Detection and quantitation of host cell proteins in monoclonal antibody drug products using automated sample preparation and data-independent acquisition LC-MS/MS / 药物分析学报

Ensuring the removal of host cell proteins (HCPs) during downstream processing of recombinant pro-teins such as monoclonal antibodies (mAbs) remains a challenge.Since residual HCPs might affect product stability or safety,constant monitoring is required to demonstrate their removal to be below the regulatory accepted level of 100 ng/mg.The current standard analytical approach for this procedure is based on ELISA;however,this approach only measures the overall HCP content.Therefore,the use of orthogonal methods,such as liquid chromatography-mass spectrometry (LC-MS),has been established,as it facilitates the quantitation of total HCPs as well as the identification and quantitation of the indi-vidual HCPs present.In the present study,a workflow for HCP detection and quantitation using an automated magnetic bead-based sample preparation,in combination with a data-independent acquisi-tion (DIA) LC-MS analysis,was established.Employing the same instrumental setup commonly used for peptide mapping analysis of mAbs allows for its quick and easy implementation into pre-existing workflows,avoiding the need for dedicated instrumentation or personnel.Thereby,quantitation of HCPs over a broad dynamic range was enabled to allow monitoring of problematic HCPs or to track changes upon altered bioprocessing conditions.

Comparison of protein precipitation methods for sample preparation prior to proteomic analysis of Chinese hamster ovary cell homogenates

BACKGROUND: Chinese hamster ovary (CHO) cells are the workhorse for obtaining recombinant proteins. Proteomic studies of these cells intend to understand cell biology and obtain more productive and robust cell lines for therapeutic protein production in the pharmaceutical industry. Because of the great importance of precipitation methods for the processing of samples in proteomics, the acetone, methanol-chloroform (M/C), and trichloroacetic acid (TCA)-acetone protocols were compared for CHO cells in terms of protein recovery, band pattern resolution, and presence on SDS-PAGE. RESULTS: Higher recovery and similar band profile with cellular homogenates were obtained using acetone precipitation with ultrasonic bath cycles (104.18 ± 2.67%) or NaOH addition (103.12 ± 5.74%), compared to the other two protocols tested. TCA-acetone precipitates were difficult to solubilize, which negatively influenced recovery percentage (77.91 ± 8.79%) and band presence. M/C with ultrasonic homogenization showed an intermediate recovery between the other two protocols (94.22 ± 4.86%) without affecting protein pattern on SDS-PAGE. These precipitation methods affected the recovery of low MW proteins (< 15 kDa). CONCLUSIONS: These results help in the processing of samples of CHO cells for their proteomic study by means of an easily accessible, fast protocol, with an almost complete recovery of cellular proteins and the capture of the original complexity of the cellular composition. Acetone protocol could be incorporated to sample-preparation workflows in a straightforward manner and can probably be applied to other mammalian cell lines as well.

Increasing transgenic expression in recombinant Chinese hamster ovary cells using introns in different directions / 生物工程学报

The aim of this study is to investigate the effect of the chimeric intron in different directions on the expression of the nerve growth factor (NGF) in recombinant Chinese hamster ovary (CHO) cells. The chimeric intron that contained the splice sequence of the first intron of the human β-globin and the human immunoglobulin heavy chain variable region intron was used. NGF gene was cloned into the expression vectors containing the chimeric intron in the forward or reverse direction, followed by transfecting into CHO cells, and screened under G418 to produce the stable transfected CHO cells. Fluorescence quantitative PCR, ELISA, and Western blotting were performed to detect the recombinant NGF gene expression in CHO cells. The results showed that the chimeric introns could significantly enhance the expression of NGF in recombinant CHO cells. Moreover, the enhancing effect on NGF expression level by the intron in the forward direction showed stronger than that of the reverse direction both at mRNA and protein level. In conclusion, the chimeric intron could increase NGF expression in stably transfected CHO cells and the effect is associated with the direction of the intron insertion.

