Method for isolation of soluble polypeptides
Polypeptides with desirable biophysical properties such as solubility, stability, high expression, monomericity, binding specificity or non-aggregation, including monomeric human VHs and VLs, are identified using a high throughput method for screening polypeptides, comprising the steps of obtaining a phage display library, allowing infection of a bacterial lawn by the library phage, and identifying phage which form larger than average plaques on the bacterial lawn. Sequences of monomeric human VHs and VLs are identified, which may be useful for immunotherapy or as diagnostic agents. Multimer complexes of human VHs and VLs are also identified. The VHs and VLs identified may be used to create further libraries for identifying additional polypeptides. Further, the VHs and VLs may be subjected to DNA shuffling to select for improved biophysical properties.
1. A method of identifying stable human or humanized target VH and/or VL antibody fragments, comprising:
(a) obtaining a VH and/or VL phage display library and reducing the library size, yielding a phage display library expressing a variety of VH and/or VL antibody fragments,
wherein the library size is reduced by panning against a target antigen, panning against a non-specific binder, or chromatography using a hydrophobic interaction column or otherwise removing wild type phage without inserts from the library;
(b) allowing infection of a bacterial lawn by the library phage;
(c) identifying phage which form larger than average plaques on the bacterial lawn;
(d) isolating the larger plaque phage in step (c); and
(e) determining the sequence or other characteristics of the VH and/or VL antibody fragments expressed by the phage forming larger plaques,
wherein the human or humanized VH or VL antibody fragment expressed in the larger plaque phage isolated in step (d)
i) is soluble,
ii) is monomeric,
iii) is nonaggregating,
iv) has relatively high thermal refolding efficiency
v) has relatively high melting temperature,
vi) maintains its functionality following long incubation at 37° C.,
vii) is relatively resistant to chemical denaturants,
viii) is relatively resistant to proteases,
ix) has a relatively long shelf life at or above room temperature, at 4° C., or below 0° C., or
x) any combination of the above;
when compared to a human or humanized VH or VL antibody fragment expressed in average plaque-forming phage.
2. A method as claimed in claim 1 , where the phage is a filamentous phage.
3. A method as claimed in claim 2 , where the phage is M13 or fd.
4. A method as claimed in claim 1 , wherein the human or humanized VH and/or VL antibody fragments are human VH or VL antibody fragments.
5. An isolated stable VH or VL antibody fragment identified by the method of claim 1 .
6. A VH or VL antibody fragment as claimed in claim 5 that is of human origin.
7. A VH antibody fragment as claimed in claim 5 having an amino acid sequence that deviates from the corresponding parental germline sequence as shown in Table 1.
8. A VH antibody fragment as claimed in claim 5 belonging to the VH3 family.
9. A VH antibody fragment as claimed in claim 5 belonging to a V germline selected from the group consisting of DP47, V3-49, DP-38, V3-53, YAC-5 and 8-1 B.
10. A VH antibody fragment as claimed in claim 5 belonging to a J germline selected from the group consisting of JH4b, JH6c, JH3b, JH4, JH3a, and JH1.
11. A VH antibody fragment as claimed in claim 5 and having a residue other than valine at position 37 of its amino acid sequence.
12. A VH antibody fragment as claimed in claim 9 having a phenylalanine or tyrosine residue at position 37 of its amino acid sequence.
13. A VH antibody fragment as claimed in claim 5 having a mutation at a position selected from the group consisting of positions 1, 5, 6, 35, 83, 84, 84a and 108 of its amino acid sequence.
14. A VH antibody fragment as claimed in claim 5 that binds to protein A.
15. A VL antibody fragment as claimed in claim 5 belonging to subgroup Vκ1, Vκ3 or Vλ1.
16. A VL antibody fragment as claimed in claim 5 belonging to the kappa class.
17. A VL antibody fragment as claimed in claim 5 belonging to a V germline selected from the group consisting of L6, A27, L2, L16, O2/O12, A30 and 1b.
18. A V L antibody fragment as claimed in claim 5 belonging to a J germline selected from the group consisting of Jκ1, Jκ4, Jκ2, and J3λb.
19. A VL antibody fragment as claimed in claim 5 having an arginine, proline, lysine, threonine, leucine, serine, tyrosine, glutamic acid, glutamine or histidine residue at position 96 of its amino acid sequence.
20. A VL antibody fragment as claimed in claim 5 having a charged amino acid residue at position 96 of its amino acid sequence.
21. A VL antibody fragment as claimed in claim 5 that binds to protein L.
22. A VL antibody fragment as claimed in claim 5 having a threonine, valine or leucine amino acid residue at positions 105, 106 and 107 of its amino acid sequence.
23. A pharmaceutical composition comprising the antibody fragment of claim 5 and a pharmaceutically suitable agent.