Patent ID: 7892790

Claim:
A Chinese Hamster Ovary (CHO) cell, wherein said CHO cell a) contains a structural gene located in the genome of said CHO cell which encodes and expresses the Epstein Barr Virus Nuclear Antigen 1 (EBNA-1); b) contains an episome, wherein said episome comprises (i) a prokaryotic origin of replication; (ii) a selection marker; (iii) a single Epstein Barr Virus (EBV) derived element, wherein the single EBV derived element is an EBV origin of replication (oriP); (iv) an expression cassette suitable for the expression of a heterologous polypeptide in said CHO cell, whereby said expression cassette comprises a promoter sequence, a 5′ untranslated region, a nucleic acid sequence encoding said heterologous polypeptide and a 3′ untranslated region comprising a polyadenylation signal; wherein said episome does not contain a nucleic acid encoding EBNA-1; and c) does not contain the large T-antigen of Polyoma virus.