The present invention relates to a new method for rescuing an influenza virus and a composition therefor. The method comprises providing a host cell stably integrated with and expressing influenza virus PA, PB1, PB2 and NP genes, and introducing an influenza virus rescue system in which a stop codon is introduced into the PA, PB1, PB2 and NP genes respectively into the host cell to achieve virus rescue. The produced virus particles can be used as a live attenuated influenza vaccine, which is characterized in that, since the genes encoding the related proteins are mutated, it has no replication and proliferation ability in human and normal animal cells, and replication and proliferation can be achieved only in the host cells constructed above and it can fully stimulate the body immunity and effectively protect the body while ensuring the safety.

Disclosed is a viral vector comprising (a) a cDNA of a recombinant viral RNA having a sequence of a Borna disease viral genome comprising a disrupted G gene of the Borna disease viral genome and an inserted G gene of an avian bornaviral genome, wherein the cDNA of the recombinant viral RNA has at least an N gene, an X gene, a P gene and an L gene of the Borna disease viral genome in the same order as in the Borna disease viral genome and has an inserted foreign gene; (b) DNAs encoding ribozymes; and (c) a promoter sequence, wherein (b) the DNAs encoding ribozymes are located upstream and downstream of (a) the cDNA of the recombinant viral RNA, and (a) the cDNA of the recombinant viral RNA and (b) the DNAs encoding ribozymes are located downstream of (c) the promoter sequence. The present invention can be used as a gene introduction technique that does not affect a host chromosome and can be suitable for the application in various fields, such as the treatment and prevention of brain and neurological diseases, visualization techniques of nerve cells in the field of neuroscience, etc.

Disclosed is a viral vector comprising (a) a cDNA of a recombinant viral RNA having a sequence of a Borna disease viral genome comprising a disrupted G gene of the Borna disease viral genome and an inserted G gene of an avian bornaviral genome, wherein the cDNA of the recombinant viral RNA has at least an N gene, an X gene, a P gene and an L gene of the Borna disease viral genome in the same order as in the Borna disease viral genome and has an inserted foreign gene; (b) DNAs encoding ribozymes; and (c) a promoter sequence, wherein (b) the DNAs encoding ribozymes are located upstream and downstream of (a) the cDNA of the recombinant viral RNA, and (a) the cDNA of the recombinant viral RNA and (b) the DNAs encoding ribozymes are located downstream of (c) the promoter sequence. The present invention can be used as a gene introduction technique that does not affect a host chromosome and can be suitable for the application in various fields, such as the treatment and prevention of brain and neurological diseases, visualization techniques of nerve cells in the field of neuroscience, etc.

The invention relates to a method for producing influenza infectious viruses wherein CHO cells are infected with a seed of infectious influenza virus which has been generated by transfecting cells with an appropriate set of expression vectors. The invention also relates to a recombination cassette, and to a vector comprising said recombination cassette, that may be used in methods for producing infectious viruses, and particularly in the method according to the invention.