The invention relates to an immunogenic composition comprising influenza virus antigens derived from at least 5 influenza virus strains and one or more compounds of formula (I) or physiologically acceptable salts or esters thereof: wherein: R.sub.1 represents hydrogen or C.sub.1-6 alkyl; R.sub.2 represents C.sub.1-6 alkyl; and R.sub.3 represents C.sub.1-6 alkyl. The invention also relates to methods of preparing the immunogenic composition, to pharmaceutical and vaccine compositions comprising the immunogenic composition and to use of the immunogenic, pharmaceutical and vaccine compositions for preventing influenza virus infection.

Provided is a production method for reassortant influenza virus having genome segments of two or more kinds of influenza virus in the case where an antigenic strain and donor strain have similar antigenicities. The production method makes use of the first influenza virus containing an antigenic protein, the second influenza virus having an antigenic protein having antigenicity similar to that of the strain, and the third influenza virus having an antigenic protein having antigenicity different from that of the strain, and includes the steps of: coculturing the strain and the strain by infecting a host therewith, to produce reassortant influenza viruses; selecting influenza virus having the antigenic protein from the viruses; then coculturing the strain and the selected strain by infecting a host therewith; and selecting influenza virus having the antigenic protein from reassortant influenza viruses produced from the strain and the strain.

Disclosed is an adapted Madin-Darby canine kidney cell line capable of suspension culture in the absence of serum, and a chemically-defined medium for culture of the adapted MDCK cell line. Further disclosed are culture methods for growing the adapted MDCK cell line and methods for producing a vaccine from the adapted MDCK cell line grown in the chemically-defined medium.

New influenza donor strains for the production of reassortant influenza B viruses are provided.

Described are methods for preparing virosomes comprising the steps of: (a) providing an enveloped virus, and optionally inactivating the virus; (b) solubilizing the viral envelopes in a first solubilizing agent; (c) pre-solubilizing exogenous components in a second solubilizing agent; (d) adding the pre-solubilized exogenous components to the solubilized viral envelopes; and (e) reconstituting virosomal membranes by removing the solubilizing agent. According to the disclosure, the viral envelopes and the exogenous components are (pre-)solubilized at a temperature below 33 C.

Disclosed is an adapted Madin-Darby canine kidney cell line capable of suspension culture in the absence of serum, and a chemically-defined medium for culture of the adapted MDCK cell line. Further disclosed are culture methods for growing the adapted MDCK cell line and methods for producing a vaccine from the adapted MDCK cell line grown in the chemically-defined medium.

Compositions and methods to prepare influenza virus-like particles (VLPs) are provided.

A method of producing a virus like particle (VLP) in a plant comprising modified 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. The nucleotide sequence encoding the HA may be selected from the group consisting of B HA, C, H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, and H16. 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.

New influenza donor strains for the production of reassortant influenza B viruses are provided.

Recombinant expression of influenza vims surface proteins in the fungus Myceliophthora thermophila strain Cl is provided. The recombinant proteins are for use in influenza vaccine compositions.