WO2017218624A1 - Influenza virus hemagglutinin proteins and uses thereof - Google Patents

Influenza virus hemagglutinin proteins and uses thereof Download PDF

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WO2017218624A1
WO2017218624A1 PCT/US2017/037384 US2017037384W WO2017218624A1 WO 2017218624 A1 WO2017218624 A1 WO 2017218624A1 US 2017037384 W US2017037384 W US 2017037384W WO 2017218624 A1 WO2017218624 A1 WO 2017218624A1
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amino acid
influenza
virus
acid residues
seq
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French (fr)
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WO2017218624A8 (en
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Peter Palese
Adolgo GARCIA-SASTRE
Florian KRAMMER
Megan ERMLER
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Icahn School of Medicine at Mount Sinai
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Icahn School of Medicine at Mount Sinai
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Priority to CN201780049845.1A priority Critical patent/CN109641041A/zh
Priority to CA3023143A priority patent/CA3023143A1/en
Priority to US16/305,845 priority patent/US11266734B2/en
Priority to JP2018565670A priority patent/JP7237344B2/ja
Priority to MX2018015755A priority patent/MX2018015755A/es
Priority to EP17813990.3A priority patent/EP3471767A4/en
Priority to BR112018075032-8A priority patent/BR112018075032A2/pt
Publication of WO2017218624A1 publication Critical patent/WO2017218624A1/en
Publication of WO2017218624A8 publication Critical patent/WO2017218624A8/en
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Priority to US17/583,088 priority patent/US11865173B2/en
Priority to JP2022133019A priority patent/JP2022176993A/ja
Priority to US18/512,751 priority patent/US12233123B2/en
Priority to US18/983,218 priority patent/US20250121049A1/en
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Definitions

  • chimeric influenza virus hemagglutinin proteins are provided herein.
  • Influenza viruses are enveloped RNA viruses that belong to the family of
  • Orthomyxoviridae (Palese and Shaw (2007) Orthomyxoviridae: The Viruses and Their
  • influenza A viruses The natural host of influenza A viruses are mainly avians, but influenza A viruses (including those of avian origin) also can infect and cause illness in humans and other animal hosts (bats, canines, pigs, horses, sea mammals, and mustelids).
  • influenza A virus circulating in Asia has been found in pigs in China and Indonesia and has also expanded its host range to include cats, leopards, and tigers, which generally have not been considered susceptible to influenza A (CIDRAP - Avian Influenza: Agricultural and Wildlife Considerations).
  • the occurrence of influenza virus infections in animals could potentially give rise to human pandemic influenza strains.
  • Influenza A and B viruses are major human pathogens, causing a respiratory disease that ranges in severity from sub-clinical infection to primary viral pneumonia which can result in death. The clinical effects of infection vary with the virulence of the influenza strain and the exposure, history, age, and immune status of the host.
  • influenza viruses infect an estimated 10-15% of the population (Glezen and Couch RB (1978) Interpandemic influenza in the Houston area, 1974-76. N Engl J Med 298: 587-592; Fox et al. (1982) Influenza virus infections in Seattle families, 1975-1979. II. Pattern of infection in invaded households and relation of age and prior antibody to occurrence of infection and related illness. Am J Epidemiol 116: 228-242) and are associated with approximately 30,000 deaths each year (Thompson WW et al. (2003) Mortality Associated with Influenza and
  • influenza viruses are constantly undergoing change: every 3-5 years the predominant strain of influenza A virus is replaced by a variant that has undergone sufficient antigenic drift to evade existing antibody responses. Isolates to be included in vaccine preparations must therefore be selected each year based on the intensive surveillance efforts of the World Health Organization (WHO) collaborating centers. Second, to allow sufficient time for vaccine manufacture and distribution, strains must be selected approximately six months prior to the initiation of the influenza season. Often, the predictions of the vaccine strain selection committee are inaccurate, resulting in a substantial drop in the efficacy of vaccination.
  • WHO World Health Organization
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within an antigenic loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL SEQ ID NO: 51.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL
  • B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and
  • RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO: 60).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5 or more amino acid substitutions within 160 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues DAAMQT (SEQ ID NO: 8).
  • underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues
  • ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues ATLKMHQ (SEQ ID NO: 70).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues PTSDMQI (SEQ ID NO: 66).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA.
  • the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from an influenza A virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the transmembrane and cytoplasmic tail domains. In some embodiments, the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza virus that is engineered to express the chimeric HA.
  • nucleic acids comprising nucleotide sequences encoding such a chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/ 16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/ 16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising one, two, three or all of the following: (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FTP and KIOLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRL S THN VIN AERAPGGP YRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A Vietnam/1203/04 (HALo).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RD KTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from an influenza A virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the
  • the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA is engineered for an influenza A virus backbone (e.g., the influenza virus comprising or engineered to express the chimeric HA is an influenza A virus)
  • the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza virus that is engineered to express the chimeric HA. Also provided herein are nucleic acids comprising nucleotide sequences encoding such a chimeric HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/ 16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • KIOLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKL S TFN VIN AET APGGP YRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVIN AEV APGGP YRL (SEQ ID NO: 59).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the first influenza B virus strain and the second influenza B virus strain are from the same lineage. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from the same lineage but are different strains. In a specific embodiment, the first influenza B virus strain is the same strain as the second influenza B virus strain. In another embodiment, the first influenza B virus strain is a different strain than the second influenza B virus strain. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from different lineages.
  • the first influenza B virus strain is from the Yamagata lineage. In other embodiments, the first influenza B virus is from the Victoria lineage. In some embodiments, the second influenza B virus strain is from the Yamagata lineage. In other embodiments, the second influenza B virus is from the Victoria lineage. In a specific embodiment, the second influenza B virus strain is the same strain as the influenza virus backbone of an influenza virus either containing, expressing, or both the chimeric HA.
  • influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior
  • H13 strain e.g., A/black headed gull/Sweden/ 1/99.
  • chimeric hemagglutinin (HA) polypeptides comprising: (a) a hemagglutinin ectodomain from a first influenza B virus strain with one, two, three or all of the following (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the first influenza B virus strain HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the first influenza B virus strain HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residue
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A vims A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 KNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/ 16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/ 16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • amino acid residues NASTGGQS SEQ ID NO: 52.
  • amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL S T SN VIN AE V AP GGP YRL (SEQ ID NO: 55).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS
  • amino acid residues HQSGTY amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and
  • RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues NIP and RIEL STHNVINAEVAPGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61).
  • NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of one, two, three, or all of the following: the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the first influenza B virus strain and the second influenza B virus strain are from the same lineage. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from the same lineage but are different strains. In a specific embodiment, the first influenza B virus strain is the same strain as the second influenza B virus strain. In another embodiment, the first influenza B virus strain is a different strain than the second influenza B virus strain. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from different lineages.
  • the first influenza B virus strain is from the Yamagata lineage. In other embodiments, the first influenza B virus is from the Victoria lineage. In some embodiments, the second influenza B virus strain is from the Yamagata lineage. In other embodiments, the second influenza B virus is from the Victoria lineage. In a specific embodiment, the second influenza B virus strain is the same strain as the influenza virus backbone of an influenza virus either containing, expressing, or both the chimeric HA.
  • influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior
  • H13 strain e.g., A/black headed gull/Sweden/ 1/99.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a
  • transmembrane domain and a cytoplasmic tail domain from an influenza A virus wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FTP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid
  • substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior Alaska_7MP0167_2007), or H13 strain (e.g., A/black headed gull/Sweden/1/99).
  • H5 e.g., A/Vietnam/1203/04(HALo)
  • H8 e.g., A/mallard/Sweden/24/2002
  • Hl l e.g., A/northern shoveler/Netherlands/18/99
  • H12 strain e.g., A_mallard_interior Alaska_7MP0167_2007
  • H13 strain e.g
  • the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza A virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • chimeric hemagglutinin (HA) polypeptides comprising: (a) a hemagglutinin ectodomain from an influenza B virus with one, two, three or all of the following (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head domain of the influenza B virus HA,
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKL S TFN VIN AET APGGP YRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVIN AEV APGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVIN AEV APGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid
  • substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior Alaska_7MP0167_2007), or H13 strain (e.g., A/black headed gull/Sweden/1/99).
  • H5 e.g., A/Vietnam/1203/04(HALo)
  • H8 e.g., A/mallard/Sweden/24/2002
  • Hl l e.g., A/northern shoveler/Netherlands/18/99
  • H12 strain e.g., A_mallard_interior Alaska_7MP0167_2007
  • H13 strain e.g
  • the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza A virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza B virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 12A and Fig. 12B or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 14A and Fig. 14B or the complement thereof. In a specific embodiment, the nucleic acid comprises the nucleotide sequence set forth in Fig. 16A and Fig. 16B or the complement thereof. In a specific embodiment, the nucleic acid comprises the nucleotide sequence set forth in Fig. 18A and Fig. 18B or the complement thereof.
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within an antigenic loop of the globular head domain of the influenza B virus HA (e.g., 120 loop, 150 loop, 160 loop and/or 190 helix), wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the loop of the globular head of the influenza B virus HA with random amino acid residues that do not affect the conformation/structure of the HA.
  • one or more substitutions outside of the antigenic loops may be introduced.
  • amino acid substitutions are selected such that the folding of the chimeric HA is not significantly impacted as determined by techniques known to one of skill in the art or described herein.
  • amino acid substitutions may be selected such that the coding sequence for N-linkd glycosylation sites (N-X-S/T) is not altered or not significantly altered.
  • the effect of amino acid substitutions on the conformation/structure may be determined by assays known to one of skill in the art, e.g., structure programs, crystallography, or functional assays. See, e.g., Section 5.11, infra, and Section 6, infra.
  • the chimeric HA polypeptides may be evaluated for antigenic conservation using a panel of monoclonal antibodies that bind to conserved epitopes in the globular head domain of HA and the stem domain of HA.
  • the methods described in Section 6, infra are used to evaluate antigenic conservation of the chimeric HA.
  • the chimeric HA polypeptides described herein may be evaluated to determine whether the antigenic loops of the influenza B virus HA were mutated using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • the chimeric HA polypeptides described herein may be evaluated to determine if the amino acid substitutions in the antigenic loop(s) of the influenza B virus HA result in loss of a variable region(s) of the influenza B virus HA using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • the chimeric HA polypeptides described herein may be evaluated to determine if the amino acid substitutions in the antigenic loop(s) of the influenza B virus HA reduce or eliminate the immundominant epitopes of the influenza B virus HA using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • a chimeric HA polypeptide described herein is assessed in an HI assay, such as described in Section 6, infra, to evaluate the replacement of the antigenic loop(s) in the influenza B virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within an antigenic loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the loop of the influenza B virus HA with amino acid residues found in a
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • HA hemagglutinin
  • KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and
  • influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL SEQ ID NO: 51.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues YIP and
  • RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • HA hemagglutinin
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues
  • LKSGOF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • LKSGQF (SEQ ID NO: 65).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B vims B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • HA hemagglutinin
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues
  • ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern shovel er/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues ATLKMHQ (SEQ ID NO: 70).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues PTSDMQI (SEQ ID NO: 66).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA.
  • the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains.
  • the chimeric HA polypeptide may also comprise the signal peptide,
  • the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the transmembrane and cytoplasmic tail domains.
  • the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA. For example, if the chimeric HA is engineered for an influenza A virus backbone (e.g., the influenza virus comprising or engineered to express the chimeric HA is an influenza A virus), then the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza virus that is engineered to express the chimeric HA.
  • nucleic acids comprising nucleotide sequences encoding such a chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA
  • amino acid position 156 glutamic acid
  • amino acid position 250 glutamic acid
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising one, two, three or all of the following: (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA; (iii) 2, 3, 4, 5 or more
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A vims A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues HQSGTY amino acid residues
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from an influenza A virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the
  • the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA is engineered for an influenza A virus backbone (e.g., the influenza virus comprising or engineered to express the chimeric HA is an influenza A virus)
  • the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza virus that is engineered to express the chimeric HA. Also provided herein are nucleic acids comprising nucleotide sequences encoding such a chimeric HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4,
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5,
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTIfNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A vims A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues HQSGTY amino acid residues
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage.
  • influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior
  • nucleic acids comprising nucleotide sequences encoding such a chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues HIP and RIRL S T YN VINAET APGGP YRL (SEQ ID NO: 51).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • amino acid residues NASTGGQS SEQ ID NO: 52.
  • amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA SEQ ID NO: 5 are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and
  • KIEL STSNVINAE VAPGGP YPvL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues LIP and KIEL S T SN VIN AE V AP GGP YRL (SEQ ID NO: 55).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56). In specific embodiments, the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • a 120 loop a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO: 64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with amino acid residues LKSGOF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTITNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues NIP and
  • RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61).
  • NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of one, two, three, or all of the following: the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA
  • amino acid position 156 glutamic acid
  • amino acid position 250 glutamic acid
  • the first influenza B virus strain and the second influenza B virus strain are from the same lineage. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from the same lineage but are different strains.
  • the first influenza B virus strain is the same strain as the second influenza B virus strain. In another embodiment, the first influenza B virus strain is a different strain than the second influenza B virus strain. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from different lineages. In some embodiments, the first influenza B virus strain is from the Yamagata lineage. In other embodiments, the first influenza B virus is from the Victoria lineage. In some embodiments, the second influenza B virus strain is from the Yamagata lineage. In other embodiments, the second influenza B virus is from the Victoria lineage. In a specific embodiment, the second influenza B virus strain is the same strain as the influenza virus backbone of an influenza virus either containing, expressing, or both the chimeric HA. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g.,
  • H8 e.g., A/mallard/Sweden/24/2002
  • Hl l e.g., A/northern shoveler/Netherlands/18/99
  • H12 strain e.g., A_mallard_interior Alaska_7MP0167_2007
  • H13 strain e.g., A/black headed gull/Sweden/1/99.
  • nucleic acids comprising nucleotide sequences encoding said chimeric HA polypeptides.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' non-coding region and 3' non-coding region from an influenza B virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of an influenza virus either comprising, containing, or both the chimeric HA.
  • chimeric hemagglutinin (HA) polypeptides comprising: (a) a hemagglutinin ectodomain from an influenza B virus with one, two, three or all of the following (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the influenza B virus HA with amino acid residues found in a corresponding region of an influenza A virus HA; (ii)
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKL S TFN VIN AET APGGP YRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHN VIN AEV APGGP YRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVIN AEV APGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVIN AEV APGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage.
  • influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior
  • nucleic acids comprising nucleotide sequences encoding said chimeric HA polypeptides.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' non-coding region and 3' non-coding region from an influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza B virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 12A and Fig. 12B or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 14A and Fig. 14B or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 16A and Fig. 16B or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 18A and Fig. 18B or the complement thereof.
  • chimeric hemagglutinin (HA) polypeptides comprising: (a) a hemagglutinin ectodomain from a first influenza B virus strain with one, two, three or all of the following (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the first influenza B virus strain HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the first influenza B virus strain HA with amino acid residues found in a corresponding region of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the first influenza B virus strain HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the first influenza B virus strain HA with amino acid residues found in a corresponding region
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/ 16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/ 16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • amino acid residues NASTGGQS SEQ ID NO: 52.
  • amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • the following underlined and bold amino acid residues in the 120 loop of infiuenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and
  • KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues LIP and KIEL S T SN VIN AE V AP GGP YRL (SEQ ID NO: 55).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56). In specific embodiments, the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • amino acid residues KFGSSNS amino acid residues KFGSSNS
  • amino acid residues HQSGTY amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • a 120 loop a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KRGNQY (SEQ ID NO: 61).
  • NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the influenza B virus HA which are outside of one, two, three, or all of the following: the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA
  • amino acid position 156 glutamic acid
  • amino acid position 250 glutamic acid
  • the first influenza B virus strain and the second influenza B virus strain are from the same lineage. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from the same lineage but are different strains.
  • the first influenza B virus strain is the same strain as the second influenza B virus strain. In another embodiment, the first influenza B virus strain is a different strain than the second influenza B virus strain. In some embodiments, the first influenza B virus strain and the second influenza B virus strain are from different lineages. In some embodiments, the first influenza B virus strain is from the Yamagata lineage. In other embodiments, the first influenza B virus is from the Victoria lineage. In some embodiments, the second influenza B virus strain is from the Yamagata lineage. In other embodiments, the second influenza B virus is from the Victoria lineage. In a specific embodiment, the second influenza B virus strain is the same strain as the influenza virus backbone of an influenza virus either comprising, containing, or both the chimeric HA. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid substitutions in one, two, three or more of the loops is an H5 (e.g.,
  • H8 e.g., A/mallard/Sweden/24/2002
  • Hl l e.g., A/northern shoveler/Netherlands/18/99
  • H12 strain e.g., A_mallard_interior Alaska_7MP0167_2007
  • H13 strain e.g., A/black headed gull/Sweden/1/99.
  • nucleic acids comprising nucleotide sequences encoding said chimeric HA polypeptides.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of an influenza virus either comprising, containing, or both the chimeric HA.
  • the nucleic acid comprises the nucleotide sequence set forth in FIG. 29 or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in FIG. 31 or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in FIG. 33 or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in FIG. 35 or the complement thereof.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the HI, H2, H3, H4, H5, H6, H7, H8, H9, H10, Hl l, H12, H13, H14, H15, H16, H17, or H18 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the H2, H4, H5, H6, H7, H8, H9, H10, Hl l, H12, H13, H14, H15, H16, H17, or H18 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the H5, H8, HI 1, H12, or H13 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the H5 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the H8 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the HI 1 subtype.
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the H12 subtype. In a specific embodiment, the influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an influenza virus of the HI 3 subtype. In a specific embodiment, the influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from an avian influenza virus. In a specific embodiment, the influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza A/Vietnam/1203/04 virus (GenBank Accession No. EF541403.1; GenBank GI No. 145284465; see, also, FIG. 22A and FIG. 22B and Steel et al., 2009, Journal of Virology, 83(4): 1742-1753 for the HA of influenza A/Vietnam/1203/04 (HALo) virus).
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza A/northern shoveler/Netherlands/18/99 virus (GenBank Accession No. CY060417.1; GenBank GI No. 294441876; see, also, FIG. 23 A and FIG. 23B).
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza A mallard interior
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza A/black headed gull/Sweden/1/99 (GenBank Accession No. AY684887.1; see, also, FIG. 41 A and FIG. 41B).
  • influenza A virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza A/Puerto Rico/8/34 virus (GenBank Accession No. AF389118.1; GenBank GI No. 21693168; see, also, FIG. 25 A and FIG. 25B).
  • influenza B virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza
  • influenza B virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from a mouse-adapted influenza B/Malaysia/2506/04 virus ⁇ see, e.g., SEQ ID NO: 73 or 83).
  • influenza B virus HA utilized in the generation of a chimeric HA polypeptide described herein is the HA from influenza B/Malaysia/2506/04 virus ⁇ see, e.g., GenBank Accession No. CY040449.1).
  • a chimeric HA polypeptide is a chimeric HA polypeptide described in Section 6, infra.
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within an antigenic loop of the influenza B virus HA (e.g., 120 loop, 150 loop, 160 loop and/or 190 helix), wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the loop of the influenza B virus HA with random amino acid residues that do not affect the conformation/structure of the HA.
  • one or more substitutions outside of the antigenic loops may be introduced.
  • amino acid substitutions are selected such that the folding of the chimeric HA is not significantly impacted as determined by techniques known to one of skill in the art or described herein.
  • amino acid substitutions may be selected such that the coding sequence for N-linkd glycosylation sites (N-X-S/T) is not altered or not significantly altered.
  • the effect of amino acid substitutions on the conformation/structure may be determined by assays known to one of skill in the art, e.g., structure programs, crystallography, or functional assays. See, e.g., Section 5.11, infra, and Section 6, infra.
  • the chimeric HA polypeptides may be evaluated for antigenic conservation using a panel of monoclonal antibodies that bind to conserved epitopes in the globular head domain of HA and the stem domain of HA.
  • the methods described in Section 6, infra are used to evaluate antigenic conservation of the chimeric HA.
  • the chimeric HA polypeptides described herein may be evaluated to determine whether the antigenic loops of the influenza B virus HA were mutated using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • the chimeric HA polypeptides described herein may be evaluated to determine if the amino acid substitutions in the antigenic loop(s) of the influenza B virus HA result in loss of a variable region(s) of the influenza B virus HA using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • the chimeric HA polypeptides described herein may be evaluated to determine if the amino acid substitutions in the antigenic loop(s) of the influenza B virus HA reduce or eliminate the immundominant epitopes of the influenza B virus HA using techniques known to one of skill in the art or described herein (see, e.g., Section 6, infra, including the HI assay described therein).
  • a chimeric HA polypeptide described herein is assessed in an HI assay, such as described in Section 6, infra, to evaluate the replacement of the antigenic loop(s) in the influenza B virus HA.
  • nucleic acid sequences comprising a nucleotide sequence encoding a chimeric HA polypeptide described herein.
  • a nucleic acid sequence comprising a nucleotide sequence encoding a chimeric HA polypeptide described herein.
  • an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • the nucleic acid sequence comprises the nucleotide sequence set forth in Figure 12, Figure 14, Figure 16, Figure 18, Figure 29, Figure 31, Figure 33, or Figure 35.
  • the HA segment or the nucleic acid sequence comprising the nucleotide sequence encoding a chimeric HA polypeptide described herein are transfected into cells (e.g., cell lines).
  • cells e.g., cell lines.
  • host cells comprising or engineered to express a chimeric HA polypeptide described herein.
  • host cells comprising a chimeric HA polypeptide described herein.
  • host cells comprising an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • embryonated eggs comprising a chimeric HA polypeptide described herein.
  • embryonated eggs e.g., chicken embryonated eggs
  • embryonated eggs comprising an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • embryonated eggs e.g., chicken embryonated eggs
  • said influenza virus comprises an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • embryonated eggs e.g., chicken embryonated eggs comprising an influenza virus, wherein the influenza virus comprises a chimeric HA polypeptide described herein.
  • influenza viruses engineered to express a chimeric HA polypeptide described herein.
  • an influenza A virus engineered to express a chimeric HA polypeptide described herein.
  • the signal peptide, transmembrane domain and cytoplasmic tail domain of the chimeric HA polypeptide are preferably derived from the same influenza A virus as the influenza A virus engineered to express the chimeric HA polypeptide.
  • a nucleic acid comprising nucleotide sequences encoding said chimeric HA polypeptide preferably comprises the 5' non-coding region, 3 ' non-coding region and nucleotide sequences encoding the signal peptide, transmembrane domain, and cytoplasmic domain derived from the same influenza A virus as the influenza A virus engineered to express the chimeric HA polypeptide.
  • an influenza A virus comprising 7 non-HA segments of an influenza A virus segments and an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • the signal peptide, transmembrane domain and cytoplasmic tail domain of the chimeric HA polypeptide are preferably derived from the same influenza A virus as influenza A virus comprising the non-HA segments.
  • a nucleic acid comprising nucleotide sequences encoding the chimeric HA polypeptide preferably comprises the 5' non-coding region and the 3' non-coding region, and the nucleic sequences encoding the signal peptide, transmembrane domain, and cytoplasmic domain derived from the same influenza A virus as the influenza A virus comprising the non-HA segments.
  • an influenza B virus comprising 7 non-HA segments of an influenza B virus segments and an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • the 7 non-HA segments are from the same influenza B virus as the ectodomain of the chimeric HA polypeptide.
  • the 7 non-HA segments are from the same influenza B virus as the globular head domain of the chimeric HA polypeptide.
  • the signal peptide, transmembrane domain and cytoplasmic tail domain of the chimeric HA polypeptide are preferably derived from the same influenza B virus as the influenza B virus engineered to express the chimeric HA polypeptide.
