Chinese Hamster Ovary Cells (CHO) are often used to make biotherapeutic proteins because of the mammalian post translational modification machinery and there are good tools to manipulate the cells as required.
However, co-purified host cell proteins (HCP) from the production cell line can cause unwanted side effects and therapeutic companies need to define and control the parameters for potential inclusions in the finished product. Of primary concern are immunogenic and co-purified proteins. There are a number of methods to determine HCP – including Mass Spectrophotometry and 2D Western blotting, as well as ELISA kits raised against a full CHO host cell lysate. There are drawbacks to each of these methods, from cost, lack of identification of proteins and inaccuracies caused by test limitation.
Phospholipase B-Like 2 (PLBL2) is a protein that can frequently be co-purified with monoclonal antibodies in such abundance that it can cause non-linear dilution results in a general HCP- ELISA assay for CHO proteins (CHOP-ELISA)The antibody species detecting PLBL-2 in these CHOP ELISA tests may not be present in enough quantity to identify the level of PLBL2 accurately within the parameters of the assay’s quantitation limit. Levels of PLBL2 may still be high in assays showing low total CHOP1
Although there may be a number of hitchhiker proteins co-purified that need to be assessed depending on the therapeutic in question, PLBL2 appears to be a single CHOP that independently co-purifies with many antibodies. CHO expression of PLBL2 can vary up to 10 fold in production runs and variation is also seen in blank runs.
Resource sites like Biophorum are collating information on CHO proteins that are potentially immunogenic, please check their website for latest updates, but here are links to reagents that may be of interest in HCP research.