In vivo neutralization of coral snake venoms with an oligoclonal nanobody mixture in a murine challenge model.

Oligoclonal mixtures of broadly-neutralizing antibodies can neutralize complex compositions of similar and dissimilar antigens, making them versatile tools for the treatment of e.g., infectious diseases and animal envenomations. However, these biotherapeutics are complicated to develop due to their complex nature. In this work, we describe the application of various strategies for the discovery of cross-neutralizing nanobodies against key toxins in coral snake venoms using phage display technology. We prepare two oligoclonal mixtures of nanobodies and demonstrate their ability to neutralize the lethality induced by two North American coral snake venoms in mice, while individual nanobodies fail to do so. We thus show that an oligoclonal mixture of nanobodies can neutralize the lethality of venoms where the clinical syndrome is caused by more than one toxin family in a murine challenge model. The approaches described may find utility for the development of advanced biotherapeutics against snakebite envenomation and other pathologies where multi-epitope targeting is beneficial.

Glycoengineered recombinant alpha1-antitrypsin results in comparable in vitro and in vivo activities to human plasma-derived protein.

Alpha-1-antitrypsin (A1AT) is a multifunctional, clinically important, high value therapeutic glycoprotein that can be used for the treatment of many diseases such as alpha-1-antitrypsin deficiency, diabetes, graft-versus-host-disease, cystic fibrosis and various viral infections. Currently, the only FDA-approved treatment for A1AT disorders is intravenous augmentation therapy with human plasma-derived A1AT. In addition to its limited supply, this approach poses a risk of infection transmission, since it uses therapeutic A1AT harvested from donors. To address these issues, we sought to generate recombinant human A1AT (rhA1AT) that is chemically and biologically indistinguishable from its plasma-derived counterpart using glycoengineered Chinese Hamster Ovary (geCHO-L) cells. By deleting nine key genes that are part of the CHO glycosylation machinery and expressing the human ST6GAL1 and A1AT genes, we obtained stable, high producing geCHO-L lines that produced rhA1AT having an identical glycoprofile to plasma-derived A1AT (pdA1AT). Additionally, the rhA1AT demonstrated in vitro activity and in vivo half-life comparable to commercial pdA1AT. Thus, we anticipate that this platform will help produce human-like recombinant plasma proteins, thereby providing a more sustainable and reliable source of therapeutics that are cost-effective and better-controlled with regard to purity, clinical safety and quality.

Combating viral contaminants in CHO cells by engineering innate immunity.

Viral contamination in biopharmaceutical manufacturing can lead to shortages in the supply of critical therapeutics. To facilitate the protection of bioprocesses, we explored the basis for the susceptibility of CHO cells to RNA virus infection. Upon infection with certain ssRNA and dsRNA viruses, CHO cells fail to generate a significant interferon (IFN) response. Nonetheless, the downstream machinery for generating IFN responses and its antiviral activity is intact in these cells: treatment of cells with exogenously-added type I IFN or poly I:C prior to infection limited the cytopathic effect from Vesicular stomatitis virus (VSV), Encephalomyocarditis virus (EMCV), and Reovirus-3 virus (Reo-3) in a STAT1-dependent manner. To harness the intrinsic antiviral mechanism, we used RNA-Seq to identify two upstream repressors of STAT1: Gfi1 and Trim24. By knocking out these genes, the engineered CHO cells exhibited activation of cellular immune responses and increased resistance to the RNA viruses tested. Thus, omics-guided engineering of mammalian cell culture can be deployed to increase safety in biotherapeutic protein production among many other biomedical applications.

Biochemical characterization of human gluconokinase and the proposed metabolic impact of gluconic acid as determined by constraint based metabolic network analysis.

The metabolism of gluconate is well characterized in prokaryotes where it is known to be degraded following phosphorylation by gluconokinase. Less is known of gluconate metabolism in humans. Human gluconokinase activity was recently identified proposing questions about the metabolic role of gluconate in humans. Here we report the recombinant expression, purification and biochemical characterization of isoform I of human gluconokinase alongside substrate specificity and kinetic assays of the enzyme catalyzed reaction. The enzyme, shown to be a dimer, had ATP dependent phosphorylation activity and strict specificity towards gluconate out of 122 substrates tested. In order to evaluate the metabolic impact of gluconate in humans we modeled gluconate metabolism using steady state metabolic network analysis. The results indicate that significant metabolic flux changes in anabolic pathways linked to the hexose monophosphate shunt (HMS) are induced through a small increase in gluconate concentration. We argue that the enzyme takes part in a context specific carbon flux route into the HMS that, in humans, remains incompletely explored. Apart from the biochemical description of human gluconokinase, the results highlight that little is known of the mechanism of gluconate metabolism in humans despite its widespread use in medicine and consumer products.

