Immunological Assays: Biotools for High Throughput Screening and Characterisation of Combinatorial Libraries

The development of high-throughput screening (HTS) technologies has become essential for initial characterization of recombinant antibodies and alternative affinity reagents, selected from large combinatorial libraries. Such binding ligands are routinely selected against a single antigen and screened for desired binding specificities. Recent progress with genome sequencing projects has led to widespread efforts to study corresponding proteomes; requiring selection of ligands against large numbers of gene products in a highly parallel manner. The capabilities of many routine HTS methods such as enzyme-linked immunosorbent assay (ELISA), or array-based methods, are limited to analysis of numerous different antibody clones against a single target or, individual antibody clones against many different targets. We have developed a multiplexed flow cytometry screening method that allows analysis of individual binding ligands against numerous targets in the same analytical sample. The method produces a complex analytical profile for each antibody clone in the primary screen, by allowing simultaneous determination of relative expression levels, identification of non-specific binding, and discrimination of fine specificities. The quality and quantity of data, combined with significant reductions in analysis time and antigen consumption, provide notable advantages over other standard screening methods, such as ELISA. By combining HT screening capabilities with multiplex technology, we have redefined the parameters for the initial identification of affinity reagents recovered from combinatorial libraries and removed a significant bottleneck in the generation of affinity reagents on a proteomic scale.

A single-step cancer cell cytotoxic assay system for anticancer drug discovery has been developed which facilitates rapid screening of large combinatorial chemical libraries synthesized using the 'one-bead-one-compound' (OBOC) methodology. Each OBOC library bead incorporates two orthogonally cleavable linkers that release the bead-bound compound at a different pH. The assay utilizes high concentrations of tumor cells mixed directly with OBOC beads and plated in soft agarose containing tissue culture medium. One of the orthogonal linkers is cleaved at neutral pH in tissue culture releasing an aliquot of compound to diffuse at a relatively high local concentration into the soft agarose immediately surrounding the bead. Active compounds are identified visually from a clear ring of tumor cell lysis which forms within 48 h around just the rare bead releasing a cytotoxic compound. The bead releasing a cytotoxin is then plucked from the agar and the remaining compound still linked to the bead can be released for structural analysis, followed by compound resynthesis and confirmatory testing. This assay system has been successfully applied to identification of lead cytotoxic compounds from model peptidic and non-peptidic combinatorial chemical libraries. Use of this methodology may facilitate anticancer drug discovery.

The emergence of multidrug resistant salmonella enterica serotype typhi in pandemic proportions throughout the world and therefore there is a necessity to speed up the discovery of novel molecules having different modes of action and also less influenced to the resistance formation that would be used as drug for the treatment of salmonellosis particularly typhoid fever. The PhoP regulon is well studied and have now been shown to be critical regulator of number of gene expression whose required for intracellular survival of S.enterica and pathophysiology of disease like typhoid. The evident roles of two component PhoP/PhoQ-regulated products in salmonella virulence have motivated attempts to target them as therapeutically. Although the discovery process of biologically active compounds for the treatment of typhoid rely on hit finding procedure using high throughput screening technology alone is very expensive, as well as time consuming when performed on large scales. With the recent advancement in combinatorial chemistry and contemporary technique for compounds synthesis, there are more and more compounds become available that gives ample growth of diverse compound library, but the time and endeavor required to screen these unfocused massive and diverse library has been slightly reduced in the past years. Hence there is demand to improve the high quality hits and success rate for high-throughput screening (HTS) that required focused and biased compound library towards the particular target. Therefore we still need an advantageous and expedient method to prioritize the molecules that will be utilized for biological screens which save time and also inexpensive. In this concept In-silico methods like Machine Learning are widely applicable technique used to build computational model for high-throughput virtual screens to prioritize molecules for advance study. Furthermore in computational analysis we extended our study to identify the common enriched structural entities among the biologically active compound towards find out the privileged scaffold.

Aging and its related diseases are severe issues in modern society. Many efforts have been made to understand the mechanisms of aging and to find the ways to prevent age-related diseases. Identifying the compounds targeting aging-related signals is a challenging work because there are so many proteins and signals involved. Recently, alone with the progresses in high throughput screening (HTS) technology, increasing numbers of small molecules targeting aging-related pathologic processes have been identified. In this review, we introduce the basic workflow, classification and assay strategies of HTS technology, and sort out known small molecules identified via HTS technology by their roles in aging related diseases, such as neural degenerative diseases, diabetes and tumors. Given the fact that application of HTS on aging research is still at an early stage, we also summarize the cellular mechanisms about aging process, paralleled with the compounds which can modulate the functions of proteins important for aging signals. Finally, we briefly discuss some advanced HTS technologies for their potent applications on the discovery of anti-aging compounds. The main purpose of this review is to provide updated and useful information to those who are interested in pharmacology and HTS technology, but not familiar with aging biology, or vice versa.

