Vaccine against

1. An oligosaccharide of general formula (II)

T*-[(—U x+4 —U x+3 —U x+2 —U x+1 —U x ) m —(V x+2 —V x+1 —V x ) 1-m ] n —O-L-E  (II)

wherein

m is an integer selected from 0 and 1;

x is 1;

n is an integer selected from 2, 3, 4, 5, 6, 7, and 8;

T*- represents H—;

-L- represents -L a -, -L a -L e -, -L a -L b -L e -, or -L a -L d -L e -;

-L a - represents —(CH 2 ) o —, —(CH 2 —CH 2 —O) o —C 2 H 4 —, or —(CH 2 —CH 2 —O) o —CH 2 ;

-L b - represents —O—, —NH—CO—NH—, —NH—CO—CH 2 —NH—, —NH—CO—;

-L d - represents —(CH 2 ) q —, —(CH(OH)) q —, —(CF 2 ) q —, —(CH 2 —CH 2 —O) q —C 2 H 4 —, or —(CH 2 —CH 2 —O) q —CH 2 —;

-L e - represents —(CH 2 ) p1 —, —(CF 2 ) p1 —, —C 2 H 4 —(O—CH 2 —CH 2 ) p1 —, —CH 2 —(O—CH 2 —CH 2 ) p1 — or —(CH 2 ) p1 —O—(CH 2 ) p2 —; and

o, q, p1 and p2 are independently of each other an integer selected from 1, 2, 3, 4, 5, and 6;

E represents —NH 2 , —N 3 , —CN, —O—NH 2 , —CH═CH 2 , —C≡CH, —Br, —Cl, —I, —CO 2 R′, —COR′, —CONH—NH 2 , —SH, or —SAc;

R′ represents —H, -Me, -Et, 4-nitrophenyl, pentafluorophenyl, —N-hydroxysuccinimidyl, -(3-sulfo-N-hydroxysuccinimidyl), or -(dibenzocyclooctyne-sulfo-N-hydroxysuccinimidyl);

or a pharmaceutically acceptable salt thereof.

2. The oligosaccharide according to claim 1 , wherein

-L- represents —(CH 2 ) o —; and

o is an integer selected from 2, 3, 4, 5, and 6,

or a pharmaceutically acceptable salt thereof.

3. The oligosaccharide according to claim 1 , wherein —O-L-E is selected from the group consisting of:

wherein R′ represents —H, -Me, -Et, 4-nitrophenyl, pentafluorophenyl, —N-hydroxysuccinimidyl, —(3- sulfo-N-hydroxysuccinimidyl), or -(dibenzocyclooctyne-sulfo-N-hydroxy succinimidyl);

X represents —Br, —Cl, —I, —CO 2 H, or —SAc,

or a pharmaceutically acceptable salt thereof.

4. The oligosaccharide according to claim 1 selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.

5. The oligosaccharide according to claim 1 selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.

6. The oligosaccharide according to claim 5 , wherein n is an integer selected from 2, 3, 4, 5, and 6,

or a pharmaceutically acceptable salt thereof.

7. The oligosaccharide according to claim 1 , wherein E represents an amino group,

or a pharmaceutically acceptable salt thereof.

8. The oligosaccharide according to claim 6 , wherein E represents an amino group,

or a pharmaceutically acceptable salt thereof.

9. A pharmaceutical composition comprising the oligosaccharide according to claim 1 together with at least one pharmaceutically acceptable adjuvant and/or excipient.

10. A conjugate comprising an oligosaccharide according to claim 1 covalently linked to an immunogenic carrier through the residue E of the —O-L-E group, wherein the immunogenic carrier is a carrier protein selected from the group consisting of: a diphtheria toxoid, a mutated diphtheria toxoid, a modified diphtheria toxoid, a mutated and modified diphtheria toxoid, a tetanus toxoid, a modified tetanus toxoid, a mutated tetanus toxoid, non-lipidated cell-surface liporotein (protein D) of non-typeable Haemophilus influenzae , outer membrane protein (OMP) complex of Neisseria meningitidis , bovine serum albumin (BSA), keyhole limpet hemocyanine (KLH), recombinant non-toxic form of Pseudomonas aeruginosa exotoxin A (rEPA) or cholera toxoid (CT).

11. A pharmaceutical composition comprising the conjugate according to claim 10 together with at least one pharmaceutically acceptable adjuvant and/or excipient.

12. A method for raising a protective immune response in a human and/or animal host, said method comprising administering at least one conjugate according to claim 10 to said human or animal host.

13. A method of treatment of a disease associated with Klebsiella pneumonia serotype O3, O3b and/or O5 bacteria in a human and/or animal host comprising administering at least one conjugate according to claim 10 to said human or animal host.

14. The method according to claim 13 , wherein the disease associated with Klebsiella pneumonia serotype O3, O3b and/or O5 bacteria is pneumonia, bronchitis, meningitis, urinary tract infection, wound infection, osteomyelitis, bacteremia, septicemia or ankylosing spondylitis.

