HyTest SARS-CoV-2 antibodies and detection of variants
Anti-nucleoprotein antibodies (Cat.# 3CV4)
Our key antibodies (Cat.# 3CV4, clones C518, C524, C527, C706, C715) bind to the N-terminal part of the nucleoprotein: N47-A173 (please see TechNotes for additional information on other clones). Several mutations found in circulating SARS-CoV-2 variants are located outside of this region, however, we aim to test all relevant and concerning mutations regardless of their location. Prevalence of nucleoprotein mutations changes over time, for up-to-date information see e.g. https://outbreak.info/compare-lineages
We screen for the variants ourselves using recombinant antigens, however, we also have received feedback from our customers that have tested selected antibody pairs with live virus variant strains. We highly appreciate the feedback from our customers as it gives valuable information on the performance of some of the pairs with live virus samples.
Below we have compiled information regarding different variants and mutations. We continue to update this information regularly. To minimize the likelihood that a COVID-19 antigen test will fail to recognize emerging variants, we recommend using more than two antibodies in the assay (see page 3.)
Figure 1. Detection of the recombinant variant UK NP in indirect ELISA. Signal from recombinant wild type NP (Cat.# 8COV3) was set as 100%. Recombinant variant antigen used was 40588-V07E7 from Sino Biological.
Table 1. Detection of SARS-CoV-2 virus variants tested with two recommended pair combinations on lateral flow.
Swab samples were used as specimen. Note that line intensity depends on virus load that can vary between samples. The results show that these two pairs detect all three virus variants in lateral flow. Source: Customer data kindly provided with permission to show.
Figure 2. Specificity of anti-SC-NP MAbs sandwich antibody pairs to different point mutations. Signal from recombinant wild type NP (Cat.# 8COV3) was considered as 100%.
Pair recommendations - we recommend using more than two clones in assay developmentWhile all 1+1 (capture-detection) pair combinations we have tested are able to detect the key variants currently circulating in the world, we recommend using more than two clones in a COVID-19 Antigen test. This will increase the likelihood of the test to efficiently recognize all future variants too. Also, including anti-SC-NP polyclonals (Cat.# PSN5) as a capture antibody could help.
Anti-Spike RBD antibodies (Cat.# 3CV2)
variant has deletions and mutations within the spike protein, one of which is within the RBD part of the protein (N501Y). We have confirmed that all our anti-RBD clones detect the N501Y variant (recombinant antigen) similarly to the wild type virus.
variant bears four mutations in its spike protein (K417N, E484K, N501Y, D614G). Our anti-Spike clones recognize recombinant variant spike protein similarly to wild type virus.
variant contains three mutations in its spike protein (K417N, E484K, N501Y). Same mutations are found in the South African variant and based on results with the South African variant protein it is expected that our anti-RBD antibodies recognize the Brazilian variant similarly to the wild type.
Figure 3. Detection of the Beta variant spike (recombinant antigen) with HyTest anti-RBD antibodies.
Signal from recombinant wild type RBD (Cat.# 8COV1) was considered as 100%.