Recombinant influenza viruses with stabilized NA
Modified influenza virus neuraminidases are described herein that have stabilized NA tetramers which may improve vaccine production efficiency, thus improving the yield of vaccine viruses.
1. An isolated recombinant influenza virus comprising stabilized NA tetramers and a neuraminidase (NA) viral segment encoding a modified NA monomer that forms virions having the stabilized NA tetramers relative to a corresponding influenza virus having a parental NA viral segment encoding an unmodified NA monomer, wherein the modified NA monomer comprises a modified NA stalk that results in the stabilized NA tetramers, wherein the modified NA has a cysteine at position 48 or position 50 or both positions of 48 and 50 relative to the numbering of NA1 of SEQ ID NO:37.
2. The recombinant influenza virus of claim 1 wherein the modified NA stalk further comprises a deletion, an insertion, at least one other amino acid substitution, or any combination thereof.
3. The recombinant influenza virus of claim 1 wherein the at least one substitution in the modified NA stalk is a cysteine substitution.
4. The recombinant influenza virus of claim 1 wherein the NA stalk is modified within residues 1 to 10 or residues 10 to 20 from the C-terminus of the transmembrane domain.
5. A vaccine comprising an effective amount of an isolated recombinant influenza virus comprising a neuraminidase (NA) viral segment encoding a modified NA monomer that forms virions having the stabilized NA tetramers relative to a corresponding influenza virus having a NA viral segment encoding an unmodified NA monomer, wherein the modified NA monomer comprises a modified NA stalk having a cysteine at position 48 or at position 50 or at both positions 48 and 50, relative to the parental NA, that results in the stabilized NA tetramers and optionally comprising an adjuvant or carrier, wherein the modified NA has a cysteine at position 48 or position 50 or both positions of 48 and 50 relative to the numbering of NA1 of SEQ ID NO:37 and wherein the vaccine is an inactivated whole virus vaccine or a split virus vaccine of influenza virus.
6. The vaccine of claim 5 which comprises an adjuvant or a carrier.
7. A method of making an influenza vaccine, comprising:
providing the recombinant virus of claim 1 ; and
combining the virus with an adjuvant or treating the virus with an agent that inactivates the virus.
8. The method of claim 7 wherein the adjuvant comprises immunostimulatory DNA sequences, bacterium-derived components, aluminum salt (alum) or a squalene oil-in-water emulsion.
9. The method of claim 7 wherein the agent chemically inactivates the virus.
10. The method of claim 7 wherein the agent comprises a detergent.
11. The method of claim 7 further comprising separating HA and NA from other viral components.
12. The method of claim 8 wherein the squalene oil-in-water emulsion system comprises MF59 or AS03.