Means and methods for producing stable antibodies

1. A method for producing a B cell having a high avidity for an antigen of interest comprising:

a) selecting at least one B cell capable of producing said antibody specific for said antigen of interest or at least one B cell capable of developing into a B cell capable of producing said antibody specific for said antigen of interest;

b) inducing, enhancing and/or maintaining expression of BCL6 and inducing, enhancing and/or maintaining expression of an anti-apoptotic nucleic acid in said at least one B cell;

c) allowing expansion of said at least one B cell into a first B cell culture;

d) selecting at least one B cell from said first B cell culture with a binding avidity for said antigen of interest that is higher than the average binding avidity for said antigen of interest of B cells in said first B cell culture;

e) optionally allowing expansion of said at least one B cell selected in step d) into a second B cell culture;

f) determining the stability of antibodies produced by said at least one B cell selected in step d) or by said second B cell culture;

g) determining affinity for said antigen of interest of said antibodies produced by said at least one B cell selected in step d) or by said second B cell culture; and

h) selecting at least one B cell, wherein said selected B cell is capable of producing antibodies with a higher stability as compared to the average stability of antibodies produced by B cells of said first B cell culture; wherein said selected B Cell exhibits affinity for said antigen of interest that is the same as, or less than, the average affinity for said antigen of interest of antibodies produced by said first B cell culture; and wherein said selected B cell is capable of producing antibodies that exhibit(s) affinity for said antigen of interest that is the same as, or less than, the average affinity for said antigen of interest of antibodies produced by said first B cell culture.

2. The method according to claim 1 , wherein allowing expansion of said at least one B cell into said B cell culture and selecting at least one B cell from said B cell culture capable of producing antibody with a binding avidity for said antigen of interest that is higher than the average binding avidity of B cell receptors or antibodies produced by said B cell culture for said antigen of interest in step d are repeated at least once.

3. The method according to claim 1 , further comprising determining at least part of the amino acid sequence of the heavy chain and/or light chain of said at least one B cell that is capable of producing antibodies with a higher stability.

4. The method according to claim 1 wherein the stability of antibodies produced by said at least one B cell selected as having a binding avidity higher than the average binding avidity of B cells in said first B cell culture or the stability of antibodies produced by said second B cell culture is determined within four months, from selecting said at least one B cell having a binding avidity higher than the average binding avidity of B cells in said first B cell culture.

5. The method according to claim 1 further comprising directly or indirectly inducing, enhancing and/or maintaining the amount of Blimp 1 expression product in said at least one B cell.

6. The method according to claim 1 , wherein said at least one B cell originates from an individual which had been previously exposed to said antigen of interest.

7. The method according claim 1 , wherein said first B cell culture is a monoclonal B cell culture.

8. The method according to claim 1 wherein the stability of antibodies produced by said at least one B cell selected as having a binding avidity higher than the average binding avidity of B cells in said first B cell culture or the stability of antibodies produced by said second B cell culture is determined within one month, from selecting said at least one B cell having a binding avidity higher than the average binding avidity of B cells in said first B cell culture.

9. The method according to claim 1 , wherein said anti-apoptotic nucleic acid comprises a gene encoding anti-apoptotic molecules of the BCL2 family.

10. The method according to claim 1 , wherein said anti-apoptotic nucleic acid comprises a gene encoding Bcl-xL, or Mcl 1, or a functional part thereof.