Decoupling Protein Concentration and Aggregate Content Using Diffusion and Water NMR.

Protein-based biopharmaceutical drugs, such as monoclonal antibodies, account for the majority of the best-selling drugs globally in recent years. For bioprocesses, key performance indicators are the concentration and aggregate level for the product being produced. In water NMR (wNMR), the use of the water transverse relaxation rate [R2(1H2O)] has been previously used to determine protein concentration and aggregate level; however, it cannot be used to separate between them without using an additional technique. This work shows that it is possible to "decouple" these two key characteristics by recording the water diffusion coefficient [D(1H2O)] in conjunction with R2(1H2O), even in the event of overlap in either D(1H2O) or R2(1H2O). This method is demonstrated on three different systems, following appropriate D(1H2O) or R2(1H2O) calibration data acquisition for a protein of interest. Our method highlights the potential use of benchtop NMR as an at-line process analytical technique.

CHO synthetic promoters improve expression and product quality of biotherapeutic proteins.

When expressing complex biotherapeutic proteins, traditional expression plasmids and methods may not always yield sufficient levels of high-quality product. High-strength viral promoters commonly used for recombinant protein (rProtein) production in mammalian cells allow for maximal expression, but provide limited scope to alter their transcription dynamics. However, synthetic promoters designed to provide tunable transcriptional activity offer a plasmid engineering approach to more precisely regulate product quality, yield or to reduce product related contaminants. We substituted the viral promoter CMV with synthetic promoters that offer different transcriptional activities to express our gene of interest in Chinese hamster ovary (CHO) cells. Stable pools were established and the benefits of regulating transgene transcription on the quality of biotherapeutics were examined in stable pool fed-batch overgrow experiments. Specific control of gene expression of the heavy chain (HC):light chain (LC) of a Fab, and the ratio between the two HCs in a Duet mAb reduced levels of aberrant protein contaminants; and the controlled expression of the helper gene XBP-1s improved expression of a difficult-to-express mAb. This synthetic promoter technology benefits applications that require custom activity. Our work highlights the advantages of employing synthetic promoters for production of more complex rProteins.

Targeted CHO cell engineering approaches can reduce HCP-related enzymatic degradation and improve mAb product quality.

Host cell proteins (HCP) that co-purify with biologics produced in Chinese hamster ovary cells have been shown to impact product quality through proteolytic degradation of recombinant proteins, leading to potential product losses. Several problematic HCPs can remain in the final product even after extensive purification. Each recombinant cell line has a unique HCP profile that can be determined by numerous upstream and downstream factors, including clonal variation and the protein sequence of the expressed therapeutic molecule. Here, we worked with recombinant cell lines with high levels of copurifying HCPs, and showed that in those cell lines even modest downregulation (≤50%) of the difficult to remove HCP Cathepsin D, through stable short hairpin RNA interference or monoallelic deletion of the target gene using CRISPR-Cas9, is sufficient to greatly reduce levels of co-purifying HCP as measured by high throughput targeted LC-MS. This reduction led to improved product quality by reducing fragmentation of the drug product in forced degradation studies to negligible levels. We also show the potential of cell engineering to target other undesired HCPs and relieve the burden on downstream purification.

A novel hydrogen peroxide evolved CHO host can improve the expression of difficult to express bispecific antibodies.

The manufacture of bispecific antibodies by Chinese hamster ovary (CHO) cells is often hindered by lower product yields compared to monoclonal antibodies. Recently, reactive oxygen species have been shown to negatively impact antibody production. By contrast, strategies to boost cellular antioxidant capacity appear to be beneficial for recombinant protein expression. With this in mind, we generated a novel hydrogen peroxide evolved host using directed host cell evolution. Here we demonstrate that this host has heritable resistance to hydrogen peroxide over many generations, displays enhanced antioxidant capacity through the upregulation of several, diverse antioxidant defense genes such as those involved in glutathione synthesis and turnover, and has improved glutathione content. Additionally, we show that this host has significantly improved transfection recovery times, improved growth and viability properties in a fed-batch production process, and elevated expression of two industrially relevant difficult to express bispecific antibodies compared to unevolved CHO control host cells. These findings demonstrate that host cell evolution represents a powerful methodology for improving specific host cell characteristics that can positively impact the expression of difficult to express biotherapeutics.

The Emerging Role of Altered Cerebellar Synaptic Processing in Alzheimer's Disease.

The role of the cerebellum in Alzheimer's disease (AD) has been neglected for a long time. Recent studies carried out using transgenic mouse models have demonstrated that amyloid-ß (Aß) is deposited in the cerebellum and affects synaptic transmission and plasticity, sometimes before plaque formation. A wide variability of motor phenotype has been observed in the different murine models of AD, without a consistent correlation with the extent of cerebellar histopathological changes or with cognitive deficits. The loss of noradrenergic drive may contribute to the impairment of cerebellar synaptic function and motor learning observed in these mice. Furthermore, cerebellar neurons, particularly granule cells, have been used as in vitro model of Aß-induced neuronal damage. An unexpected conclusion is that the cerebellum, for a long time thought to be somehow protected from AD pathology, is actually considered as a region vulnerable to Aß toxic damage, even at the early stage of the disease, with consequences on motor performance.

Motor coordination and synaptic plasticity deficits are associated with increased cerebellar activity of NADPH oxidase, CAMKII, and PKC at preplaque stage in the TgCRND8 mouse model of Alzheimer's disease.

Numerous studies indicate that the cerebellum undergoes structural and functional neurodegenerative changes in Alzheimer's disease. The purpose of this study was to examine the extent of cerebellar alterations at early, preplaque stage of the pathology in TgCRND8 mice through behavioral, electrophysiological, and molecular analysis. Balance beam test and foot-printing analysis revealed significant motor coordination and balance deficits in 2-month-old TgCRND8 mice compared to their littermates. Patch-clamp recordings performed on cerebellar slices of transgenic mice showed synaptic plasticity deficit and loss of noradrenergic modulation at parallel fiber-Purkinje cell synapse suggesting an early dysfunction of the cerebellar circuitry due to amyloid precursor protein overexpression. Finally, western blot analysis revealed an enhanced expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits p47phox and p67phox as well as Ca2+/calmodulin-dependent protein kinase and protein kinase C alpha in the cerebellum of 2-month-old transgenic mice. Therefore, we propose the existence of self-sustaining feedback loop involving the formyl peptide receptor 2-reactive oxygen species-Ca2+/calmodulin-dependent protein kinase II-protein kinase C alpha pathway that may promote reactive oxygen species generation in the early stage of Alzheimer's disease and eventually contribute to the exacerbation of pathological phenotype.