A pilot study of the modulation of sirtuins on arylamine -acetyltransferase 1 and 2 enzymatic activity

Arylamine -acetyltransferase (NAT; E.C. 2.3.1.5) enzymes are responsible for the biotransformation of several arylamine and hydrazine drugs by acetylation. In this process, the acetyl group transferred to the acceptor substrate produces NAT deacetylation and, in consequence, it is susceptible of degradation. Sirtuins are protein deacetylases, dependent on nicotine adenine dinucleotide, which perform post-translational modifications on cytosolic proteins. To explore possible sirtuin participation in the enzymatic activity of arylamine NATs, the expression levels of NAT1, NAT2, SIRT1 and SIRT6 in peripheral blood mononuclear cells (PBMC) from healthy subjects were examined by flow cytometry and Western blot. The activity of the sirtuins on NAT enzymatic activity was analyzed by HPLC, in the presence or absence of an agonist (resveratrol) and inhibitor (nicotinamide) of sirtuins. We detected a higher percentage of positive cells for NAT2 in comparison with NAT1, and higher numbers of SIRT1+ cells compared to SIRT6 in lymphocytes. NAT2 activity in the presence of NAM inhibitors was higher than in the presence of its substrate, but not in the presence of resveratrol. In contrast, the activity of NAT1 was not affected by sirtuins. These results showed that NAT2 activity might be modified by sirtuins.

Influence of ubiquitous chromatin opening element on the antibody expression in CHO cells / 中国药科大学学报

Ubiquitous chromatin opening element ( UCOE ) , composed of the promoters of human housekeeping genes, prevents transgene from silencing and produces consistent, stable and high-level gene expression irrespec-tive of the chromosomal integration site. The research studied the influence of different UCOE element parts on antibody expression in CHO cells. UCOE 1. 5 kb from chromobox homolog 3 ( CBX3 ) , UCOE 2. 5 kb from the heterogeneous ribonucleoprotein A2/B1 ( HNRPA2 B1 ) and the whole UCOE 4. 0 kb were inserted into the anti-body light and heavy chain vectors, respectively, and transfected into CHO cells using antibiotics-Zeocin and Blasticidin for pressure selection. Four groups of monoclonal cells were harvested and antibody expression of each group was detected. The monoclonal cells with UCOE 1. 5 kb and UCOE 2. 5 kb increased 1. 5 to 2-fold in the level of antibody expression, wheareas, monoclonal cells with UCOE 4. 0 kb increased 3 to 4-fold. The enhance-ment of two housekeeping promoter genes on antibody expression could stack up.

Establishment of recombinant cell line stably expressing humanα2A-adrenoceptor / 中国药理学与毒理学杂志

OBJECTIVE To establish a new cell line that can stably express humanα2A-adrenoceptor (α2A- AR). METHODS Recombinant plasmid of α2A- AR with hygromycin B (Hygro) resistance (pcDNA3.1/Hygro-HA-α2A-AR)was stably transfected into Chinese hamster ovary(CHO)cells which had expressed protein kinase A catalytic subunits(PKAcat) with labeling of enhanced green fluorescent protein(EGFP)by a Lipofectamine based method. A single positive clone expressingα2A-AR was selected through cultivation in the presence of 200 mg · L-1 hygromycin B followed by PKA redistribution assay. The transcriptional expression ofα2A-AR was detected by quantitative real-time PCR(qRT-PCR). Time-resolved fluorescence resonance energy transfer immunoassay was used to identify the function of inhibiting cAMP accumulation of α2A-AR. RESULTS The CHO-PKAcat-α2A-AR cell line No.7 exhibited stable response in PKA redistribution assay. qRT-PCR analysis demonstrated that the high expression ofα2A-AR in the cell line remained stable after a few generations compared with CHO-PKAcat-EGFP cells (P<0.01). The cAMP accumulation caused by forskolin was significantly inhibited by α2A-AR agonist in CHO-PKAcat-α2A-AR cells(P<0.01). CONCLUSION CHO-PKAcat-α2A-AR cell line is constructed successfully, which provides an effective model for drug screening and studies of mechanisms.

Cloning and expression of Bos indicus interleukin-4 in mammalian cells.

