Specific-C-peptide assay method

Abstract

The present invention relates to a specific C-peptide assay method which can eliminate all interference due to proinsulin and its intermediates, in particular des-31,32-proinsulin and/or des-64,65-proinsulin. It also relates to antibodies for carrying out this assay.

1 - 19 . (canceled)  
     
     
         20 . An antibody specific to des-31,32-proinsulin and proinsulin which is capable of interfering with binding of an anti-C-peptide antibody and which recognizes the epitope of sequence Leu Gln Lys Arg Gly Ile Val Glu Gln (SEQ ID NO: 2).  
     
     
         21 . The antibody according to  claim 20 , wherein the antibody is a monoclonal antibody produced by a hybridoma deposited at Collection Nationale de Cultures de Microorganismes at the Institut Pasteur on 4 Jun. 1997, registration number I-1873. A method for assaying C-peptide in a sample suspected of containing C-peptide, intact proinsulin, des-31,32 proinsulin, and/or des-64,65-proinsulin comprising: 
 a) contacting the sample with at least one anti-C-peptide antibody which specifically binds an epitope present entirely in the C-peptide and a second antibody which is selected from: 
 an anti-proinsulin antibody which is specific to intact proinsulin and des-31,32-proinsulin and recognizes an epitope located in an intact A-chain-C-peptide (AC) junction of proinsulin and des-31,32 proinsulin, said anti-proinsulin AC junction antibody epitope being either adjacent to or overlapping with the epitope of said at least one anti-C-peptide antibody, or  
 an anti-proinsulin antibody which is specific to intact proinsulin and des-64,65-proinsulin and recognizes an epitope located in an intact B-chain-C-peptide (BC) junction of proinsulin and des-64,65-proinsulin, said anti-proinsulin BC junction antibody epitope being either adjacent to or overlapping with the epitope of said at least one anti-C-peptide antibody, or  
 a mixture of said anti-proinsulin AC junction antibody and said anti-proinsulin BC junction antibody under conditions such that said at least one anti-C-peptide antibody binds to C-peptide in the sample, binding of the anti-proinsulin AC junction antibody to any proinsulin and/or des-31,32-proinsulin interferes with binding of said at least one anti-C-peptide antibody to intact proinsulin and des-31,32-proinsulin in the sample, and/or binding of the anti-proinsulin BC junction antibody to any proinsulin and/or des-64,65-proinsulin interferes with binding of said at least one anti-C-peptide antibody to intact proinsulin and des-64,65-proinsulin in the sample; and  
   b) detecting amount of C-peptide bound to said at least one anti-C-peptide antibody in said contacted sample as an assay of the amount of C-peptide in the sample.    
     
     
         27 . A hybridoma deposited at Collection Nationale de Cultures de Microorganismes at the Institut Pasteur on 4 Jun. 1997, registration number I-1873.