O17 Identification and characterisation of phytochemicals activating endogenous cytoprotective mechanisms

We describe a new computational approach, called Focus-2D, to the rational design of targeted combinatorial chemical libraries. This approach is based on the hypothesis that structurally similar compounds display similar biological activity profiles. Building blocks that are used in a combinatorial chemical synthesis are randomly assembled to produce virtual library compounds. Individual library compounds are represented by Kier-Hall topological descriptors. Molecular similarities between compounds are evaluated quantitatively by modified pairwise Euclidean distances in multidimensional descriptor space. Simulated annealing is used to search the potentially large structural space of virtual chemical libraries to identify compounds similar to lead molecules. Frequency analysis of building block composition of selected virtual compounds identifies building blocks that can be used in combinatorial synthesis of chemical libraries with high similarity to the lead molecules. We show that this method correctly identifies building found in active peptoids with adrenergic or opioid activities.

In recent years, combinatorial chemistry has emerged as a powerful tool for accelerating drug discovery. While industry is rapidly embracing the technology, researchers continue to develop novel library methods including resins, linkers, tagging and deconvolution techniques. Newer strategies involving computer-customized combinatorial libraries offer enormous potential for the design of more "focused" and "smart" chemical libraries with maximal diversity. In addition, miniaturized systems for synthesizing chemical libraries are also being developed, which has made it possible to carry out reactions at submicroliter volumes.

Surface Plasmon Resonance imaging (SPRi) was used to determine the presence and strength of binding of IgG, IgM and IgA against the Receptor Binding Domain (RBD) of SARS-CoV-2 in sera of 102 CoViD-19 and non-CoViD-19 patients. The SPRi assay simultaneously measures the antibody isotype levels and the strength of binding to the RBD of ultimate 384 patient samples in one run. It turns out that during the course of the disease, the IgG levels and strength of binding increased while generally the IgM and IgA levels go down. Recovered patients all show high strength of binding of the IgG type to the RBD protein. The anti-RBD immunoglobulins SPRi assay provides additional insights in the immune status of patients recovering from CoViD-19. This new high throughput method can be applied for the assessment of the quality of the immune reaction of healthy individuals to SARS-CoV-2 and its mutants in vaccination programs.•Surface Plasmon Resonance imaging is an unprecedented technology for high throughput screening of antibody profiling of CoViD19 patients.•Fingerprinting of isotypes IgM, IgG and IgA can be performed for 384 patients in one run.•An affinity maturation effect was shown for patients recovering from CoViD19.

TR-DB: An open-access database of compounds affecting the ethylene-induced triple response in Arabidopsis

Synthetic combinatorial libraries (SCLs) are collections of very large numbers of synthetic compounds, in which all possible combinations of the burlding blocks used are represented. The development and verification of the utility of combinatorial libraries represent a dramatic advance in the drug discovery process by greatly reducing the time needed to identify new drug leads. Positional scanning (PS) SCLs (,) represent a modified format of the origmal synthetic combinatorial libraries described by this laboratory (). In contrast to the original libraries, which required several iterative syntheses to identify individual active compounds, this library format provides mformation on the substituent responsible for activity at each varied position withm a structure. Therefore, only a single subsequent synthesis is required. The screening of PS-SCLs, in most instances, permits the identification of the most active substituents at each position of a compound in a single assay. Thus PS-SCLs serve to reduce further the time required to identify new drug leads. PS-SCLs are composed of individual positional SCLs, in which a single position is defined with one substituent while the remaining positions are composed of mixtures of substituents. The defined position is "walked" through the entire sequence of the PS-SCL. Therefore, the number of positional SCLs is equal to the number of residues in each compound of the PS-SCL. It should also be noted that each posrtional SCL, although addressing a single position of the sequence, represents the same collection of individual compounds For example, a hexapeptide, or a compound with six positions, can be represented as: O1XXXXX, XO2,XXXX, XXO3XXX, XXO4,XX, XXXXO5X, or XXXXXO6.

