Signal for packaging of influenza virus vectors

An influenza viral vector, comprising influenza virus incorporation sequences, which vector comprises:

• sequences corresponding to the 3N noncoding region of influenza virus PB2 vRNA and optionally about 150 to about 250 nucleotides corresponding to N-terminal PB2 coding sequences that are adjacent to the 3N noncoding region in the wild-type viral PB2 gene segment, a heterologous nucleic acid segment comprising sequences corresponding to an open reading frame, and the 5N noncoding region of PB2 vRNA and optionally about 150 to about 250 nucleotides corresponding to C-terminal PB2 coding sequences that are adjacent to the 5N noncoding region in the wild-type viral PB2 gene segment, wherein the about 150 to about 250 nucleotides include incorporation sequences, wherein the vector includes the about 150 to about 250 nucleotides corresponding to N-terminal PB2 coding sequences, the about 150 to about 250 nucleotides corresponding to C-terminal PB2 coding sequences, or the about 150 to about 250 nucleotides corresponding to N-terminal PB2 coding sequences and the about 150 to about 250 nucleotides corresponding to C-terminal PB2 coding sequences;
• wherein vRNA corresponding to sequences in the vector, when present in a cell expressing influenza virus proteins and comprising vRNAs other than the vRNA corresponding to the vector, is packaged into virions more efficiently than a corresponding vector that lacks the about 150 to about 250 nucleotides corresponding to N-terminal PB2 coding sequences and the about 150 to about 250 nucleotides corresponding to C-terminal PB2 coding sequences.