Engineered influenza antigenic polypeptides and immunogenic compositions thereof

1. An engineered mosaic influenza B hemagglutinin (HA) polypeptide produced by a method comprising

aligning HA amino acid sequences from multiple circulating strains of a particular type and/or subtype of influenza B virus to generate an alignment;

identifying positions of amino acids corresponding to epitopes and antigenic regions, or defined set of residue positions;

compiling amino acid residues across the alignment at the identified positions for epitopes and antigenic regions, or defined set of residue positions thereby generating antigenic repertoires;

defining a set of amino acid sequence patterns within the antigenic repertoires—for each epitope and antigenic region, or defined set of residue positions, wherein each amino acid sequence pattern in the set is represented only once;

selecting one or more sequences based on the defined amino acid sequence patterns in the set for each epitope or antigenic region, or defined set of residue positions, thereby resulting in combinations of selected sequences for epitopes and antigenic regions or defined set of residue positions across the alignment according to pre-determined criteria; and

inserting selected sequences into corresponding locations in a structural backbone of influenza B HA, thereby generating engineered mosaic influenza B HA polypeptides, wherein the engineered mosaic influenza B HA polypeptides are distinct from naturally circulating strains; and

evaluating each of the engineered mosaic influenza B HA polypeptides based on conformational stability and breadth of coverage across naturally occurring strains;

wherein the engineered mosaic influenza B HA polypeptide comprises a mosaic amino acid sequence pattern defined by 131H, 159P, 160N, 161A, 162T, 163N, 164K, 165S and 213K as indexed by reference to a B/Brisbane/60/2008 HA.

2. The engineered mosaic influenza B hemagglutinin (HA) polypeptide of claim 1 , wherein the mosaic amino acid sequence pattern is further defined by amino acid substitutions at residues 110, 140, 141, 143, 145, 146, 153, 154, 155, 156, 174, 175, 176, 177, 179, 180, 181, 209, 210, 211, 212, 215, 216, 217, 228, 258, 259, 279 or a subset thereof, in the receptor binding site (RBS), as indexed by reference to a B/Brisbane/60/2008 amino acid sequence.

3. The engineered mosaic influenza B hemagglutinin (HA) polypeptide of claim 2 , wherein the mosaic amino acid sequence pattern is further defined by amino acid substitutions 110F, 140I, 141D/N, 143E, 145A, 146P, 153G, 154T, 155S, 156G/R, 174A, 175V, 176P, 177K, 179D, 180N/S, 181N, 209H, 210S, 211D, 212N/D, 215Q, 216M, 217K/V, 228F, 258S, 259G, 279Q, or a subset thereof in the receptor binding site (RBS), as indexed by reference to a B/Brisbane/60/2008 amino acid sequence.

4. The engineered mosaic influenza B HA polypeptide of claim 1 , wherein the structural backbone is derived from a type B influenza virus selected from

CAA25425|HA|Human|fluB|B/Singapore/222/79|Singapore|1979|,

AGL06036|HA|Human|fluB|B/Massachusetts/02/2012|USA|2012/03/13|,

ABL76694|HA|Human|fluB|B/Panama/45/1990|Panama|1990/03/07|,or

AFH57909|HA|Human|fluB|B/Brisbane/60/2008|Australia|20081.

5. An isolated nucleic acid molecule encoding an engineered mosaic influenza B HA polypeptide of claim 1 .

6. A vector comprising the nucleic acid sequence of claim 5 .

7. An isolated cell comprising the vector of claim 6 .

8. A fusion protein comprising an engineered mosaic influenza B HA polypeptide of claim 1 .

9. A vaccine composition comprising an engineered mosaic influenza B HA polypeptide of claim 1 .

10. The vaccine composition of claim 9 , wherein the vaccine composition is a split inactivated virus.

11. A method of immunizing a subject against influenza virus, comprising administering to the subject a vaccine composition of claim 9 .

12. The engineered mosaic influenza B hemagglutinin (HA) polypeptide of claim 1 , wherein the mosaic amino acid sequence pattern is further defined by 128G, 130E, 131H, 133R, 136T/N, 137Q/H/Y, 138N, 173W, 195I, 196C, 197T/A, 198E, 199G, 200E, 213K, 214T, 225P, 227K, 245G/D, 248D/N, 250T, 251E, 257Q, and 277V/T as indexed by reference to a B/Brisbane/60/2008 HA amino acid sequence.

13. The engineered mosaic influenza B hemagglutinin (HA) polypeptide of claim 1 , comprising an amino acid sequence that is at least 98% identical to SEQ ID NO:41.

14. An engineered mosaic influenza B hemagglutinin (HA) polypeptide comprising a mosaic amino acid sequence pattern defined by 131H, 159P, 160N, 161A, 162T, 163N, 164K, 165S and 213K as indexed by reference to a B/Brisbane/60/2008 HA.

15. The engineered mosaic influenza B HA polypeptide of claim 14 , further comprising 128G, 130E, 133R, 136T/N, 137Q/H/Y, 138N, 173W, 195I, 196C, 197T/A, 198E, 199G, 200E, 214T, 225P, 227K, 245G/D, 248D/N, 250T, 251E, 257Q, and 277V/T as indexed by reference to a B/Brisbane/60/2008 HA amino acid sequence.

16. The engineered mosaic influenza B HA polypeptide of claim 14 , comprising an amino acid sequence that is at least 98% identical to SEQ ID NO:41.

17. A fusion protein comprising an engineered mosaic influenza B HA polypeptide of claim 14 .

18. A vaccine composition comprising an engineered mosaic influenza B HA polypeptide of claim 14 .

19. The vaccine composition of claim 18 , wherein the vaccine composition is a split inactivated virus.

20. A method of immunizing a subject against influenza virus, comprising administering to the subject a vaccine composition of claim 18 .