Antibodies and methods for generating genetically altered antibodies with high affinity
Dominant negative alleles of human mismatch repair genes can be used to generate hypermutable cells and organisms. By introducing these genes into cells and transgenic animals, new cell lines and animal varieties with novel and useful properties can be prepared more efficiently than by relying on the natural rate of mutation. These methods are useful for generating genetic diversity within immunoglobulin genes directed against an antigen of interest to produce altered antibodies with enhanced biochemical activity. Moreover, these methods are useful for generating antibody-producing cells with increased level of antibody production. The invention also provides methods for increasing the affinity of monoclonal antibodies and monoclonal antibodies with increased affinity.
1. A method of producing a monoclonal antibody having an increased affinity for the antigen to which it binds relative to a monoclonal antibody comprising a light chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18 that binds said antigen, the method comprising: substituting with proline an amino acid in SEQ ID NO:21 within said monoclonal antibody comprising a light chain variable region comprising SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18, thereby generating a proline-substituted monoclonal antibody, determining the binding affinity of said proline-substituted monoclonal antibody for said antigen, comparing the binding affinity of said proline-substituted monoclonal antibody for said antigen to the binding affinity of said monoclonal antibody comprising a light chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18 for said antigen, and selecting a proline-substituted antibody having increased affinity for said antigen relative to said monoclonal antibody comprising a light chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18, thereby producing said monoclonal antibody having increased binding affinity for said antigen.
2. A method as claimed in claim 1 , wherein said amino acid substituted with proline in SEQ ID NO:21 is an amino acid having a non-polar side chain.
3. A method as claimed in claim 1 , wherein said amino acid substituted with proline in SEQ ID NO:21 is leucine.
4. A method as claimed in claim 1 , wherein said amino acid substituted with proline in SEQ ID NO:21 is in the second framework region of the light chain of said monoclonal antibody comprising a light chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18.
5. A method as claimed in claim 1 , wherein said amino acid substituted with proline in SEQ ID NO:21 is in position 22 of the second framework region of the light chain variable region of said monoclonal antibody comprising a light chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:18.