The invention relates to methods for producing a propagation-competent strain of a mutant Reoviridae virus, and to a propagation-competent strain of a mutant Reoviridae virus that is obtainable by a method of the invention. The invention further relates to a propagation-competent strain of a mutant Reoviridae virus, comprising a deletion of a genetic region that is relevant for propagation of the virus, and to a vaccine, comprising a propagation-competent strain of a mutant Reoviridae virus.

A method of using a cell to produce virus is provided involving growing cells under hyperosmotic conditions during a growth phase of the cells, infecting or transfecting the cells grown under hyperosmotic conditions with a virus, and maintaining the infected or transfected cells under less stressful conditions during a production phase of the infected or transfected cells to produce more of the virus. Viral productivity is improved by this method.

Provided herein are liquid viral formulations useful for the stabilization and storage of viruses and methods of preparing these formulations. The liquid viral formulations described herein include a virus (e.g., a purified virus) and a non-viral composition including excipients and a liquid carrier. The formulations can be used, for example, to retain the infectivity or immunogenicity of viruses during periods of storage.

Provided herein are lyophilized viral formulations useful for the stabilization and storage of viruses and methods of preparing these formulations. The lyophilized viral formulations described herein include a virus (e.g., a purified virus) and a non-viral composition including excipients. The formulations can be used, for example, to retain the infectivity or immunogenicity of viruses during periods of storage.