Identification of high affinity molecules by limited dilution screening
Methods are disclosed for determining the relative binding affinities of molecules for their binding partner. One type of molecule is an antibody, which has an antigen binding partner. Antibodies are tested for binding against limited dilutions of antigen. Antibodies that bind to the most dilute antigen concentrations are determined to have a higher relative binding affinity for the antigen than antibodies that only bind to more concentrated antigen preparations.
1. A method of determining the relative binding affinities of antibodies to an antigen, comprising:
providing a set of serial dilutions of a target antigen comprising a first dilution of said target antigen and a second dilution of said target antigen;
providing a set of serial dilutions of a reference antibody that binds to said target antigen;
incubating each dilution of said reference antibody with each dilution of said target antigen;
measuring the relative degree to which the antibody in each dilution of said reference antibody binds to the target antigen in each dilution of said target antigen;
selecting the dilution of said target antigen at which differences in the relative degree to which the antibody in each dilution of said reference antibody binds to said target antigen are greater than the differences in the relative degree to which the antibody in each dilution of said reference antibody binds to said target antigen in another dilution of said target antigen, wherein the selected dilution is such that a desired signal strength is produced by the binding of said reference antibody to said target antigen;
providing a set of test antibody solutions, wherein the concentration of antibody in each test antibody solution is within the concentration range of antibody in said serial dilutions of said reference antibody;
incubating the selected dilution of said target antigen with each test antibody solution in the set of test antibody solutions;
measuring the relative degree to which the test antibody in each test antibody solution binds to the target antigen in said selected dilution of said target antigen; and
ranking the test antibodies in each test antibody solution based on said relative degree to which the test antibodies in each test antibody solution bind to the target antigen in said selected dilution of said target antigen in order to determine the relative binding-affinity of each test antibody to said target antigen.
2. The method of claim 1 , wherein the test antibodies are selected from the group consisting of: mammalian, human, humanized, non-human primate, mouse, rat, rabbit, goat, horse, guinea pig, sheep, cow, and chimeric antibodies.
3. The method of claim 1 , wherein the test antibodies are recombinant antibodies.
4. The method of claim 1 , wherein the test antibodies are antibody fragments.
5. The method of claim 1 , wherein measuring the relative degree comprises an assay selected from a group consisting of: an enzyme linked immunosorbent assay (ELISA), a fluorescence-linked immunosorbent assay, a radioisotopic assay (HA), and a surface Plasmon resonance (SPR) based assay.
6. The method of claim 1 , wherein the concentration of each test antibody is between 10 ng/ml and 100 ng/ml.
7. The method of claim 1 , wherein said concentration of each test antibody is between 10 ng/ml and 50 ng/ml.
8. The method of claim 1 , wherein said concentration of each test antibody is between 10 ng/ml and 25 ng/ml.
9. The method of claim 1 , wherein said set of test antibody solutions comprises a set of supernatants comprising monoclonal antibodies secreted from a set of hybridomas.
10. The method of claim 1 , wherein said set of test antibody solutions is between 100 and 5000 antibody solutions.
11. The method of claim 1 , wherein said set of test antibody solutions is between 2500 and 5000 antibody solutions.
12. The method of claim 1 , wherein each test antibody solution is a polyclonal antibody solution.
13. The method of claim 1 , wherein each test antibody solution is a monoclonal antibody solution.
14. A method of determining the relative binding affinities of a set of molecules to a target molecule binding partner, comprising:
providing a reference molecule that binds to a target molecule binding partner;
determining the optimal concentration of the target molecule binding partner for the reference molecule, wherein the optimal concentration is the concentration of said target molecule binding partner at which differences in the relative degree to which the reference molecule binds to said target molecule binding partner are greater than differences in the relative degree to which the reference molecule binds to said target molecule binding partner in another concentration of said target molecule binding partner, and wherein the optimal concentration is such that a desired signal strength is produced by the binding of said reference molecule to said target molecule binding partner;
providing a set of test molecule solutions, wherein the concentration of molecules in each test molecule solution is within a predetermined concentration of molecules;
incubating the optimal concentration of the target molecule binding partner with each test molecule solution in the set of test molecule solutions;
measuring the relative degree to which the test molecules in each test molecule solution bind to the optimal concentration of target molecule binding partner; and
ranking the test molecules in each test molecule solution based on said relative degree to which the test molecules in each test molecule solution bind to said optimal concentration of target molecule binding partner in order to determine the relative binding affinities of each test molecule to said target molecule binding partner.
15. The method of claim 14 , wherein said test molecules are antibodies is an antibody and said target molecule binding partner is an antigen.
16. The method of claim 15 , wherein the antibody is selected from the group consisting of: mammalian, human, humanized, non-human primate, mouse, rat, rabbit, goat, horse, guinea pig, sheep, cow, recombinant and chimeric antibodies.
17. The method of claim 15 , wherein the antibody is a monoclonal antibody.
18. The method of claim 14 , wherein said molecule is a ligand and said target molecule binding partner is a receptor.
19. The method of claim 1 , wherein the desired signal strength is an optical density (OD) of between about 0.4 and 1.6 OD units.
20. The method of claim 1 , wherein the desired signal strength is an OD of about 1.0 OD units.