  • a nucleic acid comprising nucleotide sequences encoding said chimeric HA polypeptide preferably comprises the 5' non-coding region, 3' non-coding region and nucleotide sequences encoding the signal peptide, transmembrane domain, and cytoplasmic domain derived from the same influenza B virus as the influenza B virus engineered to express the chimeric HA polypeptide.
  • an influenza B virus comprising 7 non- HA segments of an influenza B virus segment and an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • the signal peptide, transmembrane domain and cytoplasmic tail domain of the chimeric HA polypeptide are preferably derived from the same influenza B virus as the influenza B virus comprising the non-HA segments.
  • a nucleic acid comprising nucleotide sequences encoding the chimeric HA polypeptide preferably comprises the 5' non-coding region and the 3' non-coding region, and the nucleic sequences encoding the signal peptide, transmembrane domain, and cytoplasmic domain derived from the same influenza B virus as the influenza B virus comprising the non-HA segments.
  • influenza viruses containing a chimeric HA polypeptide described herein are influenza viruses containing a chimeric HA polypeptide described herein.
  • an influenza A virus containing a chimeric HA polypeptide described herein is an influenza B virus containing a chimeric HA polypeptide described herein.
  • the influenza B virus containing the chimeric HA polypeptide is from the
  • influenza B virus containing the chimeric HA polypeptide is from the Victoria lineage. In specific embodiments, the influenza B virus containing the chimeric HA polypeptide is B/Malaysia/2506/04.
  • influenza virus described in
  • a virus-like particle comprising a chimeric
  • HA polypeptide described herein in another embodiment, provided herein is a virosome comprising a chimeric HA polypeptide described herein.
  • compositions comprising a chimeric HA polypeptide described herein, a nucleic acid sequence comprising a nucleotide sequence encoding a chimeric HA polypeptide described herein, an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein, an influenza virus comprising/containing a chimeric HA polypeptide described herein, an influenza virus engineered to express a chimeric HA polypeptide described herein, a viruslike particle comprising a chimeric HA polypeptide described herein, or a virosome comprising a chimeric HA polypeptide described herein.
  • an immunogenic composition comprising a chimeric HA polypeptide described herein.
  • an immunogenic composition comprising a nucleic acid sequence comprising a nucleotide sequence encoding a chimeric HA polypeptide described herein or an HA segment comprising the nucleic acid sequence encoding a chimeric HA polypeptide described herein.
  • an immunogenic composition comprising an influenza virus comprising a chimeric HA polypeptide described herein.
  • an immunogenic composition comprising an influenza virus engineered to express a chimeric HA polypeptide described herein.
  • an immunogenic composition comprising an influenza virus engineered to express and contain a chimeric HA polypeptide described herein.
  • the influenza virus is a live attenuated influenza virus.
  • the influenza virus is an inactivated virus.
  • the composition is a subunit vaccine.
  • the composition is a split vaccine.
  • provided herein is an immunogenic composition comprising a virus-like particle described herein.
  • provided herein is an immunogenic composition comprising a virosome described herein.
  • the compositions further comprise one or more adjuvants (see, e.g., Section 5.7, infra, regarding adjuvants, such as AS03 or MF59).
  • provided herein are methods for immunizing a subject against influenza virus, comprising administering to the subject a composition described herein.
  • a method for immunizing a subject against influenza virus comprising administering to the subject an effective amount of a composition described herein.
  • a method for inducing an immune response e.g., an antibody response
  • an influenza B virus HA stem domain in a subject, comprising administering the subject a composition described herein.
  • provided herein is a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA globular head domain and stem domain in a subject, comprising administering to the subject a composition described herein.
  • a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA stem domain and an influenza A virus globular head domain in a subject comprising administering the subject a composition described herein.
  • provided herein is a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA globular head domain and stem domain, and an influenza A virus globular head domain in a subject, comprising administering to the subject a composition described herein.
  • an immune response e.g., an antibody response
  • the subject is human.
  • a method of immunizing a subject against an influenza virus disease or infection comprising (i) a first administration of a first chimeric HA polypeptide, a first nucleic acid encoding such a polypeptide(s), a first vector either containing, expressing, or both such a polypeptide(s), or cells described herein to the subject; and (ii) a second administration of a second chimeric HA polypeptide, a second nucleic acid encoding such a polypeptide(s), a second vector either containing, expressing, or both such a polypeptide(s), or cells described herein to the subject, wherein the first and second chimeric HA polypeptides comprise an ectodomain with the same stem domains but have different 120 loops, 150 loops, 160 loops, and/or 190 helices.
  • the first and second chimeric HA have either one, two, three, or four of the following: (i) different 120 loops, (ii) different 150 loops, (iii) different 160 loops, and (iv) different 190 helices.
  • administrations may be separated by at least 1 day, 2 days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3 months, or at least 6 months.
  • the first and second administrations may be separated by 1 week to 9 months, 3 weeks to 8 months, 6 weeks to 12 weeks, 4 weeks to 6 months, 5 weeks to 5 months, 6 weeks to 4 months, 7 weeks to 4 months, 8 weeks to 4 months, 8 weeks to 3 months, 3 months to 6 months, 3 months to 9 months, or 6 months to 9 months.
  • booster inoculations may be administered to the subject at 6 to 12 month intervals following the second inoculation.
  • the booster inoculation comprises a third chimeric HA polypeptide, a third nucleic acid encoding such a polypeptide(s), a third vector either containing, expressing, or both such a polypeptide(s), or cells described herein, wherein the first, second, and third chimeric HA polypeptides comprise an ectodomain with the same stem but have different 120 loops, 150 loops, 160 loops, and/or 190 helices.
  • the first, second, and third chimeric HA have either one, two, three, or four of the following: (i) different 120 loops, (ii) different 150 loops, (iii) different 160 loops, and (iv) different 190 helices.
  • composition described herein for use in a method for immunizing a subject against influenza virus wherein the method comprises administering to the subject the composition.
  • the method comprises administering to the subject an effective amount of the composition.
  • a composition described herein for use in a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA stem domain in a subject wherein the method comprises administering the subject the composition.
  • composition described herein for use in a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA globular head domain and stem domain in a subject, wherein the method comprises administering to the subject the composition.
  • an immune response e.g., an antibody response
  • a composition described herein for use in a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA stem domain and an influenza A virus globular head domain in a subject wherein the method comprises administering the subject the composition.
  • composition described herein for use in a method for inducing an immune response (e.g., an antibody response) to an influenza B virus HA globular head domain and stem domain, and an influenza A virus globular head domain in a subject, wherein the method comprises administering to the subject the composition.
  • an immune response e.g., an antibody response
  • the subject is human.
  • a first immunogenic composition for use in a method of immunizing a subject against an influenza virus disease or infection, wherein the method comprises (i) a first administration of the first immunogenic composition to the subject, wherein the first immunogenic composition comprises a first chimeric HA polypeptide, a first nucleic acid encoding such a polypeptide(s), a first vector either containing, expressing, or both such a polypeptide(s), or cells described herein; and (ii) a second administration of a second immunogenic composition to the subject, wherein the second immunogenic composition comprises chimeric HA polypeptide, a second nucleic acid encoding such a polypeptide(s), a second vector either containing, expressing, or both such a polypeptide(s), or cells described herein, and wherein the first and second chimeric HA polypeptides comprise an ectodomain with the same stem domains but have different 120 loops, 150 loops, 160 loops
  • the first and second chimeric HA have either one, two, three, or four of the following: (i) different 120 loops, (ii) different 150 loops, (iii) different 160 loops, and (iv) different 190 helices.
  • the first and second administrations may be separated by at least 1 day, 2 days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3 months, or at least 6 months.
  • the first and second administrations may be separated by 1 week to 9 months, 3 weeks to 8 months, 6 weeks to 12 weeks, 4 weeks to 6 months, 5 weeks to 5 months, 6 weeks to 4 months, 7 weeks to 4 months, 8 weeks to 4 months, 8 weeks to 3 months, 3 months to 6 months, 3 months to 9 months, or 6 months to 9 months.
  • booster inoculations may be administered to the subject at 6 to 12 month intervals following the second inoculation.
  • the booster inoculation comprises a third chimeric HA polypeptide, a third nucleic acid encoding such a polypeptide(s), a third vector either containing, expressing, or both such a polypeptide(s), or cells described herein, wherein the first, second, and third chimeric HA polypeptides comprise an ectodomain with the same stem but have different 120 loops, 150 loops, 160 loops, and/or 190 helices.
  • the first, second, and third chimeric HA have either one, two, three, or four of the following: (i) different 120 loops, (ii) different 150 loops, (iii) different 160 loops, and (iv) different 190 helices.
  • the chimeric HA polypeptides described herein when administered to a subject, focuses the immune response towards conserved epitopes in the globular head domain as well as the stem domain of an influenza B virus HA.
  • an immune response e.g., an antibody response
  • a method for inducing an immune response comprising administering to the subject a chimeric HA polypeptide described herein or a composition thereof.
  • provided herein are methods for preventing and/or treating an influenza virus infection or influenza virus disease, comprising administering to a subject in need thereof a composition described herein.
  • a method for preventing an influenza virus disease comprising administering to a subject in need thereof a composition described herein.
  • a method for treating an influenza virus infection comprising administering to a subject in need thereof a composition described herein.
  • a method for treating an influenza virus disease comprising administering to a subject in need thereof a composition described herein.
  • the subject is human.
  • a composition described herein for use in a method for preventing and/or treating an influenza virus infection or influenza virus disease wherein the method comprises administering to a subject in need thereof the composition.
  • a composition described herein for use in a method for preventing an influenza virus disease wherein the method comprises administering to a subject in need thereof the composition.
  • a composition described herein for use in a method for treating an influenza virus infection wherein the method comprises administering to a subject in need thereof the composition.
  • a composition described herein for use in a method for treating an influenza virus disease wherein the method comprises administering to a subject in need thereof the composition.
  • the subject is human.
  • the chimeric HA polypeptides, nucleic acids encoding such polypeptides, or vectors comprising such nucleic acids or polypeptides described herein may be used to elicit neutralizing antibodies against influenza, for example, against the stalk region of an influenza virus hemagglutinin polypeptide and/or subdominant epitopes in the globular head domain of an influenza virus hemagglutinin polypeptide.
  • the chimeric HA polypeptide, nucleic acids encoding such polypeptides, or vectors comprising such nucleic acids or polypeptides described herein may be administered to a non-human subject (e.g., a mouse, rabbit, rat, guinea pig, etc.) to induce an immune response that includes the production of antibodies which may be isolated using techniques known to one of skill in the art (e.g., immunoaffinity chromatography, centrifugation, precipitation, etc.).
  • a non-human subject e.g., a mouse, rabbit, rat, guinea pig, etc.
  • an immune response that includes the production of antibodies which may be isolated using techniques known to one of skill in the art (e.g., immunoaffinity chromatography, centrifugation, precipitation, etc.).
  • the term "120 loop” refers to an antigenic region in an influenza B virus HA.
  • the term "120 loop” refers to amino acid residues 116 to 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 116 to 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 116-137 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "120 loop" refers to amino acid residues 75 to 77, and 116 to 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 75 to 77, and 116 to 137 of the HAl domain of influenza B virus B/Hong
  • the term "120 loop" refers to amino acid residues 75, 77, and 116 to 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 75, 77, and 116 to 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 75, 77, and 116-137 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "120 loop” refers to amino acid residues 75, 77, 116, 118, 122, 129, and 137 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 75, 77, 116, 118, 122, 129, and 137of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 75, 77, 116, 118, 122, 129, and 137correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "120 loop” refers to the antigenic region defined by Wang et al., 2008, Journal of Virology 82: 3011- 3020 as 120 loop or the equivalent thereof in other influenza B viruses.
  • the term "150 loop” refers to an antigenic region in an influenza B virus HA.
