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The companion test to SARS-CoV-2 vaccination Innovating rapid testing to preserve and improve life

Innovating rapid testing to preserve and improve life Leading the UK RTC Contents Introduction

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03 The nature of SARS-CoV-2 testing has changed. Where Currently available tests detect antibodies targeting antibody tests were once chiefly used for charting the two different proteins on the SARS-CoV-2 virus: Introduction spread of infection within communities, today it is the Nucleocapsid or the Spike protein. However, almost 04 emerging as a key pillar of large-scale immunisation without exception, vaccine formulations are based on campaigns. the Spike protein. Vaccines and antibody tests converge on the same target However, there are stark differences between currently Testing for Nucleocapsid protein antibodies alone is 05 available antibody tests in both function and form. therefore of limited value. Though they may seem technical, these factors have Emerging evidence links prior infection with SARS-CoV-2 with immunity This short paper explains how rapid antibody testing significant implications for immunisation policy going focused on detecting the antibody response to the Spike 06 forward. protein, working hand in hand with vaccination, can help AbC-19™ Rapid Test The crucial difference is the antibody response that populations accelerate to herd immunity to SARS-CoV-2.. 06 the tests are evaluating. Trial of AbC-19™ Rapid Test with Vaccines 08 Summary 10 Contact 12 References

02 The companion test to SARS-CoV-2 vaccination 03 Vaccines and antibody tests Emerging evidence links prior infection converge on the same target with SARS-CoV-2 with immunity

The SARS-CoV-2 virus comprises a single strand of RNA As a result, vaccine research has focused overwhelmingly on Two questions have dogged researchers since the outbreak of enveloped within four structural proteins. The key ones from the Spike as the target. All of the vaccines in use today, and the pandemic: are seropositive people (those who have been an immunology perspective are the Nucleocapsid protein, virtually all of those in trial or approval, are designed to “train” infected with SARS-CoV-2 before) immune from subsequent which contains the virus RNA, and the Spike protein, dotting the immune system to recognise the Spike. infection, and if so, how long could that immunity last? the outside of the virus envelope and giving its distinctive Testing for neutralising antibodies specific to the Spike protein There is growing evidence to suggest that people who recover shape (figure 1). The Spike acts as the docking mechanism therefore allows authorities to draw far broader conclusions from COVID-19 are protected against reinfection for several with host receptors in the body. regarding immunity. months. The body produces antibodies to both Spike and Nucleocapsid Preliminary data from a study of 20,000 health workers in the proteins 10 days to two weeks after infection. A positive test UK has confirmed that prior infection with SARS-CoV-2 lowers for either can confirm prior infection with SARS-CoV-2. the risks of reinfection by 83%. This immunity was found to But, a positive Nucleocapsid antibody test does not prove last as long as five months.iii A separate study in the US, this Seropositive individuals iv whether the body has developed the capability to defeat the time of 30,000 subjects, reached similar conclusions. may only need a single infection.i A test detecting antibodies to the Spike, however, It further appears that SARS-CoV-2 infection gives a “boost” could. This is because neutralising activity – production of to the immune system similar in effect to the first vaccine vaccination to maintain antibodies which prevent the virus from reproducing – is far injection (the majority of vaccines require two injections stronger in response to the Spike.ii long-term immunity. a few weeks apart). A study of 109 volunteers found that seropositive individuals (due to previous infection prior to vaccination) had higher antibody levels after just one injection, than their seronegative counterparts (no previous infection), after two injections.v The researchers in this study concluded that seropositive individuals may only need a single vaccine injection to Spike protein (S) maintain long-term immunity.vi Though larger-scale investigations are needed, the implication is that a fixed quantity of vaccine could cover many more people than previously thought (depending upon their pre- ’’The AbC-19TM Rapid Test targets the IgG vaccination infection status). Rapid testing for Spike-specific antibodies could be what makes the difference. antibodies to the full spike protein of the Nucleocapsid SARS-CoV-2 virus and therefore has the Envelope protein (N) protein (E) potential to help identify the immune system’s response to the current three Membrane protein (M) MHRA approved vaccines. The assay could help establish whether people’s immune systems’ are responding to the RNA vaccine in the right way, and, ultimately, could be predictive of a protective immune response’’

Figure 1: coronavirus diagram PROFESSOR LAWRENCE YOUNG VIROLOGIST, UNIVERSITY OF WARWICK MEDICAL SCHOOL

04 The companion test to SARS-CoV-2 vaccination 05 AbC-19™ Rapid Test Trial of AbC-19™ Rapid Test at the intersection of antibody testing and immunisation with Vaccines

