Method for analyte detection using proximity probes

1. A method for detecting an analyte in a sample, comprising:

(a) contacting said sample with at least one set of at least first, second and third proximity probes, which probes each comprise an analyte-binding domain and a nucleic acid domain and can simultaneously bind to the analyte, the nucleic acid domain of said third proximity probe being a splint which is capable of hybridizing at least to the nucleic acid domains of said first and second proximity probes, wherein when all of the at least three proximity probes bind to said analyte, the nucleic acid domains of said first and second proximity probes are directly or indirectly conjugatable by means of a ligation reaction templated by said hybridized splint of said third proximity probe;

(b) conjugating the nucleic acids of said first and second proximity probes; and

(c) detecting said conjugation thereby detecting said analyte.

2. The method as claimed in claim 1 , wherein said detecting is quantitative.

3. The method as claimed in claim 1 , wherein said detecting is qualitative.

4. The method as claimed in claim 1 , wherein the analyte is a wholly or partially proteinaceous molecule.

5. The method as claimed in claim 1 , wherein the analyte is a complex of two or more molecular subunits.

6. The method as claimed in claim 5 , wherein said complex comprises nucleic acid and proteinaceous molecules.

7. The method as claimed in claim 1 , wherein the analyte binding domain of at least one of said at least first, second and third proximity probes is an antibody, or a binding fragment or derivative thereof.

8. The method as claimed in claim 1 , wherein at least one of said at least first, second and third proximity probes binds to said analyte indirectly by virtue of the respective analyte-binding domain having affinity for an intermediary molecule which binds directly to the target analyte.

9. The method as claimed in claim 1 , wherein the nucleic acid domains of said first and second proximity probes hybridize, immediately adjacent to each other to the nucleic acid domain of said third proximity probe.

10. The method as claimed in claim 1 , wherein the nucleic acid domains of said first and second proximity probes hybridize, not immediately adjacent to each other, to the nucleic acid domain of said third proximity probe, such that when hybridized to the nucleic acid domain of said third proximity probe the nucleic acid domains of said first and second proximity probes are separated by a gap.

11. The method as claimed in claim 10 , wherein a cassette oligonucleotide hybridizes to the nucleic acid domain of said third proximity probe in the gap between the respective ends of the nucleic acid domains of said first and second proximity probes hybridized to the nucleic acid domain of said third proximity probe.

12. The method as claimed in claim 11 , wherein conjugation of the nucleic acid domains of said first and second proximity probes occurs indirectly through the cassette oligonucleotide.

13. The method as claimed in claim 10 , wherein said gap between the nucleic acid domains of said first and second proximity probes is filled by enzymatic extension of the end of one of said first and second proximity probe nucleic acid domains.

14. The method as claimed in claim 1 , wherein two or more sets of the at least first, second and third proximity probes are used, for detecting two or more analytes.

15. The method according to claim 1 , wherein single strand binding protein is present in said contacting step.

16. The method according to claim 1 , wherein blocking oligonucleotides capable of binding to the free ends of the nucleic acid domains of said first and second proximity probes are used in said contacting step.

17. The method according to claim 16 , wherein said blocking oligonucleotides are pre-incubated with at least said first and second proximity probes.

18. The method according to claim 1 , wherein at least one of said at least first, second and third proximity probes is immobilized, or is capable of being immobilized, on a solid phase.

19. The method according to claim 1 , further comprising, prior to contacting said sample with the at least one set of at least first, second and third proximity probes, immobilizing the analyte to a solid phase by means of an immobilized, or immobilizable, capture probe comprising an analyte-binding domain.

20. The method according to claim 1 , wherein the analyte is directly immobilized, or immobilizable, to a solid phase.

21. The method according to claim 1 , wherein the analyte and the at least one set of at least first, second and third proximity probes are free in solution.

22. The method of claim 1 wherein the step of detecting the conjugation includes detecting the conjugation product.

23. The method of claim 22 , wherein detecting the conjugation product comprises amplifying the conjugation product and detecting the amplified product.

24. A kit for detecting an analyte in a sample, comprising at least one set of at least first, second and third proximity probes as defined in claim 1 .

25. The kit as claimed in claim 24 , further comprising:

(a) means for conjugating the nucleic acid domains of said first and second proximity probes; and/or

(b) means for detecting said conjugation.

26. The kit as claimed in claim 25 wherein said means for conjugating the nucleic acid domains of said first and second proximity probes comprises a nucleic acid ligase.

27. The kit as claimed in claim 25 , wherein said means for detecting said conjugation is a label or means for amplification and/or the detection thereof.

28. The kit of claim 24 further comprising one or more of:

(a) cassette oligonucleotide;

(b) blocking oligonucleotides for the nucleic acid domains of said first and second proximity probes;

(c) single strand binding protein;

(d) immobilized or immobilizable capture probe comprising an analyte-binding domain; and

(e) solid phase for immobilization of said analyte, capture probe or at least one of said at least first, second and third proximity probes.