  • the term “150 loop” refers to amino acid residues 141 to 150 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 141 to 150 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 141 to 150 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "150 loop" refers to amino acid residues 141 and 144 to 150 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 141 and 144 to 150 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 141 and 144 to 150 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • 150 loop refers to the antigenic region defined by Wang et al., 2008, Journal of Virology 82: 3011-3020 as 150 loop or the equivalent thereof in other influenza B viruses.
  • 160 loop refers to an antigenic region in an influenza B virus HA.
  • the term "160 loop” refers to amino acid residues 162 to 167 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 162 to 167 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 162 to 167 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "160 loop” refers to the antigenic region defined by Wang et al., 2008, Journal of Virology 82: 3011-3020 as 160 loop or the equivalent thereof in other influenza B viruses.
  • 190 helix refers to an antigenic region in an influenza
  • the term "190 helix" refers to amino acid residues 194 to 202 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 194 to 202 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 194 to 202 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term "190 helix” refers to amino acid residues 194 to 200 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 194 to 200 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 194 to 200 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term " 190 helix” refers to amino acid residues 194 to 200, 205 and 238 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 194 to 200, 205 and 238 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 194 to 200, 205 and 238 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term " 190 helix” refers to amino acid residues 194 to 205 and 238 of the HAl domain of influenza B virus B/Hong Kong/8/73 or amino acid residues in the HAl domain of an influenza B virus other than B/Hong Kong/8/73 that correspond to amino acid residues 194 to 205 and 238 of the HAl domain of influenza B virus B/Hong Kong/8/73 (wherein the amino acid residues 194 to 205 and 238 correspond to the numbered positions of the influenza B virus B/Hong Kong/8/73 HA not including the signal peptide, i.e., the numbering of the mature HA).
  • the term " 190 helix” refers to the antigenic region defined by Wang et al., 2008, Journal of Virology 82: 3011-3020 as 190 helix or the equivalent thereof in other influenza B viruses.
  • the terms “about” or “approximate,” when used in reference to an amino acid position refer to the particular amino acid position in a sequence or any amino acid that is within five, four, three, two, or one residues of that amino acid position, either in an N-terminal direction or a C-terminal direction.
  • the term “about” or “approximately” when used in conjunction with a number refers to any number within 1, 5 or 10% of the referenced number. In certain embodiments, the term “about” encompasses the exact number recited.
  • amino acid sequence identity refers to the degree of identity or similarity between a pair of aligned amino acid sequences, usually expressed as a percentage. Percent identity is the percentage of amino acid residues in a candidate sequence that are identical ⁇ i.e., the amino acid residues at a given position in the alignment are the same residue) or similar ⁇ i.e., the amino acid substitution at a given position in the alignment is a conservative substitution, as discussed below), to the corresponding amino acid residue in the peptide after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence homology.
  • Sequence homology may be determined using sequence alignment techniques well-known in the art, preferably computer algorithms designed for this purpose, using the default parameters of said computer algorithms or the software packages containing them.
  • Non-limiting examples of computer algorithms and software packages incorporating such algorithms include the following.
  • the BLAST family of programs exemplify a particular, non-limiting example of a mathematical algorithm utilized for the comparison of two sequences ⁇ e.g., Karlin & Altschul, 1990, Proc. Natl. Acad. Sci. USA 87:2264-2268 (modified as in Karlin & Altschul, 1993, Proc. Natl. Acad. Sci. USA 90:5873-5877), Altschul et al, 1990, J. Mol. Biol.
  • BESTFIT which uses the "local homology” algorithm of Smith and Waterman (Advances in Applied Mathematics, 2:482-489, 1981) to find best single region of similarity between two sequences, and which is preferable where the two sequences being compared are dissimilar in length
  • GAP which aligns two sequences by finding a "maximum similarity” according to the algorithm of Neddleman and Wunsch (J. Mol. Biol. 48:443-354, 1970), and is preferable where the two sequences are approximately the same length and an alignment is expected over the entire length
  • BioEdit BioEdit.
  • Constant substitution refers to replacement of an amino acid of one class is with another amino acid of the same class.
  • a conservative substitution does not alter the structure or function, or both, of a polypeptide.
  • Classes of amino acids for the purposes of conservative substitution include hydrophobic (Met, Ala, Val, Leu, He), neutral hydrophilic (Cys, Ser, Thr), acidic (Asp, Glu), basic (Asn, Gin, His, Lys, Arg), conformation disrupters (Gly, Pro) and aromatic (Trp, Tyr, Phe).
  • the terms “disease” and “disorder” are used interchangeably to refer to a condition in a subject.
  • the condition is a viral infection.
  • a term “disease” refers to the pathological state resulting from the presence of the virus in a cell or a subject, or by the invasion of a cell or subject by the virus.
  • the condition is a disease in a subject, the severity of which is decreased by inducing an immune response in the subject through the administration of an immunogenic composition.
  • the term "ectodomain" in reference to an influenza virus HA polypeptide would be understood by one of skill in the art.
  • the ectodomain does not include the signal peptide, the transmembrane domain, and the cytoplasmic tail domain of an influenza virus HA. See, e.g., Table 1A, Table IB and Table 1C, below, for an exemplary influenza B virus ectodomain sequence and location.
  • the ectodomain of an influenza B virus HA polypeptide is a region of the influenza B virus HA polypeptide that aligns with the ectodomain of influenza B/Hong Kong/8/73 vims HA ectodomain set forth in Table 1 A, below. In some embodiments, the ectodomain of an influenza B virus HA polypeptide is a region of the influenza B virus HA polypeptide that aligns with the ectodomain of influenza B/Malaysia/2506/04 virus HA ectodomain set forth in Table 1C, below.
  • an "effective amount" in the context of administering a therapy to a subject refers to the amount of a therapy which has a prophylactic and/or therapeutic effect(s).
  • an "effective amount" in the context of administration of a therapy to a subject refers to the amount of a therapy which is sufficient to achieve one, two, three, four, or more of the following effects: (i) reduce or ameliorate the severity of an influenza virus infection, disease or symptom associated therewith; (ii) reduce the duration of an influenza virus infection, disease or symptom associated therewith; (iii) prevent the progression of an influenza virus infection, disease or symptom associated therewith; (iv) cause regression of an influenza virus infection, disease or symptom associated therewith; (v) prevent the development or onset of an influenza virus infection, disease or symptom associated therewith; (vi) prevent the recurrence of an influenza virus infection, disease or symptom associated therewith; (vii) reduce or prevent the spread of an influenza virus from one cell to another cell
  • the effective amount does not result in complete protection from an influenza virus disease, but results in a lower titer or reduced number of influenza viruses compared to an untreated subject with an influenza virus infection. In certain embodiments, the effective amount results in a 0.5 fold, 1 fold, 1.5 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 25 fold, 50 fold, 75 fold, 100 fold, 125 fold, 150 fold, 175 fold, 200 fold, 300 fold, 400 fold, 500 fold, 750 fold, or 1,000 fold or greater reduction in titer of influenza virus relative to an untreated subject with an influenza virus infection.
  • the effective amount results in a reduction in titer of influenza virus relative to an untreated subject with an influenza virus infection of approximately 1 log or more, approximately 2 logs or more, approximately 3 logs or more, approximately 4 logs or more, approximately 5 logs or more, approximately 6 logs or more, approximately 7 logs or more, approximately 8 logs or more, approximately 9 logs or more, approximately 10 logs or more, 1 to 3 logs, 1 to 5 logs, 1 to 8 logs, 1 to 9 logs, 2 to 10 logs, 2 to 5 logs, 2 to 7 logs, 2 logs to 8 logs, 2 to 9 logs, 2 to 10 logs 3 to 5 logs, 3 to 7 logs, 3 to 8 logs, 3 to 9 logs, 4 to 6 logs, 4 to 8 logs, 4 to 9 logs, 5 to 6 logs, 5 to 7 logs, 5 to 8 logs, 5 to 9 logs, 6 to 7 logs, 6 to 8 logs, 6 to 9 logs, 7 to 8 logs, 7 to 8 logs,
  • HA and "hemagglutinin” refer to any hemagglutinin known to those of skill in the art.
  • the hemagglutinin is influenza hemagglutinin, such as an influenza A hemagglutinin, an influenza B hemagglutinin, or an influenza C hemagglutinin.
  • a typical hemagglutinin comprises domains known to those of skill in the art including a signal peptide (optional herein), a stem domain, a globular head domain, a luminal domain (optional herein), a transmembrane domain (optional herein) and a cytoplasmic domain (optional herein).
  • a hemagglutinin consists of a single polypeptide chain, such as HA0. In certain embodiments, a hemagglutinin consists of more than one polypeptide chain in quaternary association, e.g. HA1 and HA2. Those of skill in the art will recognize that an immature HA0 might be cleaved to release a signal peptide (approximately 20 amino acids) yielding a mature hemagglutinin HA0.
  • an immature HA0 might be cleaved to release a signal peptide (approximately 15 amino acids) yielding a mature hemagglutinin HA0.
  • a hemagglutinin HA0 might be cleaved at another site to yield HA1 polypeptide (approximately 342 amino acids of influenza B/Hong Kong/8/73 virus, including the globular head domain and a portion of the stem domain) and HA2 polypeptide (approximately 169 amino acids of influenza B/Hong Kong/8/73 virus, including the remainder of the stem domain, a luminal domain, a transmembrane domain and a cytoplasmic domain).
  • a hemagglutinin HAO might be cleaved at another site to yield HAl polypeptide (approximately 344 amino acids of influenza B/Hong Kong/8/73 virus, including the globular head domain and a portion of the stem domain) and HA2 polypeptide (approximately 223 amino acids of influenza B/Hong Kong/8/73 virus, including the remainder of the stem domain, a luminal domain, a transmembrane domain and a cytoplasmic domain).
  • HAl polypeptide approximately 344 amino acids of influenza B/Hong Kong/8/73 virus, including the globular head domain and a portion of the stem domain
  • HA2 polypeptide approximately 223 amino acids of influenza B/Hong Kong/8/73 virus, including the remainder of the stem domain, a luminal domain, a transmembrane domain and a cytoplasmic domain.
  • an influenza B virus has an elongated fusion domain (composed of the central coiled-coil structure from the HA2 domain), the extended regions from HAl (amino acid residues 1-42), and HAl (amino acid residues 288-342), a globular membrane-distal domain containing the receptor-binding subdomain, HAl (amino acid residues 116-274), and a vestigial esterase subdomain, HAl (amino acid residues 43-115) and HAl (amino acid residues 275-287) (see Wang et al., 2008, Journal of Virology, 82(6):3011-3020).
  • the delineation of the domains of an influenza B virus HA may be determined from, e.g., crystal structure and/or by using structure prediction software (for example, the website for the Center for Biological Sequence Analysis, Technical University of Denmark DTU, or Pymol) in conjunction with protein alignments.
  • structure prediction software for example, the website for the Center for Biological Sequence Analysis, Technical University of Denmark DTU, or Pymol
  • the delineation of the domains of influenza B/Hong Kong/8/73 virus HA are as set forth in Table 1 A, below.
  • the delineation of domains of the mouse adapted influenza B/Malaysia/2506/20/03 virus HA See, e.g., Table 1 B, infra, for exemplary domains for the mouse adapted influenza
  • Table 1A Exemplary domains for influenza B/Hong Kong/8/73 virus HA.
  • nt nucleotide
  • aa amino acid
  • N/A not applicable.
  • Piece 1 Domain for nt length aa residues aa residues aa residues aa residues aa residues
  • influenza (length) (positions in (positions in
  • Table IB Exemplary domains for mouse adapted influenza
  • B/Malaysia/2506/20/03 HA may be found in SEQ ID NO: 73.
  • Table 1C Exemplary domains for influenza B/Malaysia/2506/20/03 HA.
  • the full length acid sequence for influenza B/Malaysia/2506/20/03 HA may be found in SEQ ID NO: 88. domain
  • a hemagglutinin protein comprises a signal peptide, a transmembrane domain and a cytoplasmic domain.
  • a hemagglutinin protein comprises a signal peptide, an ectodomain, a transmembrane domain and a cytoplasmic domain.
