TLR9 agonists

1 . A single strand oligonucleotide comprising a nucleotide sequence motif 5′-tcgcaacgttt-n-cgacg-n-cg-nn-cg-3′ (SEQ ID NO:2), wherein n denotes any base, and wherein the total base number of the single strand oligonucleotide is 24 or 25.

2 . The oligonucleotide according to claim 1 , wherein the oligonucleotide comprises a sequence motif selected from the group consisting of:

(SEQ ID NO: 54)

5′-tcgcaacgtttgcgacgtcggtcga;

(SEQ ID NO: 55)

5′-tcgcaacgtttgcgacggcgctcga;

(SEQ ID NO: 56)

5′-tcgcaacgtttgcgacgtcgttcga;

(SEQ ID NO: 57)

5′-tcgcaacgtttgcgacggcgttcga;

(SEQ ID NO: 58)

5′-tcgcaacgtttgcgacgtcgttcg;

(SEQ ID NO: 59)

5′-tcgcaacgtttgcgacgtcgttcgg;

(SEQ ID NO: 60)

5′-tcgcaacgtttacgacgtcggtcga;

(SEQ ID NO: 61)

5′-tcgcaacgtttacgacggcgctcga;

(SEQ ID NO: 62)

5′-tcgcaacgtttacgacgtcgttcga; and

(SEQ ID NO: 63)

5′-tcgcaacgtttacgacggcgttcga.

3 . The oligonucleotide according to claim 1 , wherein the internucleotide linkage(s) of the oligonucleotide is partially or fully chemically modified.

4 . The oligonucleotide according to claim 3 , wherein the chemically-modified internucleotide linkage is phosphorothioated.

5 . The oligonucleotide according to claim 1 , wherein the oligonucleotide comprises a partially phosphorothioated oligonucleotide stretch selected from the group consisting of:

(SEQ ID NO: 16)

5′-tCgcaacgtttgcgacgtcgttcgA-3′;

(SEQ ID NO: 17)

5′-tCgcaaCgtttgcgacgtcgttcgA-3′;

(SEQ ID NO: 18)

5′-tCgCaaCgtttgcgacgtcgttcgA-3′;

(SEQ ID NO: 19)

5′-tCgCaacgtttgCgaCgtcgttcgA-3′;

(SEQ ID NO: 20)

5′-tCgCaacgtttgCgaCgtcgttCgA-3′;

(SEQ ID NO: 21)

5′-tCgCaaCgtttgcgacgtCgttCgA-3′;

(SEQ ID NO: 22)

5′-tCgCaaCgtttgCgaCgtCgttCgA-3′;

(SEQ ID NO: 23)

5′-tCgCaaCgtttgcgacgtCggtCgA-3′;

(SEQ ID NO: 24)

5′-tCgCaaCgtttgcgacggCgctCgA-3′;

(SEQ ID NO: 26)

5′-tCgCaaCgtttgcgacggCgttCgA-3′;

(SEQ ID NO: 27)

5′-tCgCaaCgtttgcgacgcCgttCgA-3′;

(SEQ ID NO: 28)

5′-tCgCaaCgtttgcgacggCgtaCgA-3′;

(SEQ ID NO: 29)

5′-tCgCaaCgtttgcgacggCgtgCgA-3′;

(SEQ ID NO: 30)

5′-tCgCaaCgtttacgacgtCggtCgA-3′;

(SEQ ID NO: 31)

5′-tCgCaaCgtttacgacggCgctCgA-3′;

(SEQ ID NO: 32)

5′-tCgCaaCgtttacgacgtCgttCgA-3′;

(SEQ ID NO: 33)

5′-tCgCaaCgtttGcgacgtCggtCgA-3′;

(SEQ ID NO: 34)

5′-tCgCaaCgtttAcgacgtCggtCgA-3′;

(SEQ ID NO: 35)

5′-tCgCaaCgtttGcgacggCgctCgA-3′;

(SEQ ID NO: 36)

5′-tCgCaaCgtttAcgacggCgctCgA-3′;

(SEQ ID NO: 37)

5′-tCgCaaCgtttGcgacgtCgttCgA-3′;

(SEQ ID NO: 38)

5′-tCgCaaCgtttAcgacgtCgttCgA-3′;

(SEQ ID NO: 39)

5′-tCgCaaCgtttGcgacgtCggtCgG-3′;

(SEQ ID NO: 40)

5′-tCgCaaCgtttAcgacgtCggtCgG-3′;

(SEQ ID NO: 41)

5′-tCgCaaCgtttGcgacggCgctCgG-3′;

(SEQ ID NO: 42)

5′-tCgCaaCgtttAcgacggCgctCgG-3′;

(SEQ ID NO: 43)

5′-tCgCaaCgtttGcgacgtCgttCgG-3′; and

(SEQ ID NO: 44)

5′-tCgCanCgittAcgacgtCgttCgG-3′;

wherein the capital letter denotes a nucleoside with no modified internucleotide linkage at 3′, and the small letter denotes a nucleoside with an internucleotide linkage with phosphorothioation at 3′.

6 . The oligonucleotide according to claim 1 , wherein the oligonucleotide comprises a partially phosphorothioated oligonucleotide stretch selected from the group consisting of:

(SEQ ID NO: 33)

5′-tCgCaaCgtttGcgacgtCggtCgA-3′;

(SEQ ID NO: 34)

5′-tCgCaaCgtttAcgacgtCggtCgA-3′;

(SEQ ID NO: 35)

5′-tCgCaaCgtttGcgacggCgctCgA-3′; and

(SEQ ID NO: 36)

5′-tCgCaaCgtttAcgacggCgctCgA-3′,

wherein the capital letter denotes a nucleoside with no modified internucleotide linkage at 3′, and the small letter denotes a nucleoside with an internucleotide linkage with phosphorothioation at 3′.

7 . A pharmaceutical composition, comprising (i) a therapeutically effective amount of the oligonucleotide according to claim 1 or a double-strand oligonucleotide comprising the oligonucleotide according to claim 1 , and (ii) a pharmaceutical acceptable carrier.