Dendritic cells (DC) which are located at the interface of innate and adaptive immunity are targets of infection by many RNA and DNA viruses. Advances in the ex vivo generation of monocyte derived non proliferating dendritic cells have been used for clinical application like immunotherapy. IL-4 cytokine plays essential role in the maturation and generation of DCs. Bos indicus interleukin 4 (boIL-4) 408 bp was amplified from PBMC’s and cloned in pBSIIKS+ vector. The sequence analysis showed N terminal 69 bp signal sequence and one N-glycosylation site. The phylogenetic tree analysis showed that Bos indicus IL-4 is closely related to the ruminant IL-4 and least sharing of genetic line of human and mouse IL-4. The recombinant boIL-4 protein was expressed in CHO cells which secreted a 16 kDa protein which was confirmed by SDS PAGE and western blotting. The rec-boIL-4 protein proliferated the bovine PBMC’s, decreased production of nitric oxide in antigen stimulated macrophages, and phagocytosed the micro particles confirming its activity on dendritic cells.

Thyroid Stimulating Antibody Assay with Chinese Hamster Ovary Cells Expressing Human Thyroid Stimulating Hormone (TSH) Receptor; Optimization of Assay Condition / 대한내분비학회지

We investigated the optimal condition of thyroid stimulating antibody(TSAb) assay using Chinese hamster ovary cells transfected with cDNA of human TSH receptor(TSHr-CHO) stably expressing functional TSH receptors. The extracellular cAMP responses of TSHr-CHO cells to the stimulation of bTSH or Graves' IgG were observed in three different incubation media. Stimulation indices of extracellular cAMP were higher when sucrose containing NaCl-free isotonic Hank's balanced salt solution(HBSS)(media A)was used as incubation media than those of NaCl-free hypotonic HBSS(media B) or those of NaCl containing isotonic HBSS(media C). The incubation of TSHr-CHO cells in media B caused marked increase in the basal cAMP level without concomittant fold-increase in the stimulated cAMP level at various doses of bTSH and Graves' IgG. Decreasing the stimulation indices of extracellular cAMP, use of media B failed to detect TSAb activities in two TSAb-positive Graves' IgG tested. In case of media C, extracellular cAMP responses are poor at 0.001 and 0.1U/L of bTSH and at all doses of Graves' IgG tested(0.5, 1, 5g/L). The incubation of TSHr-CHO cells in media B caused significant increase in the number of trypan blue-stained, nonviable cells(5.7+-1.5, 7.6+-1.9 and 8.5+-1.6% at 1, 2 and 3h of incubation, respectively; p<0.01) comparing to those incubated in media A or media C(about 2-3% in both media). Those decrease in the viability of TSHr-CHO cells when incubated in hypotonic incubation media may explain the decrease in the stimulation index of extracellular cAMP with the use of media B in contrast to the case of FRTL-5 cells. TSAb assay of 87 consecutive fresh Graves' patients with TSHr-CHO cells using media A detected TSAb activities in 90%(78 patients) of them, and moreover TSAb activities showed significant positive correlation with the pre-treatment serum T_3 and free T_4 levels of those patients. We conclude that TSAb assay with TSHr-CHO cells is a sensitive and physiologically relevant assay system to measure TSAb activities merely through measurements of extracellular cAMP provided that the cells are incubated in NaCl-free isotonic incubation media.

Construction of eukaryotic expression vector of fusion gene CD80-IgG and its expression in Chinese hamster ovary cells / 中国病理生理杂志

AIM: To construct the eukaryotic expression vector CD80-IgG by fusing the cDNA encoding extracellular portion of murine CD80 to the 5'-terminus of cDNA encoding Fc fragment of murine immunoglobulin G1 and to express the fusion protein in Chinese hamster ovary (CHO) cells. METHODS: The two cDNAs was amplified by PCR respectively from plasmid pcDNA/B7 containing the full-length cDNA of murine CD80 from murine spleen cells, and cloned to the eukaryotic expression vector pcDNA3.0 by directional cloning. The resultant recombinant plasmid pcDNA/CD80-IgG was transfected into CHO cells with liposome transfection reagent. The stably expressing cells were obtained by G418 screening. Western blot, Dot ELISA, and flow cytometry were used to detect the expression of the fusion protein and its immunological activity. RESULTS: DNA sequencing verified the correction of the construction of recombinant plasmid pcDNA/CD80-IgG. The expressed fusion protein was detected in the supernatant of transfected CHO cells and the molecular weight of the protein was similar to what we expected. Its immunological activity was also established. CONCLUSION: The recombinant plasmid pcDNA/CD80-IgG was successfully constructed and it expressed the fusion protein CD80-IgG.