Antibody-dependent enhancement of toxicity of myotoxin II from Bothrops asper.

Improved therapies are needed against snakebite envenoming, which kills and permanently disables thousands of people each year. Recently developed neutralizing monoclonal antibodies against several snake toxins have shown promise in preclinical rodent models. Here, we use phage display technology to discover a human monoclonal antibody and show that this antibody causes antibody-dependent enhancement of toxicity (ADET) of myotoxin II from the venomous pit viper, Bothrops asper, in a mouse model of envenoming that mimics a snakebite. While clinical ADET related to snake venom has not yet been reported in humans, this report of ADET of a toxin from the animal kingdom highlights the necessity of assessing even well-known antibody formats in representative preclinical models to evaluate their therapeutic utility against toxins or venoms. This is essential to avoid potential deleterious effects as exemplified in the present study.

Characterisation of two snake toxin-targeting human monoclonal immunoglobulin G antibodies expressed in tobacco plants.

Current snakebite antivenoms are based on polyclonal animal-derived antibodies, which can neutralize snake venom toxins in envenomed victims, but which are also associated with adverse reactions. Therefore, several efforts within antivenom research aim to explore the utility of recombinant monoclonal antibodies, such as human immunoglobulin G (IgG) antibodies, which are routinely used in the clinic for other indications. In this study, the feasibility of using tobacco plants as bioreactors for expressing full-length human monoclonal IgG antibodies against snake toxins was investigated. We show that the plant-produced antibodies perform similarly to their mammalian cell-expressed equivalents in terms of in vitro antigen binding. Complete neutralization was achieved by both the plant and mammalian cell-produced anti-α-cobratoxin antibody. The feasibility of using plant-based expression systems may potentially make it easier for laboratories in resource-poor settings to work with human monoclonal IgG antibodies.

Comparison of Five Commercial Molecular Assays for Mycoplasma Testing of Cellular Therapy Products.

Testing of cellular therapy products for Mycoplasma is a regulatory requirement by the United States Food and Drug Administration (FDA) to ensure the sterility and safety of the product prior to release for patient infusion. The risk of Mycoplasma contamination in cell culture is high. Gold standard testing follows USP 63 which requires a 28-day agar and broth cultivation method that is impractical for short shelf-life biologics. Several commercial molecular platforms have been marketed for faster raw material and product release testing; however, little performance data are available in the literature. In this study, we performed a proof-of-principle analysis to evaluate the performance of five commercial molecular assays, including the MycoSEQ Mycoplasma detection kit (Life Technologies), the MycoTOOL Mycoplasma real-time detection kit (Roche), the VenorGEM qOneStep kit (Minerva Biolabs), the ATCC universal Mycoplasma detection kit, and the Biofire Mycoplasma assay (bioMérieux Industry) using 10 cultured Mollicutes spp., with each at four log-fold dilutions (1,000 CFU/mL to 1 CFU/mL) in biological duplicates with three replicates per condition (n = 6) to assess limit of detection (LOD) and repeatability. Additional testing was performed in the presence of tumor infiltrating lymphocytes (TILs). Based on LOD alone, the Biofire Mycoplasma assay was most sensitive followed by the MycoSEQ and MycoTOOL which were comparable. We showed that not all assays were capable of meeting the ≤10 CFU/mL LOD to replace culture-based methods according to European and Japanese pharmacopeia standards. No assay interference was observed when testing in the presence of TILs.

Monitoring the manufacturing and quality of medicines: a fundamental task of pharmacovigilance.

The collection and assessment of individual case safety reports (ICSRs) is important to detect unknown adverse drug reactions particularly in the first decade after approval of new chemical entities. However, regulations require that these activities are routinely undertaken for all medicinal products, including older medicines such as generic medicinal products with a well-established safety profile. For the latter, the risk management plans no longer contain important risks, considered important safety concerns, on the basis that routine pharmacovigilance activity would not allow their further characterisation. Society assumes that unexpected adverse reactions causally related to pharmacological activity are very unlikely to be detected for such well-established medicines, but important risks can still occur. For these products, a change in the safety profile which is brand or source specific and usually local in nature, associated with failures with the adequate control of quality of manufacturing or distribution are important safety issues. These may be the consequence of manufacturing and pharmacovigilance quality systems that are not fully integrated over the product life cycle (e.g. inadequate control of quality defects affecting one or multiple batches; inadequate impact assessment of change/variation of manufacturing, quality control testing, storage and distribution processes; inadequate control over the distribution channels including the introduction of counterfeit or falsified products into the supply chain). Drug safety hazards caused by the above-mentioned issues have been identified with different products and formulations, from small molecules to complex molecules such as biological products extracted from animal sources, biosimilars and advanced therapy medicinal products. The various phases of the drug manufacturing and distribution of pharmaceutical products require inputs from pharmacovigilance to assess any effects of quality-related issues and to identify proportionate risk minimisation measures that often have design implications for a medicine which requires a close link between proactive vigilance and good manufacturing practice. To illustrate our argument for closer organisational integration, some examples of drug safety hazards originating from quality, manufacturing and distribution issues are discussed. PLAIN LANGUAGE SUMMARY: Monitoring the manufacturing and quality of medicines: the fundamental task of pharmacovigilance Pharmacovigilance is the science relating to the collection, detection, assessment, monitoring, and prevention of adverse reactions with pharmaceutical products. The collection and assessment of adverse reactions are particularly important in the first decade after marketing authorisation of a drug as the information gathered in this period could help, for example, to identify complications from its use which were unknown before its commercialization. However, when it comes to medicines that have been on the market for a long time there is general acceptance that their safety profile is already well-established and unknown adverse reactions unlikely to occur. Nevertheless, even older medicines, such as generic drugs, can generate new risks. For these drugs a change in the safety profile could be the result of inadequate control of their quality, manufacturing and distribution systems. To overcome such an obstacle, it is necessary to fully integrate manufacturing and pharmacovigilance quality systems in the medicine life-cycle. This could help detect safety hazards and prevent the development of new complications which may arise due to the poor quality of a drug. Pharmacovigilance activities should indeed be included in all phases of the drugs' manufacturing and distribution process, regardless of their chemical complexity to detect quality-related matters in good time and reduce the risk of safety concerns to a minimum.

