Polycistronic expression of antibodies

A polycistronic vector for expressing functional antibodies in eukaryotic host cells which vector comprises a polycistronic transcription system comprising the following elements operably linked in the 5′ to 3′ orientation:

• (i) a promoter operable in a eukaryotic cell;
• (ii) a first cistron comprising a first DNA sequence encoding an antibody light chain which optionally comprises at its 5′ terminus a signal peptide coding sequence operable in eukaryotic cells wherein said first DNA sequence does not comprise at its 3′ end a poly A sequence and wherein said first DNA sequence comprises a 5′ start codon and a 3′ terminal stop codon;
• (iii) an internal ribosome entry site (IRES) obtained from a member selected from the group consisting of a cardiovirus, a herpes virus and a poliovirus;
• and
• (iv) at least a second cistron comprising the following elements:
• (a) a second DNA sequence encoding an antibody heavy chain, wherein said second DNA optionally comprises at its 5′ terminus a signal peptide coding sequence operable in eukaryotic cells and wherein said second DNA sequence comprises a poly A sequence at its 3′ terminus only if the DNA sequence is the 3′ most coding sequence in the polycistron, and further comprises a start and stop codon at the 5′ and 3′ termini, respectively of said second DNA sequence;
• wherein the first DNA sequence is expressed at a ratio ranging between 10:1 and 1:1 with respect to the second DNA sequence in a eukaryotic host cell containing the polycistronic vector.