Recombinant influenza B strain haemagglutinin antigens, polynucleotides encoding the antigens and immunogenic compositions comprising the antigens and polynucleotides.

The present disclosure provides a polypeptide fragment comprising a polypeptide of a modified hemagglutinin protein, wherein said modified hemagglutinin protein comprises a linker peptide replacing the polypeptide in the cytoplasmic domain of hemagglutinin protein, wherein the hemagglutinin protein is obtained from at least one seasonal strain of influenza virus, wherein said polypeptide of the modified hemagglutinin protein is having at least 80%, or at least 90%, or at least 95%, or at least 97% sequence identity to at least one sequence selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14, SEQ ID NO: 16, SEQ ID NO: 18, SEQ ID NO: 20, SEQ ID NO: 22, SEQ ID NO: 24, SEQ ID NO: 26, SEQ ID NO: 28, and SEQ ID NO: 30.

A method of producing a virus like particle (VLP) in a plant comprising modified H3 hemagglutinin is provided. The method comprises introducing a nucleic acid comprising a regulatory region active in the plant and operatively linked to a nucleotide sequence encoding a modified influenza hemagglutinin (HA) protein into the plant, or portion of the plant, the modified HA protein comprises a modified proteolytic loop. Followed by incubating the plant or portion of the plant under conditions that permit the expression of the nucleic acids, thereby producing the VLP. The modified proteolytic loop may comprise one or more protease cleavage sites exhibiting reduced or abolished cleavage by a protease. Also described is a virus like particle (VLP) produced by the method, and plants expressing the VLP. The virus like particle (VLP) may comprise plant-specific N-glycans, or modified N-glycans.

The present invention relates to a messenger RNA (mRNA)-based immunogenic composition that is capable of inducing a mammalian cell to produce an influenza virus-like particle (VLP). The immunogenic composition comprises one or more mRNAs encoding an influenza virus matrix 1 (M1) protein and one or more influenza virus hemagglutinin (HA) proteins and/or one or more influenza virus neuraminidase (NA) proteins.