Adjuvant compound

1. A compound represented by the following formula [1]:

wherein R 1 and R 2 are each independently a branched or straight group having up to 17 atoms selected from carbon, nitrogen, oxygen and sulphur, n is 0 to and including 18, Y is sulphur or selenium, X is S or O and R is selected from the group consisting of an organic group comprising one or more peptides, one or more nucleic acids, one or more antibodies, and combinations thereof.

2. The compound according to claim 1 , wherein X is O.

3. The compound according to claim 1 , wherein Y is sulphur.

4. The compound according to claim 1 , wherein R 1 and R 2 are each independently a straight chain alkyl group having 10 to 17 carbon atoms.

5. The compound according to claim 4 , wherein R 1 and R 2 are straight chain alkyl groups having 15 carbon atoms.

6. The compound according to claim 1 , wherein n is 11 to and including 15.

7. The compound according to claim 1 , wherein R is an organic group comprising one or more peptides, and wherein R is optionally coupled to an antigen.

8. The compound according to claim 7 , wherein R is SK m and wherein m is 1, 2, 3, 4 or 5.

9. The compound according to claim 7 , wherein group R is represented by

in which R 4 is a K m peptide part, wherein m is 0, 1, 2, 3, 4 or 5, and wherein R 4 is optionally coupled to an antigen and in which R 5 is hydrogen or a group comprising one to six atoms chosen from carbon, nitrogen and oxygen.

10. The compound according to claim 9 , wherein R 5 is a —CH 2 —OH group, a —CH 2 —CH 3 group, a —(CH 2 ) 3 —CH 3 group, a —CH 2 C≡CH group, a —CH 2 CH═CH 2 group or a —(CH 2 ) 2 NH 2 group.

11. The compound according to claim 9 , wherein R 5 is not hydrogen and the asymmetric carbon to which R 5 is attached has the L configuration.

12. The compound according to claim 9 , wherein the K m peptide part is coupled to an antigen, a nucleic acid and/or an antibody.

13. A solid phase peptide synthesis process to prepare a compound according to claim 1 , comprising

(a) providing R-H, which is optionally immobilized and/or side-chain protected;

(b) coupling of substituted cysteine building block Fmoc-(Y-(2-(OC(O)R 2 )-3-(OC(O)R 1 ))propyl)-Cys-OH to R-H; and

(c) cleaving the Fmoc-group from the N-terminus of the resulting peptide; and

(d) treating the Fmoc-liberated peptide with H—(CH 2 ) n —N═C═X,

wherein R, R 1 , R 2 , X, Y and n are defined as in claim 1 .

14. The process according to claim 13 , wherein R is an organic group comprising one or more peptides and R-H is immobilized and/or side-chain protected.

15. The process according to claim 14 , further comprising:

(e) conjugating an antibody or a nucleic acid to the H—(CH 2 ) n —N═C═X-treated peptide.

16. A composition comprising the compound according claim 1 and an antigen.

17. The composition according to claim 16 , wherein the antigen is conjugated to the compound.

18. The composition according to claim 16 , which is a vaccine against the antigen.

19. A method for the induction, maintenance and/or enhancement of an immune response in a subject against an antigen and/or for the prevention, delay and/or treatment of a disease or condition associated with an antigen in a subject, comprising administering to the subject a composition comprising a compound according to claim 1 and an antigen.

20. The method according to claim 19 , wherein the antigen is conjugated to the compound.

21. The compound according to claim 4 , wherein R 1 and R 2 are straight chain alkyl groups having 15 carbon atoms, m is 4, n is 12 or 14, X is O, and Y is sulphur.