A recombinant cell comprising integrated in its genome, at least one copy of a nucleic acid encoding a T7 phage RNA polymerase or its nuclear form (nlsT7), at least one copy of a nucleic acid encoding a nucleoprotein of a non-segmented negative-strand RNA virus and at least one copy of a nucleic acid encoding a phosphoprotein of a non-segmented negative-strand RNA virus, or functional derivatives thereof, and at least one copy of a DNA flap functionally associated with said nucleic acid(s), and wherein said T7 phage RNA polymerase or its nuclear form (nlsT7), said N and P proteins are expressed in a stable manner, and wherein said functional derivatives of the T7 phage RNA polymerase or its nuclear form (nlsT7) and/or the nucleoprotein and/or the phosphoprotein are defined as variants of the T7 phage RNA polymerase or its nuclear form (nlsT7) and/or the N protein and/or the P protein which keep the activity of the protein they are derived from, as a ribonucleoprotein complex (RNP complex), functional in transcription and replication in a virus genome, in a rescue system enabling the production of non-segmented negative-sense RNA viruses from cloned cDNA, said variants being encoded by a nucleic acid selected from the group consisting of: a) a nucleic acid hybridizing in high stringency conditions (prewashing solution for the nitrocellulose filters 5X SSC, 0.5% SDS, 1.0 mM EDTA (pH 8.0), hybridisation conditions of 50% formamide, 6X SSC at 42°C and washing conditions at 68°C, 0.2X SSC and 0.1% SDS) with a nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 and the P protein of SEQ ID NO: 15 of an identified non-segmented negative-strand RNA strain or virus; b) a nucleic acid presenting at least 80%, preferably 90%, more preferably 95% or even 99% similarity with a nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 or the P protein of SEQ ID NO: 15, said similarity being calculated over the entire length of both sequences; and c) a nucleic acid differing from the nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 or the P protein of SEQ ID NO: 15 by at least one nucleotide, optionally conservative, substitution, preferably 1, 2, 3, 4 or 5 substitution(s),_by at least one nucleotide deletion or addition, preferably 1, 2, 3, 4 or 5 nucleotide deletion or addition; or, being a fragment representing at least 70%, particularly 80%, and more particularly 90% or even 95% of the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, N protein of SEQ ID NO: 13 or P protein of SEQ ID NO: 15. a) a nucleic acid hybridizing in high stringency conditions (prewashing solution for the nitrocellulose filters 5X SSC, 0.5% SDS, 1.0 mM EDTA (pH 8.0), hybridisation conditions of 50% formamide, 6X SSC at 42°C and washing conditions at 68°C, 0.2X SSC and 0.1% SDS) with a nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 and the P protein of SEQ ID NO: 15 of an identified non-segmented negative-strand RNA strain or virus; b) a nucleic acid presenting at least 80%, preferably 90%, more preferably 95% or even 99% similarity with a nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 or the P protein of SEQ ID NO: 15, said similarity being calculated over the entire length of both sequences; and c) a nucleic acid differing from the nucleic acid encoding the wild type T7 phage RNA polymerase of SEQ ID NO: 9 or its nuclear form (nlsT7) of SEQ ID NO: 11, the N protein of SEQ ID NO: 13 or the P protein of SEQ ID NO: 15 by at least one nucleotide, optionally conservative, substitution, preferably 1, 2, 3, 4 or 5 substitution(s),_by at least one nucleotide deletion or addition, preferably 1, 2, 3, 4 or 5 nucleotide deletion or addition;