Title of the Thesis:  “Development of a Method to Improve Host Cell Protein Identification in Biotherapeutics Using a Spiked-in Carrier Proteome”

Purification of recombinant protein-based biotherapeutics is monitored for contamination by host cell proteins (HCPs). The current method is the Enzyme-Linked Immunosorbent Assay (ELISA), which is limited by the inability to identify HCPs individually. Liquid chromatography-mass spectrometry (LC-MS)-based proteomics methods are desired to identify HCPs in biotherapeutic formulations. However, LCMS-based HCP analysis is hindered by a high background of recombinant protein amidst the HCPs of interest. Isobaric tags such as Tandem Mass Tags (TMT) have recently been used to develop the carrier proteome approach, where an isobaric mass-tagged proteome of interest is spiked into a sample to increase peptide identifications for low abundance proteins of the same proteome.

In this thesis, I investigated whether a TMT labelled carrier proteome could be used to improve the identification of HCPs by LC-MS-based proteomics. To do this, TMT-tagged E. coli peptides as an HCP model were spiked into alternatively labelled recombinant bovine serum albumin (BSA) peptides as a mock therapeutic. While the assay increased the identification of HCPs, co-isolated (isobarically-tagged) peptide ions from BSA interfered with the E. coli detection. To alleviate this, an additional spike-in of TMT-labelled BSA allowed the filtering of spectra with interfering ions from the analysis and confident E. coli peptide detection. The method represents a novel strategy for detecting HCPs in the biotherapeutics industry.

June 17 at 9:00 am in AVC, Room 278

Everyone is welcome to attend.