Recombinant influenza viruses for vaccines and gene therapy

An expression plasmid comprising an RNA polymerase I (pol I) promoter, a pol I terminator sequence, and a influenza nucleic acid segment which is selected from the group consisting of PA, PB1, PB2, NP, NA, M, M1, M2, and NS2.

A plasmid-based system for the generation of orthomyxoviruses from cloned viral cDNA comprising a plurality of plasmids sufficient to produce said viruses, said plasmids comprising;

• (a) plasmids comprising cDNA corresponding to viral genomic segments, and
• (b) plasmids comprising cDNA encoding viral polypeptides.

A method for preparing an orthomyxovirus-specific immunogenic composition comprising purifying a virion from a host cell having a plurality of plasmids comprising cDNA corresponding to viral genomic segments, and plasmids comprising cDNA encoding viral cDNA encoding viral polypeptides, wherein said plasmids are sufficient to produce said virion when introduced into a host cell.

An immunogenic composition comprising an orthomyxovirus virion, wherein viral internal proteins of the virion are from a virus strain well adapted to grow in culture or from an attenuated strain, or both, and viral antigen proteins of the virion are from a pathogenic virus strain.

An immunogenic composition comprising an orthomyxovirus virion produced in the absence of helper virus.

An immunogenic composition comprising an orthomyxovirus virion produced in the absence of helper virus or an in vitro ribonucleoprotein complex.