15. A conjugate of general formula (IV)

[T*-((—U x+4 —U x+3 —U x+2 —U x+1 —U x ) m —(V x+2 —V x+1 —V x ) 1-m ) n -T-O-L-E 1 -W] c -CP  (IV)

wherein

m is an integer selected from 0 and 1;

x is 1;

n is an integer selected from 2, 3, 4, 5, 6, 7, and 8;

T*- represents H—;

-L- represents -L a -, -L a -L e -, -L a -L b -L e -, or -L a -L d -L e -;

-L a - represents —(CH 2 ) o —, —(CH 2 —CH 2 —O) o —C 2 H 4 —, or —(CH 2 —CH 2 —O) o —CH 2 ;

-L b - represents —O—, —NH—CO—NH—, —NH—CO—CH 2 —NH—, —NH—CO—;

-L d - represents —(CH 2 ) q —, —(CH(OH)) q —, —(CF 2 ) q —, —(CH 2 —CH 2 —O) q —C 2 H 4 —, or —(CH 2 —CH 2 —O) q —CH 2 —;

-L e - represents —(CH 2 ) p1 —, —(CF 2 ) p1 —, —C 2 H 4 —(O—CH 2 —CH 2 ) p1 —, —CH 2 —(O—CH 2 —CH 2 ) p1 — or —(CH 2 ) p1 —O—(CH 2 ) p2 —; and

o, q, p1 and p2 are independently of each other an integer selected from 1, 2, 3, 4, 5, and 6;

T represents a bond;

c is comprised between 2 and 18;

-E 1 - represents a covalent bond, —NH—, —O—NH—, —O—, —S—, —CO—, —CH═CH—, —CONH—, —CO—NHNH—,

—W— is selected from:

a represents an integer selected from 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10,

b represents an integer selected from 1, 2, 3 and 4; and

CP is a carrier protein selected from the group consisting of: a diphtheria toxoid, a mutated diphtheria toxoid, a modified diphtheria toxoid, a mutated and modified diphtheria toxoid, a tetanus toxoid, a modified tetanus toxoid, a mutated tetanus toxoid, non-lipidated cell-surface liporotein (protein D) of non-typeable Haemophilus influenzae , outer membrane protein (OMP) complex of Neisseria meningitidis , bovine serum albumin (BSA), keyhole limpet hemocyanine (KLH), recombinant non-toxic form of Pseudomonas aeruginosa exotoxin A (rEPA) or cholera toxoid (CT).

16. The conjugate according to claim 15 of general formula (V)

[H—((—U x+4 —U x+3 —U x+2 —U x+1 —U x ) m —(V x+2 —V x+1 —V x ) 1-m ) n —O-L-E 1 -W] c -CRM 197   (V)

17. The conjugate according to claim 15 , wherein -E 1 - represents a covalent bond, —NH—, —CH═CH—, —CONH—, —CO—NHNH—,

18. The conjugate according to claim 16 , wherein -E 1 - represents a covalent bond, —NH—, —CH═CH—, —CONH—, —CO—NHNH—,

19. The conjugate according to claim 17 , wherein —W— represents

and a represents an integer selected from 2, 3, 4, 5, and 6.

20. The conjugate according to claim 18 , wherein —W— represents

and a represents an integer selected from 2, 3, 4, 5, and 6.

21. The conjugate according to claim 15 , wherein the conjugate has any one of the following formula (V-1), (V-6) or (V-9)

22. The conjugate according to claim 21 , wherein the conjugate has the following formula (V-6)

wherein -L- represents —(CH 2 ) o —and o is an integer selected from 2, 3, 4, 5, and 6;

—W— represents

and a represents an integer selected from 2, 3, 4, 5, and 6.

23. The conjugate according to claim 22 , wherein -E 1 - is —NH—.

24. The conjugate according to claim 23 , wherein c is between 5 and 15.

25. A pharmaceutical composition comprising the conjugate according to claim 15 together with at least one pharmaceutically acceptable adjuvant and/or excipient.

26. A pharmaceutical composition comprising at least one conjugate according to claim 21 together with at least one pharmaceutically acceptable adjuvant and/or excipient.

27. A method for raising a protective immune response in a human and/or animal host, said method comprising administering at least one conjugate according to claim 15 to said human or animal host.

28. A method of treatment of a disease associated with Klebsiella pneumonia serotype O3, O3b and/or O5 bacteria in a human and/or animal host comprising administering at least one conjugate according to claim 15 to said human or animal host.

29. The method according to claim 28 , wherein the disease associated with Klebsiella pneumonia serotype O3, O3b and/or O5 bacteria is pneumonia, bronchitis, meningitis, urinary tract infection, wound infection, osteomyelitis, bacteremia, septicemia or ankylosing spondylitis.

30. A method for raising a protective immune response in a human and/or animal host, said method comprising administering at least one conjugate according to claim 21 to said human or animal host.

31. A method of treatment of a disease associated with Klebsiella pneumonia serotype O3, O3b and/or O5 bacteria in a human and/or animal host comprising administering at least one conjugate according to claim 21 to said human or animal host.

32. The method according to claim 31 , wherein the disease associated with Klebsiella pneumonia serotype O3, O3b, and/or O5 bacteria is pneumonia, bronchitis, meningitis, urinary tract infection, wound infection, osteomyelitis, bacteremia, septicemia or ankylosing spondylitis.