  • a hemagglutinin lacks a signal peptide, i.e. the hemagglutinin is a mature hemagglutinin.
  • a hemagglutinin lacks a transmembrane domain or cytoplasmic domain, or both.
  • hemagglutinin and “HA” encompass hemagglutinin polypeptides that are modified by post-translational processing such as signal peptide cleavage, disulfide bond formation, glycosylation ⁇ e.g., N-linked glycosylation), protease cleavage and lipid modification ⁇ e.g. S-palmitoylation).
  • HA2 refers to a polypeptide domain that corresponds to the HA2 domain of an influenza hemagglutinin polypeptide known to those of skill in the art.
  • an HA2 consists of a stem domain, a luminal domain, a transmembrane domain and a
  • an HA2 consists of a stem domain, a luminal domain and a transmembrane domain.
  • an HA2 consists of a stem domain and a luminal domain; in such embodiments, the HA2 might be soluble.
  • an HA2 consists of a stem domain; in such embodiments, the HA2 might be soluble.
  • an HA2 consists of amino acid residues 1-169 of the HA2 domain of an influenza B/Hong Kong/8/73 virus (see Wang et al., 2008, Journal of Virology 82: 3011-3020). In certain embodiments, an HA2 consists of amino acid residues 345- 567 of a mature influenza B/Hong Kong/8/73 virus HA (i.e., the numbering is determined from an influenza B/Hong Kong/8/73 virus HA that does not include the signal peptide) .
  • heterologous polypeptide in the context of a polypeptide, nucleic acid or virus refers to a polypeptide, nucleic acid or virus, respectively, that is not normally found in nature or not normally associated in nature with a polypeptide, nucleic acid or virus of interest.
  • a heterologous polypeptide may refer to a polypeptide derived from a different virus, e.g., a different influenza strain or subtype, or an unrelated virus or different species.
  • the term "in combination,” in the context of the administration of two or more therapies to a subject, refers to the use of more than one therapy (e.g., more than one prophylactic agent and/or therapeutic agent).
  • the use of the term “in combination” does not restrict the order in which therapies are administered to a subject.
  • a first therapy e.g., a first prophylactic or therapeutic agent
  • a first prophylactic or therapeutic agent can be administered prior to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 16 hours, 24 hours, 48 hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks before), concomitantly with, or subsequent to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 16 hours, 24 hours, 48 hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks after) the administration of a second therapy to a subject.
  • a first therapy e.g., a first prophylactic or therapeutic agent
  • a first therapy can be administered prior to (e.g., 1 week to 9 months, 3 weeks to 8 months, 6 weeks to 12 weeks, 4 weeks to 6 months, 5 weeks to 5 months, 6 weeks to 4 months, 7 weeks to 4 months, 8 weeks to 4 months, 8 weeks to 3 months, 3 months to 6 months, 3 months to 9 months, or 6 months to 9 months before), concomitantly with, or subsequent to (e.g., about 1 week to 9 months, 3 weeks to 8 months, 6 weeks to 12 weeks, 4 weeks to 6 months, 5 weeks to 5 months, 6 weeks to 4 months, 7 weeks to 4 months, 8 weeks to 4 months, 8 weeks to 3 months, 3 months to 6 months, 3 months to 9 months, or 6 months to 9 months after) the administration of a second therapy to a subject.
  • an infection means the invasion by, multiplication and/or presence of a virus in a cell or a subject.
  • an infection is an "active" infection, i.e., one in which the virus is replicating in a cell or a subject.
  • Such an infection is characterized by the spread of the virus to other cells, tissues, and/or organs, from the cells, tissues, and/or organs initially infected by the virus.
  • An infection may also be a latent infection, i.e., one in which the virus is not replicating.
  • an infection refers to the pathological state resulting from the presence of the virus in a cell or a subject, or by the invasion of a cell or subject by the virus.
  • influenza virus disease refers to the pathological state resulting from the presence of an influenza ⁇ e.g., influenza A or B virus) virus in a cell or subject or the invasion of a cell or subject by an influenza virus.
  • influenza virus disease refers to a respiratory illness caused by an influenza virus.
  • influenza virus hemagglutinin head domain refers to the globular head domain of an influenza hemagglutinin polypeptide.
  • An influenza virus hemagglutinin head domain polypeptide or influenza virus hemagglutinin head domain may comprise or consist of a known ⁇ e.g., wild-type) influenza virus hemagglutinin head domain or may comprise or consist of a derivative, e.g. an engineered derivative, of a known ⁇ e.g., wild-type) influenza virus hemagglutinin head domain.
  • an influenza B virus HA globular head domain typically comprises the amino acid residues corresponding to amino acid residues 43-289 of the HA1 domain of influenza B/Hong Kong/8/73 virus (wherein the numbering of the amino acid residues is with respect to the mature HA sequence, which does not comprise the 15 amino acid signal peptide).
  • the amino acid sequence for the HA globular head domain for influenza B/Hong Kong/8/73 virus typically consists of the amino acid sequence:
  • influenza B virus HA globular head domain for a particular strain can be determined by alignment of the influenza B virus HA polypeptide for said strain to the sequence of an influenza A virus HA (Fig. 20).
  • influenza B virus globular head domain consists of the amino acid residues that align to amino acid residues 58-304 of the mature influenza B/Hong Kong/8/73 virus HA (i.e., wherein said numbering includes the signal peptide). See, e.g., Table 1A, above.
  • IFN deficient system or "IFN-deficient substrate” refer to systems, e.g., cells, cell lines and animals, such as pigs, mice, chickens, turkeys, rabbits, rats, etc., which do not produce interferon (IFN) or produce low levels of IFN ⁇ i.e., a reduction in IFN expression of 5-10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, 80- 90%) or more when compared to IFN-competent systems under the same conditions), do not respond or respond less efficiently to IFN, and/or are deficient in the activity of one or more antiviral genes induced by IFN.
  • IFN interferon
  • log refers to logio
  • MOI multiplicity of infection
  • nucleic acid is intended to include DNA molecules
  • RNA molecules ⁇ e.g., mRNA
  • the nucleic acid can be single-stranded or double- stranded.
  • Polypeptide refers to a polymer of amino acids linked by amide bonds as is known to those of skill in the art. As used herein, the term can refer to a single polypeptide chain linked by covalent amide bonds. The term can also refer to multiple polypeptide chains associated by non-covalent interactions such as ionic contacts, hydrogen bonds, Van der Waals contacts and hydrophobic contacts. Those of skill in the art will recognize that the term includes polypeptides that have been modified, for example by post-translational processing such as signal peptide cleavage, disulfide bond formation, glycosylation ⁇ e.g., N-linked glycosylation), protease cleavage and lipid modification ⁇ e.g.
  • the terms "prevent,” “preventing” and “prevention” in the context of the administration of a therapy(ies) to a subject to prevent an influenza virus disease refer to one or more of the prophylactic/beneficial effects resulting from the administration of a therapy or a combination of therapies.
  • the terms "prevent,” “preventing” and “prevention” in the context of the administration of a therapy(ies) to a subject to prevent an influenza virus disease refer to one or more of the following effects resulting from the administration of a therapy or a combination of therapies: (i) the inhibition of the development or onset of an influenza virus disease or a symptom thereof; (ii) the inhibition of the recurrence of an influenza virus disease or a symptom associated therewith; and (iii) the reduction or inhibition in influenza virus infection and/or replication.
  • the terms "purified” and “isolated” when used in the context of a polypeptide (including an antibody) that is obtained from a natural source, e.g., cells refers to a polypeptide which is substantially free of contaminating materials from the natural source, e.g., soil particles, minerals, chemicals from the environment, and/or cellular materials from the natural source, such as but not limited to cell debris, cell wall materials, membranes, organelles, the bulk of the nucleic acids, carbohydrates, proteins, and/or lipids present in cells.
  • a polypeptide that is isolated includes preparations of a polypeptide having less than about 30%, 20%, 10%), 5%, 2%, or 1%> (by dry weight) of cellular materials and/or contaminating materials.
  • the terms "purified” and "isolated” when used in the context of a polypeptide (including an antibody) that is chemically synthesized refers to a polypeptide which is substantially free of chemical precursors or other chemicals which are involved in the syntheses of the polypeptide.
  • a chimeric HA polypeptide is chemically synthesized.
  • polypeptide, and/or a chimeric influenza hemagglutinin polypeptide is isolated.
  • replication refers to one or more, or all, of the stages of a viral life cycle which result in the propagation of virus.
  • the steps of a viral life cycle include, but are not limited to, virus attachment to the host cell surface, penetration or entry of the host cell (e.g., through receptor mediated endocytosis or membrane fusion), uncoating (the process whereby the viral capsid is removed and degraded by viral enzymes or host enzymes thus releasing the viral genomic nucleic acid), genome replication, synthesis of viral messenger RNA (mRNA), viral protein synthesis, and assembly of viral ribonucleoprotein complexes for genome replication, assembly of virus particles, post-translational modification of the viral proteins, and release from the host cell by lysis or budding and acquisition of a phospholipid envelope which contains embedded viral glycoproteins.
  • replication refers to the replication
  • stem domain polypeptide and “influenza virus hemagglutinin stem domain polypeptide” and “stalk domain” refer to the stem domain of an influenza virus hemagglutinin polypeptide (which includes derivatives of an influenza HA polypeptide).
  • a stem domain polypeptide might be a single polypeptide chain, two polypeptide chains or more polypeptide chains.
  • a stem domain polypeptide is a single polypeptide chain (i.e. corresponding to the stem domain of a hemagglutinin HAO polypeptide) or two polypeptide chains (i.e.
  • the stem domain of an influenza B virus HA polypeptide is a trimer. See, e.g., Tables 1 A and IB, supra, for an example of the amino acid sequence and location of a stem domain of an influenza B virus.
  • a subject or “patient” are used interchangeably to refer to an animal ⁇ e.g., birds, reptiles, and mammals).
  • a subject is a bird.
  • a subject is a mammal including a non-primate ⁇ e.g., a camel, donkey, zebra, cow, pig, horse, goat, sheep, cat, dog, rat, and mouse) and a primate ⁇ e.g. , a monkey, chimpanzee, and a human).
  • a subject is a non-human animal.
  • a subject is a farm animal or pet.
  • a subject is a human.
  • a subject is a human infant. In another embodiment, a subject is a human child. In another embodiment, a subject is a human adult. In another embodiment, a subject is an elderly human. In another embodiment, a subject is a premature human infant.
  • seasonal influenza virus strain refers to a strain of influenza virus to which a subject population is exposed to on a seasonal basis.
  • seasonal influenza virus strain refers to a strain of influenza B virus.
  • seasonal influenza virus strain refers to a strain of influenza virus that belongs to the Yamagata or the Victoria lineages, i.e., the two lineages that presently persist in the human subject population.
  • the terms “therapies” and “therapy” can refer to any protocol(s), method(s), compound(s), composition(s), formulation(s), and/or agent(s) that can be used in the prevention or treatment of a viral infection or a disease or symptom associated therewith.
  • the terms “therapies” and “therapy” refer to biological therapy, supportive therapy, and/or other therapies useful in treatment or prevention of a viral infection or a disease or symptom associated therewith known to one of skill in the art.
  • the term “therapy” refers to (i) a nucleic acid encoding a chimeric HA polypeptide, (ii) a chimeric HA polypeptide), or (iii) a vector or composition comprising a nucleic acid encoding a chimeric HA polypeptide or comprising a chimeric HA polypeptide.
  • the term “therapy” refers to an antibody that specifically binds to a chimeric influenza virus
  • the terms “treat,” “treatment,” and “treating” refer in the context of administration of a therapy(ies) to a subject to treat an influenza virus disease or infection to obtain a beneficial or therapeutic effect of a therapy or a combination of therapies.
