Method for determining the in vivo interaction mode

A method for selecting the assay format for determining the binding interaction of an antibody of the human IgG1 subclass with a multimeric antigen comprising the following steps:

• 1) determining the binding affinity of the antibody for the multimeric antigen using a surface plasmon resonance method,
• 2) incubating a mixture comprising the antibody, the antigen and lysine-gingipain of Porphyromonas gingivalis at a pH of 7.5 to 8.5, in the presence of a reducing agent, at a temperature of 30° C. to 42° C., for a time of 10 mift. minutes to 240 mift. minutes to cleave the antibody into Fabs and g Fe-region, whereby the concentration of the antibody prior to said cleaving
• is higher than the concentration of the antigen, and
• determining the binding affinity of the Fabs of the antibody for their antigen using surface plasmon resonance by directly applying the incubated reaction mixture obtained in the previous step in the surface plasmon resonance method,
• whereby the binding affinity of the antibody to the multimeric antigen is i) affinity-driven if the binding affinity determined in step 1) and 2) is comparable, or ii) avidity-driven if the binding affinity determined in step 1) and 2) is different,
• and
• selecting
• i) in case of an affinity-driven interaction with a soluble multimeric antigen a solution assay,
• ii) in case of an avidity-driven interaction with a soluble multimeric antigen a solution or a surface assay,
• iii) in case of an affinity-driven interaction with a surface bound antigen a solution assay, or
• iv) in case of an avidity-driven interaction with a surface bound antigen a surface assay for determining the binding interaction of the antibody of the human IgG 1 subclass with the multimeric antigen;
• wherein the binding affinity is determined in solution using an ELISA or a surface plasmon resonance method;
• and
• wherein the binding affinities determined in steps 1 and 2 of the antibody to the multimeric antigen are comparable if the binding affinities determined in both steps differ by a factor of 2 or less, wherein the smaller value is used as basis for the calculation;
• and is different if the binding affinities determined in both steps differ by more than a factor of 2, wherein the smaller value is set to 100%.