Methods for producing high titre vectors and compositions used in such methods

A producer cell comprising:

• (ii) a first nucleotide sequence (NS) encoding a toxic viral envelope protein operably linked to a promoter;
• wherein the promoter is operably linked to at least one copy of a TRE;
• (iii) a second NS wherein the second NS comprises a sequence encoding a tetracycline modulator;
• (iii) a third NS encoding a retrovirus nucleocapsid protein;
• and
• (iv) a fourth NS comprising a retroviral sequence capable of being encapsidated in the nucleocapsid protein;
• such that the retroviral vector particle titre obtainable from the producer cell is regulatable by tetracycline and an initial stimulus with sodium butyrate or functional analogues thereof.

A virus producer cell comprising:

• (i) a first nucleotide sequence (NS) encoding a toxic viral envelope protein operably linked to a promoter;
• and wherein the promoter is operably linked to at least one copy of a TRE;
• (ii) a second NS wherein the second NS comprises a sequence encoding a tetracycline modulator;
• and
• (iii) a third NS comprising a viral sequence sufficient to produce viral vector particles from the cell;
• such that the viral vector particle titre obtainable from the producer cell is regulatable by tetracycline and an initial stimulus with sodium butyrate or functional analogues thereof.

A method for producing a retroviral vector wherein the method comprises:

• (i) selecting a host cell for retroviral vector production;
• (ii) introducing into the host cell:
• a first nucleotide sequence (NS) encoding a toxic viral envelope protein operably linked to a promoter;
• and wherein the promoter is operably linked to at least one copy of a TRE;
• a second NS wherein the second NS comprises a sequence encoding a tetracycline modulator;
• a third NS encoding a retrovirus nucleocapsid protein;
• a fourth NS comprising a retroviral sequence capable of being encapsidated in the nucleocapsid protein;
• and
• (iii) incubating the host cell in a culture medium comprising tetracycline and an initial stimulus with sodium butyrate or functional analogues thereof such that sufficient retroviral vector transducing particles are producible from the host cell.