Online Measurement of Glucose Consumption from HepG2 Cells Using an Integrated Bioreactor and Enzymatic Assay.

Hepatocytes help to maintain glucose homeostasis in response to a variety of signals, including pancreatic hormones such as insulin. Insulin is released from the pancreas with variable dynamics, yet the role that these play in regulating glucose metabolism in the liver is still unclear. In this study, a modular microfluidic system was developed to quantitatively measure the effect of insulin dynamics on glucose consumption by a human hepatocarcinoma cell line, HepG2. A microfluidic bioreactor that contained 106 HepG2 cells was cultured for up to 10 days in an incubator. For glucose consumption experiments, the bioreactor was removed from the incubator and connected with reagents for an enzymatic glucose assay. The mixed components were then delivered into a droplet-based microfluidic system where the intensity of the fluorescent product of the enzyme assay was used to quantify the glucose concentration. By optimizing the mixing time of the reagents, the dynamic range of the enzymatic assay was adjusted to 0-12 mM glucose and had a time resolution of 96 ± 12 s. The system was used to observe rapid changes in insulin-induced glucose consumption from HepG2 cells. This assay format is versatile and can be expanded to measure a variety of hepatic metabolites, such as lactate, pyruvate, or ketone bodies, which will enable the correlation of pancreatic hormone dynamics to liver metabolism.

Cysteine promoted C-terminal hydrazinolysis of native peptides and proteins.

Tagging the terminus: N→S acyl transfer in native peptides and proteins can be reliably intercepted with hydrazine. The method allows selective labeling and ligation, without recourse to the use of protein-splicing elements. NCL=native chemical ligation.

Investigation of peptide thioester formation via N→Se acyl transfer.

Native chemical ligation is widely used for the convergent synthesis of proteins. The peptide thioesters required for this process can be challenging to produce, particularly when using Fmoc-based solid-phase peptide synthesis. We have previously reported a route to peptide thioesters, following Fmoc solid-phase peptide synthesis, via an N→S acyl shift that is initiated by the presence of a C-terminal cysteine residue, under mildly acidic conditions. Under typical reaction conditions, we occasionally observed significant thioester hydrolysis as a consequence of long reaction times (~48 h) and sought to accelerate the reaction. Here, we present a faster route to peptide thioesters, by replacing the C-terminal cysteine residue with selenocysteine and initiating thioester formation via an N→Se acyl shift. This modification allows thioester formation to take place at lower temperatures and on shorter time scales. We also demonstrate how application of this strategy also accelerates peptide cyclization, when a linear precursor is furnished with an N-terminal cysteine and C-terminal selenocysteine.

Native N-glycopeptide thioester synthesis through N→S acyl transfer.

Peptide thioesters are important tools for the total synthesis of proteins using native chemical ligation (NCL). Preparation of glycopeptide thioesters, that enable the assembly of homogeneously glycosylated proteins, is complicated by the perceived fragile nature of the sugar moiety. Herein, we demonstrate the compatibility of thioester formation via N→S acyl transfer with native N-glycopeptides and report observations that will aid in their preparation.

Shifting Native Chemical Ligation into Reverse through N→S Acyl Transfer.

Peptide thioester synthesis by N→S acyl transfer is being intensively explored by many research groups the world over. Reasons for this likely include the often straightforward method of precursor assembly using Fmoc-based chemistry and the fundamentally interesting acyl migration process. In this review we introduce recent advances in this exciting area and discuss, in more detail, our own efforts towards the synthesis of peptide thioesters through N→S acyl transfer in native peptide sequences. We have found that several peptide thioesters can be readily prepared and, what's more, there appears to be ample opportunity for further development and discovery.