  • such terms refer to one, two, three, four, five or more of the following effects resulting from the administration of a therapy or a combination of therapies: (i) the reduction or amelioration of the severity of an influenza virus infection or a disease or a symptom associated therewith; (ii) the reduction in the duration of an influenza virus infection or a disease or a symptom associated therewith; (iii) the regression of an influenza virus infection or a disease or a symptom associated therewith; (iv) the reduction of the titer of an influenza virus; (v) the reduction in organ failure associated with an influenza virus infection or a disease associated therewith; (vi) the reduction in hospitalization of a subject; (vii) the reduction in hospitalization length; (viii) the increase in the survival of a subject; (ix) the elimination of an influenza virus infection or a disease or symptom associated therewith; (x) the inhibition of the progression of an influenza virus infection or a disease or a symptom associated therewith; (xi) the prevention of the spread of an
  • wild-type in the context of a viral polypeptide refers to a viral polypeptide that is found in nature and is associated with a naturally occurring virus.
  • wild-type in the context of a virus refers to the types of a virus that are prevalent, circulating naturally and producing typical outbreaks of disease.
  • wild-type in the context of a virus refers to a parental virus.
  • FIG. 1 depicts a strategy for generating influenza B virus chimeric HAs for use as universal influenza virus vaccine candidates and potential vaccination schematic.
  • FIG. 2 depicts the 120 loop, 150 loop, 160 loop, and 190 helix in the influenza
  • FIG. 3A depicts the amino acid sequence corresponding to the 150 loop of the influenza B/Yamagata/16/88 virus sequence (top, SEQ ID NO: 18) and the amino acid sequence of the modified 150 loop of the chimeric HA (bottom, SEQ ID NO: 19).
  • FIG. 3B depicts the structure of the influenza B/Yamanashi/166/1998 virus globular head domain and points out the location of the 150 loop.
  • FIG. 3C depicts an immunostain of a plaque assay used to visualize plaque morphology of the rescued virus expressing the chimeric HA.
  • FIG. 4 depicts growth curves of viruses expressing the indicated chimeric HA constructs at the indicated timepoints. The growth curves were performed in MDCK cells growth at 33 degrees Celsius.
  • FIG. 5 depicts immunofluorescent staining of 293T cells transfected with the indicated constructs and stained with anti-H5 serum.
  • FIG. 6A depicts the amino acid sequence corresponding to the 190 helix of the influenza B/Yamagata/16/88 virus sequence (top, SEQ ID NO: 7) and the amino acid sequence of the modified 190 helix of the chimeric HA (bottom, SEQ ID NO: 8).
  • FIG. 6B depicts the structure of the influenza B/Yamanashi/166/1998 virus globular head domain and points out the location of the 190 helix.
  • FIG. 6C depicts an immunostain of a plaque assay used to visualize plaque morphology of the rescued virus expressing the chimeric HA.
  • FIG. 7A depicts the amino acid sequence corresponding to the 160 loop of the influenza B/Yamagata/16/88 virus sequence (top, SEQ ID NO: 5) and the amino acid sequence of the modified 160 loop of the chimeric HA (bottom, SEQ ID NO: 6).
  • FIG. 7B depicts the structure of the influenza B/Yamanashi/166/1998 virus globular head domain and points out the location of the 160 loop.
  • FIG. 7C depicts an immunostain of a plaque assay used to visualize plaque morphology of the rescued virus expressing the chimeric HA.
  • FIG. 8A depicts the amino acid sequence corresponding to the 120 loop of the influenza B/Yamagata/16/88 virus sequence (top “B/Yam”, SEQ ID NO: 1) and the amino acid sequence of the modified 120 loop of the chimeric HA (bottom “B/Yamagata ectodomain with A/H5", SEQ ID NO: 2). Also depicted is the mutation made at amino acid position T90 of influenza B/Yamagata/16/88 virus (wherein amino acid position T90 is with respect to the immature influenza B/Yamagata/16/88 virus HA, i.e., including the signal peptide).
  • FIG. 8B depicts the structure of the influenza B/Yamanashi/166/1998 virus globular head domain and points out the location of the 120 loop.
  • FIG. 9 depicts immunofluorescence of 293T with the indicated antibodies.
  • Column 1 represents cells transfected with pDZ.
  • Column 2 represents cells transfected with Yamagata ectodomain (influenza A/Puerto Rico/8/34 virus ("PR8") background) HA.
  • Column 3 represents cells transfected with the chimeric HA comprising 150 loop, 160 loop, and 190 helix modified with influenza A virus H5 sequences.
  • Column 4 represents cells transfected with the chimeric HA comprising 120 loop, 150 loop, 160 loop, and 190 helix modified with influenza A virus H5 sequences.
  • FIG. 10A depicts HI assay titers performed with mouse serum.
  • FIG. 10B depicts
  • Yamecto/PR8 refers to a PR8 virus expressing an HA that has an influenza B/Yamagata/16/88 virus HA ectodomain.
  • 3 loop refers to a PR8 virus expressing an HA that has an influenza B/Yamagata/16/88 virus HA ectodomain, in which three antigenic loops (150 loop, 160 loop, and 190 helix) of the ectodomain have been modified based on the amino acid sequence of influenza A/Vietnam/1203/04(HALo) virus HA.
  • 4 loop refers to a PR8 virus expressing an HA that has an influenza B/Yamagata/16/88 virus HA ectodomain, in which four antigenic loops (120 loop, 150 loop, 160 loop, and 190 helix) of the ectodomain have been modified based on the amino acid sequence of influenza A/Vietnam/1203/04(HALo) virus HA.
  • FIG. 11 demonstrates that chimeric HA may be generated in which each of the
  • 120 loop, 150 loop, 160 loop, and 190 helix of an influenza B virus HA have been modified based on the amino acid sequence of an influenza A virus of the H5, H8, or H12 subtype.
  • FIG. 12A and FIG. 12B Nucleic acid sequence encoding H5-4 loop chimeric
  • HA (SEQ ID NO: 20).
  • the background of the construct is Yamagata ectodomain in PR8 HA background in pDZ plasmid made by infusion cloning.
  • Non-underlined nucleic acid sequences refer to the sequences encoding the ectodomain of Yamagata.
  • Underlined nucleic acid sequences labeled “1" refer to the PR8 3' non-coding region sequence.
  • Underlined nucleic acid sequences labeled "2” refer to the sequence encoding the PR8 signal peptide.
  • Underlined nucleic acid sequences labeled "3" refer to the mutations introduced into the sequence encoding the 120 loop.
  • Underlined nucleic acid sequences labeled “4" refer to the mutations introduced into the sequence encoding the 150 loop.
  • Underlined nucleic acid sequences labeled “5" refer to mutations introduced into the sequence encoding the 160 loop.
  • Underlined nucleic acid sequences labeled “6” refer to the mutations introduced into the sequence encoding the 190 helix.
  • Underlined nucleic acid sequences labeled “7” refer to a H- Y mutation in the Yamagata ectodomain.
  • Underlined nucleic acid sequences labeled “8” refer to the sequence encoding the PR8 transmembrane domain.
  • Underlined nucleic acid sequences labeled “9” refer to the sequence encoding the PR8 cytoplasmic tail domain.
  • Underlined nucleic acid sequences labeled “10” refer to the PR8 5' non-coding region.
  • FIG. 13 Amino acid sequence (SEQ ID NO: 21) of the nucleic acid of Fig. 12A and Fig. 12B.
  • Underlined amino acid sequences labeled “ 1" refer to the PR8 signal peptide sequence.
  • Underlined amino acid sequences labeled “2” refer to the mutations introduced into the 120 loop sequence.
  • Underlined amino acid sequences labeled “3” refer to the mutations introduced into the 150 loop sequence.
  • Underlined amino acid sequences labeled "4" refer to the mutations introduced into the 160 loop sequence.
  • Underlined amino acid sequences labeled "5" refer to the mutations introduced into the 190 helix sequence.
  • Underlined amino acid labeled “6” refers to a H- Y mutation in the Yamagata ectodomain, which matches influenza A virus HA at this position (determined by Flandorfer et al., Journal of Virology, 2003), which may lead to more efficient rescue.
  • Underlined amino acid sequences labeled “7” refer to the PR8 transmembrane domain sequence.
  • Underlined amino acid sequences labeled “8” refer to the PR8 cytoplasmic tail domain sequence.
  • FIG. 14A and FIG. 14B Nucleic acid sequence encoding H8-4 loop chimeric
  • Non-underlined nucleic acid sequences refer to the sequences encoding the ectodomain of Yamagata.
  • Underlined nucleic acid sequences labeled “1" refer to the PR8 3' non-coding region sequence.
  • Underlined nucleic acid sequences labeled "2" refer to the sequence encoding the PR8 signal peptide.
  • Underlined nucleic acid sequences labeled “3” refer to the mutations introduced into the sequence encoding the 120 loop.
  • Underlined nucleic acid sequences labeled "4" refer to an E- K mutation.
  • Underlined nucleic acid sequences labeled “5" refer to the mutations introduced into the sequence encoding the 150 loop.
  • Underlined nucleic acid sequences labeled “6” refer to mutations introduced into the sequence encoding the 160 loop.
  • Underlined nucleic acid sequences labeled “7” refer to the mutations introduced into the sequence encoding the 190 helix.
  • Underlined nucleic acid sequences labeled “8” refer to a H- Y mutation in the Yamagata ectodomain.
  • Underlined nucleic acid sequences labeled “9” refer to the sequence encoding the PR8 transmembrane domain.
  • Underlined nucleic acid sequences labeled “10” refer to the sequence encoding the PR8 cytoplasmic tail domain.
  • Underlined nucleic acid sequences labeled “ 11” refer to the PR8 5' non-coding region.
  • FIG. 15 Amino acid sequence (SEQ ID NO: 23) of the nucleic acid of Fig. 14A and Fig. 14B.
  • Underlined amino acid sequences labeled “ 1" refer to the PR8 signal peptide sequence.
  • Underlined amino acid sequences labeled “2” refer to the mutations introduced into the 120 loop sequence.
  • Underlined amino acid labeled “3” refers to an E- K mutation.
  • Underlined amino acid sequences labeled “4" refer to the mutations introduced into the 150 loop sequence. Underlined amino acid sequences labeled “5" refer to the mutations introduced into the 160 loop sequence. Underlined amino acid sequences labeled “6” refer to the mutations introduced into the 190 helix sequence. Underlined amino acid labeled “7” refers to a H- Y mutation in the Yamagata ectodomain, which matches influenza A virus HA at this position (determined by Flandorfer et al., Journal of Virology, 2003), which may lead to more efficient rescue. Underlined amino acid sequences labeled “8” refer to the PR8 transmembrane domain sequence. Underlined amino acid sequences labeled “9” refer to the PR8 cytoplasmic tail domain sequence.
  • FIG. 16A and FIG. 16B Nucleic acid sequence encoding HI 1-4 loop chimeric
  • Non-underlined nucleic acid sequences refer to the sequences encoding the ectodomain of Yamagata.
  • Underlined nucleic acid sequences labeled “1" refer to the PR8 3' non-coding region sequence.
  • Underlined nucleic acid sequences labeled "2" refer to the sequence encoding the PR8 signal peptide.
  • Underlined nucleic acid sequences labeled “3” refer to the mutations introduced into the sequence encoding the 120 loop.
  • Underlined nucleic acid sequences labeled "4" refer to the E- K mutation.
  • Underlined nucleic acid sequences labeled “5" refer to the mutations introduced into the sequence encoding the 150 loop.
  • Underlined nucleic acid sequences labeled “6” refer to mutations introduced into the sequence encoding the 160 loop.
  • Underlined nucleic acid sequences labeled “7” refer to the mutations introduced into the sequence encoding the 190 helix.
  • Underlined nucleic acid sequences labeled “8” refer to a H- Y mutation in the Yamagata ectodomain.
  • Underlined nucleic acid sequences labeled “9” refer to the sequence encoding the PR8 transmembrane domain.
  • Underlined nucleic acid sequences labeled “10” refer to the sequence encoding the PR8 cytoplasmic tail domain.
  • Underlined nucleic acid sequences labeled “ 11” refer to the PR8 5' non-coding region.
