Diagnosing and treating iga nephropathy

Abstract

Provided are methods of diagnosing IgA nephropathy in a subject. Optionally, the methods comprise isolating an IgG from the subject and determining whether the IgG binds to a galactose-deficient IgA1. Optionally, the methods comprise providing a biological sample from the subject and detecting in the sample a mutation in a IGH gene, wherein the mutation is in a nucleotide sequence encoding a complementarity determining region 3 (CDR3) of a IGH variable region. Optionally, the methods comprise determining a level of IgG specific for a galactose-deficient IgA1 in the subject. Also provided are methods of treating or reducing the risk of developing IgA nephropathy in a subject.

1 . A method of diagnosing IgA nephropathy in a subject, the method comprising:
 (a) isolating an IgG from the subject; and   (b) determining whether the IgG binds to a galactose-deficient IgA1, binding of the IgG to the galactose-deficient IgA1 indicating the subject has or is at risk of developing IgA nephropathy.   
     
     
         2 . The method of  claim 1 , wherein the IgG is isolated from a B cell. 
     
     
         3 . The method of  claim 2 , wherein the B cell is isolated from a population of peripheral blood mononuclear cells (PBMCs). 
     
     
         4 . (canceled) 
     
     
         5 . The method of  claim 3 , wherein the B cell is immortalized by transformation with an Epstein-Barr virus (EBV). 
     
     
         6 - 7 . (canceled) 
     
     
         8 . A method of diagnosing IgA nephropathy in a subject, the method comprising:
 (a) providing a biological sample from the subject; and   (b) detecting in the sample a mutation in an IGH gene, wherein the mutation is in a nucleotide sequence encoding a complementarity determining region 3 (CDR3) of an IGH variable region, a mutation in the nucleotide sequence compared to a control sequence indicating the subject has or is at risk of developing IgA nephropathy.   
     
     
         9 - 10 . (canceled) 
     
     
         11 . The method of  claim 8 , wherein the mutation in the IGH gene comprises one or more nucleotide substitutions resulting in an alanine to serine amino acid substitution in a YCAR (SEQ ID NO:45) or YCAK (SEQ ID NO:37) amino acid sequence encoded by the IGH gene. 
     
     
         12 . The method of  claim 8 , wherein the nucleotide sequence encoding the CDR3 of the IGH variable region encodes an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, and SEQ ID NO:6. 
     
     
         13 - 17 . (canceled) 
     
     
         18 . A method of diagnosing IgA nephropathy in a subject, the method comprising determining a level of IgG specific for a galactose-deficient IgA1 in the subject, an increase in the level of IgG specific for galactose-deficient IgA1 as compared to a control indicating the subject has or is at risk of developing IgA nephropathy. 
     
     
         19 . The method of  claim 18 , wherein the IgG is isolated from the subject. 
     
     
         20 . The method of  claim 19 , wherein the IgG is isolated from a B cell. 
     
     
         21 . The method of  claim 20 , wherein the B cell is isolated from a population of peripheral blood mononuclear cells (PBMCs). 
     
     
         22 . (canceled) 
     
     
         23 . The method of  claim 20 , wherein the B cell is immortalized by transformation with an Epstein-Barr virus (EBV). 
     
     
         24 - 25 . (canceled) 
     
     
         26 . The method of  claim 18 , wherein the method further comprises determining a level of galactose-deficient IgA1 in the subject, an increase in the level of galactose-deficient IgA1 in the subject as compared to a control indicates the subject has or is at risk of developing IgA nephropathy. 
     
     
         27 . A method of treating or reducing the risk of developing IgA nephropathy in a subject, the method comprising administering to the subject an agent, wherein the agent inhibits the binding of the IgG specific for galactose deficient IgA1 to galactose-deficient IgA1. 
     
     
         28 - 30 . (canceled) 
     
     
         31 . The method of treating or reducing the risk of developing IgA nephropathy in a subject, the method comprising reducing a level of IgG specific for galactose-deficient IgA1 in the subject. 
     
     
         32 . The method of  claim 31 , wherein reducing the level of IgG specific for galactose-deficient IgA1 in the subject comprises the use of plasmapheresis. 
     
     
         33 . The method of  claim 31 , wherein reducing the level of IgG specific for galactose-deficient IgA1 in the subject comprises administering to the subject an agent that reduces the level of IgG in the subject. 
     
     
         34 - 35 . (canceled) 
     
     
         36 . An isolated antibody specific for a galactose-deficient hinge-region O-linked glycan of IgA1. 
     
     
         37 . The isolated antibody of  claim 36 , wherein the antibody comprise an alanine to serine amino acid substitution in a complementarity determining region 3 (CDR3) of an IGH variable region. 
     
     
         38 - 42 . (canceled) 
     
     
         43 . A method of detecting galactose-deficient IgA1 in a subject, the method comprising:
 (a) obtaining a biological sample from a subject; and   (b) utilizing the isolated antibody of  claim 36  in an assay to detect galactose-deficient IgA1 in the subject.   
     
     
         44 . (canceled) 
     
     
         45 . An isolated polypeptide comprising a galactose-deficient hinge-region O-linked glycan of IgA1. 
     
     
         46 . A kit for performing an immunoassay, the kit comprising:
 (a) a galactose-deficient IgA1; and   (b) a container.   
     
     
         47 . The kit of  claim 46 , further comprising an IgG specific antibody. 
     
     
         48 - 50 . (canceled) 
     
     
         51 . A kit for performing an immunoassay, the kit comprising:
 (a) the isolated antibody of  claim 36 ; and   (b) a container.   
     
     
         52 . The kit of claim  50 , further comprising an IgA1 specific antibody. 
     
     
         53 - 55 . (canceled) 
     
     
         56 . A method of creating an animal model of IgA nephropathy, the method comprising:
 (a) forming immune complexes in vitro, wherein the immune complexes comprise galactose-deficient IgA1 and IgG specific for galactose-deficient IgA1; and   (b) injecting the immune complexes into the animal, wherein injection of the immune complexes into the animal results in an animal model of IgA nephropathy.   
     
     
         57 - 58 . (canceled) 
     
     
         59 . The method of  claim 56 , wherein the immune complexes deposit in the renal mesangium of the animal model. 
     
     
         60 . An animal model of IgA nephropathy made by the method of  claim 56 . 
     
     
         61 . (canceled)