We describe a new method for encoded synthesis, efficient on-resin screening, and rapid unambiguous sequencing of combinatorial peptide libraries. An improved binary tag system for encoding peptide libraries during synthesis was designed to facilitate unequivocal assignment of isobaric residues by MALDI-TOF MS analysis. The improved method for encoded library synthesis was combined with a new versatile on-resin screening strategy that permitted multiple stages and types of screening to be employed successively on one library under mild conditions. The new method facilitated a combinatorial study of transglutaminase (TGase) enzyme substrate peptides, revealing new details of the effect of amino acid composition on TGase substrates. The approach was first demonstrated for an encoded library (130,321 compounds) of lysine pentapeptide substrates of TGase, synthesized using the "split-mix" method. The library was reacted on-resin with TGase enzyme and a soluble desthiobiotin labeled glutamine substrate. Initial screening was performed by adsorbing streptavidin-coated magnetic microparticles onto library beads, followed by magnetic separation. The differential binding affinities of desthiobiotin and biotin for streptavidin were exploited to release the magnetic microparticles and regenerate the desthiobiotin-labeled resin beads for further screening by flow-cytometry-based automated bead sorting, resulting in 345 beads that were sequenced by MALDI-TOF MS analysis. A second library consisted of encoded glutamine hexapeptide substrates, which was reacted on-resin with TGase enzyme and a soluble desthiobiotin-labeled cadaverine. Two-stage screening identified 267 glutamine peptides as TGase-reactive, of which 21 were further analyzed by solution-phase enzyme kinetics. Kinetic results indicated that the peptide PQQQYV from the library has a 68-fold greater substrate specificity than the best known glutamine substrate QQIV. The new encoding and screening strategies described here are expected to be broadly applicable to synthesis and screening of combinatorial peptide libraries in the future.

This unit presents a combinatorial library method that consists of the synthesis and screening of mixture-based synthetic combinatorial libraries (SCL) of peptide molecules. The protocols employ peptide SCL to identify peptides recognized by mAbs and T cells. The first protocol uses a positional scanning SCL (PS-SCL) made up of hexapeptides to identify antigenic determinants recognized by mAbs. The 120 mixtures in the hexapeptide PS-SCL are tested for their inhibitory activity in a competitive ELISA. The second protocol uses a decapeptide PS-SCL to identify T cell peptide ligands. The 200 mixtures of the decapeptide PS-SCL are tested for their ability to induce proliferation. Support protocols cover optimization of the assay conditions for each mAb or T cell, to achieve the best level of sensitivity and reproducibility, and preparation of a hexapeptide PS-SCL, along with deconvolution approaches.

Drug discovery today requires the focused use of lab automation and other resources in Combinatorial Chemistry and HighThroughput Screening (HTS). The ultimate value of both Combinatorial Chemistry and High-Throughput Screening technologies and the lasting impact they will have on the drug discovery process is a chapter that remains to be written. Central to their success and impact is how well they are integrated with each other and with the rest of Drug Discovery - and Informatics is key to this success. This presentation will focus on Informatics and the integration of the disciplines of combinatorial chemistry and HTS in modern drug discovery. Examples from experiences at Neurogen from the last five years will be described.

Multidimensional Profiling of CSF1R Screening Hits and Inhibitors: Assessing Cellular Activity, Target Residence Time, and Selectivity in a Higher Throughput Way

In this paper, the slow evolution of combinatorial chemistry from its dawn in 1980’s to today’s oil field product development is discussed. Combinatorial chemistry comprises chemical synthetic methods that make it possible to prepare a vast number of compounds in a single process. These compound libraries can be made as mixtures, sets of individual compounds or chemical structures generated by computer software. This phenomenon was first invented by Arpad Furka (Lorand University, Budapest) in 1982. He described the principle of it, the combinatorial synthesis and a deconvolution procedure. The methodology was first used in drug discovery using a wide range of linear or wide range of macrocyclic chemical molecules: peptides, non-peptide oligomers, peptidomimetics, small-molecules, and natural product-like organic molecules. However, handling vast amounts of data and extremely small chemical recovery were a very difficult endeavor. To avoid this problem and help to refine the size of the chemical libraries, various software programs were utilized. This was achieved by utilizing a tool known as Design of Experiment (DoE). In this paper, the high throughput product screening to identify corrosion inhibitors was performed by utilizing critical micelle concentration (CMC). CMC was used to differentiate performance of libraries of chemical blends. Combinatorial synthesis (or blends) and combinatorial screening were performed by utilizing robotics methodologies. The corrosion inhibitor formulations predicted by DoE were built out by using combinatorial chemical methods and the arrays of chemical formulations were screened by utilizing high throughput robotics, using CMC as the selection guide. To validate the concept, several known corrosion inhibitor formulas were selected to optimize their efficacy. Each formula contained several active ingredients and a solvent package. These raw materials were blended in random but in a control, manner using combinatorial methodologies. After formulation of a vast array of formulation by using Design Expert solvent package. These raw materials were blended in random but in a control, manner using combinatorial methodologies. After formulation of a vast array of formulation by using Design Expert (DE) software, the products were screened for by CMC using automated surface tension workstation. Several formulations with lower CMC than the reference products were selected. The selected corrosion inhibitor formulations were identified and blended in larger scales. The efficacy of these products was tested by classical laboratory testing methods such as rotating cylinder electrode (RCE) and rotating cage autoclave (RCA) to determine their performance as anti-corrosion agents. These tests were performed against the original reference corrosion inhibitor. The testing indicated that several corrosion inhibitor formulations outperform the original blend thus validating the proof of concept.