Influenza virus immunizing epitope

A method of producing influenza virus like particles (VLPs) in a plant, a portion thereof, or a plant cell, said method comprising:

• a) introducing by agroinfiltration into the plant, the portion thereof, or the plant cell a nucleic acid comprising
• a nucleotide sequence having from 90% to 100% identity to SEQ ID NO:
• 17, the nucleotide sequence encoding an influenza virus hemagglutinin (HA) comprising a HA1 domain,
• wherein said HA1 domain is modified to be free of N-linked glycosylation sites at positions 154 and/or 156;
• at positions 165 and/or 167;
• and at positions 286 and/or 288, wherein
• at least one of positions 154, 165, or 286 are modified to be an amino acid other than asparagine, or
• at least one of positions 156, 167, or 288 are modified to be an alanine or an amino acid other than serine, or threonine,
• wherein the numbering of said positions are compared to SEQ ID NO:
• 34
• wherein the nucleotide sequence is operatively linked to a nucleic acid sequence encoding a signal peptide and a regulatory region active in the plant, the portion thereof, or the plant cell;
• and
• wherein the HA has hemagglutinin activity as determined by using a hemagglutination assay;
• b) incubating the plant, the portion thereof, or the plant cell under conditions that permit expression of the nucleic acid, thereby producing said VLPs,
• wherein the nucleic acid is transiently expressed in the plant, the portion thereof, or the plant cell;
• c) harvesting the plant, the portion thereof, or the plant cell;
• and
• d) purifying the VLPs, wherein the VLPs are characterized as not passing through a 100 kDa membrane.