This invention provides an attenuated virus which comprises a modified viral genome containing nucleotide substitutions engineered in multiple locations in the genome, wherein the substitutions introduce synonymous deoptimized codons into the genome. The instant attenuated virus may be used in a vaccine composition for inducing a protective immune response in a subject. The invention also provides a method of synthesizing the instant attenuated virus. Further, this invention further provides a method for preventing a subject from becoming afflicted with a virus-associated disease comprising administering to the subject a prophylactically effective dose of a vaccine composition comprising the instant attenuated virus.

The invention provides for methods of viral inactivation using high temperature short time (HTST) treatment and adjustment of various parameters such that generation of precipitate and depositions of precipitate are reduced and/or minimized.

The present invention relates, in general, to attenuated swine influenza viruses having an impaired ability to antagonize the cellular interferon (IFN) response, and the use of such attenuated viruses in vaccine and pharmaceutical formulations. In particular, the invention relates to attenuated swine influenza viruses having modifications to a swine NS1 gene that diminish or eliminate the ability of the NS1 gene product to antagonize the cellular IFN response. These viruses replicate in vivo, but demonstrate decreased replication, virulence and increased attenuation, and therefore are well suited for use in live virus vaccines, and pharmaceutical formulations.