T cell costimulating polypeptides and uses thereof

Abstract

A polypeptide (8F4 molecule) with a T-cell costimulating biological activity is disclosed, as well as monoclonal antibodies against the 8F4 molecule and hybridoma cells which produce the monoclonal antibodies, the use as medicaments of substances which inhibit the biological activity of the 8F4 polypeptide, in particular monoclonal antibodies, natural or synthetic ligands, agonists or antagonists, in particular for preventing or treating diseases which involve the immune system, the use of the 8F4 molecule or cells containing the 8F4 molecule as medicaments, in particular for preventing or treating diseases which involve the immune system, and the use of substances which specifically recognize the 8F4 polypeptide, in particular monoclonal antibodies, natural or synthetic ligands, agonists or antagonists, for diagnosing diseases which involve the immune system.

What is claimed is: 
     
         1 . A costimulating molecule
 a) having the biological activity of costimulation of T cells,   b) the molecule being present on activated CD4 +  and CD8 +  T lymphocytes but not resting or activated B cells, granulocytes, monocytes, NK cells or dendritic cells, and   c) the molecule having two polypeptide chains, the molecule having a molecular weight of about 55 to 60 kDa as determined by nonreducing SDS polyacrylamide gel electrophoresis, and the two polypeptide chains of the molecule having molecular weights of about 27 kDa and 29 kDa as measured by reducing SDS polyacrylamide gel electrophoresis.   
     
     
         2 . A costimulating molecule having the biological activity of costimulation of T cells, the molecule comprising an amino-acid sequence which has at least 80% homology with the sequence comprising 199 amino acids in  FIG. 15  (SEQ ID NO:2), or a biologically active fragment thereof. 
     
     
         3 . A DNA sequence which encodes a costimulating molecule according to  claim 1  or a fragment thereof. 
     
     
         4 . A DNA sequence which encodes a costimulating molecule according to  claim 2  or a fragment thereof. 
     
     
         5 . A DNA sequence encoding a costimulating molecule having the biological activity of costimulation of T cells, the sequence being selected from the group consisting of:
 a) a DNA sequence shown in SEQ ID NO:1 ( FIG. 16 ) and its complementary strand;   b) a DNA sequence capable of hybridizing with the sequences in (a); and   c) a DNA sequence which, because of the degeneracy of the genetic code, hybridizes with the sequences in (a) and (b).   
     
     
         6 . A vector comprising a DNA sequence according to either of  claim 3  or  5 . 
     
     
         7 . A host cell stably transformed or transfected with the vector according to  claim 6 . 
     
     
         8 . A method for preparing a costimulating molecule according to  claim 1 , the method comprising cultivating the host cell according to  claim 7  for expression of the molecule in the host cell. 
     
     
         9 . A pharmaceutical composition comprising a substance that inhibits the biological activity of a costimulating molecule according to  claim 1 . 
     
     
         10 . The pharmaceutical composition of  claim 9  wherein the substance comprises a monoclonal antibody, or a natural or synthetic ligand. 
     
     
         11 . A method of treating an autoimmune disease, preventing a rejection reaction in an organ transplant, or treating dysregulation of the immune system in a mammal, comprising administering to the mammal a monoclonal antibody which inhibits the biological activity of a costimulating molecule according to  claim 1  or  claim 2  in an amount sufficient to treat the autoimmune disease, prevent rejection in an organ transplant, or treat dysregulation of the immune system. 
     
     
         12 . A pharmaceutical composition comprising the costimulating molecule according to  claim 1 , a cell expressing said costimulating molecule, or an antibody which binds to said costimulating molecule. 
     
     
         13 . A method for treating cancer, AIDS, an asthmatic disorder, or a chronic viral disease in a mammal, the method comprising administering to the mammal a composition according to  claim 12  in an amount sufficient to treat the cancer, AIDS, asthmatic disorder, or chronic viral disease. 
     
     
         14 . The method of  claim 13 , wherein the chronic viral disease is caused by an HCV or HBV infection. 
     
     
         15 . A method for diagnosing a disorder involving the immune system in a subject, the method involving contacting a sample from the subject with a substance which specifically recognizes a costimulating molecule according to  claim 1 , and determining whether the level of the costimulating molecule is altered relative to the level in a reference sample. 
     
     
         16 . The method of  claim 15 , wherein the substance comprises a nucleic acid molecule or a monoclonal antibody. 
     
     
         17 . A method for producing antibodies to a costimulating molecule of  claim 1 , the method comprising administering the costimulating molecule to an animal and isolating the antibodies produced. 
     
     
         18 . A monoclonal antibody which specifically recognizes a costimulating molecule according to  claim 1 . 
     
     
         19 . A monoclonal antibody which specifically recognizes a costimulating molecule according to  claim 1 , characterized in that B cells of mice which are immunized with human T lymphocytes activated PMA and the Ca 2+  ionophore ionomycin are fused with a myeloma cell line to give an antibody-secreting hybridoma, and the monoclonal antibodies are purified in flow cytometry for 2-signal molecule-activated against resting T cells.