Influenza virus populations, methods of use and methods of making thereof

A method of inducing interferon in an individual having or suspected of having a viral infection, comprising administering to the individual a live attenuated influenza virus composition comprising

• a subpopulation of interferon inducing particles that contain a delNS1 gene, or a subpopulation of interferon inducing particles that contain a full size NS1 gene, and
• a subpopulation of defective-interfering particles,
• wherein the ratio of defective-interfering particles to interferon-inducing particles is greater than 10, and
• wherein the subpopulation of interferon-inducing particles, the subpopulation of defective-interfering particles, or both, is UV irradiated at 254±20 nm and at 500 to 2,500 ergs/mm2.

A method of screening an influenza virus preparation for hyper interferon-inducing capacity which exceeds by 10 fold or higher the basal levels induced by wild type influenza viruses, comprising

• preparing an influenza virus preparation from an influenza virus with a delNS1 gene or a full-size NS1 gene that expresses an NS1 protein lacking the capacity to suppress interferon induction, wherein the preparation contains interferon-inducing particles and defective-interfering particles, and
• quantifying the ratio of defective-interfering particles to interferon-inducing particles in mammalian cells, and
• determining that the influenza virus preparation is suitable for treating mammalian species when the ratio of defective-interfering particles to interferon-inducing particles in the influenza virus preparation is greater than 10:1 in mammalian cells, or
• quantifying the ratio of defective-interfering particles to interferon-inducing particles in avian cells, and
• determining that the influenza virus preparation is suitable for treating avian species when the ratio of defective-interfering particles to interferon-inducing particles in the influenza virus preparation is greater than 10 in avian cells.