  • FIG. 17 Amino acid sequence (SEQ ID NO: 25) of the nucleic acid of Fig. 16A and Fig. 16B.
  • Underlined amino acid sequences labeled “ 1" refer to the PR8 signal peptide sequence.
  • Underlined amino acid sequences labeled “2” refer to the mutations introduced into the 120 loop sequence.
  • Underlined amino acid labeled “3” refers to an E- K mutation.
  • Underlined amino acid sequences labeled “4" refer to the mutations introduced into the 150 loop sequence. Underlined amino acid sequences labeled “5" refer to the mutations introduced into the 160 loop sequence. Underlined amino acid sequences labeled “6” refer to the mutations introduced into the 190 helix sequence. Underlined amino acid labeled “7” refers to a H- Y mutation in the Yamagata ectodomain, which matches influenza A virus HA at this position (determined by Flandorfer et al., Journal of Virology, 2003), which may lead to more efficient rescue. Underlined amino acid sequences labeled “8” refer to the PR8 transmembrane domain sequence. Underlined amino acid sequences labeled “9” refer to the PR8 cytoplasmic tail domain sequence.
  • FIG. 18A and FIG. 18B Nucleic acid sequence encoding H12-4 loop chimeric
  • Non-underlined nucleic acid sequences refer to the sequences encoding the ectodomain of Yamagata.
  • Underlined nucleic acid sequences labeled “1" refer to the PR8 3' non-coding region sequence.
  • Underlined nucleic acid sequences labeled "2" refer to the sequence encoding the PR8 signal peptide.
  • Underlined nucleic acid sequences labeled “3” refer to the mutations introduced into the sequence encoding the 120 loop.
  • Underlined nucleic acid sequences labeled "4" refer to an E- K mutation.
  • Underlined nucleic acid sequences labeled “5" refer to the mutations introduced into the sequence encoding the 150 loop.
  • Underlined nucleic acid sequences labeled “6” refer to mutations introduced into the sequence encoding the 160 loop.
  • Underlined nucleic acid sequences labeled “7” refer to the mutations introduced into the sequence encoding the 190 helix.
  • Underlined nucleic acid sequences labeled “8” refer to a H- Y mutation in the Yamagata ectodomain.
  • Underlined nucleic acid sequences labeled “9” refer to the sequence encoding the PR8 transmembrane domain.
  • Underlined nucleic acid sequences labeled “10” refer to the sequence encoding the PR8 cytoplasmic tail domain.
  • Underlined nucleic acid sequences labeled “ 11” refer to the PR8 5' non-coding region.
  • FIG. 19 Amino acid sequence (SEQ ID NO: 27) of the nucleic acid of Fig. 18A and Fig. 18B.
  • Underlined amino acid sequences labeled “ 1" refer to the PR8 signal peptide sequence.
  • Underlined amino acid sequences labeled “2” refer to the mutations introduced into the 120 loop sequence.
  • Underlined amino acid labeled “3” refers to an E- K mutation.
  • Underlined amino acid sequences labeled “4" refer to the mutations introduced into the 150 loop sequence. Underlined amino acid sequences labeled “5" refer to the mutations introduced into the 160 loop sequence. Underlined amino acid sequences labeled “6” refer to the mutations introduced into the 190 helix sequence. Underlined amino acid labeled “7” refers to a H- Y mutation in the Yamagata ectodomain, which matches influenza A virus HA at this position (determined by Flandorfer et al., Journal of Virology, 2003), which may lead to more efficient rescue. Underlined amino acid sequences labeled “8” refer to the PR8 transmembrane domain sequence. Underlined amino acid sequences labeled “9” refer to the PR8 cytoplasmic tail domain sequence.
  • FIG. 20 Alignment of influenza B/Hong Kong/8/73 virus HA (SEQ ID NO: 28), influenza A/Puerto Rico/8/34 virus HA (SEQ ID NO: 29), and influenza B/Yamagata/16/88 virus HA (SEQ ID NO: 30).
  • the locations of the signal peptide, stalk domain, head domain, start of the HA2 domain, fusion peptide, transmembrane domain, and cytoplasmic tail domain for the influenza B viruses are delineated based on the locations of the respective domains in the influenza A virus.
  • FIG. 21A Nucleic acid sequence encoding influenza A/mallard/Sweden/24/2002 virus HA (SEQ ID NO 31). Underlined sequences are the 5' and 3' noncoding regions.
  • FIG. 21B Amino acid sequence (SEQ ID NO: 32) of the nucleic acid of Fig. 21A.
  • FIG. 22A Nucleic acid sequence encoding influenza A/Vietnam/1203/04
  • FIG. 22B Amino acid sequence (SEQ ID NO: 34) of the nucleic acid of Fig. 22 A.
  • FIG. 23A Nucleic acid sequence encoding influenza A/northern
  • FIG. 23B Amino acid sequence (SEQ ID NO: 36) of the nucleic acid of Fig. 23 A.
  • FIG. 24A Nucleic acid sequence encoding A mallard interior
  • FIG. 24B Amino acid sequence (SEQ ID NO: 38) of the nucleic acid of Fig. 24A.
  • FIG. 25A Nucleic acid sequence encoding influenza A/Puerto Rico/8/34 virus
  • FIG. 25B HA (SEQ ID NO: 39). Underlined sequences are the 5' and 3' non-coding regions.
  • FIG. 26A Nucleic acid sequence encoding influenza B/Yamagata/16/88 virus
  • FIG. 26B HA (SEQ ID NO: 41). Underlined sequences are the 5' and 3' non-coding regions.
  • Amino acid sequence (SEQ ID NO: 42) of the nucleic acid of FIG. 26 A.
  • FIG. 27 depicts the four major antigenic sites of influenza B virus HA in the influenza virus B/Yamanashi/166/1988 (PDB: 4M40): 120 loop, 150 loop, 160 loop, and 190 helix.
  • FIG. 28 Amino acid residues in four antigenic sites (120 loop, 150 loop, 160 loop, and 190 helix) of the influenza B/Yamagata/16/88 virus HA were replaced by
  • Viruses encoding the chimeric HAs were rescued in an influenza B/Malaysia/2506/04 MA virus backbone.
  • FIG. 29 Nucleic acid sequence encoding mH5/B chimeric HA based on an influenza B/Yamagata/16/88 virus HA sequence, comprising nucleic acid sequences from the influenza A/Vietnam/1203/04(HALo) virus (H5) globular head domain (SEQ ID NO: 43).
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Underlined, bold, italicized, uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequences correspond to additional mutations introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 30 Amino acid sequence (SEQ ID NO: 44) encoded by the nucleic acid of FIG. 29.
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Italicized, underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequence corresponds to an additional mutation introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 31 Nucleic acid sequence encoding mH8/B chimeric HA based on an influenza B/Yamagata/16/88 virus HA sequence, comprising nucleic acid sequences from the influenza A/Mallard/Sweden/24/2002 virus (H8) globular head domain (SEQ ID NO: 45).
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Underlined, bold, italicized, uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequences correspond to additional mutations introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 32 Amino acid sequence (SEQ ID NO: 46) encoded by the nucleic acid of
  • FIG. 31 Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Italicized, underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Underlined, bold, italicized, uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequence corresponds to an additional mutation introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 33 Nucleic acid sequence encoding mHl 1/B chimeric HA based on an influenza B/Yamagata/16/88 virus HA sequence, comprising nucleic acid sequences from the influenza A/northern shovel er/Netherlands/18/99 virus (HI 1) globular head domain (SEQ ID NO: 47).
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Underlined, bold, italicized, uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequence corresponds to an additional mutation introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 34 Amino acid sequence (SEQ ID NO: 48) encoded by the nucleic acid of FIG. 33.
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Italicized, underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Uppercase bold sequence corresponds to an additional mutation introduced into the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 35 Nucleic acid sequence encoding mH13/B chimeric HA based on an influenza B/Yamagata/16/88 virus HA sequence, comprising nucleic acid sequences from the influenza A/black headed gull/Sweden/ 1/99 (H13) globular head domain (SEQ ID NO: 49).
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIG. 36 Amino acid sequence (SEQ ID NO: 50) encoded by the nucleic acid of FIG. 35.
  • Bold, underlined, uppercase sequences correspond to mutations introduced into the 120 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Bold lowercase sequences correspond to mutations introduced into the 150 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Italicized, underlined lowercase sequences correspond to mutations introduced into the 160 loop of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • Underlined, bold, italicized, uppercase sequences correspond to mutations introduced into the 190 helix of the influenza B/Yamagata/16/88 virus HA ectodomain.
  • FIGS. 37A-37D depicts growth curves for influenza viruses expressing mH5/B chimeric HA (FIG. 37A), mH8/B chimeric HA (FIG. 37B), mHl 1/B chimeric HA (FIG. 37C), or mH13/B chimeric HA (FIG. 37D) as compared to wild type influenza B/Malaysia/2506/04 MA virus.
  • 10-day embryonated eggs were infected with 500 PFU/egg of the influenza virus expressing mH5/B chimeric HA (mH5/B Mai), mH8/B chimeric HA (mH8/B Mai), mHl 1/B chimeric HA (mHl 1/B Mai), or mH13/B chimeric HA (mH13/B Mai), or wild type influenza B/Malaysia/2506/04 MA virus (B/Mal04 MA) in triplicates and incubated at 33 degrees Celsius. Allantoic fluids were harvested at the indicated times and plaque assays were performed on Madin Darby Canine Kidney (MDCK) cells to determine virus titers.
  • PFU refers to plaque forming unit.
  • B/Mal04 MA refers to wild type influenza B/Malaysia/2506/04 MA virus.
  • mH5/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH5/B chimeric HA described in FIGS. 29 and 30.
  • mH8/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH8/B chimeric HA described in FIGS. 31 and 32.
  • mHl 1/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mHl 1/B chimeric HA described in FIGS. 33 and 34.
  • mH13/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH13/B chimeric HA described in FIGS. 35 and 36.
  • FIGS. 38A-38D demonstrate that cross-protective subdominant conserved antigenic sites within influenza B virus HA were preserved in the chimeric HA.
  • MDCK cells were infected with influenza viruses expressing mH5/B chimeric HA (FIG. 38 A), mH8/B chimeric HA (FIG. 38B), mHl 1/B chimeric HA (FIG. 38C), or mH13/B chimeric HA (FIG. 38D) at an MOI of 5 without TPCK-trypsin and compared to uninfected cells or cells infected with B/Mal04 MA at an MOI of 5 without TPCK-trypsin.
  • Cells were incubated at 33 degrees Celsius and 5% C0 2 . 17 hours post infection, cells were fixed with methanol free 5%
  • mH5/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH5/B chimeric HA described in FIGS. 29 and 30.
  • mH8/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH8/B chimeric HA described in FIGS. 31 and 32.
  • mHl 1/B Mai refers to influenza
  • mH13/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH13/B chimeric HA described in FIGS. 35 and 36.
  • TPCK refers to L-l-Tosylamide-2-phenylethyl chloromethyl ketone.
  • FIGS. 39A-39D demonstrate that immunodominant epitopes on influenza
  • B/Yamagata/88 HA head were ablated in the chimeric HAs.
  • Mouse and ferret sera were raised against wild type influenza B virus strain B/Yamagata/16/88 to acquire hemagglutination inhibition (HI) reactivity.
  • HI assays for the mouse and ferret sera were performed using turkey red blood cells (RBCs) with influenza viruses expressing mH5/B chimeric HA (FIG. 39 A), mH8/B chimeric HA (FIG. 39B), mHl l/B chimeric HA (FIG. 39C), or mH13/B chimeric HA (FIG.
  • mH5/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH5/B chimeric HA described in FIGS. 29 and 30.
  • mH8/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH8/B chimeric HA described in FIGS. 31 and 32.
  • mHl l/B Mai refers to influenza
  • mH13/B Mai refers to influenza B/Malaysia/2506/04 MA virus encoding the mH13/B chimeric HA described in FIGS. 35 and 36.
