Modified leukocyte Ig-like receptor family members (LIRs) with increased affinity for class 1 MHC and their uses in modulating T-cell activation
The present invention provides polypeptides having the property of binding to a given Class I pMHC CHARACTERISED IN THAT said polypeptide has a K D for the said given Class I pMHC of less than or equal to 1 μM and/or has an off-rate (k off ) for the said given Class I pMHC molecule of 2 S −1 or slower AND said polypeptide has at least a 45% identity and/or 55% similarity to a defined high-affinity ILT-like molecule AND said polypeptide inhibits CD8 binding to the given pMHC to a greater extent than a soluble truncated variant of Wild-Type ILT-2. Such high-affinity ILT-like molecules are useful, either alone or associated with a therapeutic agent, for the inhibition of cytotoxic T cell (CTL) responses.
1. A polypeptide which has an amino acid sequence at least 90% identical to SEQ ID NO:7, wherein said polypeptide comprises a mutation at one or more amino acid positions corresponding to amino acids 19Q, 20G, 21S, 47W, 50R, 661, 78Y, 80S, 82T, 87E, 99A, 102K, 141E, 146L, 147N, and 174R of SEQ ID NO: 3, whereby the polypeptide binds to a class I pMHC with a K D of less than or equal to 1 μM or slower and inhibits CD8 binding to the pMHC to a greater extent than the polypeptide SEQ ID NO:3.
2. A polypeptide as claimed in claim 1 comprising one or more of the following mutations 10W→L, 19Q→M, 19Q→L, 19Q→V, 20G→D, 20G→M, 20G→Q, 20G→F, 20G→S, 20G→E, 20G→R, 21S→Q, 21S→R, 21S→A, 42K→R, 47W→Q, 50R→L, 66I→V, =77Y→V, 77Y→M, 78Y→Q, 78Y→I, 78Y→G, 79G→Q, 79G→W, 79G→R, 79G→V, 80S→R, 80S→T, 80S→G, 81D→G, 81D→Q, 81D→L, 81D→V, 82T→G, 82T→E, 83A→S, 83A→G, 83A→R, 84G→L, 84G→Q, 84G→A, 87E→A, 99A→I, 99A→V, 101I→L, 101I→K, 101I→Q, 101I→V 102K→Q, 102K→A, 102K→R, 141E→G, 141E→D, 146L→D, 147N→S, 159I→E, 168S→G, 172W→R, 174R→W or 188L→D using the numbering of SEQ ID NO:3.
3. A polypeptide as claimed in claim 1 comprising mutations corresponding to 19Q→M and 21S→Q using the numbering of SEQ ID NO:3.
4. A polypeptide as claimed in claim 1 which comprises any of SEQ ID NOS:6 to 9 or 21 to 61.
5. A polypeptide as claimed in claim 1 wherein amino acids corresponding to 196L and/or 198L of NO:3 are mutated to 196D and 198D respectively.
6. A polypeptide as claimed in claim 1 which comprises any of SEQ ID NOS:63 to 80.
7. A polypeptide as claimed in claim 1 which comprises a tag on the C-terminal thereof, wherein said tag is a cysteine residue.
8. A polypeptide as claimed in claim 1 associated with a therapeutic agent.
9. A polypeptide as claimed in claim 8 wherein the therapeutic agent is IL-4, IL-10 or IL-13.
10. A polypeptide as claimed in claim 1 which is soluble.
11. An isolated cell or a particle presenting at least one polypeptide as defined in claim 1 .
12. A pharmaceutical composition comprising:
a polypeptide as claimed in claim 1 ; or a plurality of cells or particles presenting at least one polypeptide as defined in claim 1 ,
together with a pharmaceutically acceptable carrier.
13. A pharmaceutical composition according to claim 12 in a form suitable for parenteral administration, wherein the polypeptide is soluble.
14. A method of producing a polypeptide as claimed in claim 1 , comprising:
(i) transforming a host cell with a vector incorporating a nucleic acid encoding a polypeptide as claimed in claim 1 ; and
(ii) culturing the transformed cells under conditions suitable for the expression of the polypeptide; and
(iii) recovering the expressed polypeptide.
15. A polypeptide as claimed in claim 1 , further comprising a detectable label.
16. A polypeptide as claimed in claim 1 comprising one or more of the following mutations: 19Q→M, 20G→D, 21S→Q, 83A→R, 84G→Q, 87E→A, 99A→N, 141E→D, or 172W→R using the numbering of SEQ ID NO:3.