Epitope-Resolved Detection of Peanut-Specific IgE Antibodies by Surface Plasmon Resonance Imaging

A systematic review of allergen cross-reactivity: Translating basic concepts into clinical relevance

Access to the molecular culprits of allergic reactions allows for the leveraging of molecular allergology as a new precision medicine approach-one built on interdisciplinary, basic, and clinical knowledge. Molecular allergology relies on the use of allergen molecules as in vitro tools for the diagnosis and management of allergic patients. It complements the conventional approach based on skin and in vitro allergen extract testing. Major applications of molecular allergology comprise accurate identification of the offending allergen thanks to discrimination between genuine sensitization and allergen cross-reactivity, evaluation of potential severity, patient-tailored choice of the adequate allergen immunotherapy, and prediction of its expected efficacy and safety. Allergen cross-reactivity, defined as the recognition of 2 or more allergen molecules by antibodies or T cells of the same specificity, frequently interferes with allergen extract testing. At the mechanistic level, allergen cross-reactivity depends on the allergen, the host's immune response, and the context of their interaction. The multiplicity of allergen molecules and families adds further difficulty. Understanding allergen cross-reactivity at the immunologic level and translating it into a daily tool for the management of allergic patients is further complicated by the ever-increasing number of characterized allergenic molecules, the lack of dedicated resources, and the need for a personalized, patient-centered approach. Conversely, knowledge sharing paves the way for improved clinical use, innovative diagnostic tools, and further interdisciplinary research. Here, we aimed to provide a comprehensive and unbiased state-of-the art systematic review on allergen cross-reactivity. To optimize learning, we enhanced the review with basic, translational, and clinical definitions, clinical vignettes, and an overview of online allergen databases.

Allergenicity of peanut allergens and its dependence on the structure

Food allergies are a global food safety problem. Peanut allergies are common due, in part, to their popular utilization in the food industry. Peanut allergy is typically an immunoglobulin E-mediated reaction, and peanuts contain 17 allergens belonging to different families in peanut. In this review, we first introduce the mechanisms and management of peanut allergy, followed by the basic structures of associated allergens. Subsequently, we summarize methods of epitope localization for peanut allergens. These methods can be instrumental in speeding up the discovery of allergenicity-dependent structures. Many attempts have been made to decrease the allergenicity of peanuts. The structures of hypoallergens, which are manufactured during processing, were analyzed to strengthen the desensitization process and allergen immunotherapy. The identification of conformational epitopes is the bottleneck in both peanut and food allergies. Further, the identification and modification of such epitopes will lead to improved strategies for managing and preventing peanut allergy. Combining traditional wet chemistry research with structure simulation studies will help in the epitopes' localization.

Emerging Biosensors to Detect Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Review

Coronavirus disease (COVID-19) is a global health crisis caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) is the gold standard test for diagnosing COVID-19. Although it is highly accurate, this lab test requires highly-trained personnel and the turn-around time is long. Rapid and inexpensive immuno-diagnostic tests (antigen or antibody test) are available, but these point of care (POC) tests are not as accurate as the RT-PCR test. Biosensors are promising alternatives to these rapid POC tests. Here we review three types of recently developed biosensors for SARS-CoV-2 detection: surface plasmon resonance (SPR)-based, electrochemical and field-effect transistor (FET)-based biosensors. We explain the sensing principles and discuss the advantages and limitations of these sensors. The accuracies of these sensors need to be improved before they could be translated into POC devices for commercial use. We suggest potential biorecognition elements with highly selective target-analyte binding that could be explored to increase the true negative detection rate. To increase the true positive detection rate, we suggest two-dimensional materials and nanomaterials that could be used to modify the sensor surface to increase the sensitivity of the sensor.