As we have seen, the ability to test for the presence of A lateral-flow immunoassay, it tests for the presence of The AbC-19™ Rapid Test was used to test samples from Of the 193 individuals examined, 128 (66%) patients were neutralising antibodies targeting the SARS-CoV-2 Spike IgG antibodies to the Spike which includes spike-specific individuals who had been given a single dose of the Pfizer- determined as not having a previous COVID-19 infection protein could have a dramatic impact on immunisation neutralising antibodies in the blood. It is designed to yield a BioNTech vaccine. In total 193 individuals who had received and thus naïve samples, with 65 (34%) patients identified as programmes. clear, qualitative response at the point of use, in around 20 a COVID-19 vaccine were tested for the presence of IgG having a previous COVID-19 infection. minutes. It rivals laboratory-based assays for sensitivity and antibodies to the full trimeric spike using the AbC-19TM test. Such a testing regime could demonstrate whether patients specificity. Performance in testing an extended cohort of 818 When applying the above scoring to the samples taken have responded to vaccination in the right way or prove samples demonstrated sensitivity of 97.6% and specificity of Of the patients involved in the study, AbC-19TM identified 181 13 days or more after the single vaccination, 43.3% of the prior infection with SARS-CoV-2 (and thus the need for a 99.6% in samples of known status.vii (94%) as testing positive for the presence of IgG antibodies naïve samples scored medium to strong test line response single vaccine injection, rather than two). to COVID-19, with some samples from those with previous with 53.8% showing a weaker response and 2.9% having a As it tests for the presence of Spike-specific neutralising AbC-19™ Rapid Test has been designed to address this infection demonstrating a positive result as little as 1-4 days negative result. In contrast, those who had previously been antibodies in the blood, AbC-19™ Rapid Test looks for vital market need. post vaccination. Using a cut-off of 13 days post-vaccination infected with COVID-19 had a stronger response in 75% exactly the same immune response that virtually all the (which is the minimum recommendation for determining individuals, while 25% showed a weaker response with no vaccines engender. antibody status using the AbC-19TM rapid test) 137 out of 140 negative results. It would be expected for the IgG anti-spike of samples, or 98% of patients, were identified as testing antibody levels to continue to rise with time and following a positive for the presence of IgG antibodies. second vaccination.

Using the WHO classification of the lateral flow device test Further studies are being performed to expand this data set line, results were classified as: and are expected to be available in the next few weeks.

0 (negative) This data supports the rationale discussed above that vaccination programmes could benefit from determining 1 (very weak but definitely reactive) an individual’s antibody status not only after vaccination 13+ days post Pfizer Vaccination but also prior to vaccination. This is in turn may lead to 2 (medium to strong reactivity) the need for one vaccination for those individuals who are Score 0 1 2 showing high levels of immunity prior to receiving a vaccine.

Naïve 2.9% 53.8% 43.3%

Prior Infection 0.0% 25.0% 75.0% 80.0% Naïve Prior Infection 70.0% Table 1: % of Samples with 0, 1 or 2 Scores Graph 1: AbC-19TM Response 13+ days 60.0% after single Pfizer vaccination 50.0% 40.0% 30.0% 20.0% 10.0% Percentage of samples of Percentage 0.0% 0 1 2

Figure 3: Example of a Positive AbC19™ Rapid Test (medium-strong result, WHO score 2) WHO Score

06 TheCharting companion the course test toto aSARS-CoV-2 post-COVID vaccinationworld 07 Summary

Only antibody tests targeting Helping organisations track the effectiveness of responses to the SARS-CoV-2 full vaccination programmes

trimeric Spike protein can yield the Enabling vaccine supplies to stretch further by identifying insights policymakers and other people who have been previously infected and may only need a single vaccine dose. Only antibody tests targeting bodies need to chart the course to a responses to the SARS-CoV-2 COVID-19 free world. In particular, Yielding insights that can help track the development of immunity and understanding of how sustained immunity Spike protein can yield the the AbC-19™ Rapid Test can support is across populations, leading to an eventual relaxation of efforts to build immunity by: and other restrictions. insights policymakers and other bodies need to chart the course to a Covid-19 free world.

08 TheCharting companion the course test toto aSARS-CoV-2 post-COVID vaccinationworld 09 Contact

TM Contact Abingdon A trusted rapid test manufacturing partner Health today

Talk to us to learn more about

The UK Rapid Test Consortium (UK-RTC) was founded The Abc-19TM is approved in Europe and the UK for AbC-19™ Rapid Test. in response to a UK Government call for businesses and professional use and is available for sale. Click here to universities to work together on a rapid antibody test to contact us or order the AbC-19TM in boxes of 25 tests. be rolled out nationally. Led by Abingdon Health, it’s members also include, BBI Solutions, CIGA Healthcare and Omega Diagnostics. Telephone: +44 (0) 1904 406082

Sample, containing Nitrocellulose membrane Absorbent pad SARS-CoV-2 Specific IgG Antibodies Website: Control line abingdonhealth.com Spike Protein Test Line Antigen Test Line Control Line Gold-labelled signal molecule Gold-labelled signal molecule SARS-CoV-2 IgG Antibody

Reading the test results

Conjugate release pad 2 lines = Positive Covid-19 antibodies detected

Sample Pad 1 C line = Negative Test performed correctly but no antibodies detected Figure 4: schematic of AbC-19™ Rapid Test lateral flow immunoassay

10 TheCharting companion the course test toto aSARS-CoV-2 post-COVID vaccinationworld 11 References

i Andrews K et al., Heterogeneous antibodies against SARS-CoV-2 spike RBD and nucleocapsid, JCI Insight vol 5, 17 September 2020 ii Ibid iii Hall V et al., Do antibody positive healthcare workers have lower SARS-CoV-2 infection rates than antibody negative healthcare workers? preprint https://doi.org/10.1101/2021.01.13.21249642, 15 January 2021 iv Wajnberg A et al. Robust neutralizing antibodies to SARS-CoV-2 infection persist for months, Science 370, pp1227-1230, 4 December 2020 v Krammer F et al. Robust spike antibody responses and increased reactogenicity in seropositive individuals after a single dose of SARS-CoV-2 mRNA vaccine, preprint https://doi.org/10.1101/2021.01.29.21250653, 1 February 2021 vi Ibid vii Robertson et al., SARS-CoV-2 antibody testing in a UK population: detectable IgG for up to 20 weeks post infection, preprint https://www.medrxiv.org/content/10.1101/2020.09.29.20201509v1

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