Cross-Reactive Synbody Affinity Ligands for Capturing Diverse Noroviruses

Sensitive Electrochemical and Thermal Detection of Human Noroviruses Using Molecularly Imprinted Polymer Nanoparticles Generated against a Viral Target

Norovirus (NoV) is the predominant cause of foodborne illness globally; current detection methods are typically expensive, have inadequate sensitivities, and utilize biological receptors with poor stability. Therefore, accurate, cost-effective, and highly stable detection methods are needed to screen for NoV in foods. We developed molecularly imprinted polymer nanoparticles (nanoMIPs) to detect NoV using a small target epitope (12 amino acids) with a solid-phase synthesis approach. The performance of three batches of nanoMIPs with varying monomer compositions (nanoMIP-1, -2, and -3) were compared both experimentally and computationally. Surface plasmon resonance examined nanoMIP binding affinity to norovirus virus-like particles (NoV-LPs), whereby nanoMIP-1 had the lowest KD value of 0.512 μM. This is significant, as traditional targets for generation of norovirus ligands previously reported were generated against drastically larger norovirus capsid segments that have limitations in ease of production. Further, an electrochemical sensor was developed by covalently attaching the nanoMIPs to glassy carbon electrodes. In agreement with our predictions from density functional theory simulations, electrochemical impedance spectroscopy showed a sensitive response toward NoV-LPs for nanoMIP batches tested; however, nanoMIP-1 was optimal, with an excellent detection limit of 3.4 pg/mL (1.9 × 105 particles/mL). Due to its exceptional performance, nanoMIP-1 was immobilized to screen-printed electrodes and utilized within a thermal sensor, where it exhibited a low detection limit of 6.5 pg/mL (3.7 × 105 particles/mL). Crucially, we demonstrated that nanoMIP-1 could detect NoV in real food samples (romaine lettuce) by using electrochemical and thermal sensors. Consequently, the study highlights the exceptional potential of nanoMIPs to replace traditional biological materials (e.g., antibodies) as sensitive, versatile, and highly stable receptors within NoV sensors.

Detection of Norovirus Using Paper-Based Cell-Free Systems

Norovirus infections are the leading cause of foodborne illness and human gastroenteritis, afflicting hundreds of millions of people each year. Molecular assays with the capacity to detect norovirus without expensive equipment and with high sensitivity and specificity represent useful tools to track and contain future outbreaks. Here we describe how norovirus can be detected in low-cost paper-based cell-free reactions. These assays combine freeze-dried, thermostable cell-free transcription-translation reactions with toehold switch riboregulators designed to target the norovirus genome, enabling convenient colorimetric assay readouts. Coupling cell-free reactions with synbody-based viral enrichment and isothermal amplification enables detection of norovirus from clinical samples down to concentrations as low as 270 zM. These diagnostic tests are promising assays for confronting norovirus outbreaks and can be adapted to a variety of other human pathogens.

A Survey of Analytical Techniques for Noroviruses

As the leading cause of acute gastroenteritis worldwide, human noroviruses (HuNoVs) have caused around 685 million cases of infection and nearly $60 billion in losses every year. Despite their highly contagious nature, an effective vaccine for HuNoVs has yet to become commercially available. Therefore, rapid detection and subtyping of noroviruses is crucial for preventing viral spread. Over the past half century, there has been monumental progress in the development of techniques for the detection and analysis of noroviruses. However, currently no rapid, portable assays are available to detect and subtype infectious HuNoVs. The purpose of this review is to survey and present different analytical techniques for the detection and characterization of noroviruses.

High-level expression and enrichment of norovirus virus-like particles in plants using modified geminiviral vectors

Recombinant virus-like particles (VLPs) are proven to be safe and effective vaccine candidates. We have previously described a plant-based recombinant protein expression system based on agroinfiltration of a replicating vector derived from the geminivirus bean yellow dwarf virus (BeYDV). The system has been systematically optimized to improve expression and reduce cell death in Nicotiana benthamiana leaves. Using these modifications, we show that VLPs derived from genotype GII.4 norovirus, the leading cause of acute gastroenteritis worldwide, can be produced at >1 mg/g leaf fresh weight (LFW), over three times the highest level ever reported in plant-based systems. We also produced norovirus GI VLPs at 2.3 mg/g LFW. Treatment of VLP-containing crude leaf extracts with acid, detergent, or heat enhanced recovery and allowed selective enrichment of norovirus VLPs. Optimal treatment conditions allowed removal of >90% of endogenous plant proteins without any loss of norovirus VLPs. Selective enrichment of hepatitis B core antigen (HBcAg) VLPs by acid treatment was also demonstrated, with some losses in yield that were partially mitigated in the presence of detergent. Sedimentation analysis confirmed that acid and detergent did not inhibit proper assembly of norovirus VLPs, although heat treatment had a small negative effect. These results demonstrate that milligram quantities of norovirus VLPs can be obtained and highly enriched in a matter of days from a single plant leaf using the BeYDV plant expression system.

Low-cost detection of norovirus using paper-based cell-free systems and synbody-based viral enrichment

Noroviruses are a primary cause of gastroenteritis and foodborne illness with cases that affect millions of people worldwide each year. Inexpensive tests for norovirus that do not require sophisticated laboratory equipment are important tools for ensuring that patients receive timely treatment and for containing outbreaks. Herein, we demonstrate a low-cost colorimetric assay that detects norovirus from clinical samples by combining paper-based cell-free transcription-translation systems, isothermal amplification and virus enrichment by synbodies. Using isothermal amplification and cell-free RNA sensing with toehold switches, we demonstrate that the assay enables detection of norovirus GII.4 Sydney from stool down to concentrations of 270 aM in reactions that can be directly read by eye. Furthermore, norovirus-binding synbodies and magnetic beads are used to concentrate the virus and provide a 1000-fold increase in assay sensitivity extending its detection limit to 270 zM. These results demonstrate the utility of paper-based cell-free diagnostic systems for identification of foodborne pathogens and provide a versatile diagnostic assay that can be applied to the concentration, amplification and detection of a broad range of infectious agents.

Non-natural amino acid peptide microarrays to discover Ebola virus glycoprotein ligands

We demonstrate a platform to screen a virus pseudotyped with Ebola virus glycoprotein (GP) against a library of peptides that contain non-natural amino acids to develop GP affinity ligands. This system could be used for rapid development of peptide-based antivirals for other emerging or neglected tropical infectious diseases.

A Simple Platform for the Rapid Development of Antimicrobials

Recent infectious outbreaks highlight the need for platform technologies that can be quickly deployed to develop therapeutics needed to contain the outbreak. We present a simple concept for rapid development of new antimicrobials. The goal was to produce in as little as one week thousands of doses of an intervention for a new pathogen. We tested the feasibility of a system based on antimicrobial synbodies. The system involves creating an array of 100 peptides that have been selected for broad capability to bind and/or kill viruses and bacteria. The peptides are pre-screened for low cell toxicity prior to large scale synthesis. Any pathogen is then assayed on the chip to find peptides that bind or kill it. Peptides are combined in pairs as synbodies and further screened for activity and toxicity. The lead synbody can be quickly produced in large scale, with completion of the entire process in one week.