  • FIGS. 40A AND 40B depict weight loss (FIG. 40A) and survival (FIG. 40B) of chimeric HA-vaccinated mice after challenge with B/Malaysia/2506/04 (Victoria-like).
  • Vaccination with the chimeric HA regiment resulted in complete protection from mortality with minimal weight loss.
  • FIG. 41 A Nucleic acid sequence encoding influenza A/black headed
  • FIG. 41B Amino acid sequence (SEQ ID NO: 72) of the nucleic acid of Fig. 41 A.
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within an antigenic loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5 or more amino acid substitutions within 160 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • HA hemagglutinin
  • influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL SEQ ID NO: 1
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL SEQ ID NO: 2.
  • amino acid residues YQGKSS SEQ ID NO:4 from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/ 16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus
  • KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/ 16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/ 16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP and JUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RD KTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/ 1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from an influenza A virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the
  • the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA is engineered for an influenza A virus backbone (e.g., the influenza virus comprising or engineered to express the chimeric HA is an influenza A virus)
  • the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza vims that is engineered to express the chimeric HA. Also provided herein are nucleic acids comprising nucleotide sequences encoding such a chimeric HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/ 16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • chimeric hemagglutinin (HA) polypeptides comprising an HA ectodomain of an influenza B virus comprising one, two, three or all of the following: (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIOLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the influenza B virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from the influenza B virus HA but lacks the transmembrane and cytoplasmic tail domains. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from an influenza A virus HA. In other embodiments, the chimeric HA polypeptide comprises the signal peptide from an influenza A virus HA but lacks the
  • the chimeric HA comprises the signal peptide of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA is engineered for an influenza A virus backbone (e.g., the influenza virus comprising or engineered to express the chimeric HA is an influenza A virus)
  • the chimeric HA comprises the signal peptide of the influenza A virus.
  • the chimeric HA comprises the signal peptide, transmembrane domain, and cytoplasmic domain of the HA of the influenza virus backbone of the chimeric HA.
  • the chimeric HA polypeptide may also comprise the signal peptide from the HA of the influenza virus that is engineered to express the chimeric HA. In some embodiments, the chimeric HA polypeptide may also comprise the signal peptide, transmembrane domain, and cytoplasmic tail domain from the HA of the influenza virus that is engineered to express the chimeric HA. Also provided herein are nucleic acids comprising nucleotide sequences encoding such a chimeric HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza B virus HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from an influenza A virus HA. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the chimeric HA polypeptide is soluble.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/ 16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a
  • transmembrane domain and a cytoplasmic tail domain from an influenza A virus wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from an influenza A virus, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an influenza B virus with 2, 3, 4,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PYQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid
  • substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior Alaska_7MP0167_2007), or H13 strain (e.g., A/black headed gull/Sweden/1/99).
  • nucleic acids comprising nucleotide sequences encoding said chimeric HA polypeptides.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' non-coding region and 3' non- coding region from an influenza A virus.
  • chimeric hemagglutinin (HA) polypeptides comprising: (a) a hemagglutinin ectodomain from an influenza B virus with one, two, three or all of the following (i) 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the influenza B virus HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA; (ii) 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the influenza B virus HA, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head domain of the influenza B virus HA,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMQT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix,
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).
  • underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues HQSGTY (SEQ ID NO: 57) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues HQSGTY (SEQ ID NO: 57).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues TTLKMHQ (SEQ ID NO: 58) from influenza A virus A/northern
  • shoveler/Netherlands/18/99 the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues TTLKMHQ (SEQ ID NO: 58).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues ATLKMHQ (SEQ ID NO: 70) from influenza A virus A/northern
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 17.
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 34.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues YIP and RIKLSTFNVINAETAPGGPYRL (SEQ ID NO: 63).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • NNTSNQGS SEQ ID NO:64
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NNTSNQGS (SEQ ID NO:64).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues LKSGQF (SEQ ID NO: 65) from influenza A virus A/mallard/interior Alaska/7MP0167/2007.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues LKSGQF (SEQ ID NO: 65).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PTSDMQI (SEQ ID NO: 66) from influenza A virus
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 19.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • NIP andJUELSTHNVINAEVAPGGPYRL (SEQ ID NO: 59) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in influenza B virus B/Yamagata/16/88 TIP are substituted with the following underlined and bold amino acid residues from influenza A virus A/black headed gull/Sweden/1/99.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues NIP and RIEL STHNVINAE VAPGGP YRL (SEQ ID NO: 59).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 are substituted with amino acid residues PDKGASS (SEQ ID NO:60) from influenza A virus A/black headed gull/Sweden/1/99.
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PDKGASS (SEQ ID NO:60).
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KRGNQY (SEQ ID NO: 61) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues
  • KRGNQY (SEQ ID NO: 61).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with the following underlined and bold amino acid residues
  • VSTNMAK (SEQ ID NO: 62) from influenza A virus A/black headed gull/Sweden/1/99.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN (SEQ ID NO: 7) are substituted with amino acid residues VSTNMAK (SEQ ID NO: 62).
  • a chimeric HA polypeptide described herein comprises a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 36.
  • the chimeric HA polypeptides comprise 1, 2, 3, 4, 5 or more amino acid substitutions in the globular head domain of the influenza B virus HA which are outside of the 120 loop, 150 loop, 160 loop and/or 190 helix.
  • the last amino acid of the ectodomain of an influenza B virus HA may be substituted with another amino acid and amino acid 147 of influenza B virus HA (including the signal peptide) may be substituted with another amino acid.
  • amino acid position 156 (glutamic acid) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, lysine).
  • amino acid position 250 (glycine) of the immature influenza B/Yamagata/16/88 virus HA may be substituted with another amino acid (for example, glutamic acid).
  • the influenza B virus is from the Yamagata lineage. In other embodiments, the influenza B virus is from the Victoria lineage. In specific embodiments, the influenza A virus from which the amino acid residues are derived for the amino acid
  • substitutions in one, two, three or more of the loops is an H5 (e.g., A/Vietnam/1203/04(HALo)), H8 (e.g., A/mallard/Sweden/24/2002), Hl l (e.g., A/northern shoveler/Netherlands/18/99), H12 strain (e.g., A_mallard_interior Alaska_7MP0167_2007), or H13 strain (e.g., A/black headed gull/Sweden/1/99).
  • H5 e.g., A/Vietnam/1203/04(HALo)
  • H8 e.g., A/mallard/Sweden/24/2002
  • Hl l e.g., A/northern shoveler/Netherlands/18/99
  • H12 strain e.g., A_mallard_interior Alaska_7MP0167_2007
  • H13 strain e.g
  • the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza A virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding a chimeric HA polypeptide and the 5' non-coding region and 3' non-coding region from an influenza B virus. In some embodiments, the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the HA of the influenza virus backbone of the chimeric HA.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions of the influenza A virus.
  • the nucleic acids comprise nucleotide sequences encoding such a chimeric HA and the 5' and 3' non-coding regions from the influenza virus HA of the influenza virus that is engineered to express the chimeric HA.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 12A and Fig. 12B or the complement thereof.
  • the nucleic acid comprises the nucleotide sequence set forth in Fig. 14A and Fig. 14B or the complement thereof. In a specific embodiment, the nucleic acid comprises the nucleotide sequence set forth in Fig. 16A and Fig. 16B or the complement thereof. In a specific embodiment, the nucleic acid comprises the nucleotide sequence set forth in Fig. 18A and Fig. 18B or the complement thereof.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid substitutions within the 120 loop, 150 loop, 160 loop or 190 helix of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more amino acid residues in the 120 loop, 150 loop, 160 loop or 190 helix of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid substitutions within the 120 loop of the globular head domain of the first influenza B virus strain and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acid residues in the 120 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from an first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid substitutions within the 150 loop of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid residues in the 150 loop of the globular head of the in first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of a second influenza B virus strain HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin
  • ectodomain from a first influenza B virus strain with 2, 3, 4, 5 or more amino acid substitutions within the 160 loop of the globular head domain of the first influenza B virus strain HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B vims strain, wherein the amino acid substitutions substitute 2, 3, 4, 5 or more amino acid residues in the 160 loop of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • chimeric hemagglutinin (HA) polypeptides comprising (i) a hemagglutinin ectodomain from a first influenza B virus strain with 2, 3, 4, 5, 6, 7, 8 or more amino acid substitutions within the 190 helix of the globular head domain of the influenza B virus HA and (ii) a signal peptide, a transmembrane domain and a cytoplasmic tail domain from a second influenza B virus strain, wherein the amino acid substitutions substitute 2, 3, 4, 5, 6, 7, 8 or more amino acid residues in the 190 helix of the globular head of the first influenza B virus strain HA with amino acid residues found in a corresponding region of the globular domain of an influenza A virus HA.
  • the following underlined and bold amino acid residues in the 120 loop of influenza B virus B/Yamagata/16/88 TIP and NIRLSTHNVINAERAPGGPYRL are substituted with the following underlined and bold amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2) from influenza A virus A/Vietnam/1203/04 (HALo).
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • amino acid residues FIP and KIQLSTKNVINAEHAPGGPYRL (SEQ ID NO: 2).
  • NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 NVTSRNG (SEQ ID NO: 3) are substituted with amino acid residues YQGKSS (SEQ ID NO:4).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • P YQGKSS (SEQ ID NO: 19) from influenza A virus A/Vietnam/1203/04 (HALo).
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues P YQGKSS (SEQ ID NO: 19).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKNSTY (SEQ ID NO: 6) from influenza A virus A/Vietnam/1203/04 (HALo).
  • the following acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKNSTY (SEQ ID NO: 6).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues NDAAMOT (SEQ ID NO: 8) from influenza A virus A/Vietnam/1203/04 (HALo).
  • amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues NDAAMQT (SEQ ID NO: 8).
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 13.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 30.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • amino acid residues HIP and RIRLSTYNVINAETAPGGPYRL (SEQ ID NO: 51).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • NASTGGQS SEQ ID NO: 52
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues NASTGGQS (SEQ ID NO: 52).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with the following bold and underlined amino acid residues KKKADTY (SEQ ID NO: 53) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA (SEQ ID NO: 5) are substituted with amino acid residues KKKADTY (SEQ ID NO: 53).
  • the following underlined and bold amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with the following bold and underlined amino acid residues KKKPDTY (SEQ ID NO: 68) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 160 loop of influenza B virus B/Yamagata/16/88 RDNKTA are substituted with amino acid residues KKKPDTY (SEQ ID NO: 68).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues ADAKMQT (SEQ ID NO: 54) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues ADAKMQT (SEQ ID NO: 54).
  • the following underlined and bold amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNOMKN are substituted with the following underlined and bold amino acid residues PDAKMQT (SEQ ID NO: 69) from influenza A virus A/Mallard/Sweden/24/2002 virus.
  • the following amino acid residues in the 190 helix of influenza B virus B/Yamagata/16/88 NKNQMKN are substituted with amino acid residues PDAKMQT (SEQ ID NO: 69).
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 15.
  • a chimeric HA polypeptide described herein comprises one, two, three, or all of the following: a 120 loop, a 150 loop, a 160 loop, and/or a 190 helix with the amino acid sequences of the 120 loop, 150 loop, 160 loop, and/or 190 helix, respectively, set forth in Figure 32.
  • NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with the following underlined and bold amino acid residues LIP and KIEL STSNVINAE VAPGGP YRL (SEQ ID NO: 55) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in influenza B virus B/Yamagata/ 16/88 TIP and NIRLSTHNVINAERAPGGPYRL (SEQ ID NO: 1) are substituted with amino acid residues LIP and KIEL ST SNVINAEVAPGGP YRL (SEQ ID NO: 55).
  • PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues PFGSSNS (SEQ ID NO:56).
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO: 67) from influenza A virus A/northern shoveler/Netherlands/18/99.
  • the following amino acid residues in the 150 loop of influenza B virus B/Yamagata/16/88 PNVTSRNG (SEQ ID NO: 18) are substituted with amino acid residues KFGSSNS (SEQ ID NO:67).

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