         72 - 76 . (canceled) 
     
     
         77 . A method of stimulating stem cell factor synthesis, said method comprising contacting a CD24 +  dendritic cell with an effective amount of an agonist of CD24 and optionally an additional agent. 
     
     
         78 . The method of  claim 77 , wherein said dendritic cell is BDCA3 + . 
     
     
         79 . The method of  claim 77 , wherein said additional agent is a host-derived danger associated-pattern molecule. 
     
     
         80 . The method of  claim 77 , wherein said agonist is an antibody, or a biologically active fragment or homolog thereof, directed against CD24. 
     
     
         81 . The method of  claim 80 , wherein said antibody is selected from the group consisting of a polyclonal antibody, a monoclonal antibody, a chimeric antibody, a single-chain antibody, a synthetic antibody, and a humanized antibody. 
     
     
         82 . The method of  claim 81 , wherein said monoclonal antibody is selected from the group consisting of M1/69, 91, 30-F1, J11d, eBioSN3, and ML5, or biologically active fragments or homologs thereof. 
     
     
         83 - 85 . (canceled) 
     
     
         86 . The method of  claim 81 , wherein said antibody is directed against a CD24 peptide having the sequence of SEQ ID NO:2 or SEQ ID NO:4, or homologs or fragments thereof. 
     
     
         87 - 93 . (canceled) 
     
     
         94 . A method of identifying of an agonist of CD24 useful for stimulating erythropoiesis, said method comprising contacting a dendritic cell expressing CD24 with a test compound, measuring the stem cell factor level in said cell following said contact, wherein an increase in stem cell factor in said cell relative to a control cell not contacted with said test compound, is an indication that said test compound is an agonist of CD24, thereby identifying of an agonist of CD24 useful for stimulating erythropoiesis. 
     
     
         95 . The method of  claim 94 , wherein said test compound is a small molecule, drug, prodrug, or an antibody directed against CD24. 
     
     
         96 . The method of  claim 94 , wherein said test compound interacts with CD24. 
     
     
         97 . The method of  claim 94 , wherein stem cell factor or CD24 protein levels are measured. 
     
     
         98 . The method of  claim 94 , wherein stem cell factor or CD24 messenger RNA levels are measured. 
     
     
         99 . A kit for stimulating erythropoiesis, said kit comprising at least one dose of an agonist of CD24, wherein said agonist is optionally in a pharmaceutical composition, optionally at least one additional therapeutic agent, an applicator, and an instructional material for the use thereof. 
     
     
         100 - 101 . (canceled)