Direct binding between BubR1 and B56-PP2A phosphatase complexes regulate mitotic progression.

BubR1 is a central component of the spindle assembly checkpoint that inhibits progression into anaphase in response to improper kinetochore-microtubule interactions. In addition, BubR1 also helps stabilize kinetochore-microtubule interactions by counteracting the Aurora B kinase but the mechanism behind this is not clear. Here we show that BubR1 directly binds to the B56 family of protein phosphatase 2A (PP2A) regulatory subunits through a conserved motif that is phosphorylated by cyclin-dependent kinase 1 (Cdk1) and polo-like kinase 1 (Plk1). Two highly conserved hydrophobic residues surrounding the serine 670 Cdk1 phosphorylation site are required for B56 binding. Mutation of these residues prevents the establishment of a proper metaphase plate and delays cells in mitosis. Furthermore, we show that phosphorylation of serines 670 and 676 stimulates the binding of B56 to BubR1 and that BubR1 targets a pool of B56 to kinetochores. Our data suggest that BubR1 counteracts Aurora B kinase activity at improperly attached kinetochores by recruiting B56-PP2A phosphatase complexes.

Identification of RAS-mitogen-activated protein kinase signaling pathway modulators in an ERF1 redistribution screen.

The RAS-mitogen-activated protein kinase (MAPK) signaling pathway has a central role in regulating the proliferation and survival of both normal and tumor cells. This pathway has been 1 focus area for the development of anticancer drugs, resulting in several compounds, primarily kinase inhibitors, in clinical testing. The authors have undertaken a cell-based, high-throughput screen using a novel ERF1 Redistribution assay to identify compounds that modulate the signaling pathway. The hit compounds were subsequently tested for activity in a functional cell proliferation assay designed to selectively detect compounds inhibiting the proliferation of MAPK pathway-dependent cancer cells. The authors report the identification of 2 cell membrane-permeable compounds that exhibit activity in the ERF1 Redistribution assay and selectively inhibit proliferation of MAPK pathway-dependent malignant melanoma cells at similar potencies (IC(50)=< 5 microM). These compounds have drug-like structures and are negative in RAF, MEK, and ERK in vitro kinase assays. Drugs belonging to these compound classes may prove useful for treating cancers caused by excessive MAPK pathway signaling. The results also show that cell-based, high-content Redistribution screens can detect compounds with different modes of action and reveal novel targets in a pathway known to be disease relevant.

A simple cell-based HTS assay system to screen for inhibitors of p53-Hdm2 protein-protein interactions.

Green fluorescent protein-assisted readout for interacting proteins (GRIP) is a universal protein interaction discovery system that can be used to generate truly high throughput screening-compatible cellular assays to be used to screen for inhibitors of protein-protein interactions. The technology uses a "bait and prey" principle based on the distinct translocation behavior of the human cyclic AMP phosphodiesterase 4A4. Here we use the p53-Hdm2 Redistribution assay (Fisher BioImage ApS, Søborg, Denmark) as an example to describe the GRIP technology. The p53-Hdm2 Redistribution assay is a high content imaging assay based on the GRIP technology that is designed to measure the interaction between Hdm2 and the tumor suppressor p53. Hdm2 regulates p53 and inhibits its function by modulating its transcriptional activity and stability. Activation of p53 in tumor cells through inhibition of its physical interaction with Hdm2 is therefore a focus of cancer drug discovery. We have performed a pilot screen by screening 3,165 compounds from a diverse small-molecule library for inhibitors of the p53-Hdm2 interaction by using the p53-Hdm2 Redistribution assay. Here we show that by taking advantage of the translocation behavior of nonbound p53, it is possible to identify true inhibitors of the p53-Hdm2 interaction by extracting high content information from the acquired images.

Identification of Akt pathway inhibitors using redistribution screening on the FLIPR and the IN Cell 3000 analyzer.

The PI3-kinase/Akt pathway is an important cell survival pathway that is deregulated in the majority of human cancers. Despite the apparent druggability of several kinases in the pathway, no specific catalytic inhibitors have been reported in the literature. The authors describe the development of a fluorometric imaging plate reader (FLIPR)-based Akt1 translocation assay to discover inhibitors of Akt1 activation. Screening of a diverse chemical library of 45,000 compounds resulted in identification of several classes of Akt1 translocation inhibitors. Using a combination of classical in vitro assays and translocation assays directed at different steps of the Akt pathway, the mechanisms of action of 2 selected chemical classes were further defined. Protein translocation assays emerge as powerful tools for hit identification and characterization.