Characterization and inactivation of endogenous retroviruses in chinese hamster ovary cells

An engineered cell, preferably of a mammalian cell line such as an engineered CHO cell, including an engineered CHO-K1 cell, comprising:

• a genome of the cell comprising:
• a sequence comprising a gag gene, an env gene, a pol gene and long terminal repeats (LTR) and comprising at least one alteration in the gag gene, env gene, pol gene and/or the LTRs, wherein the sequence is selected from:
• (i) SEQ ID NO:
• 3,
• (ii) SEQ ID NO:
• 1,
• (iii) a variant of (i) or (ii);
• or
• (iv) a sequence having more than 95%, 96%, 97%, 98%, 99% sequence identity with (i) and/or (ii) outside the gag, env, pol gene and/or the LTRs,
• said at least one alteration being selected from the group consisting of insertions, deletions, substitutions and combinations thereof.

An engineered cell, preferably of a mammalian cell line such as an Preliminary Amendment engineered CHO cell, including an engineered CHO-K1 cell, comprising:

• a genome of the cell comprising group 1 type-C ERV sequences integrated into the genome, wherein at least one, including a singular, full-length group 1 type-C ERV sequence, such as SEQ ID NO:
• 3 or at least 10%, 20%, 30%, 40%, 50%, 60%, 70% 80% 90% or 100% consecutive nucleotides of SEQ ID NO:
• 3 and optionally 5′ and/or 3′ flanking regions of SEQ ID NO:
• 3, including 1-50, 30-100, 50-150, 100-200 or more than 200, 300, 400 or more than 500 consecutive nucleotides flanking SEQ ID NO:
• 3 are deleted from the genome.

A detection kit and its use comprising:

• (i) at least one primer against SEQ ID NO:
• 3, and/or
• (ii) at least one primer against SEQ ID NO:
• 4 or 5, and
• instructions how to use the primers of (i) and/or (ii) to detect the presence or absence of SEQ ID NO:
• 1, of SEQ ID NO:
• 3 from a genome of a CHO cell or a mutation within SEQ ID NO:
• 3 of the genome of the CHO cell.