Stabilized soluble pre-fusion RSV F polypeptides

1. A nucleic acid molecule encoding a recombinant pre-fusion respiratory syncytial virus (RSV) Fusion (F) polypeptide, wherein the polypeptide comprises at least two stabilizing mutations in the F1 and/or F2 domain as compared to the RSV F1 and/or F2 domain in a wild-type RSV F protein, wherein at least one of the stabilizing mutations is a mutation of amino acid residue L at position 203 to I.

2. The nucleic acid molecule according to claim 1 , wherein the RSV F polypeptide further comprises a mutation of amino acid residue S at position 215 to P.

3. The nucleic acid molecule according to claim 1 , wherein the RSV F polypeptide comprises at least one epitope that is specific to the pre-fusion conformation F protein, wherein the at least one epitope is recognized by a pre-fusion specific monoclonal antibody, comprising a heavy chain CDR1 region of SEQ ID NO: 1, a heavy chain CDR2 region of SEQ ID NO: 2, a heavy chain CDR3 region of SEQ ID NO: 3 and a light chain CDR1 region of SEQ ID NO: 4, a light chain CDR2 region of SEQ ID NO: 5, and a light chain CDR3 region of SEQ ID NO: 6 and/or a pre-fusion specific monoclonal antibody, comprising a heavy chain CDR1 region of SEQ ID NO: 7, a heavy chain CDR2 region of SEQ ID NO: 8, a heavy chain CDR3 region of SEQ ID NO: 9 and a light chain CDR1 region of SEQ ID NO: 10, a light chain CDR2 region of SEQ ID NO: 67, and a light chain CDR3 region of SEQ ID NO: 11.

4. The nucleic acid molecule according to claim 1 , wherein the RSV F polypeptide is trimeric.

5. The nucleic acid molecule according to claim 1 , wherein the RSV F polypeptide comprises a truncated F1 domain, wherein the RSV F polypeptide comprises a heterologous trimerization domain linked to the truncated F1 domain.

6. The nucleic acid molecule according to claim 5 , wherein the heterologous trimerization domain comprises the amino acid sequence GYIPEAPRDGQAYVRKDGEWVLLSTFL (SEQ ID NO: 14).

7. The nucleic acid molecule according to claim 5 , wherein the trimerization domain is linked to the truncated F1 domain at amino acid residue 513 of the RSV F protein.

8. The nucleic acid molecule according to claim 1 , wherein the at least one further mutation of the RSV F polypeptide is selected from the group consisting of:

(a) a mutation of the amino acid residue S at position 46 to G;

(b) a mutation of the amino acid residue N/T at position 67 to I;

(c) a mutation of the amino acid residue L at position 83 to M:

(d) a mutation of the amino acid residue E at position 92 to D;

(e) a mutation of the amino acid residue G at position 184 to N;

(f) a mutation of the amino acid residue V at position 207 to I:

(g) a mutation of the amino acid residue D at position 486 to N; and

(h) a mutation of the amino acid residue E at position 487 to Q, N or I.

9. The nucleic acid molecule according to claim 1 , wherein the F1 domain and/or the F2 domain of the RSV F polypeptide are from an RSV A strain.

10. The nucleic acid molecule according to claim 1 , wherein the F1 domain and/or the F2 domain of the RSV F polypeptide are from an RSV B strain.

11. The nucleic acid molecule according to claim 1 , wherein the RSV F polypeptide comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 21, SEQ ID NO: 23 and SEQ ID NO: 24.

12. The nucleic acid molecule according to claim 1 , wherein the nucleic acid molecule has been codon-optimized for expression in mammalian cells.

13. A vector comprising the nucleic acid molecule according to claim 1 .

14. A composition comprising the nucleic acid molecule according to claim 1 .

15. A method of inducing an immune response against RSV F protein in a subject in need thereof, the method comprising administering to the subject the nucleic acid molecule according to claim 1 .

16. A pharmaceutical composition comprising the nucleic acid molecule according to claim 1 , and a pharmaceutical carrier.