System for determining unprocessed and partially processed neurotoxin type A

A method for determining an amount of partially processed and/or unprocessed Clostridium botulinum neurotoxin A (BoNT/A) in a solution comprising processed and partially processed and/or unprocessed BoNT/A, wherein the partially processed and unprocessed BoNT/A exhibit a linker peptide, comprising the steps of:

• i) contacting a sample of the solution with a capture antibody which specifically binds to the partially processed and unprocessed BoNT/A under conditions which allow for binding for the antibody to the partially processed and unprocessed BoNT/A, whereby a complex is formed, and
• ii) determining the amount of the complex formed in step i), whereby the amount of the complex is indicative for the amount of the partially processed and/or unprocessed BoNT/A in the solution;
• wherein the capture antibody is obtained by;
• a) contacting a polyclonal antiserum from an animal which has been immunized with a peptide immunogen comprising amino acids 5 to 9 of SEQ ID NO:
• 1 and/or the amino acid sequence of SEQ ID NO:1 with capture peptides selected from those having an amino acid sequence SLD, LDK and YNK under conditions which allow for the formation of capture complexes comprising unspecific antibodies comprised by the polyclonal antiserum and the capture peptides;
• b) removing the capture complexes from the polyclonal antiserum;
• c) contacting the polyclonal antiserum from step b) with a peptide consisting essentially of SEQ ID NO:
• E under conditions which allow for the formation of a complex comprising the peptide consisting essentially of SEQ ID NO:
• 1 and an antibody which specifically binds to unprocessed BoNT/A or partially processed BoNT/A polypeptides which exhibit a linker peptide;
• d) removing the complex formed in step c) from the antiserum;
• and
• e) releasing the antibody which specifically binds to unprocessed BoNT/A or partially processed BoNT/A polypeptides from the complex.