SARS-CoV-2 ELISA Assay

For sensitive and reliable measurement of specific antibodies as a result of Covid-19 infections and vaccination programmes

We manufacture trimeric Spike protein - the most valuable Covid-19 antigen, ensuring the highest sensitivity of the resulting test. It is produced in human cell culture and therefore is the exact match of the current vaccines, providing the best tool to assess the efficacy of those vaccines.

Most of the current commercial diagnostic kits have either recombinant Nucleocapsid or much smaller fragments of Spike as their components.

The former cannot distinguish between SARS-CoV-2 and other coronaviruses such as flu or common cold, presenting specificity issues of the resulting tests. Moreover, it cannot be used to measure SARS-CoV-2 specific antibodies in the blood of vaccinated people.

The Receptor Binding Domain (RBD) based tests cause sensitivity problems since they can only detect a small portion of specific antibodies.

  • Small volumes of blood required which can be collected at home

  • Extremely sensitive and reliable antibody-measuring method

  • Minimum consumables and instruments required to run

  • Distinguishes between serological response to various mutants/variants of concern; has a potential prognostic value

Advantages:

Method

ELISA in a 96-well format based on the trimeric Spike antigen as the capture antigen and colorimetric substrate development.

The method is the most sensitive and economical compared to all current commercially available tests, requiring only few microlitres of patient’s blood (finger prick) and has been adapted for dry blood spots which can be collected at home. OD reading is performed on conventional plate-reader.

Validation

The ELISA assay has been validated on serological panel of Covid-19 patients (37) supplied by the UK National Institute of Biological Standards and Controls, NIBSC, United Kingdom. It has also been validated on 54 volunteers encompassing recovered Covid-19 patients and people immunised with various vaccines. More validation on larger patient samples will be carried out by our partners such as the Liverpool School of Tropical Medicine, LSTM, and AlphaBiolabs (Warrington).

The method has also been used to assess individual serological response to various SARS-CoV-2 mutants, for example the pandemic strain of SARS-CoV-2 D614G versus the South African variant of concern (B.1.351, beta variant).

Fig. 1. IgG Detection of COVID -19 patients’ serum panel (NIBSC 20/B770), WHO Reference panel (NIBSC 20/268) and calibrant (NIBSC 20/162) against B1.351 and the D614G pandemic form. Human specific anti-SARS-CoV-2 IgGs were detected using Daresbury Proteins ELISA.

Conclusion

With low analyte requirement (1-3 µL) and assay costs, Daresbury Trimeric spike protein ELISA IgG test provides OD/CO of B1.351 and D614G mutants in a 2-way parallel serum study. The test is very useful in gaining prognostic understanding of different immune responses and assessing the efficacy of different vaccines against certain mutant strains.

Fig. 2. IgG Detection in individuals vaccinated by 3 different vaccines against B1.351 and the D614G pandemic form. Human specific anti-SARS-CoV-2 IgGs were detected using Daresbury Proteins ELISA.

Conclusion

Daresbury Trimeric spike protein ELISA test reliably detects individual serological response and can be used to monitor the immune titre provided by various vaccines as well as to measure their efficiency against newly emerging geographical variants of concern.