E-DNA scaffold sensors and the reagentless, single-step, measurement of HIV-diagnostic antibodies in human serum

The multiplexed, point-of-care measurement of specific antibodies could improve the speed with which diseases are diagnosed and their treatment initiated. To this end, we are developing E-DNA scaffold sensors, which consist of a rigid, nucleic acid "scaffold" attached on one end to an electrode and presenting both a redox reporter and an epitope on the other. In the absence of antibody, the reporter efficiently transfers electrons when interrogated electrochemically. Binding-induced steric hindrance limits movement, reducing electron transfer in a manner that is both easily measured and quantitatively related to target concentration. Previously we have used monoclonal antibodies to explore the analytical performance of E-DNA sensors, showing that they support the rapid, single-step, quantitative detection of multiple antibodies in small volume samples. Here, in contrast, we employ authentic human samples to better explore the platform's clinical potential. Specifically, we developed E-DNA sensors targeting three HIV-specific antibodies and then compared the analytical and clinical performance of these against those of gold standard serological techniques. Doing so we find that, although the multistep amplification of an ELISA leads to a lower detection limits, the clinical sensitivity of ELISAs, E-DNA sensors and lateral-flow dipsticks are indistinguishable across our test set. It thus appears that, by merging the quantitation and multiplexing of ELISAs with the convenience and speed of dipsticks, E-DNA scaffold sensors could significantly improve on current serological practice.

Collision of Aptamer/Pt Nanoparticles Enables Label-Free Amperometric Detection of Protein in Rat Brain

Single particle collision is emerging as a powerful and sensitive technique for analyzing small molecules, however, its application in biomacromolecules detection, for example, protein, in complex biological environments is still challenging. Here, we present the first demonstration on the single particle collision that can be developed for the detection of platelet-derived growth factor (PDGF), an important protein involved in the central nervous system in living rat brain. The system features Pt nanoparticles (PtNPs) conjugated with the PDGF recognition aptamer, suppressing the electrocatalytic collision of PtNPs toward the oxidation of hydrazine. In the presence of PDGF, the stronger binding between targeted protein and the aptamer disrupts the aptamer/PtNPs conjugates, recovering the electrocatalytic performance of PtNPs, and allowing quantitative, selective, and highly sensitive detection of PDGF in cerebrospinal fluid of rat brain.

Restricted Proteolysis and LC-MS/MS To Evaluate the Orientation of Surface-Immobilized Antibodies

The molecular orientation of antibodies immobilized on solid surfaces plays a significant role in the sensitivity of immunoassays and efficiency of protein isolation using antibody-decorated nanoparticles. Optimally, nearly all antibody binding sites should be available to bind. Here we report for the first time an LC-MS/MS approach to probe antibody orientation directly, utilizing sterically restricted proteolysis. Trypsin-decorated magnetic beads (MBs, 1.5 μm) were much larger than average antibody-free areas (55 × 55 nm) of oriented antibodies on MBs, restricting proteolysis to mainly Fab regions. Randomly attached antibodies on MB surfaces served as controls. The tryptic-hydrolyzed peptides were quantified using LC-MS/MS peptide analysis as markers for average positions of Fc and Fab of antibodies on the beads. Different patterns of digestion rates were found due to proteolysis of the oriented and nonoriented antibodies on MBs. For oriented antibodies, the peptides from outer Fab regions gave a much higher digestion rate than those from Fc regions, while for randomly immobilized antibodies digestion rates for Fab and Fc peptides were similar. This novel approach is a useful and convenient tool to characterize antibody orientation for immunoassays and other applications. The relative degree of orientation can be assessed using a metric R_o denoting amount of Fab marker peptides found divided by Fc + Fab marker peptides × 100%. Oriented antibodies on the MBs also provided more efficient antigen capture compared to randomly immobilized antibodies.

Recent Advances in Surface Plasmon Resonance Imaging Sensors

The surface plasmon resonance (SPR) sensor is an important tool widely used for studying binding kinetics between biomolecular species. The SPR approach offers unique advantages in light of its real-time and label-free sensing capabilities. Until now, nearly all established SPR instrumentation schemes are based on single- or several-channel configurations. With the emergence of drug screening and investigation of biomolecular interactions on a massive scale these days for finding more effective treatments of diseases, there is a growing demand for the development of high-throughput 2-D SPR sensor arrays based on imaging. The so-called SPR imaging (SPRi) approach has been explored intensively in recent years. This review aims to provide an up-to-date and concise summary of recent advances in SPRi. The specific focuses are on practical instrumentation designs and their respective biosensing applications in relation to molecular sensing, healthcare testing, and environmental screening.