Virus Entry Receptor Binding – VERB kit
An innovative tool to isolate intact SARS-CoV-2 particles and detect the presence of neutralizing antibodies or spike protein
Assay principle
The highly efficient binding of SARS-CoV-2 via its spike protein to its cellular entry receptor ACE2 is the basis for the successful initiation of the viral infection cycle and forms the molecular principle of the VERB (Virus Entry Receptor Binding) approach developed by Covirabio. A capture matrix has been developed which allows the highly efficient isolation of intact SARS-CoV-2 particles and the determination of the presence of neutralizing antibodies in a routine lab environment.
The VERB assay is a stand-alone sample preparation method compatible with downstream detection methods such as RT-qPCR and thus can be easily integrated into existing laboratory procedures. It is a research use only (RUO) product.
Applications
Numerous publications and recent research highlight the potential applications of harnessing interactions between ACE2 and spike proteins for COVID-19 research. The VERB assay enables the isolation and enrichment of intact SARS-CoV-2 viral particles free of viral RNA fragments and debris as well as the detection of neutralizing antibodies. It is comparable to the labour-intensive viral plaque assay and can be easily adapted to various possible applications.
Key Features
The key components of the VERB assay are magnetic beads functionalized with recombinant human ACE2. The VERB assay protocol is quick, straight forward and easily adaptable to your needs. The magnetic beads allow handling in either manual mode for low sample numbers or automatic mode (e.g. Maelstrom and King Fisher systems) for medium and high throughput.
Intact SARS-CoV-2 isolation
Heat inactivation of a SARS-CoV-2 containing clinical sample abolishes isolation of RNA captured by VERB beads (< 5% input), when compared to the VERB bead captured RNA from the sample aliquot that was kept on ice (ca. 35% input). This supports the isolation of intact viral particles with the VERB beads. The data shown is normalized to the total RNA of the sample without VERB bead capture (input).
Neutralizing antibody detection
Reference serum with neutralizing antibodies against SARS-CoV-2 (EURM017) was serially diluted and incubated with SARS-CoV-2 pseudotyped virus before subjection to the VERB assay. The titer of neutralizing antibodies was determined by how much VERB-captured RNA could be detected. The IC50 determined by the VERB kit was at serum dilution of 47.3, supporting that neutralizing antibodies can be detected with the VERB beads.
Spike protein detection
The VERB assay enables trimeric spike protein isolation from human serum. Recombinantly expressed trimeric alpha spike protein was spiked into human serum and isolated with the VERB beads. The captured spike was detected with an anti-spike monoclonal antibody conjugated with horse radish peroxidase (HRP) and the colorimetric signal of the HRP substrate tetramethylbenzidine (TMB) was proportional to the spike protein present in the serum.
